Evoked Responses - Brain Stem

Auditory brain stem responses provoked by discreet sounds delivered to the ears through headphones.  These sound waves are converted to nerve impulses by receptors in the ear.  A machine is used to test whether the brain stem has received the signals.  The quality of the brain stem’s response in a comatose patient is thought to be an important indicator of the degree and site of brain injury.  Because this test requires very specialized and expensive equipment, it is not available in all hospitals.  A more common test is the EEG.