asymmetric lateral ventricles

The lateral ventricles occasionally show small side to side differences in size on CT or MRI of the brain. This asymmetry of the lateral ventricles (ALV) is an anatomic variant in most cases.


The prevalence of asymmetry in lateral ventricle size in those without evidence of underlying etiology has been found to be 5-12% . Studies generally show that when asymmetry is present, the left side more commonly appears larger.


Association between asymmetric lateral ventricles and certain neuropsychiatric conditions have been reported:

However, this is controversial and other studies have failed to find such an association .

Clinical presentation

In a Canadian study from 1990 with a cohort of 249 patients, both headaches and seizures were more common in those with asymmetric lateral ventricles . In a more recent Turkish study of 170 patients, headache was more common in those with asymmetric lateral ventricles than 'normal' controls, otherwise there was no significant difference in presentation between the two groups . In both studies patients with clear underlying neuropathological causes for the appearance or with true unilateral hydrocephalus were excluded.



Etiology of this asymmetry remains speculative .

Radiographic features


Asymmetric enlargement of one of the lateral ventricles, without evidence of space-occupying lesions, cerebral infarction, trauma, or other underlying structural abnormality.

Treatment and prognosis

It seems reasonable to perform MRI head in those patients with the more severe degrees of asymmetry; in the Turkish study 3.5% patients had underlying tumors on MRI that were occult on CT, even in retrospect.

Differential diagnosis

Most cases of asymmetry of the lateral ventricles will turn out to be anatomic variants, however it is important for radiologists to consider underlying disease first .

  • parenchymal disease
  • intraventricular lesion
  • obstruction at the foramina of Monro