A 48-year-old HIV-positive man with CD4 count 180 cells/μL presents with dementia, hyperreflexia, and Argyll Robertson pupils. Serum RPR is reactive at 1:128 and TPPA is positive. Lumbar puncture shows 25 lymphocytes/mm³, protein 80 mg/dL, glucose normal, but CSF-VDRL is non-reactive. What is the correct interpretation?

• A Neurosyphilis is excluded and no intravenous therapy is needed
• B The negative CSF-VDRL does not exclude neurosyphilis, and treatment with aqueous crystalline penicillin G is indicated ✓
• C Neurosyphilis is confirmed only if CSF-VDRL becomes reactive on repeat testing
• D The findings represent asymptomatic neurosyphilis requiring only benzathine penicillin

Explanation

CSF-VDRL is highly specific but only about 50 percent sensitive for symptomatic neurosyphilis, so a negative result never excludes the diagnosis when clinical signs, CSF pleocytosis, and raised protein are present. Treatment decisions rest on the clinical picture plus CSF abnormalities, and confirmed or suspected neurosyphilis requires aqueous crystalline penicillin G 18 to 24 MU per day intravenously for 10 to 14 days, not benzathine penicillin, which does not achieve treponemicidal CSF levels. Symptomatic disease distinguishes this from asymptomatic neurosyphilis.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.