Diagnostic Testing

Electromyography (EMG)

Electromyography (EMG) is a diagnostic exam that evaluates the health of the muscles and the nerves that control them by measuring muscle electrical activity. This test is most commonly performed to determine the cause of muscle weakness and identify cases that are caused by neurologic disorders such as carpal tunnel syndrome, peripheral neuropathy and others rather than primary muscle conditions. 

During the EMG exam, thin needle electrodes are inserted through the skin and into the muscle, where they detect electrical activity while the muscle is at rest and contracting. Patients may experience mild pain when the electrodes are inserted, but this is tolerable for most. This test is usually performed in conjunction with a nerve conduction velocity test. 

Normal results of an EMG test indicate muscles that do not produce any electrical activity while at rest and progressively increases with contraction. After the test, patients may experience feelings of tenderness or bruising on the affected muscle.

Evoked Responses

An evoked response study is a diagnostic procedure that measures electrical activity in the brain as it responds to signals from the sight, sound and touch senses. This allows doctors to assess hearing or sight (especially useful when performed on infants), diagnose optic nerve disorders or detect tumors within the brain or spinal cord.

There are several different types of evoked response studies available that can test for different problems. The three major tests include:

  • Visual Evoked Response (VER) Test - This test diagnoses problems within the optic nerve by placing electrodes on the scalp as the patient watches patterns appear on a screen. The electrical responses are then recorded.
  • Brainstem Auditory Evoked Response (BAER) Test - The BAER test detects a patient's ability to hear and is also effective in detecting brain stem tumors and diagnosing multiple sclerosis. During this test, electrodes are placed on the scalp and earlobes and subtle noises are delivered to one ear.
  • Somatosensory Evoked Response (SSER) Test - This test detects abnormalities within the spinal cord by attaching electrodes to the wrist, knee and other locations. A mild electrical signal is then sent to these areas and the brain's response is recorded.

While these tests are effective in detecting abnormalities within the sensory functions, they often cannot determine the cause of the abnormality, so additional testing may be required. 

These procedures are considered safe for most patients and are not associated with any serious complications.

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