When to have a Electrodiagnostic Study?
The most frequent symptoms for a referral for an electrodiagnostic study involve numbness, tingling, weakness, fatigue, radiating and burning pain, muscle cramping and muscle atrophy. The most common neuromuscular disorders tested include nerve entrapments such as carpal tunnel and cubital tunnel syndromes, lumbar or cervical radiculopathies, polyneuropathy, plexopathy, myopathy or neuromuscular junction disorders such as myasthenia’s gravis. The study is considered to be most accurate once three weeks have passed since the symptoms first occurred, however it can be done at anytime.
What is a electrodiagnostic study and how is it done?
Electrodiagnostic studies are usually performed by either a Physiatrist or a Neurologist and consist of two parts, the nerve conduction study (NCS) and the electromyogram (EMG). The nerve conduction study consists of recording the nerve production and velocity by applying several small shocks to a peripheral nerve with electrodes attached to skin. This records important information such as the amplitude and conduction velocity of a nerve at several locations along its path. This can provide information to diagnose nerve entrapments as well as axonal loss of a nerve. The electromyogram is the second part of the test and is usually much shorter in duration than the nerve conduction portion of the study. This involve using a fine needle (27 gauge needles are used in our office) to analyze the electrical activity of the muscle in resting state and activated states.
what occurs during an electrodiagnostic consultation?"
A complete history and physical examination will be performed to determine whether the study is appropriate to perform and if so which nerves and muscles should be studied. In essence the electrodiagnostic study is considered to be an extension of the history and physical exam. A differential diagnosis is considered based on the symptoms. For example, a patient presents with hand weakness and 4th & 5th digit numbness and tingling. Specific nerves and muscles will be tested to determine if this is a focal entrapment of the ulnar nerve, a lower trunk brachial plexopathy or a C8/T1 radiculopathy. Moreover, the test can localize an ulnar neuropathy to either the elbow or the wrist and determine the severity. The nerve conduction portion of the study is typically performed first followed by the electromyogram portion of the study. The test is not usually considered to be painful but at times may cause a little temporary discomfort. When the study is finished, we generally will discuss the results with you.
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