The term “neuromodulation” encompasses a broad array of treatments, both electrical and chemical, targeting a variety of locations in the body to best achieve the desired outcome. Some of the more frequently used techniques are described in detail below.
For explanations helpful to patients, please also visit the "For Patients" section of this site that includes definitions, fact sheets, illustrations, and therapy descriptions. (Please note: This information should not be used as a substitute for medical treatment and advice. Always consult a medical professional about any health-related questions or concerns.)
ELECTRICAL STIMULATION THERAPIES
Brain, Spinal Cord and Peripheral Nerve Therapies
Many therapies target the brain and spinal cord, the root of the nervous system, to deliver relief to patients. Brain and spinal cord neuromodulation therapies that are currently in use as well as in development today, include the following.
Spinal Cord Stimulation
SCS is the electrical stimulation, either bipolar or monopolar, over the dorsal aspect of the spinal cord for the relief of pain. Prior use was called dorsal column stimulation, because the stimulation array was placed intradural but extramedullary over the dorsum of the spinal cord. Present use includes epidural placement, therefore extradural and extramedullary.
Clinical Review Article: Spinal Cord Stimulation for Neuropathic Pain (March 2012)
Exclusive to the INS! Spinal Cord Stimulation in Chronic Critical Limb Ischemia (August 2012)
Deep Brain Stimulation (DBS)
DBS delivers a constant low electrical monopolar or bipolar stimulation to a small region of the brain through implanted electrodes connected to an implanted pulse generator. DBS, today, is used for the relief of pain, to partially restore normal movements in Parkinson's disease, essential tremor, and dystonia, and is used to treat epilepsy and certain psychiatric disorders including depression, obsessive compulsive disorder and Tourettes Syndrome.
Motor Cortex Stimulation
Electrical stimulation of the motor cortex is successfully used to treat central neurogenic pain following trigeminal deafferentation and central post stroke pain. Both monopolar and bipolar motor cortical stimulation enhances motor recovery in combination with rehabilitation for recovery from stroke.
Cerebral Cortex Stimulation
Low current stimulation of the gray matter of the cerebral cortex. The uses for electrical stimulation are experimental and are being studied for the induction of memory, the positive induction of plasticity and the learning process, and to decrease spastic cough reflexes.
Sacral Nerve Stimulation
There are five paired sacral nerve roots, S1-S5. These nerve roots innervate pelvic structures including genitourinary tract and sexual organs and non-pelvic structures such as the skin of the perineum and perianal region. Sacral nerves S1-S3 participate in the formation of the sciatic nerve, made up of the tibial and common peroneal nerves. Electrical stimulation of the sacral nerves are used for the relief of pain from the pelvic and urogenital viscera such as pudendal neuralgia and interstitial cystitis. It is used for urinary and bowel voiding difficulties and incontinence.
Exclusive to the INS! Specialty Clinic Referral for Faecal Incontinence (Aug. 2012)
Peripheral Nerve Stimulation
The electrical stimulation of a peripheral nerve to either induce activation or modulation of the activity of the nerve. Stimulation can be induced by either monopolar or bipolar stimulation. Clinically, PNS is used for neuropathic pain that follows a single nerve distribution as in traumatic median nerve neuropathy, ilio-inguinal neuralgia, trigeminal neuralgia, or complex regional pain syndrome type 2.
Occipital Nerve Stimulation
The electrical stimulation of either the greater or lesser occipital nerves, derived from nerve roots C2-3. Stimulation induces modulation (relief) of painful occipital neuralgia or may relieve the pain of migrainous headaches.
Exclusive to the INS! Review Article: Neurostimulation for Medically Refractory Head Pain Syndromes (Jan. 2012)
Pudendal Nerve Stimulation
The pudendal nerve is the main nerve supplying the pelvic floor, bladder and urethra. Damage to this nerve can cause incontinence and / or intractable pain. The pudendal nerve is derived from nerve roots S-2, S-3 and S-4. Stimulation of the pudendal nerve via a peripheral nerve stimulator, providing an electrical field over the nerve, may induce relief of pelvic pain and may relieve urinary incontinence.
Percutaneous Nerve Stimulation
The implantation of an electrode array under the skin to stimulate the most peripheral branches of a peripheral nerve for pain control.
Cranial Nerve Stimulation
There are 12 pairs of cranial nerves controlling a host of motor and sensory function. The following two therapeutic applications for cranial nerve stimulation include the following:
Vagus/Vagal Nerve Stimulation (VNS)
VNS is a form of cranial nerve stimulation, a form of peripheral nerve stimulation. Its present use is for the control of epilepsy and depression and is being studied for the control of obesity.
Trigeminal Nerve Stimulation
The use of electrical stimulation for the treatment of trigeminal neuralgia.
Functional Electrical Stimulation
Using implanted devices to generate electrical impulses to activate nerves and restore function in patients with paralysis from spinal cord injuries, stroke, head injury or other neurological disorders. These devices can also restore neural activity in cases of sensory damage, including cochlear implants for deafness and retinal stimulation for blindness caused by macular degeneration or retinitis pigmentosa. Some examples of these therapies include:
Devices are being developed to restore vision to patients blinded by retinitis pigmentosa or macular degeneration. These devices mount tiny cameras or receivers on a pair of glasses and process the images into electrical signals that are transmitted to electrode arrays implanted within the retina. The signals are travel to the brain through the optic nerve, enabling the patient to see patterns of light and darkness. With practice, these individuals can interpret these patterns into useful images that help them to navigate and identify their surroundings.
Occipital Cortex implantation
An experimental form of functional electrical stimulation to improve eyesight.
Cochlear implants are a form of a functional electrical stimulation device and are used for restoration of impaired hearing function. These devices are surgically implanted and bypass damaged structures in the inner ear and directly stimulate auditory nerve to allow some deaf individuals to learn to hear and interpret sounds and speech. The receiver has a probe with several electrodes (usually 22 now), that is implanted into the cochlea. A cochlear implant can be useful if the hearing loss is caused by problems with the cochlea (usually damaged hair cells) or where the loss is caused by problems with the middle ear that cannot be corrected.
Diaphragm (Phrenic) Pacing
The market for implanted diaphragm stimulation systems is experiencing steady developments, both in clinical and financial terms. Phrenic pacing provides ventilatory support for patients with chronic respiratory insufficiency whose diaphragm, lungs, and phrenic nerves have residual function. Typically, these patients have high spinal cord injuries, a paralyzed diaphragm, central sleep apnea or other central neurological disorders.
Pharmacological therapies work by surgically implanting pumps that deliver pain medication directly to the target site, enabling lower dosages and mitigating the side effects that certain pain medications can cause. Some examples of pharmacological therapies include:
Intrathecal Drug Delivery
The delivery of analgesic agents including opioid and non-opioid analgesics into the thecal space. Direct delivery of agents intrathecally bypasses the first pass effect of agents that are delivered orally and diffuse into the substance of the spinal cord where they work at various receptors and ion channels, depending on which agent is delivered. This delivery system requires an implanted intrathecal catheter connected either to an implanted programmable or non-programmable pump or to an external pump. Agents approved by the FDA in the USA for intrathecal therapy include morphine and ziconotide for pain, and baclofen for spasticity. Other opioid agents used for intrathecal delivery include hydromorphone, meperidine, fentanyl, sufentanil, methadone and buprenorphine. Non-opioid analgesics used for intrathecal delivery include local anesthetics such as bupivacaine, the alpha2 agonists clonidine and tizanidine. Other agents are being investigated such as gabapentin, ketorolac, somatastatin, midazolam, and many others.
Intraspinal Drug Delivery
This is the commonest route by which the intrathecal space is accessed. A silicone catheter is inserted between the laminae of the lumbar vertebrae and the tip is threaded up the thecal space to the desired level. Slow infusion of drug or combination of drugs act on the spinal cord receptors both at local level and after diffusion at higher levels. The spread of drugs will depend upon catheter level height, relative lipid solubility of drug and mass of drug per unit time delivered. The commonest indications are severe spasticity and severe pain of cancer and non cancer origin.
Intracisternal / Intraventricular drug delivery
The delivery within the cerebrospinal fluid of the cistern (C1-2) and intracranial ventricles of analgesic agents. Like intrathecal delivery, direct delivery of agents intracisternally or intraventricullarly bypasses the first pass effect of agents that are delivered orally and diffuse into the substance of the spinal cord/ and or brain where they work at various receptors and ion channels, depending on which agent is delivered. This delivery system requires an implanted intracisternal or intraventricular catheter connected either to an implanted programmable or non-programmable pump or to an external pump. Intracisternal delivery and intraventricular delivery of analgesic agents are usually used for patients with head and neck pain, as in pain of tumours of the face and neck. The agents used for these purposes are the same agents that are used for intrathecal delivery.