A 50-year-old woman was incidentally diagnosed to have unilateral disc oedema during comprehensive ophthalmological evaluation. She had a prior history of ulcerative colitis. She had normal visual function and was initially diagnosed to have incipient non-arteritic anterior ischaemic optic neuropahty. Risk factor evaluation revealed hyperhomocysteinaemia. She was asked to come for a follow-up in 2 months. However, she was lost to follow-up and returned to the clinic for the evaluation for headaches, 23 months later. Her ocular examination was stable and she had persistent unilateral disc oedema unchanged from the prior visit. Repeat MRI brain and MR venogram brain with contrast-established diagnosis of cerebral sinus venous thrombosis (CSVT). She denied any neurological symptoms. Later on, she was diagnosed to have hyperhomocysteinaemia with methyl tetrahydrofolate reductase gene mutation. This case highlights the importance of recognising although rare, unilateral disc oedema secondary to elevated intracranial pressure from CSVT.
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