Dissociation of somatosensory and motor evoked potentials in non-comatose patients after head injury

Objectives: This study was performed to evaluate the clinical value of comb ined use of somatosensory evoked potentials (SEPs) and motor evoked potenti als (MEPs) in patients with different brain lesions after head trauma. Methods: A total of 64 patients with minor and moderate head injury were in vestigated by means of SEPs recorded over the parietal and frontal areas an d MEPs following single-pulse transcranial magnetic stimulation (sTMS) and slow-rate repetitive transcranial magnetic stimulation (rTMS). Results: in almost 50% of the patients, a dissociated impairment of somatos ensory and motor evoked potentials was found. This dissociation was related to different distribution of SEP and MEP abnormalities in head injury subg roups. The higher threshold to sTMS and increased variability of the MEP am plitude during slow-rate rTMS were the most prominent features in patients with focal brain contusions, suggesting impairment of the cortical excitabi lity. SEP abnormalities, as well as central conduction impairments, were mo re noticeable in patients with diffuse brain injury. Conclusions: A combined analysis of SEPs and MEPs may improve the assessmen t of cortical dysfunctions and central conduction abnormalities in non-coma tose patients with head injury. A slow-rate rTMS may be considered as a com plementary technique to the evaluation of the threshold in assessment of th e excitability of the motor cortex in minor and moderate head injury. (C) 1 999 Elsevier Science Ireland Ltd. All rights reserved.