Define Hydrocephalus. Describe its causes, clinical features, investigations and complications.

Definition

Hydrocephalus is an abnormal accumulation of cerebrospinal fluid (CSF) within the ventricles, causing ventricular dilatation and raised intracranial pressure, due to obstruction of flow, impaired absorption, or (rarely) overproduction of CSF.

Types & Causes

• Obstructive (non-communicating) — block within the ventricular system: aqueductal stenosis, Dandy-Walker malformation, tumour.
• Communicating — impaired CSF absorption: post-meningitis, post-haemorrhage.
• Associated with neural-tube defects (spina bifida / Arnold-Chiari).

Clinical Features

• Infants — rapidly increasing head circumference, tense/bulging fontanelle, widely split sutures, 'sunset' eyes, dilated scalp veins, irritability and vomiting.
• Older children (fused sutures) — headache, vomiting, papilloedema and other signs of raised ICP.

Investigations & Management

• Cranial ultrasound (through the open fontanelle in infants); CT/MRI to define the cause and level of obstruction.
• Ventriculoperitoneal (VP) shunt or endoscopic third ventriculostomy (ETV); treat the underlying cause.
• Monitor for shunt complications — blockage and infection.

Complications of Shunts

• Blockage (recurrent raised-ICP symptoms) and infection (fever, shunt-tract signs).
• Over-drainage, and the need for revisions as the child grows.

Pathophysiology (CSF Circulation)

• CSF is produced by the choroid plexus, flows through the ventricles and is absorbed by the arachnoid villi.
• Hydrocephalus results when this pathway is obstructed or absorption is impaired, so CSF accumulates and raises intracranial pressure.

Associated Conditions

• Neural-tube defects (spina bifida, Arnold-Chiari malformation); intraventricular haemorrhage of prematurity.
• Post-meningitic and post-haemorrhagic hydrocephalus.