Hydrocephalus (summary)

Hydrocephalus describes the situation where the intracranial ventricular system is enlarged because of increased pressure. It may be caused by obstruction of CSF flow. If this is the case, the location of obstruction can be determined by the pattern of hydrocephalus. In some cases, hydrocephalus is caused by altered CSF dynamics rather than obstruction.

Reference article

This is a summary article; read more in our article on hydrocephalus.

Summary

• pathophysiology
  • pattern of ventricular dilatation dependant on cause
    • unilateral lateral ventricle
      • midline shift; mass at the foramen of Munroe
    • bilateral lateral ventricles
      • 3rd ventricular mass
    • lateral and 3rd ventricles
      • aqueduct of Silvius obstruction; 4th ventricular mass
    • lateral ventricles, 3rd and 4th
      • most likely non-obstructive
• investigation
  • CT head
    • best initial test, especially in an unwell patient
  • MRI brain
    • may be helpful for further assessment
    • usually used for further characterisation of the cause
      • e.g. tumour assessment

Radiographic features

CT

Dilatation of the ventricular system occurs in a predictable fashion. The first parts of the ventricles to dilate are the temporal horns. On the axial slices from a CT, the temporal horns should come to a point. If they are rounded, the pressure in the ventricles is likely raised and this is an early sign of hydrocephalus.

The CT can be used to determine the likely cause and look for complications.

A large stroke may result in midline shift and consequent contralateral ventricular dilatation.

Increased pressure within the ventricles causes compression of the venous return in the brain parenchyma immediately adjacent to the ventricle. This manifests as oedema (reduced density) immediately adjacent to the ventricles, especially the frontal, temporal and occipital horns.