Evoked potential tests in clinical diagnosis.

BACKGROUND

Evoked potentials are used to detect conduction disturbances in the central nervous system. This paper provides an overview of the areas in which evoked potentials are used in clinical neurophysiological diagnostics, with the emphasis on coma and demyelinating disease.

METHOD: The article is based on a literature search in PubMed and the authors' long experience of neurological and neurophysiological diagnostics.

RESULTS

Somatosensory evoked potential (SEP) can be a reliable predictor of failure to regain consciousness as early as 24 hours after anoxic coma has occurred. If coma is caused by a brain trauma, cerebrovascular episode or other neurological disease, information about which sensory brainstem pathways are damaged can be obtained from somatosensory evoked potentials and brainstem auditory evoked potentials (BAEP), which can also be useful for planning rehabilitation. Normal SEP and BAEP findings in cases of coma caused by trauma are associated with a favourable prognosis. Visually evoked potential (VEP) can often reveal signs of a history of optic neuritis. SEP and BAEP can also reveal subclinical lesions in the central nervous system and be a supplementary diagnostic test for multiple sclerosis.

INTERPRETATION: The clinical value of SEP and BAEP is high in coma cases. Evoked potentials are also important in intraoperative monitoring. The clinical value of VEP is high when a history of optic neuritis is a deciding factor for a multiple sclerosis diagnosis. Some selected patients who are being assessed for demyelinating disease will benefit from a full EP study.