Teaching Neuro Images : Traumatic blown pupil without herniation

A 29-year-old man was struck by a car and presented with coma and a fixed, dilated left pupil without oculomotor palsy (figure 1). A head CT revealed central midbrain hemorrhage in the absence of uncal herniation (figure 2). Intracranial pressure was normal. At 6 months, he had regained consciousness and reactivity of the left pupil, and was independent in activities of daily living. The syndrome of acute traumatic midbrain hemorrhage is a rare form of coma and abnormal pupils.1 The unreactive pupil and lack of oculomotor palsy in our patient reflect the somatotopic map within the midbrain, namely, that pupillomotor axons from the Edinger-Westphal nucleus run rostral and medial to the oculomotor fibers that eventually comprise the oculomotor nerve.2