A 47-year-old man presented to the clinic with two weeks of headaches, progressive diplopia and right eyelid ptosis. He had no other neurological symptoms and review of systems was negative. He was a 10 pack-year smoker but had no past medical history, prior medication use or allergies. He had no ocular history. His family history was non-contributory. His sexual history was significant for unprotected same-sex intercourse with multiple partners over the past 10 years but no history of sexually transmitted infections. His vision was 20/30 in the right eye and 20/20 in the left. Examination revealed 80 prism diopters of exotropia with significant hypotropia and severe elevation, adduction and depression deficits (no movements from primary position) in the right eye. Abduction and incyclotorsion were preserved. The right pupil was dilated and poorly reactive to light and accommodation. No relative afferent pupillary defect was seen. Examination of the remaining cranial nerves revealed no abnormalities. Anterior segment and fundus examination was normal bilaterally. Neurological examination did not reveal ataxia, tremor or hemiparesis. Right isolated complete pupil-involving ONP was diagnosed.
Given the clinical presentation, aneurysmal compression was suspected and urgent brain computed tomography angiography (CTA) was obtained but came back normal. Brain magnetic resonance imaging (MRI) revealed thickening and enhancement of the right oculomotor nerve at the level of the interpeduncular and suprasellar cisterns (Fig. 1). There was no leptomeningeal enhancement nor other cranial nerve enhancement. Complete blood count, glycated hemoglobin, erythrocyte sedimentation rate and C-reactive protein serum levels were normal. Chest radiography did not reveal hilar adenopathy or signs of tuberculosis. The initial treponemal test (Treponema pallidum enzyme immunoassay) was reactive and was confirmed by a positive rapid plasma reagin test (at a 1:16 titer). Testing for human immunodeficiency virus (HIV) and tuberculosis (interferon gamma release assay, IGRA) was negative. Cerebrospinal fluid (CSF) analysis demonstrated elevated protein levels (0.83 g/L, normal: 0.15 - 0.40) and lymphocytic pleocytosis (30 x 106/L, normal: < 5). A Venereal Disease Research Laboratory (VDRL) test performed on the CSF sample was reactive (at a 1:2 titer). Early neurosyphilis was diagnosed. The patient was treated with intravenous penicillin G, 4 million units every four hours administered at-home through a peripherally inserted central catheter for a total duration of 2 weeks. At the completion of treatment, symptomatic improvement was noted but the patient was lost to follow-up before a second ophthalmological assessment could be performed.