Spirochete Infections: Neurosyphilis
Definition
Infection of brain, meninges, or spinal cord by Treponema pallidum.
Required: (a) syndrome consistent with neurosyphilis (meningitis, meningoencephalitis, meningomyelitis, cerebral infarcts, dementia paralytica, tabes dorsalis, congenital neurosyphilis, asymptomatic neurosyphilis); (b) abnormal blood titer of treponemal antibody test; (c) positive nontreponemal antibody test in CSF.
Epidemiology
Incidence declined following introduction of penicillin, then increased with AIDS epidemic.
10% of untreated patients with early syphilis develop neurosyphilis. Of HIV-positive patients, 15% have concomitant serologic evidence of syphilis; 1% have neurosyphilis.
Pathology
Early neurosyphilis: mononuclear cell infiltration of meninges, extending to cranial nerves (causing axonal degeneration) and endothelial proliferation with vessel occlusion (focal ischemic necrosis in brain and spinal cord).
Dementia paralytica: inflammation around small cortical vessels provokes loss of cortical neurons and glial proliferation. Spirochetes in cortex.
Tabes dorsalis: degeneration of posterior roots and posterior fiber columns of spinal cord.
Investigations
Serology
Nontreponemal antibody tests: VDRL, RPR. Both performed on serum; VDRL suitable for testing CSF.
Fluorescent treponemal antibody (FTA-ABS) titer: highly sensitive and specific. Performed as confirmatory test if RPR or VDRL is positive.
CSF
CSF pleocytosis best measure of disease activity. CSF protein usually increased. Glucose low or normal.
Diagnosis
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