Hydrocephalus is an excessive accumulation of cerebrospinal fluid (CSF) within the head that results from disturbances in CSF formation, flow, or absorption. This leads to high intracranial pressure and ventricular dilation, most commonly caused by obstruction within the ventricular system or sites of CSF absorption. Symptoms depend on the age of onset and include head enlargement in infants and combinations of headaches, cognitive impairment, and features of raised intracranial pressure in adults. Treatment involves surgical insertion of a ventriculoperitoneal shunt to relieve pressure and minimize neurological damage.

1. Hydrocephalus is an excessive accumulation of
CSF within the head, caused by a disturbance
of formation, flow or absorption.
High pressureand ventricular dilation result.
Leading to dilatation of ventricular system
proximal to the site of obstruction.
Obstruction may be within ventricular system
or aqueduct(non-communication or
obstructivehydrocephalus)
Or within arachnoid villi, the site of absorption
of CSF (communicating hydrocephalus)
Infantile hydrocephalu
Head enlargement in infancy occurs in 1 in 2000 live births.

2. There are severalcauses:
• Arnold–Chiari malformations. Thecerebellar tonsils
descend into the cervical canal. Associated spina bifida is
common. Syringomyelia may develop.
• Stenosis of the aqueduct of Sylvius. Aqueductstenosis
is either congenital (genetic), or acquired following
neonatal meningitis/haemorrhage.
• Dandy–Walker syndrome. There is cerebellar
hypoplasia and obstruction to IVth ventricle outflow
foramina.
Hydrocephalus in adults
Hydrocephalus is sometimes an
unsuspected finding on imaging.
Stable childhood hydrocephalus can
become apparent in adult life (‘arrested
hydrocephalus’) butcan suddenly
decompensate.

3. Combinations of headache, cognitive impairment, features of raised intracranial pressure
and ataxia develop, depending on how high the CSF pressurerises and how rapid the onset
is.
Elderly patients with more compliant brains may presentwith gradual-onsetgait apraxia
and subtle cognitive slowing.
• posterior fossaandbrainstemtumours obstructing theaqueduct
or IVth ventricular outflow.
• subarachnoidhaemorrhage, head injury or meningitis (particularly
tuberculous), causing obstruction of CSF flow and reabsorption
• a IIIrd ventricle colloidcyst causing intermittent hydrocephalus
– recurrentprostrating headaches with episodes of lower
limb weakness
• choroidplexus papilloma (rare) secreting CSF.
Frequently, the underlying causeof hydrocephalus remains obscure.
Clinical features
 Skull sutures havenot fused
 The head circumferencemay be disproportionately largeor show an excessive rate of
growth.

4.  The skull sutures separate
 The anterior fontanelle bulges
 The scalp veins become distended.
 Fixed downward gazeor sun setting of the eyes
 Older children will develop signs and symptoms of raised intracranialpressure.
Diagnosis
Hydrocephalus may be diagnosed on antenatal ultrasoundscreening or in preterm infants
on routine cranial ultrasoundscanning.
For suspected hydrocephalus, initial assessmentis with cranial ultrasound (in infants) or
imaging with CT or MRI.
Head circumferenceshould be monitored over time on centile charts.
Management
o Treatment is required for symptomatic relief of raisedintracranial pressure and to
minimise the risk of neurological damage.
o The mainstay is the insertion of a ventriculoperitoneal shunt , butendoscopic treatment
to create a ventriculostomy can now be performed.
o Shunts can malfunction due to blockage or infection (usually with coagulase-negative
staphylococci). They then need replacing or revising.
o Overdrainageof fluid can causelow-pressureheadaches butthe insertion of regulatory
valves can help avoid this.
o Removal of tumours is carried out when appropriate.
o Endoscopic IIIrd ventriculostomy may beperformed.

5. Normal pressure hydrocephalus
This describes a syndromeof enlarged lateral ventricles in elderly
patients with the clinical triad of:
• a gait disorder – gait apraxia
• dementia
• urinary incontinence.
The term is a misnomer, as it is a low-gradehydrocephalus with intermittently raised ICP.
Ventriculoperitoneal shunting may be required. A trial of prolonged drainage of lumbar CSF
over several days predicts responseto shunt insertion.