Somatosensory evoked potentials in prolonged postcomatose unawareness state following traumatic brain injury

Somatosensory evoked potentials (SEPs) were found by several authors to have a prognostic value in traumatically brain-injured (TBI) patients and can serve for monitoring changes in the state of TBI patients. Most of the studies were performed in the acute phase of trauma and most of reports have dealt with the short-latency components. The present study reports on seven patients (mean age 26.2 years) who suffered severe blunt TBI and were in prolonged post-comatose unawareness (PCU) state, in whom early and late SEP components were recorded at least 5 weeks after sustaining trauma. The SEPs studied could not reveal a uniform pattern apart from prolonged central conduction time (CCT), which was common to all patients. This may be due to individual non-homogeneous patterns of brain damage in our severe TBI patients. Meaningful late recovery of consciousness occurred in one patient and correlated with shortening of CCT. We suggest that the prolonged CCT found in our patients is related to diffuse subcortical axonal injury and that the shortened CCT found during the second examination in this patient actually reflects late partial recovery--either structural or functional--of affected brain regions. This patient is also an example of the possible relationship between reduction of CCT and recovery of consciousness a long time after injury.