Bilateral Cavernous Sinus Thrombosis Secondary to Nocardial Sphenoid Sinusitis

A 52-year-old woman presented with severe vertex headaches of five days duration, fatigue and night sweats. Her past medical history was significant for relapsing-remitting multiple sclerosis diagnosed six years previously and presently treated with teriflunomide. Eight months prior she had an episode of subacute painless visual loss in her right eye with RAPD and dyschromatopsia, interpreted as demyelinating optic neuritis with a partial recovery. On admission she was afebrile with elevated CRP and ESR. Brain MRI without contrast was read as normal except for sphenoid sinusitis and right posterior ethmoiditis. LP revealed pleocytosis. No infectious agent was identified in blood or CSF by microscopy, serology or culture. Despite intravenous antibiotic and antiviral treatment the patient continued to deteriorate. She reported diplopia and visual loss on the seventh day of admission. On examination she had complete ptosis, chemosis, proptosis and limited motility of the left eye. Her 'unaffected' right eye showed progressive visual loss and GCL/RNFL atrophy. In retrospect, at the time of her presumed optic neuritis, she already had abnormalities in the sphenoid sinus adjacent to the right optic nerve canal. Orbital MRI with contrast confirmed sphenoiditis, bilateral cavernous sinus thrombosis and contrast enhancement along the left basal meninges. Urgent sinus surgery was recommended and performed by endoscopic sphenoidotomy with bilateral ethmoidectomy. No bacteria or fungi were observed on microscopy, sinus cultures returned negative. Sinus biopsies revealed chronic inflammation on histopathology. Biopsy culture from right sphenoid sinus was positive for Nocardia farcinica.