Neuromodulation encompasses a variable definition in both its entity and activity. It can include treatments that involve the stimulation of various nerves in the central nervous system, peripheral nervous system, autonomic nervous system, or deep cell nuclei of the brain that lead to the “modulation” of its activity. By definition, neuromodulation is a therapeutic alteration of activity either through stimulation or medication, both of which are introduced by implanted devices.
The idea and allure of neuromodulation stems from its initial direction of a reversible alteration of the nervous system. It is the idea of neural “modulation” as supposed to “ablative” or resective procedures. Treatments are reversible and have the ability to be turned off in most situations.
Implanted devices are usually neural stimulators and drug delivery devices such as pumps. The world of neuromodulation encompasses acute and chronic pain syndromes, movement disorders, dystonia and spasticity, as well as epilepsy. An emerging subset of neuromodulation includes neuroprosthetics for either nerve regeneration or rehab potential.
The neuromodulation community is based on a multidisciplinary approach that is diverse in its delivery. It involves physicians, industry, and basic science researchers. Clinicians involved in the procedures vary from neurosurgeons, anesthesiologists, pain specialists, and rehab physicians. Those involved in the multidisciplinary approach can include neurologists, psychiatrists, psychologists, primary care physicians, and physical therapy.
Targets for stimulation usually include the brain and spinal cord, but can also include the peripheral and autonomic nerves as well. Examples include spinal cord stimulation, deep brain stimulation, and cortical stimulation.
Spinal cord stimulation (SCS) delivers therapeutic doses of electrical current to the spinal cord for the management of neuropathic pain. The most common indications include post-laminectomy syndrome, complex regional pain syndrome (CRPS), ischemic limb pain, and angina. There are scattered reports regarding the treatment of intractable pain due to other causes including visceral/abdominal pain, cervical neuritis pain, spinal cord injury pain, post-herpetic neuralgia, and neurogenic thoracic outlet syndrome. Experience suggests that, in selected patients, SCS can produce at least 50% pain relief in 50%-60% of the implanted patients. Interestingly, with the proper follow-up care, these results can be maintained over several years.
Deep brain stimulation (DBS) delivers electrical current to the deep structures of the brain to treat a number of movement disorders including Parkinson’s disease, tremor, and dystonia. Targets include the subthalamic nucleus, globus pallidus, and thalamus. Many reports and research have looked at DBS for the treatment of depression, obsessive compulsive disorder, anorexia, obesity, multiple sclerosis, and pain syndromes. Most recently, DBS has been at the forefront for the treatment of epilepsy.
Cortical stimulation has been used to treat pain patients for various syndromes from post stroke pain to neuropathic pain. It has become most widely used in the treatment of epilepsy. Investigative reports are looking at cortical stimulation for the treatment of movement disorders, depression, and stroke.
Peripheral nerve stimulation (PNS) has been most commonly recognized for its use in epilepsy with vagal nerve stimulation. Occipital nerve stimulation has been favored more recently for the treatment of various headaches and neuropathic pain of the neck. Other indications include PNS stimulation for local pain, as well as trigeminal nerve stimulation to reduce seizure activity in epileptics.
Neuroprosthetics have been used for deafness with cochlear implants, as well as for blindness via retinal stimulation. Investigations have looked into artificial limbs and as an adjunct for rehab, as well as the involvement of what has been known as the brain-machine interface.
Drug Delivery Devices
Pain medication has been delivered by implantable pumps that are surgically implanted into the area of interest and deliver the medication directly to a desired target. It enables a lower dosage to be administered and decreases, if not eliminates, the side effects seen with systemic absorption.
Intrathecal implants are used in the treatment of pain syndromes such as those associated with nerve injury or cancer pain, as well as for the treatment of spasticity seen with stroke and spinal cord injury patients. Intraventricular implants are used to deliver medication directly into the CSF or CNS for the treatment of epilepsy and pain.