Central somatosensory conduction after head injury.

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.