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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.

A national group of neurologists and ophthalmologists have evaluated guidelines and recommendations for diagnosis, treatment and follow up of optic neuritis based on clinical experience and a review of relevant literature. Optic neuritis is a common, well characterised condition that appears as an isolated syndrome or as a manifestation of multiple sclerosis. Several other diseases must be considered for a differential diagnosis. Corticosteroid treatment of optic neuritis has been investigated in a number of trials, which show that corticosteroid treatment speeds up the recovery of vision without affecting the final visual outcome. The diagnostic procedure and the treatment options have changed over the last few years. Some aspects of investigation, treatment and follow up are still controversial.

In this article we describe five patients with acute or subacute weakness of flexor pollicis longus and flexor digitorum profundus. A possible diagnosis of an isolated lesion (entrapment) of the anterior interosseus nerve was considered. However, clinical and neurophysiological findings suggested a diagnosis of neuralgic amyotrophy. Three patients experienced acute shoulder pain at the onset. Sensory loss at the base of the thumb was observed in two patients, and two patients were affected bilaterally. All patients had EMG signs of involvement outside the anterior interosseus nerve innervation area. Low amplitude sensory action potentials were observed in three patients. One patient was operated upon and entrapment was not observed during surgery. Reinnervation was not seen after five months, but was noted in three patients who were investigated 13, 13.5, and 30.5 months after the onset. Thus, the prognosis in this unusual form of neuralgic amyotrophy seems to be rather good, and the length of time before reinnervation supports the theory that the site of the lesion must be located proximally, e.g. in the brachial plexus.