Isolated fourth ventricle

Trapped ventricle, also known as isolated ventricle, is a condition in which there is an obstruction to the entry and exit path of CSF through the ventricle.

Clinical presentation

The presentation is that of increased intracranial pressure due to expanded trapped ventricle.

• trapped temporal horn
  • triad
    • hemiparesis: due to compression of the internal capsule
    • memory disturbance: due to compression of the hippocampus
    • homonymous hemianopia: due to compression of Meyer loop
• trapped fourth ventricle
  • diplopia
  • ataxia
  • nystagmus

Pathology

Obstruction of the ventricular outlet (with continued CSF production) results in cystic dilation of the fourth ventricle and supratentorial hydrocephalus .

Etiology

• choroid plexitis/ventriculitis
• CNS tuberculosis
• hemorrhage obstructing exit pathway
• intracranial masses
• intraventricular cysts
• complication after lateral ventricular shunting

Location

• trigone of the lateral ventricle
• third ventricle (rare)
• fourth ventricle

Radiographic features

The involved ventricle appears as a focally dilated cystic structure that follows CSF signals on respective cross-sectional imaging. The remaining ventricular system may appear normal.

There is transependymal CSF seepage around the trapped ventricle.

Keyhole sign may be seen in cases of herniation of trapped fourth ventricle .

Treatment and prognosis

Management options include:

• treatment of the cause
• shunting of the trapped ventricle