A 6-month-old infant is brought to clinic by her mother who noticed her head is growing unusually fast. The fontanelle is tense and bulging. Head circumference is on the 99th centile and crossing upward. She has a "sunsetting" sign — eyes deviated downward with sclera visible above the iris.
Adult case: A 72-year-old man presents with a 6-month history of the triad of gait disturbance ("walking on ice"), urinary incontinence, and progressive memory loss.
What unifies these two presentations?
What is Hydrocephalus?
Hydrocephalus is the abnormal accumulation of cerebrospinal fluid (CSF) within the ventricular system, resulting in ventricular enlargement and — if untreated — raised intracranial pressure. It is not simply "water on the brain" — it represents a failure of the normal CSF circulation.
Normal CSF production is approximately 500ml per day, with a total volume of about 150ml at any one time. It is produced by the choroid plexus in the lateral ventricles, flows through the ventricular system, circulates in the subarachnoid space, and is reabsorbed by the arachnoid granulations into the venous sinuses. Any disruption to this circuit causes accumulation.
Classification
| Type | Mechanism | Common Causes |
|---|---|---|
| Obstructive (Non-communicating) | Blockage within the ventricular system preventing CSF flow | Aqueductal stenosis, posterior fossa tumour, intraventricular haemorrhage, Chiari malformation |
| Communicating | CSF flows freely from ventricles but reabsorption is impaired | Post-meningitis, post-SAH, leptomeningeal carcinomatosis, choroid plexus papilloma (overproduction) |
| Normal Pressure Hydrocephalus (NPH) | Communicating hydrocephalus with normal ICP — poorly understood | Idiopathic (elderly), post-traumatic, post-SAH |
| Ex Vacuo | Ventricles enlarge to fill space left by brain atrophy — NOT true hydrocephalus | Alzheimer's disease, vascular dementia |
Clinical Features
In Infants
The skull sutures have not fused in infants, so the head can expand to accommodate rising CSF pressure. Features include: rapidly increasing head circumference (crossing centiles), bulging anterior fontanelle, prominent scalp veins, irritability, poor feeding, and the sunsetting sign — downward deviation of the eyes from pressure on the pretectal area, with sclera visible above the iris. This is pathognomonic of raised ICP in infants.
In Adults and Children with Fused Sutures
Once sutures fuse, the skull cannot expand — pressure rises rapidly. Features of raised ICP dominate: headache (worse in morning), vomiting, papilloedema, deteriorating consciousness, and Cushing's triad in severe cases.
The classic triad of NPH: Wet, Wobbly, and Weird — urinary incontinence, gait apraxia ("magnetic gait," shuffling, feet stuck to floor), and dementia. Gait disturbance is typically the first and most prominent feature. Shunting can dramatically improve all three — but gait responds best.
Investigations
CT head is the first-line investigation — shows enlarged ventricles (particularly temporal horns of the lateral ventricles), periventricular lucency (transependymal CSF seepage in acute hydrocephalus), and any underlying cause.
MRI brain gives more detail — shows aqueductal flow void, posterior fossa pathology, and is essential before surgical planning.
In NPH: high-volume lumbar puncture tap test (30–50ml removed) — improvement in gait within hours suggests shunt will help.
Surgical Treatment
Surgical Options
- Ventriculoperitoneal (VP) shunt: Most common surgical treatment. A silicone tube drains CSF from the lateral ventricle to the peritoneal cavity where it is reabsorbed. Programmable pressure valves allow non-invasive adjustment. Complications include: infection (5–10%), blockage, over-drainage (subdural haematoma), and shunt fracture.
- Endoscopic Third Ventriculostomy (ETV): A hole is made in the floor of the third ventricle endoscopically, allowing CSF to bypass the obstruction. Best for obstructive hydrocephalus (aqueductal stenosis). Advantage: no hardware, so no shunt infection/failure risk. Not suitable for communicating hydrocephalus.
- External Ventricular Drain (EVD): Temporary measure in acute hydrocephalus — a catheter drains CSF externally into a collection bag. Used in acute SAH, post-neurosurgical monitoring, or as a bridge to definitive shunting.
- Treat the cause: If hydrocephalus is caused by a tumour obstructing CSF flow, tumour resection may resolve it without a permanent shunt.
Infant: Congenital obstructive hydrocephalus from aqueductal stenosis. MRI confirmed. Underwent ETV — excellent result, no shunt required. At 2-year follow-up, normal neurodevelopment.
Elderly man: Normal pressure hydrocephalus. High-volume LP tap test improved his gait significantly. VP shunt inserted with programmable valve. At 3-month follow-up — gait and continence markedly improved, mild cognitive improvement.
Hydrocephalus = CSF accumulation from obstruction or impaired reabsorption. In infants — expanding head, bulging fontanelle, sunsetting sign. In adults — features of raised ICP. NPH triad: wet, wobbly, weird (incontinence, gait apraxia, dementia). VP shunt is the most common treatment; ETV for obstructive type. Always look for and treat the underlying cause.
References
- Kahle KT et al. Hydrocephalus in children. Lancet. 2016;387(10020):788–799.
- Relkin N et al. Diagnosing idiopathic normal-pressure hydrocephalus. Neurosurgery. 2005;57(3):S4–S16.
- Warf BC. Hydrocephalus in Uganda: the predominance of infectious origin and primary management with endoscopic third ventriculostomy. Journal of Neurosurgery. 2005;102(1):1–15.
