Abstract:Of the symptomatic disorders associated with neurosyphilis, the earliest manifestation is syphilitic meningitis. Approximately 5% of patients with secondary syphilis develop associated meningitis. Headaches, meningismus, cranial nerve palsies (chiefly, in descending order of frequency, VII, VIII, VI, and II. Here, we report a case of neurosyphilis presenting as unilateral oculomotor nerve palsy with bilateral pupil involvement (Argyll-Robertson pupil).A 43-year-old male presented with diplopia in both eyes at a neurology clinic 2 weeks before. He had right paralytic blepharoptosis, and both pupils were fixed and both pupils were not observed direct and indirect reflex and anisocoric. We observed Argyll Robertson pupil. He had 35 prisms of right exotropia, 2 prisms of right hypertropia at near and distance in the state of primary deviation and 60-prism right exotropia and 4-prism hypertropia in the state of secondary deviation. He had extraocular movement disorder in all gazes except abduction. We considered oculomotor nerve palsy associated with neurosyphilis based on the Argyll Robertson pupil. His orbit MRI suggested right oculomotor neuritis due to the presence of diffuse thickening of the right oculomotor nerve with enhancement. Finally, he was diagnosed with syphilis as a result of CSF protein 96.0, VDRL 7.5, and FTA-ABS (+) and was administered penicillin (4,000,000 units) and oral steroid (50 mg). One week after, his intraocular pressure was in the normal range. Extraocular movement examination findings were favorable as a result of 20-prism right exotropia at near and distance in the state of primary deviation and 35-prism right exotropia in the state of secondary deviation. He had extraocular movement disorder only in upper gaze.A diagnosis of neurosyphilis should be considered in patients with serologic evidence of syphilis and one or more of the following cerebrospinal fluid abnormalities; mononuclear pleocytosis, elevated protein, increased immunoglobulin G, or the presence of oligoclonal bands.