Tabes Dorsalis

What is Tabes Dorsalis?

Tabes dorsalis, also known as locomotor ataxia, is a rare disease that slowly damages nerve cells in the spinal cord. It is caused by an infection with a bacterium (a type of germ) called Treponema pallidum. This bacterium is also responsible for causing sexually transmitted syphilis.

This disease is seen as a late-stage manifestation of neurosyphilis – a condition that affects the brain and spinal cord due to untreated syphilis. Among different forms of neurosyphilis, tabes dorsalis takes the longest to show symptoms, typically around 20 years after the initial infection. There are instances, though, where symptoms might show up early. This disease was more common before antibiotics were used, but it is now rare.

Patients with tabes dorsalis often face symptoms like sensory imbalance and sudden, sharp pains that can appear in the limbs, back, or face and last from a few minutes to several days. They might also experience less common symptoms like tingling or numbness, stomach pain and discomfort, vomiting, and early bladder issues leading to difficulty passing urine or inability to control urination. Eye abnormalities, particularly a condition called Argyll Robertson pupil, are also commonly seen in these patients. Other neurological effects may include absent reflexes in the lower legs, impaired sensation related to vibration and position, and shortcomings in touch, pain, and sight. Chronic damage in the large joints can happen in severe cases.

Diagnosing neurosyphilis can be complex, requiring doctors to be very thorough and consider a wide range of possibilities. However, if the disease is recognized early and treated appropriately, patients can have positive outcomes.

What Causes Tabes Dorsalis?

Treponemes are bacteria that are thin, twisted into a spiral shape, like a tiny corkscrew. A type of Treponemes, known as T pallidum, has different forms that cause various diseases in humans. T pallidum subspecies pallidum causes syphilis, a sexually transmitted disease, while T pallidum subspecies pertenue and endemicum cause skin diseases called yaws and endemic syphilis respectively. On the other hand, T carateum causes another skin disease named pinta. It’s noteworthy that humans are the only creatures that can naturally host, or carry, T pallidum.

Risk Factors and Frequency for Tabes Dorsalis

It’s tricky to know the exact number of neurosyphilis cases, which includes a form called tabes dorsalis. This is despite an increase in syphilis cases across the globe. In fact, primary and secondary syphilis cases rose by 28.6% from 2020 to 2021. The current prevalence of syphilis is estimated to be around 16.2 cases per 100,000 people.

About three-quarters of primary and secondary syphilis infections occur in men aged 25 to 34. This is mainly due to rising cases among men who have sex with men (MSM). Risk factors associated with MSM include using methamphetamine and meeting recent sexual partners online. MSM diagnosed with syphilis often have HIV as well. The incidence of HIV coinfection among MSM, men who exclusively have sex with women, and women is 45%, 7%, and 4% respectively. Since 2012, the rate of syphilis among women has risen by 700%, likely due to increased drug use. Due to the rising syphilis cases among women, instances of congenital syphilis (syphilis present at birth) are also increasing.

Worldwide, about 25% to 35% of syphilis cases develop into serious neurosyphilis. Approximately one-third of these cases can evolve into tabes dorsalis. Experts estimate that between 1.5% to 9% of syphilis patients will develop tabes dorsalis. Black patients in the United States have a significantly higher rate of syphilis than their white counterparts. The highest rates of syphilis globally can be found in low-income regions in Africa and Southeast Asia.

Signs and Symptoms of Tabes Dorsalis

Diagnosing neurosyphilis, an infection of the nervous system, requires a suspicious medical outlook. Doctors may suspect it in patients who have had signs of syphilis, eye or ear problems, or in those who are HIV positive. It’s important to know, though, that syphilis doesn’t always show clear symptoms or stages.

The disease has distinct stages that are split into early and late periods, with more subdivisions within them such as:

• Early-stage disease: This includes primary, secondary, and early latent syphilis.
• Primary syphilis: Here, a single, painless sore appears at the infection site, with an average emergence time of about 21 days.
• Secondary syphilis: Around a quarter of patients will experience a rash, fever, sore throat, liver inflammation, warty growths, and hair loss a few months after infection.
• Early latent syphilis: People with this stage won’t show symptoms, but will test positive for the disease.

Then, there are:

• Late-stage diseases: Including tertiary and late latent syphilis, with some patients not presenting symptoms until decades after the initial infection.
• Tertiary syphilis: Symptoms here involve heart disease or firm, rubbery skin growths.
• Late latent syphilis: Similar to early latent syphilis, a patient won’t show symptoms but a blood test will detect the disease.

There’s also neurosyphilis, and it has two periods too:

• Early neurosyphilis: Around 40% of people will unknowingly have neurological involvement, with symptoms such as meningitis, stroke, and sight or hearing loss. This is especially common in people with HIV.
• Late neurosyphilis: Known for symptoms such as cognitive impairment, personality changes, difficulty speaking, muscle weakness, shaking, and abnormal reflexes.

Early neurosyphilis is more common these days, particularly among those with HIV. Late neurosyphilis, on the other hand, often results in tabes dorsalis, a condition that affects the nerves in the spine, with symptoms like loss of pain sensation, body position and vibration senses, tingling, imbalance, severe pain, stomach problems, and urinary issues.

A careful physical exam is crucial for diagnosing tabes dorsalis. This might reveal an abnormal pupil response to light (Argyll Robertson pupil), diminished reflexes and pain sensation, difficulty walking and maintaining balance, impaired sense of body movement, progressive joint damage, or severe nerve damage leading to muscle weakness in both legs.

Moreover, Charcot joints, characterized by progressive degeneration of joint structures, can also occur. A condition called Charcot spine, or spinal neuroarthropathy, is rare but represents a deteriorating spine because of long-term sensory and body position sense loss. This condition is associated more with spinal cord injuries and often leads to spinal deformities, usually hunched back (kyphosis).

Repeated minor injuries to the spine, along with local inflammation and fractures, can lead to deformities and other complications, such as spinal masses and nerve pinching, which can cause additional neurological symptoms.

Testing for Tabes Dorsalis

Diagnosing tabes dorsalis, a condition brought about by late-stage syphilis, can be difficult. Doctors need to consider things like how you present your symptoms, your medical history, and any other diseases that you might have, like HIV. The bacteria causing syphilis, T pallidum, cannot be grown in a lab, so doctors have to use blood and cerebrospinal fluid (fluid from around your brain and spine) tests to diagnose the disease. They might also use imaging studies (like an MRI or CT scan) and measure the speed of your sensory nerve responses.

There are two types of tests for syphilis: nontreponemal and treponemal-specific tests. It’s important that doctors don’t only use one — both types are needed because a single test might give a false-positive or a false-negative result. Nontreponemal tests measure antibodies against lipoidal antigens (a type of protein) and can give a rough idea of how active the infection is. Treponemal antibody tests look for antibodies against specific parts of the T pallidum bacteria, and can tell whether or not you’ve ever been infected with syphilis. However, they can’t tell if your case is new, old, or relapsed.

The interpretation of these tests depends on a variety of factors, like whether you’ve had syphilis before, and what your immune system is like. If both tests come back positive, and you’ve never had syphilis before, it’s likely that you’ve got a new syphilis infection. In people who’ve had syphilis in the past, a positive nontreponemal test could mean a new infection, successful treatment, or treatment failure. These patients might need a lumbar puncture (a test where fluid from around the spinal cord is collected) if they have symptoms of neurosyphilis, show signs of active tertiary syphilis (the third and final stage of the disease), or haven’t responded to treatment.

If you’ve got an unknown history of syphilis, doctors will use these tests to confirm that you have a T pallidum infection. If you’re known to have had syphilis before, a lumbar puncture will be needed if you’ve got neurological symptoms or symptoms similar to syphilis-related conditions.

The fluid collected via lumbar puncture can help confirm a diagnosis of neurosyphilis. If you’ve got neurosyphilis, you’ll likely have elevated protein levels, increased white blood cells, and a positive Venereal Disease Research Laboratory (VDRL) test in your cerebrospinal fluid.

Imaging can be used in a diagnosis, but abnormalities shown by MRIs in tabes dorsalis are infrequent. But when they do show, there might be swelling and high signal enhancement in the affected part of the spinal cord, sometimes called the “flip-flop” sign. This enhancement can show focal inflammation of the spinal cord compatible with tabes dorsalis. Additionally, strong signalling along the spinal columns and atrophy (shrinking) of the spinal cord may be seen, which can indicate a poorer prognosis.

Diagnosing a condition called the Charcot spine, where there’s excessive mobility in the spine, especially at the lumbosacral and thoracolumbar junctions (lower back), can also be challenging. MRI and CT scans play an important part in diagnosing this condition, especially if they show gas within the disc space, a sign of excessive motion.

Treatment Options for Tabes Dorsalis

The Centers for Disease Control and Prevention (CDC) recommends penicillin as the primary treatment for all stages of neurosyphilis, which includes a severe type called tabes dorsalis. This treatment involves direct delivery of the drug into the bloodstream. Doctors test patients’ HIV status before they start this treatment. Penicillin is advised for 10 to 14 days. For patients where this short regimen is not enough, some medical professionals suggest getting an extra dose of a different form of penicillin, benzathine penicillin G. However, there’s not a lot of evidence supporting this routine, and further research is necessary. Unfortunately, options other than intravenous therapy don’t currently exist.

In some cases, certain tests may not confirm neurosyphilis even though the person has the disease. In such scenarios, doctors may still recommend penicillin if the patient shows symptoms, has risk factors for syphilis, has a reactive blood test for syphilis, and an inflammatory response in the cerebrospinal fluid (CFR)— the fluid surrounding the brain and spinal cord. If the disease symptoms continue, additional courses of penicillin might be recommended. HIV patients have a high risk of disease relapse. The disease can be arrested, and disease progression stopped if proper treatment is taken in the early stages of neurosyphilis. The disease might cause serious nerve damage in the spine (tabes dorsalis), but the symptoms can improve with treatment. However, if the disease has progressed late into neurosyphilis or tabes dorsalis, the treatment might just limit the disease’s progression and not necessarily improve the existing symptoms.

If a patient is allergic to penicillin, the CDC recommends ceftriaxone, another antibiotic, given either directly into the bloodstream or a muscle for a similar duration. Some patients might also need to switch to doxycycline, another antibiotic, which is given orally for 21 to 28 days in severe cases. Close to 90% of people who say they are allergic to penicillin, may not actually be so. Those with confirmed penicillin allergies should consider evaluation by an allergist to see if they can be desensitized or given another trial with penicillin.

A reaction called the Jarisch-Herxheimer reaction could occur within the first 24 hours of starting treatment for syphilis. It’s an inflammation reaction to the medications where the body might have symptoms like fever, muscle pain, sweating, and low blood pressure which might resolve within a day. Though it’s not fully clear why it happens, it’s probably due to the body’s response to the dead bacterial cells given the medicine. There are no preventive measures for this, and patients should be aware. Patients could use over-the-counter treatments to help with the symptoms.

Additional treatment depends on the patient’s specific situation. This could include pain relief medications like opioids, physical therapy to prevent muscle wasting and weakness, and prevention strategies for sexual partners. There should be close monitoring after treatment with neurological examinations and lumbar puncture tests (a doe done in the lower back to extract cerebrospinal fluid for testing) at regular intervals.

Charcot spine is a severe condition that results from tabes dorsalis. Its treatment includes managing individual symptoms like autonomic dysreflexia (a sudden high blood pressure) and surgery to stabilize the spine. If surgery is not possible or decided against, non-surgical measures like braces and bed rest are alternatives. Some researchers have also suggested a type of drug treatment in managing Charcot foot syndrome, though this needs more research to be certain of its impact.

What else can Tabes Dorsalis be?

There are many health conditions that affect the spinal cord and result in symptoms similar to each other. To diagnose these accurately and start the appropriate treatment quickly, a thorough examination is required. Here are some conditions that doctors have to consider and differentiate from each other:

• Genetic and other diseases that strip the protective coating of nerves, including:
  • Hereditary spastic paraplegia
  • Amyotrophic lateral sclerosis
  • Spinal muscular atrophy
  • Friedreich ataxia
  • Adrenomyeloneuropathy
• Diverse spinal cord diseases such as:
  • Vitamin B12 deficiency
  • Copper deficiency
  • Effects of nitrous oxide and heroin use
  • Lathyrism – an irreversible nerve condition caused by eating too many grass peas that leads to paralysis of the legs
• Excessive intake of zinc
• Non-syphilitic Argyll Robertson pupil – A particular eye condition that involves abnormal pupils. This can be observed in diabetes and multiple sclerosis, among other conditions. Consultation with an eye specialist is advised when diagnosing spinal diseases accompanied by pupil abnormalities.
• Other conditions doctors need to keep in mind:
  • Demyelination caused by infection
  • Myelopathy due to vascular diseases leading to insufficient blood flow and tissue death
  • Neurological issues caused by spinal tumors

Symbolizing features of demyelinating diseases include gradual nerve damage, removal of nerve protection, muscle thinning and weakness, loss of muscle control, paralysis, and loss of sensation. Doctors also take into account associations with diabetes, cerebellar disease, scoliosis, and the absence of lesions associated with syphilis. Negative results in syphilis tests are also helpful in ruling out one spinal condition called tabes dorsalis. Scans of the brain and spinal cord using MRI are necessary to correctly identify the condition.

When vitamin B12 is deficient, it can trigger subacute combined degeneration of the posterior and lateral sections of the spinal cord. If this is combined with a type of anemia called megaloblastic anemia, blood tests, and syphilis tests help differentiate it from tabes dorsalis. Copper deficiency leads to spinal cord changes that greatly resemble tabes dorsalis. Other substances, like nitrous oxide and heroin, can also cause posterior and lateral cord damage. Findings on MRI scans can help distinguish these conditions from tabes dorsalis.

What to expect with Tabes Dorsalis

The future outlook for tabes dorsalis, a condition that affects the nerves, is generally positive provided it is identified and treated early. However, if it is not treated, it can potentially lead to severe conditions such as paralysis, dementia, or blindness. It’s important to note that once nerve damage occurs, it can’t be reversed.

Possible Complications When Diagnosed with Tabes Dorsalis

Syphilis can lead to several complications, some of which are:

• Inflammation and swelling in the aorta (aortitis and aortic aneurysm)
• Mental decline or dementia
• Stroke
• A type of kidney damage (membranous glomerulonephritis)
• A rare blood disorder causing sudden anemia during cold weather (paroxysmal cold hemoglobinemia)
• A type of non-cancerous sore causing physical changes (disfigurement by gummas)
• Hearing loss
• Kidney failure (renal failure)

Moreover, a specific condition associated with late-stage syphilis, Tabes Dorsalis, can also result in complications including:

• Decay of joints leading to changes in shape or Charcot joints
• Fractures occurring near a joint (periarticular pathological fractures)
• Mental decline or dementia
• Paralysis
• Loss of vision (blindness)
• A drop in blood pressure when standing up (postural hypotension)
• Damages to spine or Charcot spine

Preventing Tabes Dorsalis

Syphilis is an infection that is typically spread through sexual contact, and it’s been on the rise globally, raising concerns about a potential outbreak. However, a combination of health programs, comprehensive sex education, and easy availability of cost-effective condoms and other protection methods can help keep it under control.

Doctors and other healthcare providers should take the time to educate people who are sexually active about the dangers of having sex without using protection. They should also make efforts to familiarize individuals with the signs and symptoms of different sexually transmitted infections, like syphilis. This will help lower the stigma attached to these diseases and inspire people to seek medical help in a timely manner, for themselves and their partners as well. Pregnant women should also be routinely checked for syphilis, as this is a crucial step for public health safety.

When treated early, the outlook for people with syphilis, including a form known as tabes dorsalis, is usually good. However, if not managed properly or left untreated, it can lead to serious complications like dementia, paralysis, blindness, and inflammation of the aorta (aortitis). Healthcare professionals should emphasize to patients the importance of completing the full treatment plan and keeping all follow-up appointments to ensure successful treatment. Encouraging people to seek medical attention quickly if new symptoms appear is also extremely important, especially in areas where societal stigma might deter individuals from seeking care.