Ischemic Stroke of Midbrain and Cerebellum Involving Reticular Activating System.

The reticular activating system is the part of the brain that maintains the sleep/wake cycle. Any damage to this region can cause hypersomnolence and drowsiness along with altered sensorium. This case presents a patient with cerebellar and midbrain stroke with infarct of the reticular activating system, leading to hypersomnolence, drowsiness, and altered sensorium.