Snapshot A 44-year-old man presents with episodes of back pain and unintentional falls. The patient describes these pain episodes as a brief and stab-like sensation that lasts a few minutes. He reports that the falls are most frequent when he is in a dark room. Medical history is significant for HIV infection, which is being managed with anti-retroviral therapy. However, he states that he forgets to take his medication on multiple occasions. On physical examination, the patient's pupils do not respond when exposed to light, but has normal accommodation. There is impaired vibratory and proprioception sense of the lower extremity along with absent patellar reflexes. Introduction Clinical definition a clinical manifestation of late neurosyphilis that results in degeneration of the spinal cord dorsal columns dorsal roots Presentation Symptoms sensory ataxia lancinating pain e.g., sudden, brief, and severe stab-like pain Physical exam Argyll-Robertson pupil absent lower extremity reflexes impaired vibratory and propioception sense positive Romberg sign