Hiding Without Plain Sight - Third Ventricular Dilation and Optic Pathway Compression Without Disc Edema

Elevated intracranial pressure (ICP) is thought to cause vision loss mainly by axoplasmic stasis, a mechanical nonvascular phenomena, of the optic nerve.1 Dilation of the third ventricle is a rarely reported cause of visual pathway dysfunction in the literature.2-4 Mechanistically, the most common cause is a posterior fossa tumor causing increased ICP and subsequent dilation. Papilledema is typically present. Visual field cuts vary but are thought to be related to direct compression or relative chiasmal fixation: normal and postfixed often result in a bilateral depression of the inferior temporal central field due to superior pressure, while prefixed chiasm can result in bilateral central, nasal or superior hemianopic scotomas due to posterior inferior pressure.5 Regardless, indications for shunt placement or revision by neurosurgery rely on the presence of papilledema. We describe 5 cases of hydrocephalus with dilated third ventricle and vision loss without papilledema.