What stage can syphilis be treated but not cured?

Syphilis can be treated but not cured in its late stage, specifically during neurosyphilis. At this point, the infection has progressed and can cause significant damage to the nervous system, and while antibiotics can manage symptoms and prevent further damage, any neurological impairments that have already occurred may not be reversible. Early detection and treatment are crucial for a complete cure, so timely medical intervention is essential.