The brainstem auditory evoked response (BAER) test measures brain wave activity that occurs in response to clicks or certain tones.

You lie on a reclining chair or bed and remain still. Electrodes are placed on your scalp and on each earlobe. The earphones give off a brief click or tone. The electrodes pick up the brain's responses to these sounds and record them.

You may be asked to wash your hair the night before the test.

There is little discomfort.

The test is performed to help diagnose nervous system abnormalities and hearing losses (especially in low birth weight newborns), and to assess neurological functions.

The auditory brain stem values are in a normal range. This range varies among patients and instruments used.

Abnormal findings may indicate a hearing loss, multiple sclerosis, or stroke.

Additional conditions under which the test may be performed:

• Acoustic neuroma
• Central pontine myelinolysis

There are no risks.