Electrical Neuromodulation

Neuromodulation or modifying nerve function can occur in a variety of ways, including chemical or electrical stimulation. Last week, chemical neuromodulation was discussed. This week the focus is on electrical stimulation. Other ways of affecting nerve function are through the use of adjusting the nerve’s magnetic field, optogenetics or use of light-sensitive proteins, thermal, which is temperature changes to affect ionic channels, and acoustic or mechanical methods that uses ultrasound waves.

Neuromodulation is the modification of nerve function which either enhances nerve transmission or slows nerve transmission depending on the source used and the outcome desired. The effect of neuromodulation is the manipulation of the neurotransmitters of the nerves. Neurotransmitters are the chemicals that cause nerve impulses to jump across the gap from nerve to nerve. Neuromodulation creates a ‘speed-up’ or ‘slow-down’ of these neurotransmitters.

Electrical stimulation can be added to therapeutic treatment to supply impulses to nerves that are not receiving messages due to a brain injury, including stroke or spinal cord injury. There are a variety of health concerns that electrical stimulation supports. These include blocking pain signals, which slow messages from the brain or interrupt pain signals from reaching the brain. Blood circulation can be improved, which is often used for wound healing in those with limited sensation ability. It can also be used to improve muscle strengthening and now, to improve physical function.

There are many individuals who are concerned about electrical stimulation for a variety of reasons. One is that they are concerned about pain, like electrical shocks. However, the stimulation is modulated for those with varying levels of sensation. You may be able to tolerate higher levels of stimulation if you have less sensation. Those who have sensations will use lower levels of electrical current.

Personally, I have tried electrical stimulation to see how it feels. I do not have issues with sensation. At the level of stimulation for pain control, the sensation feels like tingling in the area where the electrodes are applied. It is actually quite pleasant. For movement, I did not feel much of anything from the stimulation, however, seeing my arm, wrist, and hand move without the control of my brain was a bit odd.

Others are concerned about the direction or flow of the current. Typically, messages flow from the brain through the spinal cord to the nerve causing action in the muscles. In electrical stimulation therapy, the impulse is supplied to the muscle or to the nerve, which causes function. Many individuals have used electrical stimulation at high levels for years without damage to their bodies or nerves. There seems to be a general misunderstanding or misrepresentation of electrical stimulation. As with any treatment, there are risks, but so far, electrical stimulation appears to be a low-risk opportunity. You should always check with your healthcare provider to make sure it is appropriate for you as an individual.

Another concern is for individuals who have lower-level injuries in the lumbar and sacral areas of the spinal cord. If your injury is at these levels, you probably will not be able to stimulate your nerves. This is because lower spinal cord injury generally affects lower motor neurons which leaves your body without tone. This is seen by the physical attributes of smaller muscles in the legs, and bladder and bowel function without tone. However, people with atonal nerves do have options for nerve grafting and nerve transfers to improve their function in movement, as well as bowel and bladder function. Sexual function can be improved in men. Individuals with cervical or thoracic spinal cord injuries have upper motor neuron injuries, which include reflexive or tone in their muscles, which can be manipulated by electrical stimulation.

When electrical stimulation is used to enhance function, it is called functional electrical stimulation (FES). There are many examples of FES in use today that individuals do not think about these therapies as electrical stimulation, even though they are. The following are often used by those with paralysis or neurological issues. These FES devices include:

• Cochlear implants to improve hearing.
• Deep brain stimulation to treat Parkinson’s disease, essential tremor, and dystonia.
• Hypoglossal nerve stimulation to treat sleep apnea.
• Vagal nerve stimulation for treatment of epilepsy and depression, anxiety, and Alzheimer’s Disease
• Cardiac pacemakers for improving heart rhythm.
• Diaphragmatic pacemakers assist individuals in breathing without mechanical ventilation.
• Nerve stimulators in the arm to improve arm and finger function.
• Baclofen pumps consist of a tube placed in the spinal canal to bathe the spinal cord with baclofen to reduce tone or spasticity. A delivery system is placed in the abdomen. Medication for pain can also be placed in these pumps either alone or in combination with baclofen for tone and pain control.
• Bladder and bowel stimulation to improve bladder and bowel function in men and women as well as sexual function in men.
• Nerve stimulators in the legs improve standing and walking function as well as muscle strengthening.

Some electrical stimulation is delivered by an electrode patch on the skin (transcutaneous) with an external unit to deliver the therapy. Others include implants within the body in the brain or on or close to the spinal cord.

Most often, individuals can have more than one electrical device implanted or used on the skin (transcutaneous). The devices are given separate frequencies so there is no miscommunication between the devices. This must be coordinated by your healthcare professional.

Today there are a variety of functional electrical stimulation treatments available with many more in research. Looking back over history, earlier devices consisted of electrodes placed on the skin to trigger specific muscles and nerves. The purpose was stationary bicycle riding to enhance muscle function, improve cardiac function, and improve the general health of individuals with mobility issues. As the process evolved, implanted devices were devised which could generate more electrical impulses over a wider area of the body. Now, transdermal (skin surface) electrodes are placed over areas of the spinal cord with similar results to implants but without complications of surgery. It is interesting to note that after the transdermal electrodes are turned off, there appears to be a ‘hangover’ time where the body still functions as if the stimulation is still turned on. Today, all these delivery systems are used based on the needs of the individual.

There are benefits to functional electrical stimulation. These include a cardiovascular workout, as the largest muscles in the body are in the thighs. Stimulating the thigh muscles provide that cardiovascular benefit. Bone density can be improved as the tendons pull on the bone with electrically stimulated movement. This provides bone strength. Muscles become bulkier, which reduces the risks of pressure injury. You still need to perform pressure releases and use pressure dispersing equipment, but muscles do provide some cushion to your boney prominences. Fat adds pressure to pressure points as it does not cushion but increases pressure. Range of motion can improve. Mental well-being can improve. Of course, the nerves are being stimulated below the level of injury, which improves the chance of getting messages to your brain as well as from your brain.

Risks of functional electrical stimulation include dislodging an unknown blood clot, or damage or pain if your joints are out of alignment. You must be medically cleared to undertake electrical stimulation to avoid hidden health issues.

Some individuals do not feel the effects of exercise as in fatigue. As with any physical effort, you must start slowly and build over time. This cannot be stressed enough. Episodes of autonomic dysreflexia (AD) as well as tone or spasticity, can interfere with your progress. More information about blood clots (deep vein thrombosis) and AD can be found here.