On CT or MRI: enlargement of ventricles proximal to block (e.g. obstruction of the aqueduct of Sylvius → lateral and 3rd ventricular enlargement out of proportion to the fourth ventricle, sometimes referred to as triventricular hydrocephalus)
In patients under 1 month, the third ventriculostomy technique may be a better option than the shunt in selected cases 1).