Early magnetic resonance imaging of brainstem lesions after severe head injury

Object. The availability of magnetic resonance (MR) imaging data obtained i n comatose patients after head injury is scarce, because MR imaging is some what cumbersome to perform in patients requiring ventilation and because, i n the first hours after injury, its relevance is clearly inferior to comput erized tomography (CT) scanning. The authors assessed the value of MR imagi ng in the early postinjury period. Methods. In this prospective study MR imaging was performed in 61 consecuti ve patients within 7 days after they suffered a severe head injury. An init ial CT scan had already been obtained. To understand the clinical significa nce of the lesions whose morphological appearance was identified with MR im aging, brainstem function was assessed by registration of somatosensory and auditory evoked potentials. Brainstem lesions were visualized in 39 patients (64%). Bilateral pontine l esions proved to be 100% fatal and nonbrainstem lesions carried a mortality rate of 9%. In singular cases circumstances allowed for a clear clinical distinction be tween primary and secondary brainstem lesions. On MR imaging all lesions we re hyper- and hypointense after intervals longer than 2 days. Within shorte r intervals (< 2 days) after the injury, primary lesions appeared isointens e on MR imaging. in one secondary brainstem lesion there were no traces of blood. Conclusions. Because mean intracranial pressure (ICP) levels in patients wi thout brainstem lesions were similar to those in patients with brainstem le sions, the authors conclude that it was not mainly increased ICP that accou nted for the high mortality rates in patients with brainstem lesions. The authors also conclude that brainstem lesions are more frequently found in severe head injury than previously reported in studies based on neuropat hological or CT scanning data. Early MR imaging after head injury has a hig her predictive value than CT scanning.