Asked if they've had nerve conduction studies previously, some patients in my neurological practice answer, "I'm not sure."My response: "Then you probably haven't." Nerve conduction studies are generally memorable. And it's not because they're particularly painful or otherwise unpleasant. (They're not.) Rather, it's because they're completely unlike any other medical test in existence.
The uniqueness of nerve conduction studies is also their advantage. They have
ability to look at certain medical conditions from a point of view completely different from that of other tests, and can therefore discover and pinpoint problems that are invisible to other tests.
Nerve conduction studies are usually requested to help diagnose nerve and muscle disorders. They are often paired with electromyographic (EMG) studies, performed during same testing session by same physician and making use of same equipment.
Nerve conduction studies evaluate physiology and functioning of peripheral nerves. Unlike scans or x-rays that evaluate anatomy and structure, nerve conduction studies look at nerves' performance.
How is this done? In a nutshell, a brief electrical pulse or shock is applied through a pair of electrode probes to skin overlying a nerve, generating a precisely timed set of nerve-impulses. With another electrode taped to skin over another portion of same nerve or over a muscle connected to nerve being studied, physician can measure how quickly nerve-impulses travel from point of stimulation to point of recording.
In healthy nerves nerve-impulses travel at a rate of 40-60 meters per second (120-180 feet per second) so that only a few thousandths of a second are required to cover a distance of several inches. In order to capture a signal traveling that fast, an oscilloscope is required.
The two most important features of recording are length of time required to traverse nerve-segment in question and size or amplitude of resulting electrical response. Electrical responses recorded from nerves are typically 2-50 millionths of a volt in amplitude, while responses from muscles are typically 1-20 thousandths of a volt.
The body's peripheral nerves are like telephone cables bundling together numerous individual fibers. Some of nerve-fibers carry instructions from brain and spinal cord to muscles, causing them to contract. These are called motor nerve-fibers. Sensory nerve fibers, often intermixed with motor fibers in same nerve-bundle, carry messages in opposite direction, informing spinal cord and brain about stimuli—such as touch, pain and temperature—generated in skin, joints and other peripheral tissues.
