An Overview of Neurosyphilis

Neurosyphilis is an infection of the central nervous system

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Neurosyphilis occurs when a syphilis infection spreads to the central nervous system. Syphilis is primarily thought of as a sexually transmitted infection that causes sores known as chancres. Syphilis can also affect the central nervous system (CNS)⁠—the spine and the brain. When this happens, it can cause serious or even debilitating symptoms. Neurosyphilis can happen during any stage of a syphilis infection.

Doctor talking with patient in a hospital room
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Symptoms of neurosyphilis are highly variable. They depend on which nerves are infected with the syphilis pathogen.

People with neurosyphilis may have one or more symptoms. They may also have no symptoms at all.

Possible symptoms of neurosyphilis include:

  • Partial paralysis or weakness, affecting one or more areas of the body
  • Emotional lability, a difficulty controlling emotions. Emotions may change quickly or fail to match the situation.
  • Difficulty with memory
  • Psychosis, where someone hears, sees, or believes things that aren't real
  • Personality changes
  • Changes in sensation in the limbs
  • Loss of, or changes in, coordination
  • Progressive dementia

Neurosyphilis is so dangerous because the CNS is the central information system of the body. The brain controls all conscious, and many unconscious, functions of the body. The spine sends information from the rest of the body to the brain to be interpreted. Therefore, infections that disrupt the brain or spine can damage the flow of important information from the brain to the body and back again.

Syphilis infections of the eye are also sometimes included in the category of neurosyphilis. More correctly referred to as ocular syphilis, eye infections can lead to vision problems and blindness.


Syphilis is caused by infection with Treponema pallidum. It is spread almost exclusively through oral, vaginal, or anal sex. However, it can also be transmitted from mother to child during pregnancy. Transmission during pregnancy is particularly dangerous, as congenital syphilis can be fatal for a newborn.

Doctors do not understand why some individuals with syphilis go on to develop neurosyphilis and others do not. Neurosyphilis is most likely to occur in individuals whose syphilis has gone undiagnosed and untreated for long periods of time.

That is why regular syphilis screening is recommended for people at high risk of the disease or in whom the infection would be particularly serious. This includes those who are:

Although there was a long period where syphilis infections were on the decline, this is no longer true. There have been a growing number of cases of syphilis since 2000, most of which have occurred in men who have sex with men.

Most cases of syphilis will not become neurosyphilis, particularly with prompt screening and treatment. However, historical evidence suggests that partial or incomplete treatment of syphilis may somewhat increase risk.


Syphilis infections are diagnosed via a blood test. However, neurosyphilis is somewhat harder to diagnose. This is particularly true as there are no gold standard tests for neurosyphilis. Instead, diagnosis is usually based on the combination of symptoms and screening of the cerebrospinal fluid (CSF).

Identifying the presence of syphilis in the CSF usually requires a spinal tap. During this procedure, a needle is stuck in between the bones of the lower back and some of the protective fluid surrounding the spine is removed. Then this fluid is tested for syphilis using the same VDRL test that is used to look for syphilis in the blood. Doctors will also look for increased protein or cell counts in the CSF.

It is important to note that some people will have abnormal CSF syphilis tests without any clinical symptoms. Those patients are usually diagnosed as having asymptomatic neurosyphilis.

It's also possible to have neurosyphilis symptoms and a positive syphilis test without a positive CSF test. Those patients are usually diagnosed with neurosyphilis.

It is generally recommended that anyone with neurosyphilis also be tested for HIV


Treating neurosyphilis requires patients to take all of their medication, and take it reliably. Therefore, in order to make certain people are getting their medication, treatment often takes place in the hospital.

This involves receiving an IV of aqueous crystalline penicillin G every four hours, or continuously, for 10 to 14 days.

For people who will definitely be compliant with medication, it is possible to combine penicillin injections with oral Probenecid (a uric acid reducer) for 10 to 14 days. Longer treatment may be necessary.


The personality changes associated with neurosyphilis can make it hard to cope with⁠—for both the infected person and their loved ones. Fortunately, in the early stages of neurosyphilis, treatment is very effective. It can reverse many of the physical and psychiatric side effects of the disease.

However, for people with later stage neurosyphilis, treatment may not be as effective at restoring function. Damage to the brain, of the sort associated with dementia, is not always reversible even if the infection is cured.

A Word From Verywell

Neurosyphilis can be a scary diagnosis. It is also a largely preventable one. Reliably practicing safer sex, including oral sex, can vastly reduce a person's risk of acquiring a syphilis infection.

In addition, neurosyphilis is much more common in later stages of syphilis than in early stages. Therefore, regular screening and prompt treatment can also have a big impact on reducing risk.

If you're someone who is at risk for syphilis, you can always ask to be screened at your annual doctor's visit. If they're drawing blood already, you may not even notice when they run the test.

1 Source
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  1. Mattei PL, Beachkofsky TM, Gilson RT, Wisco OJ. Syphilis: a reemerging infection. Am Fam Physician. 2012;86(5):433-40.

Additional Reading

By Elizabeth Boskey, PhD
Elizabeth Boskey, PhD, MPH, CHES, is a social worker, adjunct lecturer, and expert writer in the field of sexually transmitted diseases.