Like all diseases, early diagnosis is important for syphilis symptoms and treatment. The first two stages of syphilis are not too dangerous, but it can cause irreparable damage after the second stage. And the treatment becomes harder too because the antibiotic dose required to kill the bacteria are much larger.
My mom is a nurse and I remember her telling me that if for example two million units of antibiotics are used to treat someone in the early stage of syphilis, seven million units is necessary for tertiary syphilis.
For neurosyphilis, the dose is much higher, something unbelievable like 200 million units if I remember right. That's a lot of antibiotics! It won't be too easy on the system or the kidneys.