Tumefactive demyelination: an unusual cause of a spontaneously resolving homonymous hemianopia.

A 21-year-old man presented to eye casualty complaining of altered vision associated with headache and vomiting upon waking. Clinical examination was unremarkable except for a right-sided homonymous hemianopia. The MRI scan of the brain revealed a space occupying lesion within the occipital lobe and MR spectroscopy highlighted this to be inflammatory in nature, most likely a tumefactive demyelinating lesion (TDL). Lumbar puncture displayed positive oligoclonal bands. The patient was managed conservatively and made a full recovery, with normal visual fields recorded after a 3 month follow-up. This is a case of a TDL manifesting itself as an unusual cause of homonymous hemianopia; misdiagnosis of TDL is common and potentially damaging to the patient.