Clinical Reasoning: compressive optic neuropathy secondary to intracranial Rosai-Dorfman disease.

SECTION 1 A 60-year-old man presented to our clinic with a 6-month history of progressive visual loss in the left eye. Twelve months prior, he experienced an acute left hemianopia secondary to a stroke. He was anticoagulated and fully recovered. Six months following the stroke, he began to notice blurred vision in his left eye. There was no formal ophthalmic examination performed at that time, but a plastic surgeon believed that a left medial upper eyelid mass lesion was causing distortion of his vision, and proceeded to excision biopsy. Histopathology revealed Rosai-Dorfman disease (RDD). Postoperatively, the patient’s visual loss continued to worsen and he was referred to our clinic. On examination, visual acuity was 6/6 on the right and 6/12 on the left. The patient correctly identified all Ishihara color plates with the right eye, and only the test plate and one other plate with the left eye. There was also a left relative afferent pupillary defect. Funduscopy revealed subtle left optic disc pallor. Orbital examination was normal. Humphrey visual field of the left eye showed superior and inferior arcuate defects and a normal right visual field (figure, A). Neuroimaging revealed a dural-based, intensely enhancing mass in the left anterior cranial fossa, which had been documented as a small incidental meningioma 6 months earlier (figure, B and C).