Spirochetal diseases of the CNS.

The neurotropism of the spirochete is evident from the above discussions of syphilis, Lyme disease, leptospirosis, and relapsing fever. In all of these diseases, the organism very likely enters the CNS very early in the course of the disease. The fate of the organism then depends on the virulence of the spirochete, the host defenses, and any antibiotic treatment administered. Why Treponema pallidum lays dormant in the CNS and then somehow reactivates is a mystery; the same mystery occurs in Lyme disease. Leptospirosis and relapsing fever seem to be infections much more limited in time, and are not reported to cause these long-term sequelae. The treatment of these last two infections seems to be fairly straightforward. However, the appropriate treatment for the various stages of the disease in both syphilis and Lyme disease in order to prevent long-term sequelae is not universally accepted. At this time, it seems that high-dose intravenous penicillin is the treatment of choice for each of these infections shown to be active in the nervous system.