[Congenital obstruction of the foramen of Monro causing unilateral hydrocephalus. A propos of a case].

Isolated hydrocephalus of the lateral ventricle may result from unilateral occlusion of the foramen of Monro. The most common causes are tumours of the lateral ventricles or in the area of the third ventricle. Non-tumoural stenosis of the foramen is rare and can be due to inflammatory, vascular or congenital conditions. A full-term infant was prenatally diagnosed with unilateral hydrocephalus. After birth, progressive unilateral ventricular dilatation was confirmed in successive ultrasounds so surgery was indicated. The patient underwent endoscopic fenestration of the foramen of Monro and septostomy with good postoperative clinical evolution and reduction of ventricular size. Intraoperative findings demonstrated membranous obstruction of the right foramen of Monro. A successful treatment can be accomplished through a neuroendoscopic approach avoiding the use of ventricular shunts.