Engaging the cervical spinal cord circuitry to re-enable volitional control of hand function in tetraplegic subjects

Abstract

In various embodiments, methods are provided for applying transcutaneous and/or epidural spinal cord stimulation with and without selective pharmaceuticals to restore voluntary control of hand function in tetraplegic subjects.

Description

BACKGROUND

Serious spinal cord injuries (SCI) affect approximately 1.3 million people in the United States, and roughly 12-15,000 new injuries occur each year. Of these injuries, approximately 50% are complete spinal cord injuries in which there is essentially total loss of sensory motor function below the level of the spinal lesion.

Paralysis of the upper limbs results in an enormous loss of independence of one's daily life. Meaningful improvement in hand function is generally rare after one year of tetraparesis.

SUMMARY

In various embodiments, methods are provided for applying spinal cord stimulation with and without selective pharmaceuticals to restore voluntary control of hand function in tetraplegic subjects. The spinal cord stimulation can be transcutaneous and/or epidural. In various embodiments the electrical stimulation alone or in combination with pharmaceuticals can be applied to facilitate restoration of motor control and/or force generation in subjects suffering with spinal cord injury and/or as other neurological injury and illness that effects motor control of the hand or paw. Successful application can provide a device for widespread use in rehabilitation of neurologic injury and disease.

In particular illustrative embodiments, the devices, optional pharmacological agents, and methods described herein stimulate the spinal cord with, e.g., electrodes that modulate the proprioceptive and supraspinal information that controls the hands during reaching and/or grasping and/or manipulating conditions. Without being bound by a particular theory, it is believed the proprioceptive and cutaneous sensory information guides the activation of the muscles in a coordinated manner and in a manner that accommodates the external conditions.

Unlike approaches that involve specific stimulation of motor neurons to directly induce a movement, the methods described herein can enable the spinal circuitry to control the movements. More specifically, the devices, optional pharmacological agents, and methods described herein can exploit the spinal circuitry and its ability to interpret proprioceptive information and to respond to that proprioceptive information in a functional way. In various embodiments, this is in contrast to other approaches where the actual movement is induced/controlled by direct stimulation (e.g., of particular motor neurons).

Accordingly, in various aspects, the invention(s) contemplated herein may include, but need not be limited to, any one or more of the following embodiments:

Embodiment 1: A method of improving motor control and/or strength in a hand of a subject with a neuromotor disorder affecting motor control of the hand, said method including: neuromodulating the cervical spinal cord of the subject by administering stimulation to the cervical spinal cord or a region thereof and by administering to the subject at least one monoaminergic agonist. In some instances of Embodiment 1, the spinal cord stimulation can be transcutaneous and/or epidural.

Embodiment 2: The method of embodiment 1, wherein said method includes administering transcutaneous stimulation to the cervical spinal cord or a region thereof.

Embodiment 3: The method of embodiment 1, wherein said method includes administering epidural stimulation to the cervical spinal cord or a region thereof.

Embodiment 4: The method of embodiment 1, wherein said method includes administering a monoaminergic agonist to said subject.

Embodiment 5: The method of embodiment 1, wherein said method includes administering transcutaneous stimulation to the cervical spinal cord or a region thereof in conjunction with administration of a monoaminergic agonist.

Embodiment 6: The method of embodiment 1, wherein said method includes administering epidural stimulation to the cervical spinal cord or a region thereof in conjunction with administration of a monoaminergic agonist.

Embodiment 7: The method of embodiment 1, wherein said method includes administering transcutaneous stimulation to the cervical spinal cord or a region thereof in conjunction with epidural stimulation of the cervical spinal cord or a region thereof.

Embodiment 8: The method of embodiment 1, wherein said method includes administering transcutaneous stimulation to the cervical spinal cord or a region thereof in conjunction with epidural stimulation of the cervical spinal cord or a region thereof in conjunction with administration of a monoaminergic agonist to said subject.

Embodiment 9: The method according to any one of embodiments 1, 2, 5, 7, and 8, wherein said transcutaneous stimulation is at a frequency ranging from about 3 Hz, or from about 5 Hz, or from about 10 Hz to about 100 Hz, or to about 80 Hz, or to about 40 Hz, or from about 3 Hz or from about 5 Hz to about 80 Hz, or from about 5 Hz to about 30 Hz, or to about 40 Hz, or to about 50 Hz.

Embodiment 10: The method according to any one of embodiments 1, 2, 5, and 7-9, wherein said transcutaneous stimulation is applied at an intensity ranging from about 10 mA to about 150 mA, or from about 20 mA to about 50 mA or to about 100 mA, or from about 20 mA or from about 30 mA, or from about 40 mA to about 50 mA, or to about 60 mA, or to about 70 mA or to about 80 mA.

Embodiment 11: The method according to any one of embodiments 1, 2, 5, and 7-10, wherein said transcutaneous stimulation is at a frequency and amplitude sufficient to improve hand strength and/or fine hand control.

Embodiment 12: The method according to any one of embodiments 1, 2, 5, and 7-11, wherein said transcutaneous stimulation is applied to the dorsal aspect of the neck in the area of C5.

Embodiment 13: The method according to any one of embodiments 1, 3, and 6-12, wherein said epidural stimulation is at a frequency ranging from about 3 Hz, or from about 5 Hz, or from about 10 Hz to about 100 Hz, or to about 80 Hz, or to about 40 Hz, or from about 3 Hz or from about 5 Hz to about 80 Hz, or from about 5 Hz to about 30 Hz, or to about 40 Hz, or to about 50 Hz.

Embodiment 14: The method according to any one of embodiments 1, 3, and 6-13, wherein said epidural stimulation is at an amplitude ranging from 0.05 mA to about 30 mA, or from about 0.1 mA to about 20 mA, or from about 0.1 mA to about 15 mA or to about 10 mA.

Embodiment 15: The method according to any one of embodiments 1, 3, and 6-14, wherein said pulse width ranges from about 150 μs to about 600 μs, or from about 200 μs to about 500 μs, or from about 200 μs to about 450 μs.

Embodiment 16: The method according to any one of embodiments 1, 3, and 6-15, wherein said epidural stimulation is at a frequency and amplitude sufficient to improve hand strength and/or fine hand control.

Embodiment 17: The method according to any one of embodiments 1, 3, and 6-16, wherein said epidural stimulation is applied paraspinally over vertebrae spanning C2 to T1.

Embodiment 18: The method according to any one of embodiments 1, 3, and 6-16, wherein said epidural stimulation is applied paraspinally over vertebrae spanning C5 to T1.

Embodiment 19: The method according to any one of embodiments 1, 3, and 6-18, wherein said epidural stimulation is applied via a permanently implanted electrode array.

Embodiment 20: The method of embodiment 19, wherein said electrode array is a parylene based microelectrode implant.

Embodiment 21: The method according to any one of embodiments 1, 4, 5, 6, and 8-20, wherein the at least one monoaminergic agonist includes a drug selected from the group consisting of a serotonergic drug, a dopaminergic drug, a noradrenergic drug, a GABAergic drug, and a glycinergic drug.

Embodiment 22: The method of embodiment 21, where the agent is selected from the group consisting of 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), 4-(benzodioxan-5-yl)1-(indan-2-yl)piperazine (S15535), N-{2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl}-N-(2-pyridinyl)cyclo-hexanecarboxamide (WAY 100.635), Quipazine, Ketanserin, 4-amino-(6-chloro-2-pyridyl)-1 piperidine hydrochloride (SR 57227A), Ondanesetron, Buspirone, Methoxamine, Prazosin, Clonidine, Yohimbine, 6-chloro-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine-7,8-diol (SKF-81297), 7-chloro-3-methyl-1-phenyl-1,2,4,5-tetrahydro-3-benzazepin-8-ol (SCH-23390), Quinpirole, and Eticlopride.

Embodiment 23: The method of embodiment 21, wherein said monoaminergic agonist is buspirone.

Embodiment 24: The method of embodiment 22, wherein said drug is 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT).

Embodiment 25: The method of embodiment 22, wherein said drug is 4-(benzodioxan-5-yl)1-(indan-2-yl)piperazine (S15535).

Embodiment 26: The method of embodiment 22, wherein said drug is N-{2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl}-N-(2-pyridinyl)cyclo-hexanecarboxamide (WAY 100.635).

Embodiment 27: The method of embodiment 22, wherein said drug is Quipazine.

Embodiment 28: The method of embodiment 22, wherein said drug is Ketanserin.

Embodiment 29: The method of embodiment 22, wherein said drug is 4-amino-(6-chloro-2-pyridyl)-1 piperidine hydrochloride (SR 57227A).

Embodiment 30: The method of embodiment 22, wherein said drug is Ondanesetron.

Embodiment 31: The method of embodiment 22, wherein said drug is Methoxamine.

Embodiment 32: The method of embodiment 22, wherein said drug is Prazosin.

Embodiment 33: The method of embodiment 22, wherein said drug is Clonidine.

Embodiment 34: The method of embodiment 22, wherein said drug is Yohimbine.

Embodiment 35: The method of embodiment 22, wherein said drug is 6-chloro-1-phenyl-2.

Embodiment 36: The method of embodiment 22, wherein said drug is 3,4,5-tetrahydro-1H-3-benzazepine-7.

Embodiment 37: The method of embodiment 22, wherein said drug is 8-diol (SKF-81297).

Embodiment 38: The method of embodiment 22, wherein said drug is 7-chloro-3-methyl-1-phenyl-1,2,4,5-tetrahydro-3-benzazepin-8-ol (SCH-23390).

Embodiment 39: The method of embodiment 21, wherein said drug is Quinpirole.

Embodiment 40: The method of embodiment 21, wherein said drug is and Eticlopride.

Embodiment 41: The method according to any one of embodiments 1 and 4-40, wherein a combination of transcutaneous and/or epidural stimulation and monoaminergic agonist provides a synergistic improvement in hand strength and/or fine hand control.

Embodiment 42: The method according to any one of embodiments 1-41, wherein said subject is a human. In some embodiments, the subject is a non-human mammal.

Embodiment 43: The method according to any one of embodiments 1-42, wherein said subject has a spinal cord injury.

Embodiment 44: The method of embodiment 43, wherein said spinal cord injury is clinically classified as motor complete.

Embodiment 45: The method of embodiment 43, wherein said spinal cord injury is clinically classified as motor incomplete.

Embodiment 46: The method according to any one of embodiments 1-42, wherein said subject has an ischemic brain injury.

Embodiment 47: The method of embodiment 46, wherein said ischemic brain injury is brain injury from stroke or acute trauma.

Embodiment 48: The method according to any one of embodiments 1-42, wherein said mammal has a neurodegenerative pathology.

Embodiment 49: The method of embodiment 48, wherein said neurodegenerative pathology is associated with a condition selected from the group consisting of Parkinson's disease, Huntington's disease, Alzheimer's disease, amyotrophic lateral sclerosis (ALS), primary lateral sclerosis (PLS), dystonia, and cerebral palsy.

Embodiment 50: The method according to any one of embodiments 1-49, wherein the stimulation is under control of the subject.

Embodiment 51: The method according to any one of embodiments 1-50, wherein said method further includes physical training of said subject.

Embodiment 52: The method of embodiment 51, wherein said physical training includes hand contraction against a resistance.

Embodiment 53: The method according to any one of embodiments 51-52, wherein said physical training includes tracing a displayed pattern by hand manipulation of a hand controller.

Embodiment 54: An electrical stimulator configured to induce epidural and/or transcutaneous electrical stimulation in the cervical region of a mammal according to any one of embodiments 1-20.

DEFINITIONS

As used herein “electrical stimulation” or “stimulation” means application of an electrical signal that may be either excitatory or inhibitory to a muscle or neuron and/or to groups of neurons and/or interneurons. It will be understood that an electrical signal may be applied to one or more electrodes with one or more return electrodes.

As used herein “epidural” means situated upon the dura or in very close proximity to the dura. The term “epidural stimulation” refers to electrical epidural stimulation. In certain embodiments epidural stimulation is referred to as “electrical enabling motor control” (eEmc).

The term “transcutaneous stimulation” or “transcutaneous electrical stimulation” or “cutaneous electrical stimulation” refers to electrical stimulation applied to the skin, and, as typically used herein refers to electrical stimulation applied to the skin in order to effect stimulation of the spinal cord or a region thereof. The term “transcutaneous electrical spinal cord stimulation” may also be referred to as “tSCS”. The term “pcEmc” refers to painless cutaneous electrical stimulation.

The term “motor complete” when used with respect to a spinal cord injury indicates that there is no motor function below the lesion, (e.g., no movement can be voluntarily induced in muscles innervated by spinal segments below the spinal lesion.

The term “monopolar stimulation” refers to stimulation between a local electrode and a common distant return electrode.

The term “co-administering”, “concurrent administration”, “administering in conjunction with” or “administering in combination” when used, for example with respect to transcutaneous electrical stimulation, epidural electrical stimulation, and pharmaceutical administration, refers to administration of the transcutaneous electrical stimulation and/or epidural electrical stimulation and/or pharmaceutical such that various modalities can simultaneously achieve a physiological effect on the subject. The administered modalities need not be administered together, either temporally or at the same site. In some embodiments, the various “treatment” modalities are administered at different times. In some embodiments, administration of one can precede administration of the other (e.g., drug before electrical stimulation or vice versa). Simultaneous physiological effect need not necessarily require presence of drug and the electrical stimulation at the same time or the presence of both stimulation modalities at the same time. In some embodiments, all the modalities are administered essentially simultaneously.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1, panels A-I, illustrates improvement in hand function with interventions. Assessments of grip strength were made in 6 paralyzed subjects on 6 days of testing over 6 weeks Pre-Treatment (Phase 1, Pre Treat), followed by 4 days of testing over 2 weeks with pcEMC (Phase 2, +Stim, −Busp), followed by 4 days of testing over 2 weeks with pcEMC plus oral buspirone (Phase 3, +Stim, +Busp), followed by 4 days of testing over 2 weeks with pcEmc plus placebo (Phase 4, +Stim, −Busp), and followed by 4 days of testing over 2 weeks Post-Treatment after a 3-6 month delay (Phase 5, Post Treat) (Panels A-F). Mean (±SEM) grip strength for all 6 subjects (G), EMG amplitudes as percent increase over baseline (Pre Treat) levels (panel H), ARAT and upper extremity ASIA functional scores (panel I) are shown. Horizontal lines indicate significant differences at P<0.05, P<0.01, or P<0.001. FD, flexor digitorum; ED, extensor digitorum; Brac, brachioradialis; Bicep, biceps brachii; tricep, triceps brachii.

FIG. 2, panels A-L, shows motor performance relative to eEmc parameters. Subject E (C5 injury, ASIA panel B) was implanted with a 16-channel cervical epidural stimulation paddle array spanning spinal cord levels C5-T1, arrow pointing to electrode array (panels A and B). Prior to permanent implant, two parallel, temporary percutaneous linear electrodes were implanted. To assess hand control, the ability to accurately follow a targeted sign wave (panel C) and to perform rapid oscillations (panel D), and the maximal voluntary contraction (panel E) were determined during the initial day of eEmc before (Pre), during (Stim), and after (Post) stimulation (cathodes at C3 and anodes at T2, 30 Hz, 3.0 mA). After permanent paddle electrode implantation, stimulation at electrodes #13 and #14 (refer to schematic in panel B) was performed with the subject passive (Baseline) and when the subject attempted a voluntary contraction (Voluntary). Mean (±SEM, 3 trials for each condition) grip force during Baseline and Voluntary testing at varying stimulation frequencies (panel F) and intensities (panel G) are shown. Optimal stimulation parameters to affect hand function were assessed (panels H-J). Time to actuate the handgrip device (response time) was assessed at different stimulation frequencies and intensities (±SEM, 3 trials for each condition) (panel H). The parameter of 20 Hz, 0.7 mA elicited the shortest response time. Likewise, eEmc facilitated handgrip oscillation with doubling of oscillation ability compared to Pre and Post conditions of no stimulation (representative tracings shown) (panel I). Accuracy score during sinusoidal wave testing in response to varying frequencies of stimulation was assessed with the best scores observed at 20 Hz (±SEM, 3 trials for each condition) (panel J). Assessment of accuracy score over different sessions revealed chronic improvement with sinusoidal wave test (±SEM, 24 trials for each condition at electrode combinations of +13-14 and +13-6, 5-30 Hz, 0.7 mA) (panel K). These improvements in hand function in response to eEmc were evident in the acute improvements in clinical ARAT score with multi-site electrode combination (Stim) (70% at −12+3, 30% at −12+4, 5 Hz, 0.9 mA) (panel L). The improvement of 6 points in ARAT score reflects a clinically significant event. This 20% increase reflects improvements in all categories measured by ARAT and is above the minimal clinically important difference of 5.7 points established for this instrument (van der Lee et al. (2001)J. Rehabil. Med. 33: 110-113), demonstrating the relevance of this intervention in improving upper extremity function.

FIG. 3, panels A-E, shows hand grip force and evoked potentials in Subject E. Handgrip force and EMG during a maximum handgrip performed without (panel A) and with eEmc (panel B) of the cervical spinal cord (electrodes +13-14, 10 Hz, 1 mA). In (panel B), the initial stimulation phase without any voluntary effort (blue shaded area), the voluntary contraction phase (red shaded area), and the relaxation phase of the voluntary effort (green shaded area) are shown. At least twenty evoked potentials in each muscle were averaged during each phase. Note that an evoked potential was clearly evident in all muscles during the contraction and relaxation phases, but only in the H. thenar during the initial stimulation phase without any voluntary effort. The effect of frequency of stimulation on the average evoked potentials for 3 sec during the initial stimulation phase without any voluntary effort and during the voluntary contraction phase in each muscle are shown in panel C. The data demonstrate a substantially reduced evoked response in all muscles at the higher frequencies (20 and 30 Hz) during the voluntary contraction phase, but no substantial loss of force. The increase in force and two components of the EMG signal of the FD muscle during the initial phase of contraction is shown in panel E. The iEMG is divided into the energy (pV.sec) derived from evoked potentials synchronized with the stimulation pulses (20 Hz) and the total iEMG energy, i.e., the combination of the synchronized signals and that occurring randomly with respect to the stimulation pulses. The samples used for plotting the force are separated into those time bins when the EMG signals are largely alternating in amplitude. The + sign represents bins with the lowest amplitude and the triangles represent those with the highest amplitudes. The presence or absence of the lower synchronized signal had no impact on the force generated during a given time bin. H. Thenar, hypothenar; ER evoked response.

FIG. 4, panels A-H, shows handgrip forces and evoked responses at different % maximum efforts in Subject E. Handgrip force for a maximum contraction at the beginning of testing (100% Pre) followed by 7 consecutive contractions (5 sec between each contraction, and 5 min of rest between different efforts) at 10 (red), 25 (blue), 75 (green) % effort, and after 10 min of rest for a maximum contraction at the end of testing (100% Post) with no stimulation (A). The FD integrated EMG (iEMG) within this series of efforts is shown in (B). Numbers above the bars in (B), (D), and (F) are linked to the contraction numbers as labeled in (A). Fifteen min after the completion of (A), the same series of contractions were repeated in the presence of increasing intensities of stimulation ((C) and (D)). In this case, fatigue was evident at 0.7 and 0.5 mA when the subject was exerting 25 and 75% effort, respectively. Stimulation at the higher intensities enabled the subject to overcome substantial levels of fatigue. Additionally, there was an associated increase in iEMG compared to the initial contractions without fatigue as well as those in which fatigue occurred (D). To determine whether this fatigue effect was associated with repetitive contractions on the same day as in (A) and (C), on a separate day the same series of efforts at the same level of stimulation intensities were examined. In this case, there was no obvious fatigue (E) at any stimulation intensity as indicated by the constant forces and only minor increases in iEMG (F). The patterns of evoked potentials at selected percent efforts and at different strengths of stimulation when there was substantial fatigue and when there was no apparent fatigue is shown in (G) and (H), corresponding to iEMG (D) and (F), respectively. In spite of the absence of evidence of fatigue as indicated by the force with repeated contractions, to maintain that force may require higher intensities of stimulation to sustain the forces generated at the end of each series of contractions at a given percent effort (H). Stimulation parameters were electrode pattern of −13+14, 20 Hz, 0-1.3 mA.

FIG. 5, panels A-F, shows sagittal T2 MRI Imaging demonstrating location of cervical spinal cord injury of subjects A-F, approximating C2 (panel C), C5 (panels B, D, E) or C6 (panels A, F) spinal cord segment. Normal tissue at injury location is replaced by a high intensity signal representing a glial scar. Spinal cord tissue distal and proximal to the injury locus is seen to be intact without evidence of post-traumatic syrinx formation or on-going compressive lesion.

FIG. 6, panels A-C, shows that baseline testing (Phase 1) demonstrates stable hand function by handgrip device (panel A) and ARAT and ASIA scores (panel B) prior to initiation of any intervention. Maximal handgrip force on the last day of testing is not different from the first day of testing in the 6 subjects (panel A). Testing during this phase spanned a period of 6 weeks with bi-weekly testing sessions. Each data point represents an average of 3 maximal handgrip contractions. Clinical testing by ARAT and ASIA scores demonstrated no evidence of improvement during this initial baseline testing period (panel B).

FIG. 7, panels A-I, show amplitudes of spinal cord evoked potentials induced by cathode-anode epidural electrode pairs with a range of currents and frequencies starting from the rostral to caudal spinal cord (refer to FIG. 2B for electrode configuration). The amplitude of the potentials demonstrates the relative responsiveness of each motor pool to the stimulation at a specific spinal location at a given level of current and frequency. The cathode-anode pair of −13+14 produced the most activation of muscles associated with hand function, i.e., H. Thenar and FD, and was used for most of the study.

FIG. 8 shows upper extremity motor ASIA Impairment Score of Subject E. Motor function was assessed at the beginning and conclusion of the study, demonstrating a clinically significant 23-point increase during the study period.

DETAILED DESCRIPTION

Embodiments described herein provide methods for applying spinal cord stimulation with and without selective pharmaceuticals to restore voluntary control of upper extremity function in tetraplegic subjects. In some embodiments, the upper extremity or extremities can be the hands. The spinal cord stimulation can be transcutaneous, epidural, or a combination thereof. The spinal cord stimulation alone or in combination with pharmaceuticals can be applied to facilitate restoration of motor control and/or force generation in individuals with spinal cord injuries.

As demonstrated herein in the Examples, an injured cervical spinal cord (e.g., a human cervical spinal cord) can be modulated using painless cutaneous electrical stimulation (pcEmc), monoaminergic agonist (fEmc) treatment, and/or eEmc to regain voluntary hand function. In some embodiments, mean hand strength can be increased by greater than 300% after pcEmc plus fEmc (buspirone) treatment. This was demonstrated in 6 subjects with a chronic motor complete cervical injury. One subject that was implanted with a cervical epidural electrode array realized significantly improved hand strength and fine hand control in the presence of cervical eEmc. Thus, the cervical circuitry can be neuromodulated to improve volitional control of hand function in tetraplegic subjects with one or more interventions: transcutaneous electrical stimulation (e.g., pcEMC), and/or monoaminergic agonist administration (fEmc), and/or epidural electrical stimulation (eEmc). In some embodiments, the impact of the herein described methods on individuals with upper limb paralysis can be dramatic functionally, psychologically, and economically.

Accordingly, in various embodiments, methods are provided for improving motor control and/or strength in a hand (or paw) of a subject with a neuromotor disorder affecting motor control of the hand (or paw). In various embodiments, the methods involve neuromodulating the cervical spinal cord of the subject by administering transcutaneous stimulation to the cervical spinal cord or a region thereof, and/or neuromodulating the cervical spinal cord of said subject by administering epidural stimulation to the cervical spinal cord or a region thereof; and/or by administering to the subject a monoaminergic agonist (or other neuromodulatory pharmaceutical).

In some embodiments, neuromodulatory strategies can be used to improve fine motor control of the upper limbs, i.e., performance of motor tasks considered to be less “automatic” than posture and locomotion. These strategies can neuromodulate the lumbosacral spinal circuitry via epidural stimulation (electrical enabling motor control, eEmc)

In various embodiments, these methods can, optionally, be used in combination with physical training regimen. And in some embodiments, the pharmaceutical can be buspirone.

The methods described herein are for use with a mammal (e.g., a human, a mamal (e.g., a non-human primate, equine, feline, canus, etc.) who has a spinal cord with at least one dysfunctional spinal circuit that inhibits motor control and/or strength in a hand or paw and/or who exhibits another neuropathology that inhibits motor control and/or strength in a hand or paw. In one embodiment, the mammal is a human. As described herein, ranscutaneous electrical stimulation of the cervical spinal cord or a region thereof, and/or epidural stimulation of the cervical spinal cord, or a region thereof, and/or use of a neuromodulatory agent (e.g., a monoaminergic agent) can improve and/or restore motor control and/or strength to a hand or paw.

In some embodiments, hand function can be improved by neuromodulating the cervical spinal cord. Six subjects with chronic (18-36 months) spinal cord injury (SCI, traumatic cervical injury, ASIA B with no motor strength below the injury) were tested. All subjects initially had minimal hand strength, a condition characteristic of the majority of cervical SCI patients. The experimental approach began with six weeks of baseline testing (Phase 1), followed by three 2-week treatment periods (phases 2-4), and then by a period of approximately three months without any treatment at the end of which there was a final two week testing period (Phase 5). pcEmc at the C5 spinal segment (Phase 2) increased hand strength in 4/6 subjects compared to baseline Phase 1. During buspirone treatment (Phase 3), 4/6 subjects increased hand strength compared to Phase 1 and 2. The next 2 weeks buspirone was withdrawn but pcEmc continued (Phase 4), and again 4/6 subjects showed further improvement in grip strength compared to Phase 3. For all subjects combined, the mean grip strength tended to increase after each successive treatment phase. EMG amplitudes were generally consistent with increases in grip force, i.e., digit flexor and extensor EMG amplitudes tended to increase progressively across phases. After approximately three months without treatment, 4/6 subjects improved their performance relative to Phase 4.

These results show that the cervical spinal cord can be neuromodulated using two paradigms, i.e., electrically and pharmacologically. Moreover, these data indicate that non-functional networks can become engaged and progressively improve motor performance. In addition, the further improvement in hand function after withdrawing pcEMC and fEMC suggests that once functional connections are established they remain active.

Accordingly, the methods described herein are useful to improve and/or restore motor function to the hand or paw of a subject having paralysis affecting that hand or paw. In various embodiments, the methods provide that the spinal circuitry is neuromodulated to a physiological state that facilitates or enables the recovery or improved control of movement or improved strength of a hand or paw following some neuromotor dysfunction.

In some embodiments the paralysis effecting the hand or paw may be a motor complete paralysis or a motor incomplete paralysis. In certain embodiments the paralysis may have been caused by a spinal cord injury classified as motor complete or motor incomplete. The paralysis may have been caused by an ischemic or traumatic brain (or spinal) injury. In certain embodiments the paralysis may have been caused by an ischemic brain injury resulting from a stroke or acute trauma. By way of another example, the paralysis may have been caused by a neurodegenerative condition affecting the brain and/or spinal cord. In certain embodiments the neurodegenerative injury may be associated with a disease such as Parkinson's disease, Huntington's disease, Alzheimer's disease, frontotemporal dementia, dystonia, amyotrophic lateral sclerosis (ALS), primary lateral sclerosis (PLS), and other conditions such as cerebral palsy and multiple sclerosis (MS).

By way of non-limiting example, in certain embodiments, the methods described herein comprises application of electrical stimulation to the cervical spinal cord or a portion thereof of the subject. The electrical stimulation may be applied by a surface electrode(s) that is applied to the skin surface of the subject to provide a transcutaneous stimulation. Additionally, or alternatively, the electrical stimulation can be provided epidurally (e.g., via an implanted electrode or electrode array).

In various embodiments, the electrodes may; be implanted along, and/or the stimulation may be applied to the entire cervical spine (e.g., C1-T1) or to a region therein (e.g., C2-C7, C3-C7, C3-C6, C3-C5, C4-C7, C4-C6, C4-C5, C5, etc.). The electrical stimulation is delivered, e.g., as described herein (e.g., at 5-40 Hz at 20-100 mA). While not a requirement, the electrical stimulation may not directly activate muscle cells in the portion of the patient's body having the paralysis. In certain embodiments the electrodes (surface and/or implanted) may include an array of one or more electrodes stimulated in a monopolar biphasic configuration.

In various embodiments, the stimulation may include tonic stimulation and/or intermittent stimulation. The stimulation may include simultaneous or sequential stimulation, or combinations thereof, of different cord regions (e.g., different regions within the cervical spinal cord, or a region within the cervical spinal cord and another regions outside the cervical spinal cord). Optionally, in certain embodiments, the stimulation pattern may be under control of the subject.

In certain embodiments, the method(s) may include administering one or more neuropharmaceutical agents to the subject. The neuropharmaceutical agents may include, for example, a monoaminergic agent (e.g., buspirone).

In certain embodiments, the electrical stimulation is defined by a set of parameter values (e.g., frequency, amplitude, pulse width, etc.), and activation of the selected spinal circuit may (but need not) generate a quantifiable result. Optionally, the method may be repeated using electrical stimulation having different sets of parameter values to obtain quantifiable results generated by each repetition of the method. In certain embodiments a machine learning method may be executed by at least one computing device. The machine learning method builds a model of a relationship between the electrical stimulation applied to the spinal cord and the quantifiable results generated by activation of the at least one spinal circuit. A new set of parameters may be selected based on the model. By way of a non-limiting example, the machine learning method may implement a Gaussian Process Optimization, e.g., as described in PCT Publication No: WO/2012/094346 (PCT/US2012/020112).

In various embodiments, the methods described herein may further incorporate physical training. In certain embodiments, the physical training may include inducing a resistance-providing positional change in the region of the subject where locomotor activity is to be facilitated (e.g., the hand and/or finger(s)). The positional change in the subject may include, but need not be limited to grasping and/or tracking. In certain embodiments, the physical training may include robotically guided training.

Another exemplary embodiment is a method that includes placing an electrode on the subject's cervical spinal cord, positioning the patient in a training device configured to assist with physical training that is configured to induce neurological signals in the hand or paw, and applying electrical stimulation to a portion of the cervical spinal cord of the subject.

Transcutaneous Stimulation of a Region of the Cervical Spine.

The location of the electrode and its stimulation parameters are important in defining motor response. Use of surface electrode(s), as described herein, facilitates selection or alteration of particular stimulation sites as well as the application of a wide variety of stimulation parameters. Additionally surface stimulation can be used to optimize location for an implantable electrode or electrode array for epidural stimulation.

In various embodiments, the methods described herein involve transcutaneous electrical stimulation of the cervical spine or a region of the cervical spine of the subject. Illustrative regions include, but are not limited to one or more regions straddling or spanning a region selected from the group consisting of C1-C1, C1-C2, C1-C3, C1-C4, C1-C7, C1-C6, C1-C7, C1-T1, C2-C2, C2-C3, C2-C4, C2-C5, C2-C6, C2-C7, C2-T1, C3-C3, C3-C4, C3-C5, C3-C6, C3-C7, C3-T1, C4-C4, C4-C5, C4-C6, C4-C7, C4-T1, C5-C5, C5-C6, C5-C7, C5-T1, C6-C6, C6-C7, C6-T1, C7-C7, and C7-T1.

In certain embodiments, the stimulation is stimulation at a frequency ranging from about 3 Hz, or from about 5 Hz, or from about 10 Hz to about 100 Hz, or to about 80 Hz, or to about 40 Hz, or from about 3 Hz or from about 5 Hz to about 80 Hz, or from about 5 Hz to about 30 Hz, or to about 40 Hz, or to about 50 Hz.

In certain embodiments, the transcutaneous stimulation is applied at an intensity ranging from about 10 mA to about 150 mA, or from about 20 mA to about 50 mA or to about 100 mA, or from about 20 mA or from about 30 mA, or from about 40 mA to about 50 mA, or to about 60 mA, or to about 70 mA or to about 80 mA.

In certain embodiments, the transcutaneous stimulation is at a frequency and amplitude sufficient to improve hand strength and/or fine hand control when applied in conjunction with a neuromodulatory agent (e.g., a monoaminergic agent). In certain embodiments the transcutaneous stimulation is at a frequency and amplitude sufficient to improve hand strength and/or fine hand control when applied in conjunction with an epidural stimulation of the cervical spinal cord or a region thereof. In certain embodiments the transcutaneous stimulation is at a frequency and amplitude sufficient to improve hand strength and/or fine hand control when applied in conjunction with a neuromodulatory agent (e.g., a monoaminergic agent) and epidural stimulation of the cervical spinal cord or a region thereof. In certain embodiments the transcutaneous stimulation is at a frequency and amplitude sufficient to improve hand strength and/or fine hand control when utilized without epidural stimulation and/or without a neuromodulatory agent.

Epidural Stimulation of a Region of the Cervical Spine

In various embodiments, the methods described herein involve epidural electrical stimulation of the cervical spine or a region of the cervical spine of the subject. Illustrative regions include, but are not limited to, one or more regions straddling or spanning a region selected from the group consisting of C1-C1, C1-C2, C1-C3, C1-C4, C1-C7, C1-C₆, C1-C7, C1-T1, C2-C2, C2-C3, C2-C4, C2-C5, C2-C6, C2-C7, C2-T1, C3-C3, C3-C4, C3-C5, C3-C6, C3-C7, C3-T1, C4-C4, C4-C5, C4-C6, C4-C7, C4-T1, C5-C5, C5-C6, C5-C7, C5-T1, C6-C6, C6-C7, C6-T1, C7-C7, and C7-T1.

In certain embodiments, the epidural stimulation is at a frequency ranging from about 3 Hz, or from about 5 Hz, or from about 10 Hz to about 100 Hz, or to about 80 Hz, or to about 40 Hz, or from about 3 Hz or from about 5 Hz to about 80 Hz, or from about 5 Hz to about 30 Hz, or to about 40 Hz, or to about 50 Hz.

In certain embodiments, the epidural stimulation is at an amplitude ranging from 0.05 mA to about 30 mA, or from about 0.1 mA to about 20 mA, or from about 0.1 mA to about 15 mA or to about 10 mA.

In certain embodiments, the pulse width ranges from about 150 μs to about 600 μs, or from about 200 μs to about 500 μs, or from about 200 μs to about 450 μs.

In certain embodiments, the epidural stimulation is at a frequency and amplitude sufficient to improve hand strength and/or fine hand control. In certain embodiments the epidural stimulation is applied paraspinally over a cervical region identified above (e.g., over vertebrae spanning C2 to T1, over vertebrae spanning C5 to T1, etc.).

In certain embodiments, the epidural stimulation is applied via a permanently implanted electrode array (e.g., a typical density electrode array, a high density electrode array, etc.).

In certain embodiments, the epidural electrical stimulation is administered via a high density epidural stimulating array (e.g., as described in PCT Publication No: WO/2012/094346 (PCT/US2012/020112). In certain embodiments, the high density electrode arrays are prepared using microfabrication technology to place numerous electrodes in an array configuration on a flexible substrate. In some embodiments, epidural array fabrication methods for retinal stimulating arrays can be used in the methods described herein (see, e.g., Maynard (2001)Annu. Rev. Biomed. Eng., 3: 145-168; Weiland and Humayun (2005) IEEE Eng. Med. Biol. Mag., 24(5): 14-21, and U.S. Patent Publications 2006/0003090 and 2007/0142878). In various embodiments, the stimulating arrays comprise one or more biocompatible metals (e.g., gold, platinum, chromium, titanium, iridium, tungsten, and/or oxides and/or alloys thereof) disposed on a flexible material. Flexible materials can be selected from parylene A, parylene C, parylene AM, parylene F, parylene N, parylene D, other flexible substrate materials, or combinations thereof. Parylene has the lowest water permeability of available microfabrication polymers, is deposited in a uniquely conformal and uniform manner, has previously been classified by the FDA as a United States Pharmacopeia (USP) Class VI biocompatible material (enabling its use in chronic implants) (Wolgemuth, Medical Device and Diagnostic Industry, 22(8): 42-49 (2000)), and has flexibility characteristics (Young's modulus ˜4 GPa (Rodger and Tai (2005) IEEE Eng. Med. Biology, 24(5): 52-57)), lying in between those of PDMS (often considered too flexible) and most polyimides (often considered too stiff). Finally, the tear resistance and elongation at break of parylene are both large, minimizing damage to electrode arrays under surgical manipulation. The preparation and parylene microelectrode arrays suitable for use in the epidural stimulation methods described herein is described in PCT Publication No: WO/2012/100260 (PCT/US2012/022257).

The electrode array may be implanted using any of a number of methods (e.g., a laminectomy procedure) well known to those of skill in the art.

In various embodiments, the arrays are operably linked to control circuitry that permits selection of electrode(s) to activate/stimulate and/or that controls frequency, and/or pulse width, and/or amplitude of stimulation. In various embodiments, the electrode selection, frequency, amplitude, and pulse width are independently selectable, e.g., at different times, different electrodes can be selected. At any time, different electrodes can provide different stimulation frequencies and/or amplitudes. In various embodiments, different electrodes or all electrodes can be operated in a monopolar mode and/or a bipolar mode, using constant current or constant voltage delivery of the stimulation.

In certain embodiments, the electrodes can also be provided with implantable control circuitry and/or an implantable power source. In various embodiments, the implantable control circuitry can be programmed/reprogrammed by use of an external device (e.g., using a handheld device that communicates with the control circuitry through the skin). The programming can be repeated as often as necessary.

Any present or future developed stimulation system capable of providing an electrical signal to one or more regions of the cervical spinal cord may be used in accordance with the teachings provided herein. In various embodiments, the system may comprise an external pulse generator. In other embodiments the system may comprise an implantable pulse generator to produce a number of stimulation pulses that are sent to the a region in proximity to the cervical spinal cord by insulated leads coupled to the spinal cord by one or more electrodes and/or an electrode array. In certain embodiments the one or more electrodes or one or more electrodes comprising the electrode array may be attached to separate conductors included within a single lead. Any known or future developed lead useful for applying an electrical stimulation signal in proximity to a subject's spinal cord may be used. For example, the leads may be conventional percutaneous leads, such as PISCES® model 3487A sold by Medtronic, Inc. In some embodiments, it may be desirable to employ a paddle-type lead.

Any known or future developed external or implantable pulse generator may be used in accordance with the teachings provided herein. For example, one internal pulse generator may be an ITREL® II or Synergy pulse generator available from Medtronic, Inc, Advanced Neuromodulation Systems, Inc.'s GENESIS™ pulse generator, or Advanced Bionics Corporation's PRECISION™ pulse generator. One of skill in the art will recognize that the above-mentioned pulse generators may be advantageously modified to deliver therapy in accordance with the teachings provided herein.

In certain embodiments systems can employ a programmer coupled via a conductor to a radio frequency antenna. This system permits attending medical personnel to select the various pulse output options after implant using radio frequency communications. While, in certain embodiments, the system employs fully implanted elements, systems employing partially implanted elements may also be used in accordance with the teachings provided herein.

In one illustrative, but non-limiting system, a control module is operably coupled to a signal generation module and instructs the signal generation module regarding the signal to be generated. For example, at any given time or period of time, the control module may instruct the signal generation module to generate an electrical signal having a specified pulse width, frequency, intensity (current or voltage), etc. The control module may be preprogrammed prior to implantation or receive instructions from a programmer (or another source) through any known or future developed mechanism, such as telemetry. The control module may include or be operably coupled to memory to store instructions for controlling the signal generation module and may contain a processor for controlling which instructions to send to signal generation module and the timing of the instructions to be sent to signal generation module. In various embodiments, leads are operably coupled to signal generation module such that a stimulation pulse generated by signal generation module may be delivered via electrodes.

While in certain embodiments, two leads are utilized, it will be understood that any number of one or more leads may be employed. In addition, it will be understood that any number of one or more electrodes per lead may be employed. Stimulation pulses are applied to electrodes (which typically are cathodes) with respect to a return electrode (which typically is an anode) to induce a desired area of excitation of electrically excitable tissue in a region of the cervical spine. A return electrode such as a ground or other reference electrode can be located on same lead as a stimulation electrode. However, it will be understood that a return electrode may be located at nearly any location, whether in proximity to the stimulation electrode or at a more remote part of the body, such as at a metallic case of a pulse generator. It will be further understood that any number of one or more return electrodes may be employed. For example, there can be a respective return electrode for each cathode such that a distinct cathode/anode pair is formed for each cathode.

The epidural electrode stimulation systems described herein are intended to be illustrative and non-limiting. Using the teachings provided herein, alternative epidural stimulation systems and methods will be available to one of skill in the art.

Use of Neuromodulatory Agents.

In certain embodiments, the transcutaneous and/or epidural stimulation methods described herein are used in conjunction with various pharmacological agents, particularly pharmacological agents that have neuromodulatory activity (e.g., are monoamergic). In certain embodiments, the use of various serotonergic, and/or dopaminergic, and/or noradrenergic, and/or GABAergic, and/or glycinergic drugs is contemplated. These agents can be used in conjunction with epidural stimulation and/or transcutaneous stimulation and/or physical therapy as described above. This combined approach can help to put the spinal cord (e.g., the cervical spinal cord) in an optimal physiological state for controlling a range of hand movements.

In certain embodiments, the drugs are administered systemically, while in other embodiments, the drugs are administered locally, e.g., to particular regions of the spinal cord. Drugs that modulate the excitability of the spinal neuromotor networks include, but are not limited to combinations of noradrenergic, serotonergic, GABAergic, and glycinergic receptor agonists and antagonists.

Dosages of at least one drug or agent can be between about 0.001 mg/kg and about 10 mg/kg, between about 0.01 mg/kg and about 10 mg/kg, between about 0.01 mg/kg and about 1 mg/kg, between about 0.1 mg/kg and about 10 mg/kg, between about 5 mg/kg and about 10 mg/kg, between about 0.01 mg/kg and about 5 mg/kg, between about 0.001 mg/kg and about 5 mg/kg, or between about 0.05 mg/kg and about 10 mg/kg.

Drugs or agents can be delivery by injection (e.g., subcutaneously, intravenously, intramuscularly), orally, rectally, or inhaled.

Illustrative pharmacological agents include, but are not limited to, agonists and antagonists to one or more combinations of serotonergic: 5-HT1A, 5-HT2A, 5-HT3, and 5HT7 receptors; to noradrenergic alpha 1 and 2 receptors; and to dopaminergic D1 and D2 receptors (see, e.g., Table 1).

TABLE 1
Illustrative pharmacological agents.
				Typical	Typical
				Dose	Range
Name	Target	Action	Route	(mg/Kg)	(mg/kg)
Serotonergic receptor systems
8-OHDPAT	5-HT1A7	Agonist	S.C.	0.05	0.045-0.3
Way 100.635	5-HT1A	Antagonist	I.P.	0.5	0.4-1.5
Quipazine	5-HT2A/C	Agonist	I.P.	0.2	0.18-0.6
Ketanserin	5-HT2A/C	Antagonist	I.P.	3	1.5-6.0
SR 57227A	5-HT3	Agonist	I.P.	1.5	1.3-1.7
Ondanesetron	5-HT3	Antagonist	I.P.	3	1.4-7.0
SB269970	5-HT7	Antagonist	I.P.	7	2.0-10.0
Noradrenergic receptor systems
Methoxamine	Alpha1	Agonist	I.P.	2.5	1.5-4.5
Prazosin	Alpha1	Antagonist	I.P.	3	1.8-3.0
Clonidine	Alpha2	Agonist	I.P.	0.5	0.2-1.5
Yohimbine	Alpha2	Antagonist	I.P.	0.4	0.3-0.6
Dopaminergic receptor systems
SKF-81297	D1-like	Agonist	I.P.	0.2	0.15-0.6
SCH-23390	D1-like	Antagonist	I.P.	0.15	0.1-0.75
Quinipirole	D2-like	Agonist	I.P.	0.3	0.15-0.3
Eticlopride	D2-like	Antagonist	I.P.	1.8	0.9-1.8

The foregoing methods are intended to be illustrative and non-limiting. Using the teachings provided herein, other methods involving transcutaneous electrical stimulation and/or epidural electrical stimulation and/or the use of neuromodulatory agents to improve motor control and/or strength of a hand or paw will be available to one of skill in the art.

EXAMPLES

The following examples are offered to illustrate, but not to limit the claimed invention.

Example 1

Engaging the Cervical Spinal Cord Circuitry to Re-Enable Volitional Control of Hand Function in Tetraplegic Patients

The present Example demonstrates whether herein described neuromodulatory strategies can be used to improve fine motor control of the upper limbs, i.e., performance of motor tasks considered to be less “automatic” than posture and locomotion. Here we show that the injured human cervical spinal cord can be modulated using painless cutaneous electrical stimulation (pcEmc), monoaminergic agonist (fEmc) treatment, and/or eEmc to regain voluntary hand function. Mean hand strength increased greater than 300% after pcEmc plus fEmc (buspirone) treatment in 6 subjects with a chronic motor complete cervical injury. One subject that was implanted with a cervical epidural electrode array realized significantly improved hand strength and fine hand control in the presence of cervical eEmc. Thus, we now demonstrate that the cervical circuitry can be neuromodulated to improve volitional control of hand function in tetraplegic subjects with three novel interventions. The impact of these observations on individuals with upper limb paralysis could be dramatic functionally, psychologically, and economically.

Six subjects with chronic (18-36 months) spinal cord injury (SCI, traumatic cervical injury, ASIA B with no motor strength below the injury) were tested to determine if hand function can be improved by neuromodulating the cervical spinal cord. All subjects initially had minimal hand strength, a condition reflecting the majority of cervical SCI patients. Our experimental approach began with 6 weeks of baseline testing (Phase 1), followed by three 2-week treatment periods (Phases 2-4), and then by a period of approximately three months without any treatment at the end of which there was a final 2-week testing period (Phase 5). pcEmc at the C5 spinal segment (Phase 2) increased hand strength in 4/6 subjects compared to baseline Phase 1 (FIG. 1, panels A-G). During buspirone treatment (Phase 3), 4/6 subjects increased hand strength compared to Phase 1 and 2. The next 2 weeks buspirone was withdrawn but pcEmc continued (Phase 4), and again 4/6 subjects showed further improvement in grip strength compared to Phase 3. For all subjects combined, the mean grip strength tended to increase after each successive treatment phase (FIG. 1, panel G). EMG amplitudes were generally consistent with increases in grip force, i.e., digit flexor and extensor EMG amplitudes tended to increase progressively across phases (FIG. 1, panel H). After approximately three months without treatment, 4/6 subjects improved their performance relative to Phase 4.

These results show that the cervical spinal cord can be neuromodulated using two paradigms, i.e., electrically and pharmacologically. In some embodiments, the present methods are highly interactive and perhaps synergistic. Synergy and interactivity were observed in animal experiments. These data suggest that non-functional networks can become engaged and progressively improve motor performance. In some embodiments, further improvement in hand function after withdrawing pcEMC and fEMC can be a result of functional connections remaining active once they are established.

The improvements are unlikely to be due to natural recovery or from repeated practice as large cohort studies of SCI patients have demonstrated that the majority of functional improvements occur within 6 months of the injury and that minimal recovery of function is observed past the 12 month time-point. All of our subjects were 18 months beyond the initial injury when recruited. Furthermore, baseline motor function testing for 6 weeks prior to any therapeutic intervention revealed stable function (FIG. 6). Concomitant to significantly improved hand strength, gains in upper extremity functional metrics by ARAT (13 point improvement) and ASIA (7 point improvement) tests, reflecting the impact of these interventions on the patient's overall upper extremity motor function (FIG. 1, panel I).

Given the results above, we then asked whether the cervical spinal circuitry could be neuromodulated to improve hand function by stimulating via an epidural array implant (implanted in subject shown in FIG. 1, panel E). The implanted stimulating electrodes spanned the caudal portion of C5 to the rostral portion of T1 (FIG. 2, panel A, arrow; FIG. 2, panel B, electrode diagram). After mapping of the cervical motor pools by spinal cord evoked potentials (FIG. 7) we mainly used electrodes 13 and 14 to modulate hand function (FIG. 2, panel B, shaded boxes).

In the initial acute phase after implantation of a temporary trial array, the subject's ability to accurately follow a targeted force presented with a cursor moving in a sine wave pattern on a video screen was improved with eEmc (FIG. 2, panel C). The subject also could generate a more rapid oscillating force above and below a pre-selected target force in the presence of stimulation (FIG. 2, panel D). Additionally handgrip force was increased with stimulation at 5 and 30 Hz (FIG. 2, panel E). Importantly, some of these improvements were observed after stimulation.

After implantation of the permanent electrode array, we next performed a series of motor tests over the next 9 months comparing the effects of different stimulation parameters in facilitating maximum force and fine control. Maximal forces were generated at 10-20 Hz (FIG. 2, panel F) and 0.7-1.3 mA (FIG. 2, panel G). These forces were lower than the force generated in normal subjects (approximately 400 N), but substantially more than baseline. Evidence of the importance of selecting the optimal frequency and intensity of stimulation was reflected in the time that it took to respond to a signal to begin generating a force (FIG. 2, panel H). However, there were extremely long delays (sec) relative to uninjured subjects (approximately 200 ms) in voluntarily initiating a force regardless of the stimulation parameters. We compared the performance of these motor tasks to a commonly used clinical assessment tool and found a 6-point increase in ARAT with eEmc on vs. off during the same testing session, demonstrating the clinical relevance (FIG. 2, panel L).

Accuracy in controlling force was performed approximately weekly over a period of eight months to identify the optimal stimulation parameters. Rapid oscillatory movements were performed at 20 Hz and 0.5 mA and at 10 and 30 Hz and 0.7 mA (FIG. 2, panel I). Accuracy in following a targeted force occurred at 20 Hz (FIG. 2, panel J). In addition, the accuracy of controlling force in a sine wave pattern almost doubled over a two-month period (FIG. 2, panel K).

The present methods and systems provide that: 1) optimal stimulation parameters generating the highest forces differed from those generating the greatest accuracy at sub-maximal forces; 2) effects of stimulation intensity and frequency on maximum force production and accuracy are highly interdependent; 3) accuracy of force generation can be improved over time in the presence of eEmc; and 4) time needed to initiate a force following a command was prolonged, but could be improved with specific stimulation parameters. Each of these observations demonstrates the importance of matching the stimulation parameters with the task to be performed. In some embodiments, eEmc can yield improvement (e.g., meaningful) in upper extremity function in subjects with a cervical SCI.

Accuracy in controlling force was performed approximately weekly over a period of eight months to identify the optimal stimulation parameters. Rapid oscillatory movements were performed at 20 Hz and 0.5 mA and at 10 and 30 Hz and 0.7 mA (FIG. 2, panel I). Accuracy in following a targeted force occurred at 20 Hz (FIG. 2, panel J). In addition, the accuracy of controlling force in a sine wave pattern almost doubled over a two-month period (FIG. 2, panel K).

The present methods and systems provide that: 1) optimal stimulation parameters generating the highest forces differed from those generating the greatest accuracy at sub-maximal forces; 2) effects of stimulation intensity and frequency on maximum force production and accuracy are highly interdependent; 3) accuracy of force generation can be improved over time in the presence of eEmc; and 4) time needed to initiate a force following a command was prolonged, but could be improved with specific stimulation parameters. Each of these observations demonstrates the importance of matching the stimulation parameters with the task to be performed. In some embodiments, eEmc can yield improvement (e.g., meaningful) in upper extremity function in subjects with a cervical SCI.

A dysfunctional interaction may exist between supraspinal and sensory networks given the externally imposed neuromodulation of the spinal circuitry and since neither the descending motor control nor the spinal circuitry had functioned in any significant interactive way since the injury. This interaction was explored between supraspinally derived descending volitional drive and sensory-derived input to the spinal networks and motor pools when the spinal circuitry was being neuromodulated with eEmc. Could supraspinal networks volitionally accommodate the ‘level of effort’ to the level of motor pool excitability imposed by eEmc? To address this question we asked the subject to generate a series of seven contractions at different levels of maximum efforts with and without stimulation (FIG. 4). Without stimulation, the force level was maintained for all seven contractions at the lowest percentage effort, but force declined during the later contractions at the higher percentage efforts (FIG. 4, panel A). Over a wide range of stimulation intensities at the lowest percent effort, there were no marked differences in the subject's ability to estimate a target force (FIG. 4, panel C). At higher percent efforts fatigue was evident at moderate stimulation intensities, but this was overcome at the higher levels of stimulation, suggesting a neural deficit (FIG. 4, panels A and C). We repeated the experiments shown in FIG. 4, panels A and C (which occurred within 15 min period) on another day to avoid possible neuromuscular fatigue (FIG. 4, panel E). At the lower percent effort without stimulation, there was greater recruitment during the later contractions that enabled a constant force, whereas at the higher percent efforts the subject was unable to compensate with greater recruitment (FIG. 4, panel B). With stimulation, however, even at the higher efforts the targeted force could be reached as the result of greater motor pool excitation (FIG. 4, panel D). A similar but less dramatic change in excitation of the motor pools was present even when the targeted forces were reached at the different percent efforts (FIG. 4, panels D, F-H). In spite of the wide range in levels of neuromodulation there was remarkable consistency in volitionally generated forces. These results suggest that the subjects consciously perceived rather accurately the combined physiological state of supraspinal, spinal, and sensory networks to achieve the targeted levels of force simply defined conceptually as a “percent maximum effort” even in the presence of fatigue.

PcEmc, fEmc, and eEmc interventions can enhance the level of excitability of pre-motor spinal circuitries that mediate hand function. The importance of these data is that they identify three novel interventional strategies having significant potential for high clinical impact in a relatively short timeframe on a function considered to be of highest priority among paralyzed patients. The impact of these results is significant from the following perspectives: 1) neuromodulation is not dependent on the physiological phenomenon of central pattern generation but also applies to fine neuromotor control of less “automatic” movements; 2) they raise the possibility that the neuromodulatory concept could apply to other neural networks and therefore could be applied to neuromotor disorders such as stroke and Parkinson disease; and 3) they demonstrate the potential of enhancing maximum neuromuscular force, as well as fine control of movements. The improved force potential was associated with improved performance in upper extremity tasks (ARAT). Importantly, even after more than a year of inactivity of the sensorimotor circuits, significant levels of activity-dependent plasticity persist.

Methods Summary

The University of California, Los Angeles Institutional Review Board approved all procedures. Subjects were enrolled based on the enrollment criteria of traumatic cervical injury, ASIA B, greater than 1 year from injury, and stable motor function as documented by sequential clinical exams. Baseline clinical scores (ARAT, ASIA) prior to study intervention were assessed (FIG. 1, panel I).

Voluntary motor control data were assessed using a handgrip force measurement device. EMG data were collected via surface electrodes placed unilaterally on upper extremity muscles. Stimulation and data collection was obtained using the Konigsberg EMG system (Konigsberg, Pasadena, California). Functional assessments by validated assessment tools were performed weekly during each study phase: American Spinal Injury Assessment (ASIA), and Action Research Arm Test (ARAT) (Carroll (1965) J, Chronic Dis., 18: 479-491). Two blinded examiners conducted the functional tests.

The transcutaneous stimulation device is non-invasive. Stimulation parameters ranged from 5-30 Hz and 20-100 mA, located at C5. From the midpoint of Phase 1 to the end of Phase 4 all subjects were informed that they would receive either a placebo or the monoaminergic agonist (7.5 mg buspirone twice daily for 2 weeks beginning the day before biweekly testing). All subjects received buspirone during Phase 3 and a placebo during Phases 1, 2, and 4. All subjects and testers were blinded.

A temporary trial with two 16-contact percutaneous epidural leads (Linear Lead, Boston Scientific, Valencia, CA) spanning C2 to T1 was conducted prior to permanent implantation in one subject. Indication for implantation was for treatment of pain. Stimulation intensity ranged between 0.1-10.0 mA, frequencies ranged between 5-60 Hz, and pulse width was at 210 or 450 ps. After 7 days, one Boston Scientific Artisan (Valencia, CA) 16-electrode epidural array and one Boston Scientific Precision Plus Spinal Cord Stimulator (Valencia, CA) were implanted encompassing C5 to T1. The effects of various combinations of stimulation parameters were assessed to obtain the best response for hand function. Stimulation intensity ranged between 0.13.0 mA, frequencies ranged between 5-60 Hz, and pulse width was at 210 or 450 ps.

Outcomes were averaged across all observations in a given phase/period for each subject. Group mean changes across subjects in grip strength, EMG amplitude, ARAT score and ASIA score from baseline over the 5 phases were compared using a non-parametric repeated measure analysis of variance model using re-sampling. A two sided p value of p<0.05 was considered significant. Means±standard error of the mean (SEM) are reported.

Methods.

Subject Profiles

The University of California, Los Angeles Institutional Review Board approved all procedures. Subjects were enrolled based on the enrollment criteria of traumatic cervical injury, ASIA B, greater than 1 year from injury, and stable motor function as documented by sequential clinical exams. The clinical profiles of the subjects upon enrollment into this study are as follows: Subject A was a 20 year old male who suffered a C6 SCI after a motor vehicle accident and was 36 months from initial injury; Subject B was a 18 year old male who suffered a C5 SCI after a diving accident and was 18 months from initial injury; Subject C was a 21 year old female who suffered a C2 SCI after a motor vehicle accident and was 45 months from initial injury; Subject D was a 20 year old male who suffered a C5 SCI sustained during football game and was 30 months from initial injury; Subject E was a 18 year old male who suffered a C5 SCI after a diving accident and was 24 months from initial injury; and Subject F was an 18 year old female with C6 SCI sustained after a fall from height and was 18 months from initial injury. Magnetic resonance imaging was obtained in all subjects to confirm location and description of injury (FIG. 5). Baseline clinical scores (ARAT, ASIA) were assessed prior to and throughout the study (FIG. 1, panel I).

Hand Testing

Voluntary motor control data were assessed using a handgrip force measurement device. Motor assessment was conducted on the arm that was most functional post-injury regardless of the pre-injury dominant side. Briefly, the device measures displacement against springs with a range in spring constants. Measurement of maximal voluntary contraction was conducted by asking the subject to contract his/her hand against the springs to maximally displace the handgrip. The contraction lasted for approximately 3-5 sec and was repeated twice. For hand oscillation/repeated contractions, the subject was asked to contract and release the hand as fast as possible above and below two lines on a computer screen that was preset at 12.5 and 37.5% of maximum voluntary contraction. The number of completed contraction-release sequences across the lines was determined. For hand control, the subject was asked to trace a sinusoidal wave (0.15 Hz) that appeared on the computer screen by squeezing the handgrip. The percentage of data points that fell inside a circular window at a sampling of 15 Hz was determined. The EMG data were collected via surface electrodes placed unilaterally on the biceps brachii (biceps), triceps brachii (triceps), brachioradialis (Brac), extensor digitorum (ED), flexor digitorum (FD), thenar, and hypothenar (H. Thenar) muscles. Stimulation and data collection was obtained using the Konigsberg EMG system (Konigsberg, Pasadena, California). Functional assessments by validated assessment tools were performed weekly during each phase of study: American Spinal Injury Assessment (ASIA), and Action Research Arm Test (ARAT) (Carroll (1965) J, Chronic Dis., 18: 479-491).

ARAT was selected due its focus on arm motor ability and because it has been validated and applied in the SCI setting. Scoring was conducted by two experienced examiners who were not informed of the treatment phase (blinded). If discrepancy existed between the scores, the exam was repeated and a consensus reached.

Prior to initiation of the study, the stability of hand function and training effect of utilizing the handgrip was assessed over the course of 6 weeks during which the subjects were tested and trained with the handgrip twice/week. In all subjects assessed, there was no improvement in hand function during this baseline testing (FIG. 6). Testing and training during this assessment period involved asking the subject to maximally contract the hand using the handgrip device. A total of 9-36 maximum hand contractions were performed during each session over a period of one to two hours.

pcEMC and fEMC

The transcutaneous stimulation device is non-invasive. A surface stimulation cathode electrode was attached on the dorsal aspect of the neck (C5 area) and the grounding electrode was placed on the anterior superior iliac spine. Stimulation parameters ranged from 5-30 Hz and 20-100 mA. Varying combinations of these stimulation parameters were systematically assessed to obtain optimum facilitation of voluntary hand contraction by identification of the relative activation levels of the motor pools studied (data not shown). During each of the three treatment periods (Phases 2-4) a series of nine 3.5-sec maximum hand grip strength tests were performed per treatment session. In each session of Phase 2, three contractions were performed without pcEmc, followed by three in the presence of pcEmc (twice weekly at 30 Hz and 20-40 mA), followed by three without pcEmc. The same pcEmc protocol was followed during Phases 2-4. The duration of pcEmc during each testing session was approximately 15-30 min. The total number of maximum hand contractions was 9-36 and each session lasted 1 to 2 hours. During pcEMC, the subjects reported a non-painful, tingling sensation down the arms at the higher stimulation intensities at the site of stimulation with some associated tonic paraspinal muscle contractions at the neck.

From the midpoint of the Phase 1 to the end of Phase 4 all subjects were informed that they would receive either a placebo or the monoaminergic agonist buspirone. All subjects and testers were blinded as to which treatment was administered and were given buspirone (7.5 mg buspirone twice daily for 2 weeks beginning the day before biweekly testing) during Phase 3 and a placebo during Phases 1, 2, and 4.

eEMC

Planning for surgical placement of spinal cord epidural stimulator (eEmc) on subject E was initiated prior to study enrollment. The criteria for selection was based on Federal Drug Administration approved use for the treatment of pain and Dr. Lu and two other physicians confirmed the indication for implantation. A temporary trial with two 16-contact percutaneous epidural leads (Linear Lead, Boston Scientific, Valencia, CA) spanning C2 to T1 was conducted prior to permanent implantation. After implantation, testing was conducted over a 2-hour session to assess the efficacy for improving hand function. Stimulation amplitude ranged between 0.110.0 mA, frequencies ranged between 5-60 Hz, and pulse width was at 210 or 450 ps. Total time of stimulation was 30 min.

After 7 days of confirmed efficacy in the treatment of pain, one Boston Scientific Artisan (Valencia, CA) 16-electrode epidural array and one Boston Scientific Precision Plus Spinal Cord Stimulator (Valencia, CA) were implanted encompassing C5 to T1. The effects of various combinations of stimulation parameters were assessed to obtain the best response for hand function. A combined total of 60 testing sessions were conducted on Subject E over the course of 20 months (epidural implant occurred between testing session 21 and 22). Each testing session lasted up to 180 min. During each testing session, stimulation duration lasted between 30-120 min. Stimulation amplitude ranged between 0.1-3.0 mA, frequencies ranged between 5-60 Hz, and pulse width was at 210 or 450 ps. During low intensity eEMC, the subject reported a tingling sensation at the neck that migrated toward the arms and hands. At the optimal stimulation parameters, the subject reported the perception of increased hand strength and control similar to pre-injury ability.

Statistical Analysis

Outcome measures (grip strength force, EMG amplitude, ARAT score, ASIA score) were averaged across all observations in a given Phase for each subject. Using these values, group mean changes across subjects for each outcome measure from baseline over the 5 phases were compared using a non-parametric repeated measure analysis of variance model using re-sampling (bootstrap). The repeated measure mixed model takes into account the correlation across time on the same subjects. A two-sided p value of p<0.05 was considered significant. Standard error of the mean (SEM) are reported. Individual mean profiles and the corresponding within person SEM also are reported.

It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims. All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety for all purposes.

Claims

1. An electrical stimulation system, comprising: a pulse generator configured to neuromodulate the cervical spinal cord of a patient by providing an electrical signal to at least one surface stimulation electrode attached to a dorsal aspect of the neck of the patient; andwherein at least one of an amplitude and a frequency of the electrical signal are selected to improve, when the electrical signal is provided to the at least one surface stimulation electrode, at least one of voluntary motor control or grip strength of a hand of the patient.

2. The electrical stimulation system of claim 1, wherein: the at least one of the amplitude and the frequency of the electrical signal, when the electrical signal is provided to the at least one surface stimulation electrode, does not evoke a painful sensation.

3. The electrical stimulation system of claim 1, wherein: the pulse generator is electrically connected to: a cathode electrode attached to the dorsal aspect of the neck, the at least one surface stimulation electrode comprising the cathode electrode; and a grounding electrode attached to the patient remote from the cathode electrode.

4. The electrical stimulation system of claim 1, wherein: the at least one of the amplitude and the frequency of the electrical signal are further configured to reduce a time needed to initiate a force following a patient command.

5. The electrical stimulation system of claim 1, wherein: the at least one of the amplitude and the frequency of the electrical signal are further configured to increase activation levels of motor pools of the hand of the patient.

6. The electrical stimulation system of claim 5, wherein: the increase in activation levels of motor pools of the hand of the patient comprises an increase in surface EMG amplitudes of at least one intrinsic or extrinsic muscle of the hand.

7. The electrical stimulation system of claim 5, wherein: the amplitude of the electrical signal is between 20 mA and 100 mA; andthe frequency of the electrical signal is between 5 Hz and 30 Hz.

8. An electrical stimulation system, comprising: a pulse generator configured to neuromodulate the cervical spinal cord of a patient by providing an electrical signal to at least one implanted stimulation electrode positioned to provide stimulation to at least a portion of the cervical spinal cord of the patient; andwherein at least one of an amplitude and a frequency of the electrical signal are selected to improve, when the electrical signal is provided to the at least one implanted stimulation electrode, at least one of voluntary motor control or grip strength of a hand of the patient.

9. The electrical stimulation system of claim 8, wherein: a implanted epidural electrode array comprises the at least one implanted stimulation electrode.

10. The electrical stimulation system of claim 8, wherein: the at least one implanted stimulation electrode comprises at least one cathode and at least one anode selected based on activation of hand muscles.

11. The electrical stimulation system of claim 8, wherein: the at least one of the amplitude and the frequency of the electrical signal are further configured to reduce response time.

12. The electrical stimulation system of claim 8, wherein: the at least one of the amplitude and the frequency of the electrical signal are further configured to increase activation levels of motor pools of the hand of the patient.

13. The electrical stimulation system of claim 8, wherein: the amplitude of the electrical signal is between 0.1 mA and 10 mA; andthe frequency of the electrical signal is between 5 Hz and 60 Hz.

14. A neuromodulation method, comprising: providing an electrical signal to at least one electrode, the at least one electrode positioned to provide cervical stimulation to a patient;measuring at least one of a maximum of a grip force of a hand of the patient, accuracy in controlling the grip force of the hand of the patient, or response time in changing the grip force of the hand of the patient; andconfiguring a stimulator to provide an updated electrical signal to the at least one electrode, the updated electrical signal based on the measured at least one of the maximum of the grip force, the accuracy in controlling the grip force, or the response time in changing the grip force.

15. The neuromodulation method of claim 14, wherein: an implanted extradural array comprises the at least one electrode.

16. The neuromodulation method of claim 14, wherein: the at least one electrode comprises at least one cathodic electrode and at least one anodic electrode; andthe neuromodulation method further comprises selecting at the at least one cathodic electrode and the at least one anodic electrode based on spinal cord evoked potentials induced by the at least one cathodic electrode and the at least one anodic electrode.

17. The electrical stimulation system of claim 14, wherein: the updated electrical signal has an amplitude between 0.1 mA and 10 mA and a frequency between 5 Hz and 60 Hz.

18. The neuromodulation method of claim 14, wherein: the at least one electrode comprises a cathodic surface stimulation electrode.

19. The neuromodulation method of claim 14, wherein: the updated electrical signal has an amplitude between 20 mA and 100 mA and a frequency between 5 Hz and 30 Hz.

20. The neuromodulation method of claim 14, wherein: the updated electrical signal does not evoke a painful sensation.