Acute traumatic midbrain hemorrhage.

A syndrome resulting from traumatic midbrain hemorrhage is described in 5 patients, 3 of whom had intracranial pressure measurements and 2 of whom had pathological examinations. The major clinical signs, evident immediately after injury, are coma, dilated (4 to 8 mm diameter) pupils that are fixed to light and dark, diminished limb tone, and impaired horizontal eye movements. The hemorrhages are single and linear or oval-shaped in the midsagittal rostral midbrain, extending several millimeters bilaterally. The appearance of the hematoma may be delayed on computed tomographic scanning, but early abnormalities of wave V of the brainstem auditory evoked potentials aid in diagnosis. Pathological features suggest that secondary brainstem distortion occurred soon after injury, perhaps resulting from a transiently raised intracranial pressure, but shearing injuries caused by acceleration-deceleration forces were also found.