Electromyography
Electrodiagnostic testing of the peripheral nervous system is adjunct to patient history, physical exam, and other laboratory studies in the overall evaluation of neuromuscular disease. Although the nature of neurologic dysfunction for a specific diagnosis may be suggested by symptoms and signs of pain during the physical exam, electrodiagnostic testing frequently provides additional information that can be obtained in no other manner.The widespread use of electrodiagnostic testing is based on several principles:
- When used appropriately, it can result in markedly improved diagnostic accuracy and effective treatment.
- It provides quantitative data on the severity or prognosis of a disease process.
- It is an objective measure of neurologic function.
In the scope of a physiatrist's practice, the most commonly made electrodiagnoses are ulnar neuropathy, carpal tunnel syndrome, and cervical or lumbar radiculopathy. Other less common problems such as myesthenia gravis, myopathy and peripheral polyneuropathy can also be diagnosed using advanced electrodiagnostic techniques.
Electrophysiologic studies can be broken down into two major techniques. The first is nerve conduction studies, which are performed by stimulating a nerve at one point and measuring a response at another point. The speed of the impulse travelling along the nerve, whether the impulse is blocked at any point along its path, and whether there is normal transmission of the impulse from the nerve to the muscle are all questions answered by nerve conduction studies.
The second technique, needle electrode examination, is performed by inserting a small recording electrode into the skeletal muscle and recording the electrical activity present at rest and during voluntary activation of the muscle. Needle examination evaluates the following muscle characteristics: insertional activity, spontaneous activity, motor unit action potential shape and amplitude, and motor unit recruitment patterns. The information provided by the examination is complementary to that provided by the nerve conduction studies. In addition, needle electrode exam is a more sensitive technique when determining whether there is damage to the nerve itself.
Although some patients find these tests uncomfortable, many report that their level of anxiety was disproportionate to the actual level of discomfort experienced. In our attempt to decrease concern, MRA patients are provided with an informative, easy to read pamphlet which answers frequently asked questions and describes testing procedures.