Evoked potential tests in clinical diagnosis

Abstract

BACKGROUND Evoked potentials (EP) are used to demonstrate conduction disturbances in the central nervous system. This paper provides an overview of the areas in which EP is 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 neurophysiological diagnostics.RESULTS Somatosensory evoked potential (SEP) can provide reliable prognostic information about failure to return to 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, SEP and brainstem auditory evoked potential (BAEP) provide information about which sensory brainstem paths are damaged, which can also be useful for planning rehabilitation. Normal SEP and BAEP 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 CNS lesions and be a supplementary test in the diagnosis of multiple sclerosis.INTERPRETATION SEP and BAEP have a high clinical value for comatose patients. Evoked potentials are also important in intraoperative monitoring. The clinical value of VEP is high when the question of a history of optic neuritis is crucial for a diagnosis of multiple sclerosis. Some selected patients who are being assessed for demyelinating disease will benefit from a full EP study.