An Unusual Case of Cranial Metastasis Masquerading as Foster Kennedy Syndrome

A 23-year-old male with adenocarcinoma of the rectum presented with sudden and painless loss of vision in his right eye, lasting for a month. Upon examination, there was no perception of light in the right eye along with relative afferent pupillary defect, and the best-corrected visual acuity of the left eye was 6/9p on Snellen’s chart. Fundus examination revealed a pale appearance of the right optic disc and Grade 2 disc edema in the left optic disc. A subsequent magnetic resonance imaging scan showed a space-occupying lesion in the right parietal vault of the skull, as well as an ill-defined sclerotic area in the right zygomatic bone abutting the right optic canal. The presence of a bony metastasis causing increased intracranial pressure but no intracerebral metastasis or direct cerebral mass suggests an atypical presentation of Foster Kennedy syndrome. The patient was then initiated on aggressive chemotherapy and intracranial pressure-lowering agents for management.