Are there any non-beta-lactam antibiotic options for treatment of neurosyphilis in non-pregnant adults?

Doxycycline is a consideration. There are no conclusive data, but a few anecdotal reports are supportive -- the most recent (in a brief PubMed search) cited below. On the other hand, there is at least one case report (also cited) of a patient treated with doxycycline who subsequently re-presented with neurosyphilis. If used, close follow-up is indicated for at least a year or two.

As you likely know, the tetracyclines are active against T. pallidum and from limited data and consistent clinical experience, doxycycline seems to be universally effective except for the doubts about neurosyphilis. It is advised by the CDC as the main backup when penicillin can't be given: 100 mg bid for 14 days for early syphilis and 28 days for late syphilis. In...