To discuss a previously unreported presentation of idiopathic Fourth Ventricle Outlet Obstruction causing tetraventricular hydrocephalus.

Idiopathic Fourth Ventricular Outlet Obstruction (FVOO) is a rare cause of tetraventricular hydrocephalus. Symptomatology of idiopathic FVOO ranges from chronic headaches and nausea to symptoms mimicking Normal Pressure Hydrocephalus (NPH). Presentation of FVOO in adults is a rare phenomenon. Axial tonic posturing and stereotyped movements associated with FVOO have not been reported. 

We present a video case report of a 45-year-old lady presenting with a negative affect followed by paroxysmal events characterized by falls and abnormal posturing some of which were preceded by a bout of cough. The use of prolonged Video EEG (VEEG) and MRI was done to reach the diagnosis of tetraventricular hydrocephalus due to idiopathic FVOO.

VEEG revealed habitual events characterized by atonic posturing and stereotyped movements. However, no ictal correlate was found. MRI Brain revealed tetraventricular dilatation with no obvious obstruction. Administration of Endoscopic Third Ventriculostomy (ETV) successfully led to immediate resolution of symptoms.

While FVOO in adults is associated with multiple etiologies, we present the first video case of true idiopathic FVOO with atypical features. The atypical presentation of negative affect with paroxysmal falls, hypomotor posturing, and stereotyped movements can lead to a misdiagnosis. MRI and VEEG should be used as diagnostic tools in patients with these symptoms. Clinical corroboration of radiological findings in such presentations is necessary to avoid overlooking of diagnosis of idiopathic FVOO. The study broadens our understanding of FVOO symptomatology and will play a part in establishing a definitive diagnostic protocol for the disorder.