Background: Early secondary neurologic deterioration after aneurysmal subarachnoid hemorrhage (SAH) may have many causes including rebleeding, hydrocephalus, parenchymal hematoma, or seizures.
Methods: Case report.
Results: A 69-year-old woman presented with thunderclap headache and nausea. A head computed tomography (CT) showed SAH. On initial evaluation she was awake, alert, and confused without focal neurologic deficits. Two episodes of marked clinical deterioration occurred, manifesting as acute unresponsiveness and fixed anisocoria. Serial head CTs showed massive extension of hemorrhage into the brainstem parenchyma and ventricles.
Conclusions: Sudden clinical deterioration after SAH with coma and a fixed "blown" pupil may result from hemorrhage extension into the brainstem parenchyma rather than oculomotor nerve injury from compression or stretch.