Central somatosensory conduction after head injury

Abstract

In 94 patients with head injuries, conduction between the lower brainstem and the cerebral cortex was studied by recording evoked potentials from the scalp and neck following stimulation of the median nerves. A conduction time 3 SD or more above the normal mean (5.74 +/- 0.46 msec) or the absence of an evoked potential over one or both hemispheres was considered abnormal. During successive periods in the first 35 days after injury, the evoked potentials correlated with the outcome (classified as good or not good) in 75 to 84% of patients. Within 3 1/2 days the outcome was correctly predicted in 38 of 49 patients (78%). Six of the 7 surviving patients with persistent asymmetries of the cerebral evoked potentials remained hemiplegic. Serial studies over one year showed that both conduction time and amplitude recovered exponentially over many months, but differences persisted between the patients who made a good recovery and those who remained disabled.

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]. In the literature, primary bilateral loss of cortical responses (BLCR) is regarded as one of the best prognostic indicators, predicting that most of the patients will die or the outcome will be a persistent vegetative state at best [11].…”

Severe brain injury in children: long-term outcome and its prediction using somatosensory evoked potentials (SEPs)

“…In the remaining 105 children SEPs were recorded within the first week of admission (median 16.8 h, range 1±163.5 h). Causes of brain injury were trauma (40), hypoxic-ischaemic encephalopathy (38), infection (18) and other (9). The latter group included haemorrhage (6), emboli (1), cerebral vasculitis secondary to haemolytic uremic syndrome (1) and septic shock (1).…”

The Effect of Experimental Concussion on Somatosensory Evoked Potentials

“…1973;Ommaya and Gennarelli, 1974). More recently, evoked piitentials have been used to study the later stages of head injuries, and in some of these Shaw, 1979: Hume andCant. 1981) evidence of delayed transmission of somatosensory information to the primary sensory cortex has been found.…”