by S. Todd Stolp MD
©December 2008
Reading “Batteries Not Included” when one is preparing to bring a device to life can inspire disappointment. On Christmas morning, surrounded by children with giddy expectations, a battery deficiency can lead to downright panic. Nevertheless, we have a pretty clear understanding that most hi-tech devices these days require some source of electricity to do their magic. It may not be as clear that our own nervous systems are equally as dependent upon electricity. In an organism, the electrical charges are generated by the elegant movement of salts across membranes, but the principles otherwise follow the same rules as the electrical systems in our homes and appliances. Therefore, many of the nervous system diseases would make perfect sense to an electrician.
In the 1800s, Lord Kelvin conducted experiments to describe how electrical signals decayed as they were conducted through transatlantic underwater telegraph cables. In the early 1900s, the same formulas were found to accurately describe the way signals were transmitted through our nerve fibers. It was determined that many of our nerves, much like the electrical cords on a T.V., are covered with insulation in order to increase the speed of conduction and diminish the loss of electrical energy as the signals travel to our muscles or sensory machinery. Once an electrical signal comes to the end of a fiber in a particular nerve cell, the signal is passed on to the next nerve or muscle cell across a microscopic gap via chemicals that act like an elbow in the ribs. Thus, the signal travels on throughout the system to have its intended effect, whether to raise a cup of coffee to the lips or remember a figure for your checkbook.
The disease “Multiple Sclerosis” results from the loss of insulation from nerve fibers scattered throughout the central nervous system (the brain or spinal cord). As a result, various malfunctions begin to occur in different locations controlled by the affected areas of the brain, or less frequently the spinal cord. Typical early symptoms can be perplexing, with difficulty speaking, problems with vision, loss of coordination, muscle spasms, numbness, tremors (fine shaking) or even personality changes. This condition may be progressive, or it may progress to a point and become relatively quiescent. Newer treatments promise to benefit some patients with this disorder.
Another similar condition known as “Amytrophic Lateral Sclerosis” (also known as ALS or Lou Gehrig’s disease) occurs in the spinal cord or brain stem and typically first involves the arms, legs or speech and swallowing functions. This condition is also slowly progressive and not yet well understood.
A more common slightly different condition is called “peripheral neuropathy,” and involves damage to the nerves that travel throughout our bodies outside of the central nervous system. Most people with peripheral neuropathy find that the earliest symptoms occur in the feet or legs because the longest nerves in our bodies provide service to those locations, and the longer the nerve the greater is the amount of nerve tissue available to be targeted by the malady. This is the type of neuropathy that people with diabetes may experience, and usually causes symptoms of numbness or tingling. Other people develop neuropathy with no other underlying illness. Special testing, called a “nerve conduction test,” by a neurologist can usually detect abnormalities in peripheral nerves at an early point.
Other people with peripheral neuropathy may have symptoms that result from repeated injury to the nerve due to physical work. There is a place in the wrist called the “carpal tunnel’ through which a nerve passes that supplies sensation and some muscle function to the thumb and first two fingers. Some people who use power tools or use their wrists for much of their work day may develop pressure on the nerve in this tunnel, leading to weakness, numbness and tingling in the hand affecting those three fingers, called “carpal tunnel syndrome.”
Perhaps the most well known neurologic disorder is the seizure disorder. This is a condition in which electrical activity in the brain produces a discharge of a large number of the nerve cells. In some patients the brain electrical activity may simply travel to limited areas causing symptoms of eye-blinking, temporary inattention or limited movements of a hand or limb. In other patients the electrical discharge may travel throughout a large portion of the brain, causing loss of consciousness, loss of urine and/or an alarming shaking movement of the arms and legs (a generalized seizure). While frightening to witness, if you should see a person having this type of seizure, simply keep the person from falling or hurting themselves on surrounding objects and call for help if the patient fails to recover after 4 or 5 minutes. Virtually any person can be induced to have a seizure if the nerve cells are irritated enough by a high fever, a toxin, an electrical shock or even by temporary loss of circulation. People with a seizure disorder simply possess an area in the brain with a greater than usual amount of irritability. To control seizures, therefore, these people often take medications which diminish the irritability of those nerve cells.
When we think about how quickly we respond to setting our fingers on the stove burner, we can be grateful that our nervous systems work with the assistance and speed of electricity. Now if we could just reboot ourselves on a day when the old mother board is not up to speed…