Development of normal pressure hydrocephalus following post-traumatic external hydrocephalus in an adult patient.

We report the case of 74-year-old patient suspected of post-traumatic external hydrocephalus (EH) following a mild traumatic brain injury with a progressive neurological decline and a concomitant enlargement of subarachnoid spaces without ventriculomegaly on CT scan. A lumbar puncture revealed raised ICP and a careful CSF withdrawal was performed, resulting in an immediate neurological improvement, confirming the diagnosis of EH. During the 20-month follow-up, the patient presented progressive signs of normal pressure hydrocephalus (NPH): gait and cognitive decline, ventriculomegaly and the lumbar infusion study confirmed disturbed CSF dynamics. The patient underwent a ventriculoperitoneal shunt surgery, resulting in a long-lasting improvement.