Case Presentation:
A 68‐year‐old man with history of bladder cancer and hypertension presented with gait ataxia and proprioception difficulties for one year. Social history was remarkable for alcohol consumption of 1.75 liters of vodka weekly and thirty years of crack cocaine use. Vital signs, including orthostatics, were normal. He was diffusely hyper‐reflexic with decreased sensory and vibratory sensation in the left foot. He had a positive Romberg’s sign, normal muscle tone, and 5/5 strength in all extremities. Pupils were constricted, but reactive to light and accommodation.
Routine laboratory studies, including urine drug screen and HIV test, were normal as was computed tomography of the head. Serum rapid plasma reagin (RPR) titer was 1:128, and serum treponema pallidum particle agglutination assay (TP‐PA) was positive. Cerebrospinal fluid (CSF) studies revealed protein 66 mg/dL, glucose 61 mg/dL, white blood cells 12/µL (PMN 4%, lymphocyte 80%, monocyte 11%), and red blood cells 2/µL. CSF cultures for bacteria, fungi and acid‐fast bacilli were negative. CSF venereal disease research laboratory test (VDRL) and TP‐PA were both positive.
The patient was treated with three days of penicillin G intravenously followed by procaine penicillin intramuscularly for eleven days. At follow‐up one month later, he reported some improvement in ambulation and proprioception.
Discussion:
Internists commonly encounter gait ataxia, and its differential includes several diagnoses such as neurosyphilis. Neurosyphilis can also present with personality changes, dementia, seizures, pain, and paralysis.
Tabes dorsalis, also called locomotor ataxia, affects the posterior columns of the spinal cord and the dorsal roots, and it has the longest latency between primary infection and symptom onset of all forms of neurosyphilis, averaging twenty years.
Because non‐treponemal tests are usually non‐reactive in late neurosyphilis, particularly tabes dorsalis, the diagnostic algorithm begins with a treponemal antigen test, such as an enzyme immunoassay. Positive treponemal tests should be confirmed with a serum fluorescent treponemal antibody‐absorption (FTA‐ABS) or TP‐PA. Positive treponemal studies in the presence of neurologic abnormalities warrant a lumbar puncture. A lumbar puncture is also indicated in the absence of neurologic findings with an RPR titer greater than 1:32. Treatment should be initiated if CSF‐VDRL or CSF‐FTA‐ABS are reactive, or there are CSF findings of greater than 45mg/dL of protein and greater than 5/µL of WBC.
Treatment for neurosyphilis includes intravenous penicillin G 3‐4 million units every four hours for three days or 24 million units continuously for ten to fourteen days. Alternatively, daily procaine penicillin G can be given intramuscularly along with oral probenecid 500 mg four times daily for 10 to 14 days.
Conclusions:
With the widespread use of penicillin, neurosyphilis is a rare occurrence in HIV‐negative people and carries a misdiagnosis rate of 85%. Internists should, therefore, consider neurosyphilis in patients with new neurologic or psychiatric symptoms.