This is defined as an distension of the ventricular system within the brain as a result of an imbalance between CSF absorption and production.

In general hydrocephalus can classified into three main categories:

  1.  Overproduction of CSF- rare circumstances due to choroid plexus carcinoma
  2.  Non-Communicating (obstructive) hydrocephalus due to an obstruction of flow within the ventricular system
  3. Communicating- disruption of absorption of at the level of arachnoid granulations or ‘out’ of the ventricular system

Non-Communicating (Obstructive Hydrocephalus)

This can be described as either acquired or congenital


  1. Infectious- acquired aqueduct stenosis following infection- causes adhesions, abscesses
  2. Neoplastic- e.g interventricular tumours, 3rd ventricular colloid cysts, pineal gland tumours
  3. Vascular- Interventricular Haemorrhage
  4. Arachoid cysts
  5. Posterior fossa masses compressing the 4th ventricle e.g tumour, or Intra-cerebral haemorrhage


  1. Acqueduct stenosis
  2. Dandey-Walker Malformation-atresia of Foramen of Magendie and Luschka
  3. Arnold Chiari Malformation


Normal Pressure Hydrocephalus


Hydrocephalus ex-vacuo- not strictly hydrocephalus enlarged appearance of the ventricles due to cerebral atrophy


  1. Infectious- post meningitis, sub-arachnoid haemorrhage
  2. Increased CSF Viscosity- high protein count

Radiological Findings

The key to distinguishing the cause of hydrocephalus is to determine where the level of obstruction is. If all four ventricular systems in the brain are open than it is determined as a communicating hydrocephalus.

If the 4th ventricle system is open and there is dilation of the 3rd and lateral ventricles than the pathology is at the at the cerebral acqueduct of Sylvius hence knowledge of the ventricular system is important. Sure you would have access to all the imaging not available on this website.

The arrows are pointing to peri-ventricular lucency. This is  an area of hypodensity close to the tips of the frontal horns of the lateral ventricles and indicates acute hydrocephalus.


Clinical Findings

In children:

  1. Tense anterior fontanelle
  2. Enlarged skull circumference
  3. Thin scalp with distended veins
  4. Cracked pot sound on skull percussion
  5. Late sign but severe impaired upward gaze from pressure related transmission to the midbrain tectum

In Adults:

  1. Nausea, vomiting and papilloedema
  2. Impaired upward gaze
  3. Bilateral 6th nerve palsy- this is due to compression of the 6th nerve from raised Intra-cranial Pressure


  1. ABCDE
  2. Remember if GCS<8, intubation and ventilated!
  3. Acute deterioration- VP Shunt or an External Ventricular Drain, if communicating LP to drain of CSF, or LP Shunt, if at 3rd ventricle- 3rd ventriculostomy
  4. Chronic- VP Shunt Shunt or LP Shunt