Motor and somatosensory evoked potentials in coma: analysis and relation to clinical status and outcome.

Abstract

Central sensory and motor conduction were studied in 23 comatose and three brain-dead patients. Motor evoked potentials (MEPs)

How reliable is the predictive value of SEP (somatosensory evoked potentials) patterns in severe brain damage with special regard to the bilateral loss of cortical responses?

“…Our findings of a highly significant correlation of initial SEP scores with later outcome (measured by the GOS) correspond well with the results of earlier studies [1][2][3][4][5][6][7][8][9], demonstrating the predictive value of median nerve SEP recording in the early phase of posttraumatic coma for both a favorable and an unfavorable prognosis, even during treatment with sedatives and muscle relaxants. As the severity of evoked potential abnormalities (SEP score according to Anderson et al [1], CNC, am- plitude ratio N20/N13) increased in our study, favorable outcomes decreased.…”

“…Under these conditions, somatosensory evoked potentials (SEP) after median nerve stimulation correlated best with later prognosis and neurological deficit [1][2][3][4][5][6][7][8][9], comparable to other neurophysiological, neuroradiological, or clinical features [10]. The following SEP criteria have been suggested to define the extent of cortical and brainstem dysfunction: (a) (NC) central nerve conduction time (between lower brainstem and cerebral cortex) [4,6]; (b) amplitude ratio cortical N20/cervical N13 [1,11]; (c) complex SEP scoring, integrating the criteria above particularly with the presence or loss of the primary cortical response N20/P25 [1,6].…”

Current density threshold for the stimulation of neurons in the motor cortex area

“…To come to an understanding of the actual electromagnetic sensitivity of the brain and subsequently to determine a current density threshold for the excitation of neuronal structures in the motor cortex area, reliable and reproducible effects must be examined. In clinical practice, such effects are already used for the diagnosis of nerve lesions and neuropathy, e.g., by the measurement of the conduction latency, response amplitude, and threshold of stimulation, by means of transcranial magnetic stimulation (TMS) and electrical transcranial stimulation [Annions et al, 1991;Murray, 1991;Ying et al, 1992;Brunholzl and Claus, 1994;Ho et al, 1999].…”

Therapeutic hypothermia does not diminish the vital and necessary role of SSEP in predicting unfavorable outcome in anoxic-ischemic coma

“…Numerous studies confirm that the absence of short-latency N20 cortical potentials in normothermic patients are associated with a uniformly unfavorable prognosis [16,17,[32][33][34][35][36][37][38][39][40][41][42][43][44][45][46]. Robinson et al performed a meta-analysis of 336 normothermic patients with absent cortical SSEP after day 1 and all died or became vegetative [44].…”