Somatosensory evoked potentials in chronic inflammatory demyelinating polyradiculoneuropathy.

Abstract

Somatosensory evoked potentials (SEPs) offer complementary results to those of nerve conduction studies and contribute to the electrodiagnostic criteria of chronic inflammatory demyelinating polyradiculoneuropathy. We performed nerve conduction studies and SEPs in patients with symmetrical motor weakness, areflexia, and/or sensory disturbances lasting for at least 8 weeks. We determined two groups according to the electrodiagnostic criteria of the European Federation of Neurological Societies. Group 1 included patients who met the definite or probable electrodiagnostic criteria, and group 2 included patients who met the possible electrodiagnostic criteria. We also compared SEPs results with those of controls (group of healthy subjects). Sixteen patients (14 men; mean age, 59 ± 17.3 years) were included in the study. The latencies of potentials N9, N13, N7, and N22 and the intervals N9-N13 and N7-N22 were significantly increased in patients compared with controls. The N9/iP14 amplitude ratio was significantly lower in patients. There was no significant difference in the latencies of SEPs between the two groups of patients. We confirm the contribution of SEPs as complementary information to nerve conduction studies in chronic inflammatory demyelinating polyradiculoneuropathy diagnosis. In addition to the usual abnormalities, a decrease in the N9/iP14 amplitude ratio could potentially be used as an electrodiagnostic criterion.