A 53-year-old male with past medical history of rectal polyps, prior stroke, motor vehicular accident, and type 2 diabetes, presented with severe constipation for two months with a two-week history of blurry vision, ataxia, bilateral ptosis, dysphagia, and dysarthria. Physical examination revealed ? strength in the bilateral lower extremities, areflexia, and decreased sensation to pinprick and light touch. He was initially diagnosed with Myasthenia Gravis, for which he was started on Mestinon. Imaging studies yielded no acute intracranial abnormalities or large vessel occlusion/stenosis. A lumbar puncture was performed, which showed elevated protein and leukocytosis. He was then started on a 5-day course of IVIG for suspected Miller-Fisher syndrome.

CSF culture was negative for GQ1b antibody, and viral PCR for VZV and HSV 1 & 2 yielded negative results. ANA, MPO IgG, and proteinase–3 IgG were also negative.  His RPR titer result was positive at 1:64, as well as a positive CSF VDRL, which confirmed the diagnosis of neurosyphilis. He was started on IV penicillin, and showed marked improvement in his symptoms. 

Patients presenting with subacute neurologic symptoms and indeterminate workups should have neurosyphilis as a differential diagnosis. CSF analysis and serologic testing facilitate early diagnosis and treatment planning, which are critical for timely clinical recovery.