Management of Asymptomatic Neurosyphilis

Definition and Epidemiology

Asymptomatic neurosyphilis is the most common form of central nervous system involvement by Treponema pallidum and is defined by cerebrospinal fluid (CSF) abnormalities (mononuclear pleocytosis and elevated protein) without clinical neurological signs, according to the MMWR Recommendations (2004) 1.

In patients living with HIV, a CD4⁺ T‑cell count ≤ 350 cells/µL is associated with a higher likelihood of central nervous system involvement, as reported by the MMWR Recommendations (2010) 2.
Advanced immunosuppression in HIV‑coinfected individuals accelerates progression of syphilis to symptomatic neurological disease, per the MMWR Recommendations (2004) 1.

The CSF VDRL test is highly specific for neurosyphilis but has limited sensitivity; a non‑reactive result does not exclude the diagnosis (MMWR Recommendations, 2010) 3.
Clinicians should retain neurosyphilis in the differential diagnosis of any neurological disorder, especially in persons with HIV infection (MMWR Recommendations, 2010) 3.

Aqueous crystalline penicillin G 18–24 million units per day, administered as 3–4 million units IV every 4 hours or by continuous infusion, for 10–14 days (MMWR Recommendations, 2010) [4][3][5][6].

Procaine penicillin 2.4 million units IM once daily plus Probenecid 500 mg orally four times daily, both for 10–14 days (MMWR Recommendations, 2010) [2][4][3][5]6.

Because the duration of the above regimens is shorter than that used for late syphilis without neurosyphilis, a single dose of benzathine penicillin G 2.4 million units IM weekly for up to 3 weeks may be given after completing the primary therapy to achieve an equivalent total treatment length (MMWR Recommendations, 2010) [4][5]6.

If CSF pleocytosis was present at baseline, repeat lumbar puncture every 6 months until the CSF white‑cell count normalizes (MMWR Recommendations, 2010) [4][5]6.
The CSF leukocyte count is a sensitive indicator of treatment efficacy (MMWR Recommendations, 2010) [4][6].
If the CSF cell count has not decreased after 6 months, or if CSF parameters remain abnormal after 2 years, re‑treatment should be considered (MMWR Recommendations, 2010) [4][5]6.

All patients diagnosed with syphilis should be screened for HIV, because coinfection markedly alters the risk profile and management of neurosyphilis (MMWR Recommendations, 1993; 1998; 2002; 2010) [7][4][8][9][5][6].

Neurosyphilis can develop at any stage of syphilis infection, not only in late disease, according to CDC recommendations. 10, 11

HIV‑infected patients with early syphilis have a modestly increased risk of neurologic complications, although the absolute magnitude of this risk is small (CDC). 12, 13
Cerebrospinal fluid (CSF) abnormalities—elevated protein and mononuclear pleocytosis—are frequently observed in early syphilis even when patients lack neurologic symptoms (CDC). 14, 15
Serum nontreponemal titers of RPR ≥ 1:32 are consistently associated with a higher likelihood of neurosyphilis (Clinical Infectious Diseases). 16
HIV infection with CD4 counts ≤ 350 cells/µL correlates with increased rates of central nervous system involvement (CDC). 14, 17
Advanced immunosuppression accelerates progression of syphilitic disease, including neurologic manifestations (CDC). 10

The CSF VDRL test is highly specific but lacks sensitivity; a non‑reactive result does not rule out neurosyphilis (CDC). 18, 15
Relying solely on a negative CSF VDRL can lead to missed diagnoses because the test’s sensitivity is limited (CDC). 18, 15
Clinicians should maintain neurosyphilis on the differential diagnosis of any neurologic disorder in HIV‑infected individuals, even when other causes seem plausible (CDC). 12, 19