Clinical question

A 74-year-old retired male scientist reported visual misperceptions over 3 weeks. These included seeing objects as if through a camera lens, fluctuating brightness despite no change in ambient light, photopsia, light sensitivity, objects appearing closer than they were, horizontal diplopia, altitudinal field loss and ‘looking from the inside outward’. When walking, he felt the floor curved upwards and the world moved around him abnormally. He reported multidirectional falls.

His family reported that he was less proactive and had developed episodic memory loss over the preceding 2 months.

He had a history of axonal neuropathy, pernicious anaemia and degenerative spinal disease. There was no history of sleep disorder, psychosis or anosmia and no significant family history.

On examination, he had an inferior visual field defect and reported bilateral horizontal diplopia on eye movements but without objective ophthalmoplegia. There was no muscle wasting or fasciculations. Tone and strength were normal throughout. He had depressed reflexes in keeping with longstanding neuropathy. He had slight bradykinesia and an intention tremor. He was hesitant when walking but stride length and arm swing were normal. There was no gait ataxia. Cognitive testing showed deficits in attention, memory and visuospatial …