[Idiopathic acute obstructive hydrocephalus. Case report].

Acute hydrocephalus is rarely encountered in adults without venticuloperitoneal or venticuloatrial shunts. The purpose of this report is to describe a case of acute hydrocephalus due to no identifiable cause. A 40-year-old man developed a typical clinical picture of intracranial hypertension within a 24-hours period. On the morning of hospitalization, the patient consulted his physician for severe headache followed quickly by nausea and vomiting. After cerebral CT-scan, the patient was referred to our department. His condition rapidly worsened, with confusion, then drowsiness. Magnetic resonance imaging (MRI) demonstrated quadri-ventricular hydrocephalus with a Chiari I malformation. In view of his rapidly deteriorating clinical condition, emergency endoscopic third ventriculostormy was performed. The patient recovered rapidly and was discharged 8 days after the procedure. Diagnostic work-up included lumbar puncture showing normal cerebrospinal fluid (thereby eliminating multiple sclerosis, low-grade intracranial hemorrhage, and meningitis (bacterial, viral, fungal)), spinal MRI depicting no medullary lesions, and brain angiography revealing no vascular abnormalities. Follow-up brain MRI carried out at six months after hospitalization demonstrated normal ventricles and complete disappearance of the Chiari I malformation. No conclusion can be drawn as to whether the Chiari I malformation was the consequence or cause of hydrocephalus. The explanation of this acute hydrocephalus is the acute decompensation without identifiable cause of idiopathic stenosis of the foramen of Magendie and Luschka. Treatment with endoscopic third ventriculostomy is effective.