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EEG is a diagnostic examination used to measure and record electrical activity of the brain over a short period of time. The examination consists of applying multiple electrodes on the scalp, which fire neurons within the brain. The examination typically requires 20-40 minutes plus preparation time. EEG exams are used clinically to:
- Distinguish/diagnose epilepsy
- Diagnose coma and as an adjunct test of brain death
- Diagnose encaphalopathies
An electromyogram (EMG) measures the electrical activity of muscles at rest and during contraction to determine whether they react in a normal or abnormal way. During an EMG a neurologist will insert sterile pins with microscopic electrodes on the tip into certain muscles of the patient’s limbs or back. This test can be helpful in evaluating the causes of numbness, tingling, pain, weakness, fatigue and muscle cramping.
Nerve Conduction Studies
A nerve conduction velocity test (NCV) is done by a neurologist or EEG technician who places several electrodes on the appropriate limb and then applies mild electric stimulus to the site. This test is often done at the same time as an EMG, in order to detect or rule out muscle disorders.
An evoked potential (EP) is a test to evaluate the condition of certain nerve pathways. The test quickly and safely measures the speed of the signals carried by the nerves. There are two types of EPs: brainstem auditory evoked potential (BAEP) and a visual evoked potential (VEP). During the procedure, a few electrodes are pasted on to the scalp while a mild "stimulus" (a clicking noise or a flashing checkerboard screen) is applied to the ears or eyes. The stimulus causes the nerves to react and send messages to the brain.
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