Assessment of Brainstem Distortion Associated with Supretentorial Lesions by Magnetic Resonance Imaging

Summary

Quantitative measurements of brainstem distortion and neural dysfunction were obtained in 25 cases of chronic subdural hematoma. The horizontal and rotational brainstem displacements were measured on axial and coronal magnetic resonance (MR) images in all patients pre-operatively, and brainstem auditory evoked responses (BAERs) were obtained in 11 cases. Logarithmic relationships were noted on both horizontal and rotational displacements of the brainstem and cerebrum. The type of shift changed in the rostro-caudal direction, and the difference in magnitude of distortion between cerebrum and brainstem results in midbrain kinking. The prolongation of BAER latencies and central conduction times correlated with septum shift. The results of peak-V latency indicated that brainstem rotation in the coronal plane reflects upper brainstem dysfunction most closely. This study presents objective measurements of brainstem displacement as noted on MRI, and clarifies the relationships between anatomic and physiologic changes in the brainstem that are associated with supratentorial lesions. These results suggest the importance of brainstem distortion itself affecting on brainstem dysfunction with or without transtentorial herniation.