[Intracranial hypovolemic syndrome with subdural hygroma developed massive hematoma: timing of treatment and histology of dural hypertrophy].

We report a case of a 43-year-old man treated by craniotomy for chronical subdural hematoma (CSH) due to spontaneous intracranial hypovolemia. The patient complained of sudden onset severe headache. Initial CT scan showed normal brain structure, and his headache improved with bed rest in a few days. However, MR images obtained for vertigo one month later demonstrated bilateral subdural hygroma extending to the supracerebellar space and diffuse dural enhancement after gadolinium infusion. We diagnosed bilateral subdural hygroma due to spontaneous intracranial hypovolemia, and observed him conservatively. Four months after onset, he complained of severe headache again and MR images revealed enlargement of bilateral CSH with mass effect, which had heterogenous intensity on the right convexity. We evacuated hematoma on the right by craniotomy and aspirated the left side hematoma using a burr hole. His headache improved 2 weeks after the operation with strict bed rest. The follow-up MR images showed disappearance of abnormal meningeal enhancement and improvement of brain sagging.