Neuromodulation, or Neuromodulatory Effect
The International Neuromodulation Society defines therapeutic neuromodulation as “the alteration of nerve activity through the delivery of electrical stimulation or chemical agents to targeted sites of the body.” (1) In appropriate patients, this growing class of therapies, in common use since the 1980s, can help restore function or relieve symptoms that have a neurological basis. Neuromodulation devices stimulate nerves – with pharmaceutical agents, electrical signals, or other forms of energy – by modulating abnormal neural pathway behaviour caused by the disease process. Profound effects occur including relief of pain, restoration of function or normal bowel and bladder control, Parkinson’s and tremor control and many more. (2)
The reversible therapy delivers stimulation to specific neural circuits in the brain, spine, or peripheral nerves. Depending on the target, the therapy may be non-invasive or minimally invasive.
Whether the devices are implanted or external, neuromodulation therapies can help reestablish neural balance, similar to the way a cardiac pacemaker or defibrillator corrects heartbeat abnormalities.
The most common neuromodulation treatment is spinal cord stimulation for chronic neuropathic pain. (3 – 10) In addition to chronic pain relief, other neuromodulation treatments now used or studied include deep brain stimulation for essential tremor, Parkinson’s disease, dystonia, epilepsy and psychiatric disorders such as depression, obsessive compulsive disorder and Tourette syndrome; sacral nerve stimulation for pelvic disorders and incontinence; gastric and colonic stimulation for gastrointestinal disorders such as dysmotility or obesity; vagus nerve stimulation for epilepsy, obesity or depression; carotid artery stimulation for hypertension; and spinal cord stimulation for ischemic disease such as angina and peripheral vascular disease. (2, 10 – 19)
Neuromodulation therapy may be considered for select patients, through a multidisciplinary assessment, either as an adjunct to other care, or when symptoms do not adequately respond to more conservative measures, for instance, when existing drugs are ineffective or become problematic for long-term use due to development of tolerance, addiction, adverse side-effects or toxicity.
Neuromodulation therapy continues to undergo refinement and research elucidating its effects and applications. Electrical neurostimulation implants are believed to activate natural biological responses, such as nerve transmission and release of the body’s own pain-reducing substances, in the neural circuits receiving stimulation. Central to the operation of electrical-stimulation implants are thin insulated leads, placed beneath the skin, that are tipped by electrical contacts. The contacts, no bigger than a grain of rice, are positioned beside the nerve or nerves that influence the condition being treated. Pulses of mild electrical current are sent down the leads to the nerves. A battery-operated generator that is about the size of a stopwatch powers the pulses. If a patient responds well to several days of trial treatment, this sort of pulse generator will be implanted too. After the system has been implanted, a clinician will work with the patient to program the stimulation pattern, which can be adjusted over time. At home, patients use hand-held controllers to turn off or switch between programs. Recuperation from the implant procedure may take a few weeks.
In the case of pharmacological agents delivered through implanted pumps – such as pain relief medication or anti-spasm agents – medication can be given in smaller doses because it does not have to be absorbed through the intestines, like a drug taken by mouth, and then pass through the liver before circulating to the target area. Smaller doses – in the range of 1/300th of an oral dose – can mean fewer side effects, increased patient comfort, and improved quality of life. Patients return periodically to have the drug reservoir refilled. (20)
Patients will be briefed to watch for potential complications, such as signs of infection or a mechanical issue, and their caregivers should be sure to consult the implant provider if any questions arise with this or other treatments over the years. Patients with an implant should not pass through security gates, and will be given a card to show security personnel.
While they are not a cure for an underlying condition, neuromodulation therapies provide an additional means of managing symptoms of chronic conditions. Despite their technological complexity, neuromodulation devices, when introduced relatively early in treatment, may be more cost-effective at controlling certain conditions over time than medical management approaches. Examples include spinal cord stimulation for the treatment of neuropathic pain and intrathecal baclofen for the treatment of severe spasticity. (2-4, 7, 10, 20)
Overall, neuromodulation therapies have become an integral tool for healthcare professionals since first becoming available in the 1960s. As with most medical technologies, neuromodulation devices have progressed, becoming smaller, more easily implanted and removed, and more highly targeted. Those advances, combined with an increasing body of knowledge and practitioner skill, can all contribute to cost-effective use of the therapy in chronic conditions.
The development of neuromodulation therapies has been truly multidisciplinary, requiring close collaboration between neuroscientists, engineers and clinicians to aid many patients who face vexing and long-term conditions.
Reviewed Jan. 24, 2013
Simon Thomson, MBBS, FRCA, FIPP, FFPMRCA
President, International Neuromodulation Society, 2009-2015
Consultant in Anaesthesia and Pain Management, Basildon and Thurrock University NHS Trust, U.K.
|Last Updated on Tuesday, March 05, 2013 07:35 PM|