The leading cause of lower back pain arises from rupture or degeneration of lumbar intervertebral discs. Pain in the lower extremities is caused by the compression of spinal nerve roots by a bulging disc, while lower back pain is caused by collapse of the disc and by the adverse effects of articulation weight through a damaged, unstable vertebral joint. One proposed method of managing these problems is to remove the problematic disc and replace it with a porous device that restores disc height and allows for bone growth therethrough for the fusion of the adjacent vertebrae. These devices are commonly called “fusion devices”. Although the use of fusion devices to treat back pain has become increasingly popular, there remains a significant proportion of patients who undergo this surgery and yet still experience chronic back pain. This phenomenon is called “failed back syndrome”.
Deep Brain Stimulators (DBS) have been used to treat chronic pain, including failed back syndrome. In this treatment, electrodes are often placed in the periaqueductal grey (PAG) region of the brain. The periaqueductal gray (PAG) has a very important antinociceptive function, and its stimulation decreases pain. When the DBS electrodes are activated, the periaqueductal grey is stimulated and releases pain-reducing endorphins. In one study examining the efficacy of DBS in relieving chronic pain, 47% of the patients treated with DBS electrodes suffered from failed back syndrome. Therefore, it appears that stimulation of the PAG can provide significant pain relief for patients suffering from failed back syndrome.
Although DBS has had some success as a medical implant, this mode of treatment also has some drawbacks. For example, it appears that scar tissue forms around the electrodes, causing their failure in many cases after about two years. In addition, Since the patient's anatomy controls the flow of electrical current, it is difficult to control the location and dose of the current. Moreover, it is believed that electricity jolts or provokes cellular response,rather than enabling or eliciting response. Accordingly, it is not clear whether such jolting will yield adurable effect or merely tire the provoked cells.
US Patent Publication No. 2006/0155348 (deCharms) teaches irradiation of a number of brain regions, including the PAG, with various wavelengths of light. However, deCharms teaches that the irradiation should be of a sufficiently large scale as to cause electrical current to flow through the irradiated region. The level of irradiation required to cause such a current greatly exceeds the level commonly used in low level laser therapy (LLLT).
It has been reported in the literature that low level irradiation of tissue with red light stimulates the release of pain-reducing endorphins from the irradiated cells. For example, Laakso, Photomed Laser Surg. February 2005;23(1):32-5 induced inflammation in the hind-paws of Wistar rats. Two groups of rats then received 780-nm laser therapy at one of two doses (2.5 J/cm2 and 1 J/cm2). Scores of nociceptive threshold were recorded using paw pressure and paw thermal threshold measures. Laakso found that a dose of 2.5 J/cm2 provided a statistically significant effect on paw pressure threshold (p<0.029) compared to controls. Laakso further found normal beta-endorphin containing lymphocytes in control inflamed paws but no beta-endorphin containing lymphocytes in rats that received laser at 2.5 J/cm2. Without wishing to be tied to a theory, it is believed that these results appear to show the release of endorphins from the lymphocytes of the irradiated rats. Lastly, Zalewska-Kaszubska, Lasers Med Sci. 2004;19(2):100-4, reported treating patients with 20 consecutive daily helium-neon laser neck biostimulations and 10 auricular acupuncture treatments with argon laser (every 2nd day), and finding that the beta-endorphin plasma concentration in those patients was increased.
Therefore, it is believed that low level red light irradiation of the PAG should also cause release of pain-reducing endorphins from the PAG, thereby affording pain relief to the patient suffering from chronic pain.
In the present invention, the PAG is locally stimulated through low level laser therapy to elicit pain relief. In some embodiments, the placement of a light-diffusing tube in the cerebral aqueduct and the transmission of red light through it will result in the irradiation of the adjacent PAG, thereby causing the release of endorphins and pain relief.
Therefore, in accordance with the present invention, there is provided a method of treating a patient having chronic pain, comprising the steps of:
a discloses a cross-section of the first translucent tube and the distal end of the optical wave guide implanted in the cerebral aqueduct.
b discloses a cross-section of the longer translucent tube and the distal end of the optical wave guide implanted in the cerebral aqueduct.
c and 3d disclose cross-sections of a light diffuser comprising a central element and a plurality of radially-extending standoffs.
e discloses a transparent replacement material between the implant and the epidermis.
a is a cross-section of an implanted optical wave guide implant irradiated by a light source.
b is a cross-section of an implanted optical wave guide implant having a gasket irradiated by a light source.
Now referring to
In one preferred embodiment of the present invention, the distal end of the optical wave guide is attached to a translucent light diffuser, which is often in the form of a tube. The light diffuser is placed in the cerebral aqueduct and acts not only as a light delivery device to the PAG (which surrounds the cerebral aqueduct), but also as an anchor within the compliant cerebral aqueduct that holds the device in place.
The literature has repeatedly reported the successful placement of stents in the cerebral aqueduct as a method of managing blockage of the cerebral aqueduct or fourth ventricle. See, for example, Shin, J. Neurosurg., June 2000 92(6) 1036-9; Cinalli, J. Neurosurg., January 2006, 104(1 Supp.) 21-7; Sagan, J. Neurosurg. (4 Supp pediatrics) 105: 275-280, 2006; Schroeder, Operative Neurosurgery, 1, 60, February 2007 ONS-44-52. Therefore, placement of the translucent light diffuser in the form of a tube of the present invention in the cerebral aqueduct is a procedure that should be well within the expertise of the neurosurgeon.
The placement of the translucent light diffuser essentially adjacent the PAG has special advantage in that there is no intervening brain tissue between the tube and the PAG. Therefore, there is no need to estimate how much light would be attenuated or diffracted or reflected by the intervening tissue as the light proceeds from the translucent light diffuser through that intervening tissue and on to the target tissue. Thus, the amount of light that exits the light diffuser is essentially equal to the amount of light that irradiates the PAG, and so energy fluency at the PAG can be reasonably estimated by using the outer surface area of the light diffuser. Since there is no need for overirradiating any intervening tissue in order to obtain sufficient fluency at the PAG, there is no danger of overheating or destimulating any intervening brain tissue.
Therefore, in accordance with the present invention, and now referring to
Because of the ability of the cerebral aqueduct to accommodate large changes in diameter, it might be possible to directly illuminate the PAG by implanting the light source directly in the cerebral aqueduct without any intervening optical wave guides (see LED chain image copied from
In general, the longer the length of the translucent light diffuser, the more reliable will be its fit within the cerebral aqueduct (which has a length of about X cm in the typical adult). Therefore, in some embodiments, the length of the translucent light diffuser is at least 25% of the length of the cerebral aqueduct, preferably at least about 50% of the length of the cerebral aqueduct, and more preferably at least about 75% of the length of the cerebral aqueduct. However, in some embodiments, the length of the translucent light diffuser is no more than 90% of the length of the cerebral aqueduct. In this condition, the ends of the cerebral aqueduct will form front and back lips that function as shoulders to keep the light diffuser in place and resist its migration.
The translucent light diffuser can include a rim, lips, ribs, threads, flair, stand-offs, folds, hooks, posts, trumpet end flair, loops, or helix to prevent migration of the device. Additionally, several of these embodiments would enable increased local tissue diffusion at the light diffuser-tissue interface thereby mitigating any metabolic issues resulting from device placement.
In some embodiments, the translucent light diffuser comprises silicone. Silicone tubes are currently used as ventricular catheters in the treatment of hydrocephalus. In addition, the literature has reported the use of silicone tubes as lumen-opening stents in general surgery. See, for example, Westaby, British Journal Surgery. May 1983;70(5):259-60; Roh, Dsphagia. April 2006;21(2):112-5. In addition, silicone is fairly translucent to red light. In some embodiments, the translucent light diffuser consists essentially of silicone.
Additional silicone embodiments can include hollow channels with reflective internal/external coatings.
In some embodiments, and now referring to
Although the tube shape beneficially diffuses light to the entirety of the aqueduct perimeter, it may also restrict fluid flow from the aqueduct to the PAG. Therefore, and now referring to
In some embodiments, antibiotics such as BACTISEAL™, are impregnated into the silicone tube. Additionally, silver coatings can be used to increase surface reflectance and impart anti-biotic and anti-bacterial colonization attributes to the part (SilvaGard™ silver nano particles by AcryMed of Beaverton, Oreg.).
In preferred embodiments, the translucent light diffuser possesses features that increase the radial transmission of light through its outer surface. In some embodiments, diffractive elements, such as metallic particles, are embedded within the translucent tube in order to diffract light that is traveling down the length of the tube to cause that light to exit the tube in a radial direction. In other embodiments, the outer surface of the tube is etched in order to diffract light that is traveling down the length of the tube to cause that light to exit the tube in a radial direction. In some embodiments, the distal end of the tube is coated with a reflective coating to deflect axially-traveling light back into the tube. In some embodiments, the inner surface of the tube is coated with a reflective coating to deflect light back into the tube. In further embodiments, the tube is allowed to “leak” light through the internally reflective coating to achieve radial illumination. Similarly, the external contours of the tube wave guide can be designed to allow radial light diffusion (sinusoidal or crenulated surfaces will leak more light than smooth surfaces).
In some embodiments, the outer surface of the translucent tube is coated with an adhesive in order to insure the retention of the tube within the cerebral aqueduct. One adhesive, polyethylenimine, has been tested as an adhesive for bonding electrodes to neurons. He, Biomaterials 26 (2005) 2983-2990. It appears to be a non-resorbing adhesive and promotes neuron attachment to itself. However, test data is limited to about 15 days. Sutures, staples, stents, lock & key, in situ curing/stiffening of the device to contour to the unique shape of the aqueduct.
In some embodiments, an implanted optical wave guide is used to deliver photonic energy from the proximal light collector to a location within the brain. The optical wave guide can be embodied as an optical fiber, internally-reflective tube (or “light pipe”), diffusion/diffraction surface(s), optical lens and mirror system, etc. or a combination of these elements.
In some embodiments, the optical wave guide is a light pipe. In one embodiment, the light pipe is a truncated form of the Flexible Light Pipe FLP 5 Series, marketed by Bivar Inc., which is a flexible light pipe that is 12 inches long and 2 mm in diameter, and has an outer tubing of fluorinated polymer TFE.
In some embodiments, the optical wave guide is a coiled sheet or convoluted surface that guides optical energy (light) from a source, through the light diffuser to a final target (in this case, a tissue or anatomical region of the brain, PAG). The benefit of a hollow optical wave guide is the decreased amount of light energy being absorbed by the material conduit. This benefit is mitigated by optical inefficiencies due to imperfect reflectance, but light attenuation by absorption will be greatly reduced in a hollow internally reflecting optical wave guide.
Silicone might also be used as the core and/or cladding of an optical fiber as long as the materials have different optical refractive indices. Those practiced in the art will appreciate how to manufacture silicone cores with silicone cladding.
Alternatively, a traditional optical material like glass or clear acrylic can be used as the optical wave guide core with silicone cladding that also serves as a biological boundary to impart overall device biocompatibility.
Because the delivery and placement of the light diffuser takes places entirely within the ventricular system of the brain, such delivery and placement may be performed endoscopically. The endoscopic delivery and placement of this system represents a significant advantage over the conventional stereotactically-guided placement of medical devices in the brain. First, whereas stereotactically guided systems require the use of expensive and complicated hardware, endoscopic placement of a tube within the cerebral aqueduct is relatively straightforward and can be performed without expensive and time-consuming support equipment. Second, stereotactically guided systems typically require blunt invasion of the brain parenchyma and its related vasculature, and so generate a risk of producing neural deficits and hemorrhage. For example, Kleiner-Fisman, Mov. Disord., Jun. 21, 2006, Suppl. 14 S290-304 reports a 3.9% hemorrhage rate for Parkinson's patients receiving deep brain stimulation implants. In contrast, endoscopic placement of a stent in the cerebral aqueduct does not produce any injury to the brain tissue or its related vasculature whatsoever, and so therefore should completely eliminate the risk of hemorrhage.
In sum, endoscopically accessing the ventricular system is much less complicated than placing a catheter directly into the brain parenchyme. Endoscopic access could be performed by most neurosurgeons and so there would be no need to require stereotactic-trained surgeons or stereotactic/navigation equipment. Most neurosurgeons are capable of and would be comfortable placing a tube into the lateral ventricle and driving that catheter into the floor of the third ventricle endoscopically and then into the cerebral aqueduct. Anatomic landmarks would facilitate its placement and this would obviate the need for complex stereotactic localizing techniques. It would a simpler procedure for patients and could be performed by most neurosurgeons.
Therefore, in accordance with the present invention, there is provided a method of treating a patient having chronic pain, comprising the steps of:
In some embodiments using endoscopic placement, a modified procedure of Farin, “Endoscopic Third Ventriculostomy” J. Clin. Neurosci. August;13(7):2006,763-70 is used. In particular, a burr hole is made through the skull at the intersection of the coronal suture and the midpupillary line, approximately 2-3 cm lateral to the midline. The endoscope trajectory is aimed medially toward the medial canthus of the ipsilateral eye and toward the contralateral external auditory meatus in the anterior/posterior plane. This approach leads to the foramen of Monro and floor of the third ventricle. The lateral aspect of the anterior fontanelle is targeted. The dura is opened. The lateral ventricle is tapped using a peel-away sheath with ventricular introducer. The sheath is secured in place to the scalp. A rigid neuroendoscope is then inserted into the lateral ventricle, and the choroid plexus and septal and thalamostriate veins are identified in order to locate the foramen of Monro. The endoscope is advanced into the third ventricle. The mamillary bodies are some of the more posterior landmarks of the third ventricle; moving anteriorly, the basilar artery, dorsum sellae and infundibular recess may be obvious based on the degree of attenuation of the ventricular floor. The endoscope is then moved farther posteriorly to the posterior end of the third ventricle to reach the mouth of the cerebral aqueduct. The endoscope is then inserted into the cerebral aqueduct, wherein it deposits the translucent tube portion of the device.
Without wishing to be tied to a theory, it is believed that the therapeutic effects of red light described above may be due to an increase in ATP production in the irradiated neurons. It is believed that irradiating neurons in the brain with red light will likely increase ATP production from those neurons. Mochizuki-Oda, Neurosci. Lett. 323 (2002) 208-210, examined the effect of red light on energy metabolism of the rat brain and found that irradiating neurons with 4.8 W/cm2 of 830 nm red light increased ATP production in those neurons by about 19%.
Without wishing to be tied to a theory, it is further believed that the irradiation-induced increase in ATP production in neuronal cell may be due to an upregulation of cytochrome oxidase activity in those cells. Cytochrome oxidase (also known as complex IV) is a major photoacceptor in the human brain. According to Wong-Riley, Neuroreport, 12:3033-3037, 2001, in vivo, light close to and in the near-infrared range is primarily absorbed by only two compounds in the mammalian brain, cytochrome oxidase and hemoglobin. Cytochrome oxidase is an important energy-generating enzyme critical for the proper functioning of neurons. The level of energy metabolism in neurons is closely coupled to their functional ability, and cytochrome oxidase has proven to be a sensitive and reliable marker of neuronal activity.
By increasing the energetic activity of cytochrome oxidase, the energy level associated with neuronal metabolism may be beneficially increased.
Preferably, the red light of the present invention has a wavelength of between about 600 nm and about 1000 nm. In some embodiments, the wavelength of light is between 800 and 900 nm, more preferably between 825 nm and 835 nm. In this range, red light has not only a large penetration depth (thereby facilitating its transfer to the optical wave guideand SN), but Wong-Riley reports that cytochrome oxidase activity is significantly increased at 830 nm, and Mochizuki-Oda reported increased ATP production via a 830 mn laser.
In some embodiments, the wavelength of light is between 600 and 700 nm, and preferably is 670 nm. In this range, Wong-Riley reports that cytochrome oxidase activity was significantly increased at 670 nm. Wollman reports neuroregenerative effects with a 632 nm He—Ne laser.
In some embodiments, the light source is situated to irradiate adjacent tissue with between about 0.01 J/cm2 and 20 J/cm2 energy. Without wishing to be tied to a theory, it is believed that light transmission in this energy range will be sufficient to increase the activity of the cytochrome oxidase around and in the target tissue. In some embodiments, the light source is situated to irradiate adjacent tissue with between about 0.05 J/cm2 and 20 J/cm2 energy, more preferably between about 2 J/cm2 and 10 J/cm2 energy.
In accordance with US Patent Publication 2004-0215293 (Eells), LLLT suitable for the neuronal therapy of the present invention preferably has a wavelength between 630-1000 nm and power intensity between 25-50 mW/cm2 for a time of 1-3 minutes (equivalent to an energy density of 2-10 J/cm2). Eells teaches that prior studies have suggested that biostimulation occurs at energy densities between 0.5 and 20 J/cm2, whereas energy densities above 20 J/cm2 may exert bioinihibitory effects. Preferable energy density of the present invention is between 0.5-20 J/cm2, most preferably between 2-10 J/cm2. In summary, a preferred form of the present invention uses red and near infrared wavelengths of 630-1000, most preferably, 670-900 nm (bandwidth of 25-35 nm) with an energy density fluence of 0.5-20 J/cm2, most preferably 2-10 J/cm2, to produce photobiomodulation. This is accomplished by applying a target dose of 10-90 mW/cm2, preferably 25-50 mW/cm2 LED-generated light for the time required to produce that energy density.
In general, the amount of light irradiating the PAG should be less than about 20 J/cm2. Above this 20 J/cm2 amount, it is believed that LLLT works to inhibit biometabolism. For example, Byrnes, Lasers Surg. Med., 9999:1-15(2005) found high laser dosages to be inhibitory and cited another reference (Tuner, “Laser Therapy: Clinical Practice and Scientific Background”. Tallinn, Estonia: Prima Books AB, 2002) for the proposition that doages greater than 10 J/cm2 are inhibitory.
In some embodiments, the light source is situated to produce an energy intensity of between 0.1 watts/cm2 and 10 watts/cm2. In some embodiments, the light source is situated to produce about 10-90 milliwatt/cm2, and preferably 7-25 milliwatt/cm2.
Wong-Riley Neuroreport 12(14) 2001:3033-3037 reports that a mere 80 second dose of red light irradiation of neuron provided sustained levels of cytochrome oxidase activity in those neurons over a 24 hour period. Wong-Riley hypothesizes that this phenomenon occurs because “a cascade of events must have been initiated by the high initial absorption of light by the enzyme”.
Therefore, in some embodiments of the present invention, the therapeutic dose of red light is provided on approximately a daily basis, preferably no more than 3 times a day, more preferably no more than twice a day, more preferably once a day.
In some embodiments, the red light irradiation is delivered in a continuous manner. In others, the red light irradiation is pulsed in order to reduce the heat associated with the irradiation. In some embodiments, red light is combined with polychrome visible or white light
Thus, there may be a substantial benefit to providing a local radiation of the PAG with red laser light. The red light can be administered in a number of ways:
Now referring to
In use, the surgeon implants the device into the brain of the patient so that the device is adjacent to a portion of the PAG. The Red light produced by the implant will then irradiate that portion of the PAG.
In order to protect the active elements of the device from cerebrospinal fluid (“CSF”), in some embodiments, and again referring to
In some embodiments, it may be desirable to locate the light emitting portion of the implant at a location separate from the LED, and provide a light communication means between the two sites. The light communication means may include any of a optical wave guide, a wave guide, a hollow tube, a liquid filled tube, and a light pipe.
Now referring to
In use, the surgeon implants the device into the brain of the patient so that the antenna is adjacent the cranium bone and the distal end of the optical wave guide is adjacent to the PAG region of the brain.
In some embodiments, the proximal end portion of the optical wave guide is provided with a cladding layer 41 of reflective material to insure that Red light does not escape the guide into untargeted regions of brain tissue.
Because long wavelength red light can penetrate up to many centimeters, it might be advantageous to transcutaneously deliver the light the fiber optic. Now referring to
In some embodiments, as in
To enhance the propagation of light emitted from the end of the fiber, a lens could be placed at the distal end of the fiber to spread the light, or a diffuser such as a small sheet or plate of optical material could be used to create more surface area. Alternatively, one could create a series of lateral diffusers, such as grooves or ridges, along the distal portion of end of the fiber to spread light out from 360 degrees perpendicular to the axis of the fiber, as well as emanating directly out from the end of the fiber.
In some embodiments using the transcutaneous delivery of red light, the receiving portion of the device is fitted with a lens to focus the light into the proximal end portion of the optical wave guide. In particular, and now referring to
In some embodiments, red light is provided to the brain via delivery through the scalp. These are highly preferred embodiments because they are non-invasive. However, it is recognized that there may be some light loss associated with this mode of delivery. The literature reports that while the epidermis portion of the scalp is essentially transparent to light, the dermis and fascia portions of the scalp are light-attenuating and light-diffracting due to the presence of blood vesssels and fat in these layers.
Therefore, in some embodiments of the present invention, a core is taken of at least a portion of the subepidermal tissue residing between the skull and the epidermis, and that cored volume of tissue is replaced with a transparent material. Preferably, a core is taken of substantially all of the subepidermal tissue between the skull and the epidermis, and that tissue is replaced with a transparent material. In this condition, light delivered from an ex vivo source will need only to pass through the transparent epidermis and then the transparent replacement material in order to enter the light collector portion of the implant. This should greatly attenuate any light loss associated with transcutaneous light delivery.
Preferably, the transparent material is a gel. When it is in a gel state, the transparent material has the ability to smoothly and evenly respond to external pressures on the epidermis, thereby mitigating concerns of the transparent replacement material breaching the epidermis due to external pressures on the epidermis.
The literature reports that the thickness of the epidermis in the scalp is about 2-3 mm. Bukhari, Ann. Saud. Med. 24(6) November-December 2004 484-485. It is believed that such a thickness would be adequate to safely cover and house the cylinder of transparent gel material that will lie beneath it.
In some embodiments, the transparent material comprises hyaluronic acid (HA). HA is a biocompatible material that has been approved by the FDA as a subcutaneous injectable for cosmetic use. HA is a clear, transparent, colorless material when in the form of a gel. Therefore, it has excellent light transmission properties. Preferably, the HA is cross-linked. When it is cross-linked, HA has enhanced resistance to proteolytic degradation. HA also appears to have interesting anti-microbial properties. Zaleski, Antimicrob. Agents Chemother., 50(11) November 2006 3856-60, reports that HA-binding peptides prevent experimental staph. aureus wound infections. HA has also been used as an anti-infective coating upon implants. See US Patent Publication No. 2005-0153429. In some embodiments, the HA is Juvederm™, marketed by Allergan.
In some embodiments, the transparent gel material may be mixed with antibiotics or angiogenesis-inhibiting materials.
Therefore, in accordance with the present invention, there is provided a method comprising the steps of:
Now referring to
Now referring to
Now referring to
In some embodiments, there is provided a red LED implant whose power requirements are provided by transcutaneous Rf induction to create red light in vivo. As the transcutaneous delivery of Rf energy is highly predictable, this mode of energy delivery would result in the production of a guaranteed high and uniform level of light. Therefore, this mode of energy delivery eliminates the light loss issues associated with the transcutaneous delivery of red light. In some embodiments, the Rf powdered LED implant is located above the skull surface in order to provide a tactile locater for the user directing the Rf wand (to help a spouse or other provider accurately deliver the Rf energy).
Now referring to
In some embodiments, and now referring to
When the implant is coupled with external energy, power can be transmitted into the internal device to re-charge the battery.
In some embodiments, the light generated by the implant is powered by wireless telemetry integrated onto or into the implant itself. In the
In one embodiment, the implant may have an internal processor adapted to intermittently activate the LED.
In some embodiments, the telemetry portion of the device is provided by conventional, commercially-available components. For example, the externally-based power control device can be any conventional transmitter, preferably capable of transmitting at least about 40 milliwatts of energy to the internally-based antenna. Examples of such commercially available transmitters include those available from Microstrain, Inc. Burlington, Vt. Likewise, the internally-based power antenna can be any conventional antenna capable of producing at least about 40 milliwatts of energy in response to coupling with the externally-generated Rf signal. Examples of such commercially available antennae include those used in the Microstrain Strainlink™ device. Conventional transmitter-receiver telemetry is capable of transmitting up to about 500 milliwatts of energy to the internally-based antenna.
In some embodiments, and now referring to
In some embodiments, the light source is provided on the implant and is adapted to be permanently implanted into the patient. The advantage of the internal light source is that there is no need for further transcutaneous invasion of the patient. Rather, the internally-disposed light source is activated by either a battery disposed on the implant, or by telemetry, or both. In some embodiments of the present invention using an internal light source, the light source is provided by a bioMEMs component.
Because use of the present invention may require its repeated activation by Rf energy, it would be helpful if the user could be guaranteed that the implant remained in the same place within the skull. Accordingly, in some embodiments, and now referring to
In some embodiments, the light source comprises a chest-implanted capacitor with a 10 year life span as the energy source thereto. In some embodiments, a red light source or red light collector and the proximal end of the optical wave guideare placed in the chest. This allows the surgeon to conduct maintenance activity on an implanted light source without having to re-open the cranium. In addition, location within the chest also lessens the chances of surface erosion.
The present invention may also be used to treat head and neck pain caused by cancer.