Evoked Potentials in Nondemyelinating Diseases

Evoked potentials (EPs) represent the only noninvasive method available to assess in “real time” the processing of sensory information in the human central nervous system. Most of the successes of this low cost investigation in clinical practice is due to its ability to disclose silent lesions causing delayed response in demyelinating diseases. In nondemyelinating processes the clinical appUcations of EPs have not yet been clearly defined; however in such diseases, EPs may be helpful: 1) to test sensory functions when clinical examination is not reliable (young children, comatose patients, suspected conversion disorder); 2) to decide whether more sophisticated or more invasive morphological investigations should be entertained in patients with purely subjective symptoms; 3) to assess the causative mechanisms of the neurological deficit or of the functional recovery. There are two questions that should be discussed before looking at the diagnostic yield of EPs in nondemyelinating processes: what is the specificity and localizing value of abnormal EP patterns? Is it possible to give unequivocal pathophysiological interpretation of abnormal waveforms?