Hydrocephalus

Question 1

Define hydrocephalus

Answer 1

An accumulation of cerebrospinal fluid (CSF) within the brain. This typically causes raised ICP.

There are four types of hydrocephalus:
• Communicating (Non-Obstructive) Hydrocephalus: Impaired CSF reabsorption in the absence of any obstruction between the ventricles and subarachnoid space.
• Non-Communicating (Obstructive) Hydrocephalus: Caused by a CSF-flow obstruction.
• Hydrocephalus Ex-vacuo: A compensatory enlargement of the CSF spaces in response to brain atrophy and parenchyma loss; it is not the result of increased CSF pressure.
• Normal pressure Hydrocephalus: A particular form of communicating hydrocephalus, characterized by enlarged ventricles, with only intermittently elevated CSF pressure.

Question 2

What are the causes/risk factors of hydrocephalus?

Answer 2

Obstructive:
outflow of the CSF from the ventricular system:
• Lesions of the third ventricle, fourth ventricle, cerebral aqueduct
• Posterior fossa lesions (e.g. tumour, blood) compressing the fourth ventricle
• Cerebral aqueduct stenosis

Non-Obstructive:
Impaired CSF resorption in the subarachnoid villi:
• Tumours
• Meningitis (typically TB Meningitis)

Congenital Hydrocephalus: The most common cause of congenital hydrocephalus is aqueductal stenosis. 80-90% of infants with spina bifida (myelo)meningocele develop hydrocephalus.

Acquired Hydrocephalus: CNS infections, meningitis, brain tumours, head trauma and haemorrhages.

Question 3

What are the signs and symptoms of hydrocephalus?

Answer 3

• The clinical presentation of hydrocephalus varies with chronicity.
• Acute dilatation of the ventricular system is more likely to manifest with the nonspecific features of raised ICP.
• Chronic dilatation may have a more insidious onset presenting.
• NPH –Presents with Adams Triad/ Hakim’s Triad:
- Gait Instability
- Dementia
- Urinary Incontinence
• Focal neurological deficits.
• The presentation of hydrocephalus in children can include:
- Fontanel bulging
- Vomiting
- Irritability
- Seizures
- Learning disability (low IQ)
- Precocious puberty

Question 4

What investigations are carried out for hydrocephalus?

Answer 4

• CT head - First-line investigation to detect hydrocephalus. May also detect the cause (e.g. tumour in the brainstem).
• MRI
• CSF - Obtained from ventricular drains or lumbar puncture may indicate an underlying pathology (e.g. tuberculosis). Check for MC&S, protein, glucose (CSF and plasma).
• Lumbar puncture - This is contra-indicated in obstructive hydrocephalus as it can cause tonsillar herniation and death. May be necessary in NPH as a therapeutic trial.