Causes of lateral ventricular hydrocephalus

Causes of lateral ventricular hydrocephalus could be divided into causes leading to unilateral and causes leading to bilateral lateral hydrocephalus.

1-Causes of unilateral lateral ventricular hydrocephalus:

-Congenital stenosis of the Foreman of Monroe leading to unilateral dilatation of the epsilateral lateral ventricle with normal size of the rest of the ventricles.

The left foramen of Monro points in the direction of the third ventricle and and incontinuity with third ventricle consistent with normal, unobstructed flow of CSF. Right foramen of Monro ending abruptly, show marked blunting, not pointing towards the third ventricle so the site of obstruction appears to be foramen of Monro and cause appears to be congenital. No obvious adjacent space occupying lesion.

-Inflammatory as in encephalitis.

-Presence of a mass in the epsilateral side of the dilated lateral ventricle causing obstruction of the Foreman of Monroe on the same side.

-Presence of a mass on the contralateral side of the dilated ventricle causing shifting of the midline structures leading to kinking of the Foreman of Monroe and dilatation of the lateral ventricle on the opposite side.

Subfalcine herniation, the most common intracranial herniation pattern, is characterised by displacement of the brain beneath the free edge of the falx cerebri due to raised intracranial pressure.
Unilateral mass effect from pathology in the frontal, parietal or temporal region, such as haemorrhage or tumour, causes displacement of the brain away from the mass. Complications are contralateral hydrocephalus (due to obstruction of the foramen of Monro) and anterior cerebral artery territory infarct (due to compression of ACA branches).

2-Causes of bilateral lateral ventricular hydrocephalus:

-Colloid cyst.

Cyst obstructing ventricles (arrow pointing at cyst).

Colloid Cyst (gold arrow) in the center of the Brain causing back-up of CSF (Brain fluid)

-Giant cell astrocytoma seen in cases of tuberous sclerosis.

Look to sub ependymal calcified foci characteristic of tuberous sclerosis

-Most of supra-sellar lesions may extend upward causing kinking of both Foreman of Monroes leading to bilateral lateral ventricular dilatation.

Sagittal MR image obtained in a 2.5-year-old girl with visual failure and macrocephaly. A large midline optic chiasmatic/hypothalamic glioma is seen, with accompanying obstructive hydrocephalus.