The Findings of Brainstem Auditory Evoked Pontential(BAEP) and Somatosensory Evoked Potential(SSEP) in Head Injury

ABSTRACT

There were 84 cases of brainstem auditory evoked potential(BAEP) and 90 cases of somatosensory evoked potential(SSEP) from the 124 cases of head injury. The studies were performed within the first three days after head injury in most cases and after ten days in emergency operative cases. The results of BAEP and SSEP studies recorded from 67 normal volunteers were used as a control group. The latency, amplitude and wave pattern of the evoked potential were examined and a peak or interpeak latency were considered abnormal when it exceeded the corresponding mean(2SD found in the control group. The wave patterns were arranged in BAEP as grade Iall waves were normal; grade II waves I, II, III were abnormal;grade IIIwaves IV, V, VI were abnormal;grade IVall waves were abnormal. In SSEP as grade Iall waves were normal;grade IIN13 wave was abnormal;grade IIIN19wave was abnormal;grade IVall waves were abnormal. The abnormal findings by percentage were47.6% in latency of BAEP, 68.9% in latency of SSEP, 49.4% in wave pattern of BAEP and 87.8% in wave pattern of SSEP. The BAEP was superior to SSEP in correlation to clinical parameters including GCS, duration of coma, basal cisterns in initial brain CT scan and Glasgow outcome scale(GOS). As a BAEP criterion, the wave V latency and the BCT(III-V interpeak latency) and as a SSEP criterion, the central conduction time(N19-N13) were more correlated to duration of coma and GOS. The appearance of the basal cisterns on initial brain CT is significantly correlated with wave V and BCT of BAEP only. Grade I and II were reliable predictors of a good prognosis. Therefore, we concluded that BAEP and SSEP are adjunctively diagnostic tests for determining the outcome of head injuried patients.