Clinical Reasoning: An 83-Year-Old Female Patient With a Pupil-Involving Oculomotor Nerve Palsy.

We report a case of an 83-year-old female patient who presented with binocular diplopia associated with left periorbital pain. She was diagnosed with a left pupil-involving third nerve palsy initially believed to be either microvascular or aneurysmal. However, negative vascular neuroimaging and further serologic workup suggested the possibility of neurosyphilis. Her clinical course was significant for persistent periorbital pain and a new seventh nerve palsy, despite syphilis treatment, prompting repeat neuroimaging and lumbar puncture. This case highlights the importance of the clinical history, imaging, CSF studies, and repeated workup in distinguishing between infectious and noninfectious causes of cranial neuropathies.