A 50-year-old female marine ecologist presented to the emergency department following 3 weeks of persistent headache, nausea, vomiting, disturbed vision, intermittent aural pulsations, unsteady gait and acroparesthesias. She had previously been healthy, specifically with no history of autoimmune disease.
Mental status, vital signs and general medical examination were normal. Corrected visual acuity 6/60 right; 6/9 left. There were bilateral scotomata extending from the point of fixation towards the temporal field, worse on the right. She had a right afferent pupillary light defect. Funduscopy showed bilateral disc swelling with obscuration of vessels within the disc margins, without haemorrhage. Gait was slightly ataxic. There were no other abnormalities of the cranial nerves, motor or sensory examination.
Haematology, chemistry and liver function tests were normal. Immunoglobulin (Ig)G 5.8 g/L (7.0–16.0) with IgA and IgM normal serum concentrations. Complement (C4) 0.18 g/L (0.2–0.6), with normal C3. Rheumatoid factor, anti-CCP IgG, antinuclear antibody, extractible nuclear antigen, anti-neutrophil cytoplasmic antibody…