Cerebral Venous Thrombosis Due to Overdrainage in a Patient With Normal Pressure Hydrocephalus: A Case Report.

Mechanical shunting of cerebrospinal fluid (CSF) is an effective treatment for hydrocephalus but is not exempt from complications. A 67-year-old male with a history of normal pressure hydrocephalus (NPH) and ventriculoperitoneal shunting (VPS) one year ago presented with gait disturbance and memory impairment. His head computed tomography (CT) was normal, and the shunting pressure was reduced from 110 to 70 mmH20 with gait and memory improvement. One week later, he reported persistent pressure headaches, which worsen when lying down, accompanied by nausea and vomiting. His neurological examination was notable for a short-stepped wide-based gait. Two generalized seizures were observed. CT cerebral venography revealed sinus venous thrombosis (SVT). After two days, a new CT was performed, and bilateral subdural hygromas were found. The shunting pressure was readjusted to 110 mmH20, and symptom improvement was noted. One week later, CT showed enlargement and bleeding of subdural collections. The drainage system was closed, and the patient continue to recover. The temporal association between pressure adjustment and symptom onset and the evidence of progressive subdural effusions suggest that the decrease of CSF volume by overdrainage led to an increase in cerebral blood volume and the dilatation of the venous sinus, which precipitated thrombus formation.