Computed tomography in the hydrocephalic patient after shunting.

The interpretation of postshunt computed tomographic (CT) scans of hydrocephalic patients presents numerous difficulties unless the interpreter has a thorough knowledge of the clinical symptoms, type and cause of hydrocephalus, preshunt morphology of ventricles and subarachnoid spaces, possible complications of shunt placement, and signs of shunt failure. A review of 368 scans from 108 hydrocephalic patients included subgroup statistical analysis of the development of ventricular asymmetry and of subarachnoid space changes after shunting. The situation and appearance of ventricular catheters were quite variable. Subarachnoid space enlargement after shunting usually was related to long-standing high-grade ventriculomegaly, and was observed most commonly in congenital or acquired nonneoplastic hydrocephalus with little relationship to the site of blockage. Ventricular asymmetry developed in one third of the cases and was related to the site of the shunt catheter tip. Preshunt asymmetry persisted in spite of shunt placement in the larger ventricle. Accurate diagnosis of shunt failure usually required baseline CT studies, correlation with clinical findings, and, in some cases, serial scans.