Significance and clinical suggestions for the Somatosensory Evoked Potentials increased in amplitude revealed by a large sample of neurological patients

Abstract

Background and purpose So far, giant Somatosensory Evoked Potentials (SEPs) in amplitude are usually related to the presence of cortical reflex myoclonus and epilepsy, even if growing evidences lead to rethink about their significance. To investigate the relationship between N20-P25 peak-to-peak amplitude (N20p-P25p) of SEPs and the occurrence of abnormalities of the sensory pathways and of myoclonus/epilepsy, in 308 patients with increased SEPs amplitude from upper limbs stimulation Methods We compared N20p-P25p in different groups of patients identified by demographic, clinical and neurophysiological factors and performed a cluster analysis for classifying the natural occurrence of subgroups of patients. Results No significant differences of N20p-P25p were found among different age-dependent groups, and in patients with or without PNS/CNS abnormalities of sensory pathways, while myoclonic/epileptic patients showed higher N20p-P25p than other groups. Cluster analysis identified four clusters including patients with myoclonus/epilepsy, patients with CNS abnormalities, patients with PNS abnormalities, patients with neither myoclonus nor CNS/PNS abnormalities. Conclusions Increased N20p-P25p correlated to different pathophysiological conditions: strong cortical hyperexcitability in patients with cortical myoclonus and/or epilepsy and enlarged N20p-P25p, while milder increase of N20p-P25p could be underpinned by plastic cortical changes following abnormalities of sensory pathways, or degenerative process involving the cortex. SEPs increased in amplitude cannot be considered a specific correlated for myoclonus/epilepsy, but it in several neurological disorders may represent a sign of adaptive, plastic and/or degenerative cortical changes