Blocked ventriculoperitoneal shunt causing raised intracranial pressure diagnosed by prominent sinus pericranii.

We present a 3.5-year-old male infant who had been treated at 3 weeks of age with a ventriculoperitoneal (VP) shunt for intraventricular haemorrhage with resultant hydrocephalus. Since his initial treatment he had normal developmental milestones. On this occasion he presented with difficulty in walking, vomiting and irritability. His mother was concerned this was due to his shunt malfunctioning. It had not required revision since insertion as a neonate. He was initially managed at a peripheral hospital without neurosurgical services for 4 weeks as an outpatient. The major clinical concern was a gradually enlarging lesion confined to the top of his head consistent with a vascular malformation. Investigations were focused towards this, with an initial diagnosis made of a cerebral arteriovenous malformation (AVM) with involvement of scalp vessels. His initial head CT scan did not show enlarged ventricles and the shunt was clinically assessed as functioning satisfactorily. The patient's condition worsened and he was referred with a diagnosis of scalp AVM for neurosurgical attention. After neurosurgical review a clinical diagnosis of raised intracranial pressure (ICP) due to shunt malfunction was made. This was supported by a CT scan that showed an enlarging ventricular system. After revision of the shunt there was complete resolution of the pulsatile scalp swelling with clinical recovery of the child. To our knowledge this is the first reported incidence of a blocked VP shunt causing raised ICP presenting with a localised extracranial pulsatile venous dilation consistent with a "true" sinus pericranii.