Treponema pallidum, the bacterium that causes syphilis, invades the central nervous system in about 40% of patients with syphilis. This happens early after infection. Patients with neuroinvasion are at risk of developing serious neurological complications, including vision or hearing loss, stroke and dementia. Because neuroinvasion can happen without symptoms, the only way to identify it is by performing a lumbar puncture (LP) to examine cerebrospinal fluid (CSF).The overall hypothesis to be tested in this study is that a strategy of immediate LP, followed by therapy based on CSF evaluation, results in better serological and functional outcomes in patients with syphilis who are at high risk for neuroinvasion.