Evaluation of SEP grading and prognosis of severe TBI patients in long-term unconscious state

Objective To evaluate the consciousness prediction of somatosensory evoked potentials in(SEP) patients with severe traumatic brain injury(TBI).Methods A consecutive sample of 46 patients after severe TBI with disturbance of unconsciousness 1 week from Jan.2001 to Aug.2008 were recorded.Six prognostic factors including age,gender,operation,mechanism of injury,classification of SEP,duration of unconsciousness and history of temporal craniectomy were selected and analyzed in the 46 cases.The SEP was classified into 3 grades according to the presence of N20-P25 wave.GradeⅠ: bilateral N20 waves existed,(1)bilateral N20 waves were normal and symmetrical;(2)bilateral N20 waves were normal but asymmetrical.GradeⅡ: unilateral N20 wave existed,the other side disappeared.Grade Ⅲ: bilateral N20 waves disappeared.The prognosis of outcome was judged by Glasgow Outcome Scale(COS).Results Classification of SEP had significant correlation with the probabilities of awakening and the Glasgow Outcome Scale(P0.05).The SEP grade was negatively related with the probabilities of consciousness and the GOS.The other factors including age,gender were excluded(P0.05).Duration of unconsciousness was not correlated with these factors like gender,age,mechanism of injury,classification of somatosensory evoked potentials as well as history of temporal craniectomy.The accuracy of predicting the outcome of consciousness was 78.26%,the sensitivity and the specificity was 80.77% and 75%,respectively.Conclusion The classification of SEP grading can objectively and accurately demonstrate the outcome of unconscious patients and probabilities of their consciousness.