Aqueductal pathology are common causes of obstructive non communicating hydrocephalus characterized by supratentorial ventricular dilatation and normal size 4th ventricle. Note the lack of transependymal spread of CSF, indicating a more insidious / chronic nature of the hydrocephalus. Aqueductal stenosis is the commonest pathology while diaphragm/web are rare. Treatment was done by endoscopy.