The term "neurosyphilis" refers to infection of the central nervous system (CNS) by Treponema pallidum (T. pallidum), subspecies pallidum. Neurosyphilis can occur at any time after initial infection.
Early in the course of syphilis, the most common forms of neurosyphilis involve the cerebrospinal fluid (CSF), meninges, and vasculature (asymptomatic meningitis, symptomatic meningitis, and meningovascular disease). Late in disease, the most common forms involve the brain and spinal cord parenchyma (general paralysis of the insane and tabes dorsalis). Each form has characteristic clinical findings, but in some cases there is overlap between these findings.
This topic will review the pathogenesis, epidemiology, clinical findings, diagnosis, and treatment of neurosyphilis. Other aspects of syphilis are discussed separately. (See "Pathophysiology, transmission, and natural history of syphilis" and "Pathogenesis, clinical manifestations, and treatment of early syphilis" and "Pathogenesis, clinical manifestations, and treatment of late syphilis" and "Epidemiology, clinical presentation, and diagnosis of syphilis in the HIV-infected patient".)
Neurosyphilis begins with invasion of the cerebrospinal fluid (CSF), a process that probably occurs shortly after acquisition of Treponema pallidum (T. pallidum) infection. The organism can be identified in the CSF from approximately one-quarter of untreated patients with early syphilis [1,2]. Although investigators in the first half of the 20th century did not believe that there were "neurotropic strains" of T. pallidum, a study conducted in the antibiotic era suggested that strain variability may affect the characteristics of the infection .
Unlike other bacteria that can infect the CSF, invasion of CSF with T. pallidum does not always result in persistent infection, as spontaneous resolution may occur in some cases without an inflammatory response. In other cases, spontaneous resolution may occur after a transient meningitis.