BACKGROUND – Colpocephaly is a congenital abnormality in the ventricular system of the brain. The radiological diagnosis is usually made in the perinatal period and later presages intellectual disability. Adult cases of newly diagnosed colpocephaly have only rarely been reported.

CASE SUMMARY –  The patient is a 15–year–old right–handed female presented to the emergency

room for evaluation after a series of falls along with a noticeable foot deformity on left side Questioning revealed lifelong gait instability. She was alert, appropriately oriented and had normal language function. Mental status review showed a flattened affect and deficits in recent memory Non–contrast brain MRI revealed massive symmetrical dilation of the posterior lateral and the third ventricles, thin parieto–occipital white matter and partial agenesis of the corpus callosum. She was diagnosed with congenital colpocephaly because of the radiological findings. She came to a rehabilitation facility for gait training and management of the foot deformity.

CONCLUSION – When encountering ventriculomegaly in an adult, one must distinguish between the different forms of obstructive and nonobstructive ventriculomegaly. We propose that colpocephaly be considered in the differential for adults with non–obstructive ventriculomegaly. When secondary causes have been ruled out, distinguishing between colpocephaly and NPH can be done through a careful history, physical examination and evaluation of the radiological characteristics. Doing so can prevent the iatrogenic risk associated with surgical shunting.