Testing for Neurological Conditions
In order to correctly diagnose a neurological disorder many patients will be sent for a series of tests and neurologic studies. These tests include EMGs, NCS studies, EEGs, and IOM (Intraoperative Monitoring).
Two of these tests, an EMG and a NCS study are special tests used to detect neuromuscular disorders (nerve and muscle problems).
What is an EMG?
EMG (electromyography) studies the peripheral nervous system by evaluating the passive and active electrical discharges of the muscles.
Each muscle of the body is innervated by a specific nerve and nerve root. By testing muscles of each nerve root of interest, the physician may isolate the area of the spine, plexus, and/or distal nerve that has been damaged. EMG is performed by inserting a needle electrode into the muscle and recording motor unit action potentials during contraction and normal quiet baseline or abnormal positive sharp waves, fibrillations, and occasionally fasciculation’s during rest.
What is a NCS study?
NCS (nerve conduction study) evaluate the peripheral nervous system by testing the function of individual nerves. This is done by stimulating the nerve at a specific point and recording a response from a specific location. The latency, amplitude and conduction velocity of the response are measured and compared to the lab’s established normal values to determine whether there is a problem in the physiological function of the nerve. Both motor and sensory components of the nerve can be tested. The stimulation starts off with no current and is gradually increased until the best response is obtained.
What are these tests used for?
The EMG combined with the nerve conduction study will give a clear picture of the amount and location of peripheral nervous system damage.
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