Acute Hydrocephalus

Acute hydrocephalus is rapid ventricular enlargement caused by impaired CSF circulation or absorption, producing raised intracranial pressure over hours to days.

It can be:

Obstructive, noncommunicating

CSF flow is blocked within the ventricular system.

Examples:

Aqueduct obstruction
Posterior fossa mass
Intraventricular haemorrhage obstructing the aqueduct or fourth ventricular outlets
Colloid cyst

Communicating

CSF passes through the ventricular outlets but absorption is impaired.

Examples:

Subarachnoid haemorrhage
Meningitis
Diffuse leptomeningeal disease

Acute hydrocephalus can produce rapid neurological deterioration and herniation.

CT head: rapidly demonstrates ventricular enlargement and often identifies the cause.

MRI: better defines:

Aqueduct obstruction
Posterior fossa tumour
Third ventricular lesion
CSF flow anatomy

but should not delay emergency CSF diversion in a deteriorating patient.

Do not perform lumbar puncture in a patient with obstructive hydrocephalus and significant intracranial pressure gradient because downward herniation can occur.

Emergency EVD

External ventricular drainage is the standard emergency treatment for acute hydrocephalus with neurological deterioration.

A ventricular catheter is usually inserted into the frontal horn of the lateral ventricle and connected to a calibrated external drainage system.

The EVD provides:

Immediate CSF drainage
ICP measurement
Temporary control while the underlying cause is treated.

Drainage height is set relative to the ventricular reference level, commonly around 10 to 15 cm H₂O, then adjusted according to:

ICP
Ventricular size
Cause of hydrocephalus
Neurological response

Avoid uncontrolled rapid overdrainage because it can produce:

Ventricular collapse
Subdural hygroma
Subdural haematoma
Upward or downward shifts in posterior fossa pathology

Treat the cause

Examples:

Intraventricular haemorrhage

Drain CSF and manage the underlying haemorrhage.

Posterior fossa mass

Definitive tumour or haematoma treatment is often required.

Colloid cyst

Endoscopic or microsurgical removal can relieve obstruction definitively.

Meningitis

Treat infection while using temporary CSF diversion when required.

Endoscopic third ventriculostomy

ETV creates a fenestration in the floor of the third ventricle, allowing CSF to bypass an obstruction.

It is particularly useful for:

Aqueduct stenosis
Selected obstructive third or fourth ventricular pathway lesions
Some shunt failures

It avoids permanent implanted shunt hardware in appropriately selected patients.

EVD complications

Monitor for:

Ventriculitis
Catheter obstruction
Overdrainage
Intracranial haemorrhage
Malposition

Routine daily CSF sampling without clinical indication can increase manipulation and is generally avoided.

Suspect EVD infection with:

New fever
CSF pleocytosis
Falling CSF glucose
Positive culture
Unexplained neurological deterioration

Brain Abscess

A focal, encapsulated collection of pus within brain parenchyma, from contiguous spread (sinusitis, otitis media/mastoiditis, dental infection), hematogenous spread (endocarditis, particularly right-to-left cardiac shunts allowing bypass of pulmonary filtration, and bronchiectasis or lung abscess), direct inoculation (trauma, neurosurgery), or, in a significant minority, no identifiable source.

Often polymicrobial, particularly with a contiguous or dental source (streptococci, anaerobes).

Contrast-enhanced MRI is the investigation of choice, with diffusion-weighted imaging particularly useful for distinguishing abscess (restricted diffusion within the cavity) from necrotic tumor.

Lumbar puncture is contraindicated given the mass effect and herniation risk.

Stereotactic or CT-guided aspiration provides microbiological diagnosis and, often, therapeutic decompression simultaneously.

Blood cultures and screening for the underlying source (sinus imaging, echocardiography if endocarditis or a cardiac shunt is suspected, dental assessment).

Aspiration or excision, combined with prolonged antibiotics, is standard for most abscesses over roughly 2.5 cm; small (under 2.5 cm), non-mass-effect abscesses in a stable patient may occasionally be managed with antibiotics alone with close imaging follow-up
Empirical antibiotics (before or pending culture): a combination such as ceftriaxone 2 g bd plus metronidazole, with vancomycin added where post-surgical, post-traumatic, or hematogenous S. aureus spread is a concern; regimen rationalized once organism identified
Total antibiotic duration typically 6 to 8 weeks IV, sometimes longer with a subsequent oral course, guided by serial imaging showing resolution
Corticosteroids (dexamethasone) are used for significant surrounding edema and mass effect, but only as an adjunct given a theoretical concern about reduced antibiotic penetration and capsule formation, not as a substitute for source control
Anticonvulsants for seizures; treatment of the underlying source (sinus, ear, dental, cardiac) is essential alongside abscess management

Referral: neurosurgical emergency for aspiration/drainage; infectious disease for antibiotic duration; source-specific specialty (ENT, cardiology, dentistry) for the underlying cause.

Acute Hydrocephalus

Overview

Clinical Features

Diagnosis

Management

Overview

Clinical Features

Diagnosis

Management