Central Nervous System Infection in Congenital Syphilis

In infants with suspected congenital syphilis, the detection of central nervous system infection by Treponema pallidum remains an elusive but important diagnostic goal. Neurosyphilis is believed to occur in 60 percent of infants with congenital syphilis, as judged by the presence of cerebrospinal fluid abnormalities such as reactivity on a Venereal Disease Research Laboratory (VDRL) test, pleocytosis, and elevated protein contents. However, it is not known whether the results based on these criteria accurately reflect the prevalence of central nervous system infection by T. Pallidum, since rabbit-infectivity testing has not validated this approach.

In the current study, using infants prospectively enrolled if they were born between July 1989 and July 1999 and whose mother had syphilis during pregnancy, the researchers used rabbit-infectivity testing of cerebrospinal fluid to identify infants with T. pallidum infection of the central nervous system. The researchers compared the results of this test with results of clinical, radiographic, and conventional laboratory examination; IgM immunoblotting of serum and cerebrospinal fluid; PCR assay of serum, blood, and cerebrospinal fluid; and rabbit-infectivity testing of serum and blood.

Of the 76 infants who were born to women with syphilis who had no in utero or postnatal exposure to antibiotics, 17 (22 percent) had spirochetes detected in the cerebrospinal fluid. Most of the infants (16 of 17) with central nervous system infection could be identified by abnormalities on the physical examination, radiographic studies, or conventional tests, such as the cerebrospinal fluid white-cell count and the VDRL test. However, the results of IgM immunoblotting of serum and the polymerase-chain-reaction assay of serum or blood proved to be the best predictors (17 or 17) of the detection of central nervous system infection by the rabbit-infectivity test.

According to the researchers, the results show that central nervous system involvement is common in infants infected with Treponema pallidum. Although identifying central nervous system infections has been difficult in infants with congenital syphilis, such testing is important because the result affects the treatment strategy. It is possible a new pair of blood tests can detect the presence of syphilis and be able to save newborns from unnecessary antibiotic treatments. The federal government currently recommends that every baby born to a mother with syphilis be kept in the hospital for an additional 10 days to receive antibiotic therapy. But according to researchers, 20 percent to 40 percent of those infants do not need the antibiotics because they have not contracted the disease.

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