Hydrocephalus and shunt emergencies: Viva

Branch 1: Definition and classification

The candidate should define hydrocephalus as the active distension of the cerebral ventricular system from an imbalance between the production and the absorption of cerebrospinal fluid, and rarely from overproduction. A strong candidate gives the traditional divide into communicating, where the ventricular outflow is open and the defect lies at the arachnoid granulations, and non-communicating or obstructive, where a physical block halts the flow within the ventricular system, classically at the aqueduct of Sylvius. ^[2]

If the examiner presses for a more functional approach, the candidate should describe the Rekate classification by the site of the disturbance, naming obstruction at the foramina of Monro, the aqueduct, the fourth ventricle outlets, the basal cisterns, and the arachnoid granulations, with overproduction from a choroid plexus papilloma the sixth category. The candidate should explain that the value of the functional approach is that it directs the surgeon to the right operation, because an aqueductal block is bypassed by an endoscopic third ventriculostomy while an absorptive failure is drained by a shunt. ^[2]