Tabes dorsalis, also known as locomotor ataxia, is a rare but serious neurological complication of untreated syphilis. It occurs when Treponema pallidum, the bacterium that causes syphilis, invades the nervous system and gradually damages the posterior columns and dorsal roots of the spinal cord. This late manifestation of neurosyphilis typically develops 10–30 years after the initial infection if it remains untreated. Although now rare in developed countries due to effective antibiotic therapy, it continues to pose significant health challenges in underserved populations where access to healthcare and syphilis treatment may be limited.

This article provides a comprehensive overview of Tabes dorsalis, including its causes, progression, symptoms, diagnosis, treatment, complications, prognosis, and preventive strategies.

Tabes dorsalis is a chronic, progressive neurological disorder caused by the destruction of sensory neurons in the dorsal columns of the spinal cord. These structures are responsible for proprioception (the sense of body position), vibration sense, and fine touch. As these pathways deteriorate, patients experience unsteady gait, loss of coordination, sharp nerve pains, and other disabling neurological features. Without treatment, the condition can result in profound disability and reduced quality of life.

Distinction from other neurosyphilis forms

Unlike other forms of neurosyphilis, such as meningovascular or general paresis, Tabes dorsalis specifically targets the posterior columns and roots. This leads to a clinical picture dominated by sensory ataxia, lightning-like pains, and characteristic ocular findings such as Argyll Robertson pupils.

Tabes dorsalis results from untreated or inadequately treated syphilis infection.

Key causes and risk factors include:

• Untreated syphilis: Lack of early antibiotic therapy allows Treponema pallidum to persist and eventually invade the nervous system.
• Immunosuppression: Conditions such as HIV/AIDS increase susceptibility to neurosyphilis.
• Poor access to healthcare: Inability to obtain timely diagnosis and treatment facilitates progression.
• Incomplete treatment: Past infections treated inadequately can still progress to neurosyphilis.

Although rare in developed nations today, Tabes dorsalis remains a risk in populations with limited access to healthcare or where syphilis remains underdiagnosed.

The development of Tabes dorsalis unfolds over years to decades:

1. Initial syphilis infection: Transmission occurs via sexual contact or, in some cases, congenital transmission from mother to child.
2. Early and latent syphilis: The infection progresses through primary (chancre), secondary (rash, systemic symptoms), and latent phases. In latency, the infection is clinically silent but bacteria persist.
3. Central nervous system involvement: In some individuals, Treponema pallidum infiltrates the nervous system, leading to neurosyphilis.
4. Spinal cord degeneration: Over decades, the dorsal columns and roots degenerate, impairing sensory pathways.

This degeneration disrupts proprioception and reflexes, giving rise to ataxia, lightning pains, and characteristic neurological deficits.

Historically, Tabes dorsalis was relatively common before the advent of antibiotics. Today, it is rare in developed nations due to widespread syphilis screening and penicillin treatment. However, in regions with limited healthcare access, neurosyphilis—including Tabes dorsalis—still occurs. The condition typically develops in middle-aged adults, often 10–30 years after the initial syphilis infection. Men are somewhat more commonly affected than women, reflecting syphilis prevalence patterns.

Symptoms develop gradually and may initially be subtle. Over time, progressive neurological deficits appear due to spinal cord degeneration. Early complaints are often vague, such as mild imbalance or fleeting sensory changes, and may be overlooked. As degeneration continues, however, the loss of proprioception and reflexes becomes more pronounced, eventually resulting in the classic triad of sensory ataxia, lightning pains, and pupillary abnormalities.

Classic symptoms

• Locomotor ataxia: A broad-based, stomping gait known as “Dawson’s gait” caused by impaired proprioception.
• Lightning pains: Sudden, stabbing or shock-like pains in the legs or back that are intermittent but severe.
• Positive Romberg sign: Patients sway or fall when standing with eyes closed, due to loss of position sense.
• Sensory loss: Reduced vibration and position sense, especially in the legs. Tendon reflexes such as the knee-jerk may be absent.
• Argyll Robertson pupils: Pupils that constrict with near focus but not in response to light, a hallmark of neurosyphilis.

Other neurological and systemic features

• Bladder dysfunction: Incontinence or urinary retention.
• Trophic changes: Skin ulcers, Charcot joints, and muscle wasting.
• Additional neurological deficits: Sexual dysfunction, muscle weakness, and balance problems.

The combination of sensory ataxia, lightning pains, and Argyll Robertson pupils is highly characteristic of Tabes dorsalis.

Accurate diagnosis requires correlating clinical findings with laboratory and imaging tests. Because symptoms often overlap with other neurological conditions, combining patient history, physical examination, serology, and imaging provides the most reliable assessment. This integrated approach allows clinicians to confirm neurosyphilis while excluding other potential causes of ataxia and sensory loss.

Clinical evaluation

• History of untreated or inadequately treated syphilis.
• Neurological signs such as ataxia, lightning pains, and absent reflexes.
• Ophthalmological findings including Argyll Robertson pupils.

Serological testing

• Nontreponemal tests (RPR, VDRL): Useful for initial screening.
• Treponemal tests (FTA-ABS, TP-PA): Confirmatory for syphilis exposure.
• A combination of these tests helps establish current or past infection.

CSF analysis

• Lumbar puncture often reveals elevated white blood cell count, increased protein, and positive CSF-VDRL.
• Findings confirm neurosyphilis.

Neuroimaging

• MRI may show atrophy of the dorsal spinal cord columns.
• Imaging also rules out other spinal cord pathologies.

Electrophysiologic studies

• Somatosensory evoked potentials and nerve conduction studies can demonstrate sensory pathway impairment.

Differential diagnosis for Tabes Dorsalis

Conditions that may resemble Tabes dorsalis include:

• Multiple sclerosis
• Peripheral neuropathies (e.g., diabetic neuropathy)
• Vitamin B12 deficiency (subacute combined degeneration)
• Spinal cord compression or tumors
• Other causes of ataxia or neuropathy

Treatment halts disease progression but cannot reverse established neurological damage. Management focuses on eliminating infection and addressing complications.

Antibiotic therapy

• High-dose intravenous penicillin G is the gold standard: 18–24 million units per day, administered every 4 hours for 10–14 days.
• Penicillin allergy requires desensitization, as penicillin remains the most effective treatment.

Symptomatic management

• Pain control: Medications such as gabapentin or carbamazepine relieve lightning pains.
• Bladder dysfunction: May require catheterization or medications like oxybutynin.
• Ataxia and weakness: Physical therapy and rehabilitation improve mobility and reduce fall risk.
• Orthopedic care: Bracing and wound management help with Charcot joints and skin ulcers.

Follow-up and monitoring

• Repeat CSF and serological tests ensure treatment success.
• Long-term neurological monitoring is needed to manage residual deficits.

Screening and prevention

• All patients diagnosed with syphilis should be screened for HIV.
• Sexual partners must be notified, tested, and treated if necessary.

Complications arise from progressive neurological impairment and secondary consequences:

• Severe gait instability leading to falls and injuries.
• Chronic neuropathic pain from lightning pains.
• Bladder dysfunction causing infections and kidney problems.
• Trophic ulcers and Charcot joints resulting in disability.
• Sexual dysfunction impacting quality of life.
• Permanent disability due to irreversible spinal cord damage.

With treatment, progression can be halted, but neurological deficits are usually permanent. Without therapy, the condition leads to severe disability. Early recognition and antibiotic therapy are essential to improving outcomes. Patients require lifelong management of residual symptoms and complications.

The best prevention is early detection and treatment of syphilis:

• Routine STI screening in at-risk populations.
• Prompt antibiotic therapy for all syphilis cases.
• Public health education on safe sexual practices.
• Partner notification and treatment to prevent reinfection.
• HIV testing and management due to high co-infection rates.

Living with Tabes dorsalis requires a multidisciplinary approach. Physical therapy, pain management, and supportive care improve daily function. Orthopedic interventions may be needed for joint damage, while occupational therapy helps maintain independence. Emotional and social support is vital, as chronic disability can cause isolation and depression.

Patients benefit from long-term follow-up with neurologists, infectious disease specialists, and rehabilitation teams to manage complications and maintain quality of life.

Tabes dorsalis is a preventable but potentially devastating late complication of untreated syphilis. Characterized by sensory ataxia, lightning pains, and Argyll Robertson pupils, it results from degeneration of the posterior spinal cord columns. While antibiotic therapy halts progression, it does not reverse established damage. Prevention through early syphilis diagnosis, treatment, and public health measures remains the most effective strategy to eliminate this condition.

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