Homonymous quadrantanopsia in a case of disproportional hydrocephalus caused by pneumocephalus

Abstract

A 29-year-old man with a posterior fossa arachnoid cyst presented with headache. A shunt revision was performed following the diagnosis of a malfunction of a previously inserted cyst-peritoneal shunt. Four days later, he developed right lower homonymous quadrantanopsia with sparing of the temporal crescent of the right eye. MRI revealed pneumocephalus and disproportional hydrocephalus, with enlargement of the occipital horn of the left lateral ventricle. This ventricular enlargement had stretched the optic radiation and caused the visual field defect. Of the fibers associated with right vision passing along the left lateral ventricle, those for peripheral vision of the right eye were located medially. The perimetry of the patient corresponded to the characteristic sparing of the visual field defect when the superior wall of the occipital horn was selectively stretched. The mechanism of enlargement of the occipital horn was thought to be air disturbance of CSF outflow and amplified pulsation of the brain.