[Permanent visual loss resulting from bilateral occipital infarction after shunt malfunction]

The commonest cause of malfunction of shunts for cerebrospinal fluid is obstruction of the catheter, which may be of subacute or sudden onset. When onset is sudden, the complication is serious as this implies risk of death or permanent damage to vision.

We describe the case of a 13 year old girl who, 8 days after insertion of a ventriculo-peritoneal shunt valve, complained of the sudden onset of headache, reduced level of consciousness, pupil changes and permanent loss of vision secondary to a bilateral occipital infarct.

The visual pathways and oculomotor nerves are particularly sensitive to changes in intracranial pressure and displacement of intracranial structures. Therefore, neuro-ophthalmic signs are more sensitive than computerized tomography (CT) in detection of mechanical malfunction of the valve. Although CT shows structural anomalies, it cannot assess their function. The intracranial pressure may be high enough to cause damage to the visual pathways, although no enlargement of the ventricles can be seen on CT. A normal CT, or one similar to previous scans, does not rule out malfunction of the shunt. If clinical signs of raised intracranial pressure are observed, the possibility of mechanical malfunction of the valve should be considered and this should be explored as a neurosurgical emergency in view of the risk of death or permanent loss of vision.