Patent Application
20080255582
Electrodes can be used to electrically monitor and/or stimulate a patient by positioning them on or within the patient's head. The electrodes may be used to monitor brain signals such as EEG or MEG, and/or may be used to delivery neuromodulation therapy to portions of the brain. The electrodes may be positioned on or within the scalp, or above, within, or under the skull, including on or within portions of the brain.
Conventional methods of positioning electrodes in a patient's skull comprise creating a burr hole in the skull, positioning the electrodes above or underneath the dura mater, and advancing the electrode array, typically a strip electrode, until the physician believes that the electrodes are placed in an appropriate position. More invasive methods of implanting electrodes require a craniotomy, in which a portion of the patient's skull is removed, and the electrode array, typically grid electrodes, are placed above or underneath the dura mater.
A number of different methods have been described in the patent literature. For example, U.S. Patent Application Publication No. 2005/0070810 to Kennedy is related to detecting neural activity using conductive skull screws implanted in the skull of a patient. The locations of the skull screws are chosen so that a change in neural electrical potential between the first and second conductive skull screws occurs when a patient performs a neural task.
While not related to implanting electrodes, U.S. Patent Application Publication No. 2006/0291968 to Greenberg discloses a template that may be used in stereotaxic surgery.
The deficiency of these systems and with conventional methods of electrode placement in a patient's skull is that they do not address the need for accurately placing a plurality of electrodes that are in a preformed pattern or configuration in the patient's skull.
The present invention provides methods and systems for identifying relative positions of burr holes in the patient's skull. The positions of the burr holes identified by a template will typically correspond to the orientation of at least some of the individual electrode contacts from a selected electrode array. The selected electrode array may be selected from a bank of preformed templates or the selected electrode array may be custom made for the particular patient. Since most of the electrode arrays will typically have between 4 electrodes and 16 electrodes, it is desirable to have the burr holes be created in a position that corresponds to the electrode contacts of the electrode array so that the electrode contacts may be positioned in and/or through the burr holes created in the patient's skull.
One aspect of the invention is a template for creating a plurality of openings at locations in the skull of a patient, wherein the plurality of openings are configured to receive an electrode array. The template comprises a substrate configured to be coupled to an outer surface of the patient's skull. The template also includes a plurality of markers in a pattern on the substrate, wherein the markers are configured to identify locations for creating a plurality of openings in the skull, and the openings are configured to receive an electrode array comprising a plurality of electrodes that are positioned in a pattern that corresponds to the pattern of the plurality of markers.
The substrate can be configured to be removably or permanently coupled to the outer surface of the skull. In some embodiments the plurality of markers are configured to identify patient-specific locations. In some embodiments the plurality of markers includes a plurality of channels in the substrate, wherein the plurality of channels are adapted to receive a drill element, such as a drill bit. The plurality of markers may also comprise a plurality of visual markings on the substrate.
In some embodiments the locations for creating a plurality of openings are based on the location of the patient's seizure foci. The plurality of electrodes can be configured to monitor brain signals and/or deliver a neuromodulation therapy (e.g., electrical stimulation, drug delivery, etc.) to the patient's brain.
Another aspect of the invention is a system for implanting a plurality of electrodes at locations within a patient's skull. The system comprises a template comprising a substrate and a plurality of markers in a pattern, wherein the substrate is configured to be coupled to the outer surface of the skull, and wherein the markers are configured to identify locations at which to create a plurality of openings in the skull. The system also includes an electrode array comprising a plurality of electrodes that are in a pattern that corresponds to the pattern of the plurality of markers. The plurality of openings in the skull is configured to receive the plurality of electrodes.
The substrate can be configured to be removable or permanently coupled to the outer surface of the skull. In some embodiments the plurality of markers comprises a plurality of channels in the substrate, wherein the plurality of channels are configured to receive a drill element such as a drill bit. The plurality of markers may also comprise a plurality of visual markings on the substrate. In some embodiments the plurality of markers are configured to identify patient-specific locations. In some embodiments the locations are based on the location of seizure foci.
The system may also include a template lid shaped to mate with the template, wherein the electrode array is configured to be disposed between the template lid and the template when the template lid mates with the template.
The plurality of electrodes can be configured to monitor brain signals and/or to deliver a neuromodulation output to the patient's brain. The electrode array can include at least one lead and the template can include at least one lead channel adapted to mate with the at least one lead.
In some embodiments, the system may further include an implantable medical device configured to be implanted below the head of the patient. The electrode array may include at least one lead that is connected to the implanted medical device, or the electrodes may be wirelessly connected to the implanted device.
Another aspect of the invention is a method for implanting a plurality of electrodes at locations in a patient's skull. The method includes positioning a template comprising a plurality of markers on an exterior surface of the skull, the markers identifying a plurality of locations on the skull for creating a plurality of openings. The method also includes creating the plurality of holes in the skull at the plurality of locations, and positioning a plurality of electrodes in the plurality of holes.
In some embodiments the method also includes selecting a template from a plurality of templates based on the determination of the plurality of locations. In other embodiments, the template may be custom-made for the particular patient.
In some embodiments the markers comprise a plurality of channels in the template, and creating a plurality of openings comprises drilling into the skull through the plurality of channels. In other embodiments the markers comprises a plurality of channels and the method also includes creating a visual reference on the exterior surface of the skull at the identified locations after positioning the template on the exterior surface of the skull, and removing the template from the exterior surface of the skull before creating a plurality of openings.
Typically, the holes or openings are created above or over seizure foci. After the holes or openings are created in the skull, a plurality of electrodes may be positioned in the plurality of holes or opening. After the electrodes are positioned in the holes or openings, a lid may be placed on the template, thereby securing the electrode array. The method may also include connecting the plurality of electrodes to an implantable medical device.
For a further understanding of the nature and advantages of the present invention, reference should be made to the following description taken in conjunction with the accompanying drawings.
All publications and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.
The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings of which:
The present invention is related to methods and devices for creating openings in a patient's skull for implanting an array of electrodes. The pattern of the openings in the patient's skull is preferably predetermined using a template. The template will generally be designed for a specific electrode array, but may also be customized for an individual patient. The template may be coupled, either temporarily or permanently, to the skull and will provide, with markings, an indication as to where to create the openings in the skull. After the openings are created, the template may be left in place or removed, and the electrodes can then be positioned within the openings. One goal of the present invention is to accurately place a plurality of electrodes in a patient's skull such that the electrodes are positioned in predetermined locations.
As used herein, the term “skull” includes the bones within a patient's head, including the cranium, facial bones, jaw bones, and crossbones.
The markers 4 may have a generic pattern that has conventional or predetermined spacing between the markings (e.g., 3×3 grid, 2×4 grid as shown in
In preferred embodiments, the markers 4 identify locations for openings to be in created in the patient's skull for the placement of an electrode array. The electrode array, or arrays, is generally in a pattern that corresponds to the marker pattern.
The template 1 may further comprise one or more attachments 6 for removably or permanently coupling the template 1 to an outer surface of the patient's skull 8. The anchors 6 may comprise adhesive, screws, double sided tape, or other biocompatible means to couple the template 1 to the skull 8.
The template substrate 2 is generally flexible and substantially flat, but may be curved to correspond to the general curvature of the outer surface of the patient's skull 8, if desired. The template substrate 2 may also have different portions with varying degrees of curvature to suitably mate with the skull 8. If desired, a mold of a portion of the patient's skull may also be taken to better fit the template substrate 2 to the skull 8.
The template substrate 2 may be composed of any number of different materials. The materials should generally be biocompatible, MRI safe, and preferably does not interfere with CT scans or other imaging techniques. Some useful materials include stainless steel, titanium, polymers, or other substantially flexible materials.
The template substrate 2 may include markings or other indications that indicate to the physician which side is to be placed on the outer surface of the skull (e.g., text that says “this side up” or “this side down”). Furthermore, particularly for the patient-specific templates in which the electrode arrays may or may not be the same, the templates may include an indication or instruction for the physician as to which portion of the skull the template should be placed. For example, if the physician is placing two electrode arrays over each of the patient's temporal lobes, the electrode arrays for each of the temporal lobes may indicate whether the template 1 is for a mesial or lateral strip and/or indicate which lobe the template is for.
In some embodiments the template 1 may comprise means for receiving one or more leads 20 of the electrode array, such as, for example, pre-formed grooves or channels sized and shaped to receive the one or more leads from the electrode array. If desired, the leads may further be encapsulated by template lid 22 that can be shaped to mate with the template to further protect the electrodes and any leads that may be connected to the array.
The electrodes 16 that may be used with the template 1 may extend only through a portion of the skull, through one layer of the table, through at least a portion of two layers of the table, may extend into an epidural space, contact CSF, or may even extend through the dura mater (e.g., subdural), and/or into the patient's brain (e.g., deep brain electrodes). The electrode array may be used to monitor brain signals, such as, for example, EEG and MEG, deliver neuromodulation signals to the brain, or a combination thereof.
Some exemplary configurations of electrode arrays 24 are shown in
The electrodes that are implanted into the openings created using the template can also be wireless devices, similar to the Advanced Bionics BION device or the devices described in co-assigned U.S. Patent Application Ser. No. 60/805,710, filed on Jun. 23, 2006. Such wireless electrodes may be in wireless communication with a device implanted in the patient or external to the patient.
The system comprises one or more electrode arrays 24 that are implanted in openings created in the skull, and the arrays are configured to measure signals from the patient 34. In one embodiment, one or more of the electrode arrays 24 will be implanted adjacent a previously identified epileptic focus, a portion of the brain where such a focus is believed to be located, or adjacent a portion of a seizure network.
The electrodes are shown electrically joined via lead 20 to a communication unit 36, but could be in wireless communication with the communication unit or other external devices. In one embodiment, the lead 20 and the communication unit 36 will be implanted in the subject. For example, the communication unit 36 may be implanted in a sub-clavicular cavity of the subject. In alternative embodiments, the lead 20 and communication unit 36 may be implanted in other portions of the subject's body (e.g., in the head) or attached to the subject externally.
The communication unit 36 may be configured to facilitate the sampling of brain signals from the electrodes. Sampling of brain activity is typically carried out at a rate above about 200 Hz, and preferably between about 200 Hz and about 1000 Hz, and most preferably at or above about 400 Hz. The sampling rates could be higher or lower, depending on the specific features being monitored, the subject, and other factors. Each sample of the subject's brain activity is typically encoded using between about 8 bits per sample and about 32 bits per sample, and preferably about 16 bits per sample. In alternative embodiments, the communication unit 36 may be configured to measure the signals on a non-continuous basis. In such embodiments, signals may be measured periodically or aperiodically.
An external device 38 may be carried external to the body of the patient. The external device 38 can receive and stores signals, including measured brain signals and possibly other physiological signals, from the communication unit 36. Communication between the external device 38 and the communication unit 36 (or the wireless electrodes) may be carried out through wireless communication, such as a radiofrequency link, infrared link, optical link, ultrasonic link, or other conventional or proprietary wireless link. The wireless communication link between the external device 38 and the communication unit 36 may provide a one-way or two-way communication link for transmitting data.
The methods of the present invention are directed toward methods of implanting a plurality of electrodes at locations in a patient's skull. In a preferred embodiment, the method is directed toward implanting an electrode array substantially over a seizure foci or seizure network to monitor brain signals that are predictive or indicative of a patient's susceptibility of a seizure (e.g., seizure prediction or seizure detection) and/or to deliver stimulation to the patient's brain. The electrode array may, however, be used for any other type of system or method that is used to monitor brain activity. Furthermore, the present invention is relevant to any type of head-mounted electrodes (e.g., pressure sensor, CSF monitors, temperature monitors, stimulation electrodes, etc.) that embed into or through the skull.
The following steps are directed toward one preferred non-limiting embodiment of a method 40 encompassed by the present invention. Other methods of the present invention may include additional or fewer steps than described. First as shown in
In some embodiments the method 50 is particular for implanting a plurality of electrodes in a patient susceptible to having a seizure. An exemplary method is shown in
The electrodes may be used in other brain activity monitoring/stimulation systems such as sleep apnea and other sleep disorders, migraine headaches, depression, Alzheimer's, Parkinson's Disease, essential tremor, dementia, bipolar spectrum disorders, attention deficit disorder, stroke, cardiac disease, diabetes, cancer, eating disorders, or the like.
A description of some systems that may use the electrodes described herein to delivery a neuromodulation output to a patient are described in commonly owned U.S. Pat. Nos. 6,366,813 and 6,819,956, U.S. Patent Application Publication Nos. 2005/0021103 (published Jan. 27, 2005), 2005/0119703 (published Jun. 2, 2005), 2005/0021104 (published Jan. 27, 2005), 2005/0240242 (published Oct. 27, 2005), 2005/0222626 (published Oct. 6, 2005), and U.S. patent application Ser. Nos. 11/282,317 (filed Nov. 17, 2005), 11/321,897, 11/321,898, and 11/322,150 (all filed Dec. 28, 2005).
While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. For example, instead of an electrode, it may be desirable to position a catheter or other output from an implanted drug dispenser so as to position the one or more localized drug delivery outputs over the desired portion of the patient's brain. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.
