When Syphilis is left untreated, it causes neurosyphilis. Neurosyphilis is damage done to the brain as a result of syphilis not treated at all or well.
SYMPTOMS OF NEUROSYPHILIS
Asymptomatic: This means that a person could have neurosyphilis without showing any symptoms. However, the person later become symptomatic by showing the following symptoms-
Vertigo: It is a sensation of feeling off balance as if your environment is spinning.
Muscular atrophy: This is when muscle shrinks.
Sudden change in personality
Dysarthria: Slurred or slow speech often difficult to understand because muscle controlling them are weak or damaged.
All these symptoms and damages to the brain could have all been avoided if syphilis is treated on time.
For the test your doctor might possibly request: https://www.healthgist.net/syphilis-lets-talk-about-it/
Steroids should be given with all treatment regimens for late syphilis with cardiovascular or neurological involvement; 40–60mg prednisolone OD for three days starting 24 hours before antibiotics-
Benzylpenicillin 10.8–14.4g daily, given as 1.8–2.4g intravenously (IV) every 4 hours for 14 days
Amoxicillin 2g PO TDS plus probenecid 500mg PO QDS for 28 days
Procaine penicillin G 1.8–2.4 MU IM OD plus probenecid 500mg PO QDS for 14 days
Doxycycline 200mg PO BD for 28 days
Ceftriaxone 2g IM or IV OD for 10–14 days (dependent on allergy)
To avoid damage done to the brain by syphilis, make sure you treat syphilis symptoms well early enough.
For other advice: https://www.healthgist.net/syphilis-lets-talk-about-it/