During the secondary stage of syphilis, the infection may affect the brain, spinal cord, and nerves. This can cause swelling (inflammation) of the membrane covering the brain and spinal cord (meningitis) and can also cause damage to the blood vessels of the nerves.

Nervous system signs of secondary syphilis include:

• Headache and irritability.
• Stiff neck.
• Unequal reflexes.
• Irregular pupils.
• Blurry vision.
• Blindness caused by damage to the nerve going to the eye (optic neuritis).
• Deafness.