Galvanic vestibular tests in the assessment of coma and brain death.

Galvanic stimulation over the mastoid process elicits oculovestibular responses that provide a measure of brainstem function. The equipment is simple and is available in most neurodiagnostic laboratories. This type of test provides an advantage over caloric testing in the presence of external and middle ear disease and basal skull fracture and can be a useful adjunct in the evaluation of coma and brain death.