Evoked potentials in acute head injured patients with MRI-detected intracerebral lesions

Background. Magnetic resonance imaging (MRI) allows precise detection of intracranial lesions in head injured patients. We compared intracranial lesions detected in MRI to somatosensory evoked potentials (SEP) and brainstem auditory evoked potentials (BAEP) concerning their prognostic value. Methods. Thirty patients with traumatic brain injury and prolonged recovery were studied. Size, side and number of 474 intra-and extraparenchymal lesions as well as lesion localisation based on a specific anatomical classification were entered into a database (a total of 7080 data). In addition, we recorded median-nerve SEP (M-SEP), tibial nerve SEP (T-SEP) and BAEP in all of the patients. Findings. M-SEP and Glasgow-Outcome-Score (GOS) one year after injury correlated significantly to patients with lesions in the brainstem (p < 0.0001) and corpus callosum (p < 0.001). Similar results were found for T-SEP (p < 0.0001). All patients with bicortical loss of M-SEP had an unfavourable outcome (GOS 2). Among the analysis of lesion volume, only the volume of brainstem lesions correlated to GOS (p < 0.001), but this was not found for callosal lesions. However, comparing the vegetative (GOS 2) to the nonvegetative group (GOS 3-5), for both callosal (p <less than> 0.02) and brainstem (p < 0.005) lesions a significant correlation was found. Interpretation. MRI does not improve the prognostic reliability of SEP in head injury but offers possibilities for clarifying electrophysiological and clinical pathologies. This explains that the volume of brainstem lesions, essentially influencing the clinical outcome, is strongly correlated to T-SEP and M-SEP. In contrast, callosal lesions did not show a clear relationship to outcome despite large callosal lesions (> 4 ml) which tended to poor outcome. In conclusion, we suggest that MRI and SEP are supplementary to each other concerning prognostic evaluation.