Idiopathic Normal Pressure Hydrocephalus with Brain Herniation into the Arachnoid Granulation of the Lateral Lacuna of the Superior Sagittal Sinus: A Case Report.

Idiopathic normal pressure hydrocephalus is a disease of unknown cause that occurs in people aged 60 years or older and causes gait disturbance, cognitive decline, and urinary problems. A 63-year-old man with untreated diabetes presented with unsteady gait and amnesia. Head magnetic resonance imaging revealed disproportionately enlarged subarachnoid-space hydrocephalus and brain herniation into the para-superior sagittal sinus arachnoid granulation. Although the patient experienced generalized convulsions immediately before surgery, a lumbo-peritoneal shunt was performed, and symptoms improved. These brain herniations into the arachnoid granulation might accelerate the pathology, and idiopathic normal pressure hydrocephalus with brain herniation into the arachnoid granulation of the lateral lacuna of the superior sagittal sinus is extremely rare and has not been reported previously.