Tabes Dorsalis  

Tabes Dorsalis 

Tabes dorsalis is a form of late neurosyphilis affecting the dorsal columns of the spinal cord and peripheral nerves, characterized by paroxysmal pain, particularly in the abdomen and legs; sensory ataxia; normal strength; autonomic dysfunction; and Argyll Robertson pupils. 

Synonyms

Posterior spinal sclerosis

Tabetic neurosyphilis

Syphilitic myeloneuropathy

Neurosyphilis

Epidemiology

Incidence (In U.S.)

Rare, but increasing with HIV/AIDS

Prevalence (In U.S.)

Rare; more common with HIV/AIDS epidemic. Neurosyphilis is twice as likely to develop in coinfections with HIV than without.

Approximately 10% of untreated patients with syphilis develop neurosyphilis, 2% to 5% of whom may develop tabes dorsalis. Relative prevalence of tabes dorsalis is reduced compared with the preantibiotic era.

Predominant Gender

Male

Peak Incidence

More than 10 yr after initial infection

Physical Findings & Clinical Presentation

• Argyll Robertson pupils are common. The pupil reacts poorly to light but well to accommodation (light-near dissociation)
• Loss of position and vibration at ankles (wide-based gait, inability to walk in the dark, sensory ataxia)
• Loss of deep pain sensation, resulting in deep foot ulcers
• Degenerative joint disease, especially in knees, caused by severe neuropathy (Charcot joints)
• Normal strength with areflexia in the legs
• Lightning pains in the legs
• Severe intermittent visceral pains, such as gastrointestinal and laryngeal (visceral crises)
• Autonomic dysfunction (urinary and fecal incontinence due to sphincter dysfunction)
• Hearing loss secondary to otosyphilis or syphilitic uveitis may occur in isolation or associated with other neurosyphilis symptoms

What causes Tabes Dorsalis?

Infectious (Treponema pallidum). Neurosyphilis occurs as a consequence of treponemal penetration of the blood-brain barrier and destruction of adjacent neural tissue, sometimes coupled with cerebral infarction due to meningovascular disease.

How is this condition diagnosed?

Differential Diagnosis

• Vitamin B ₁₂ deficiency (subacute combined degeneration of the spinal cord)
• Vitamin E deficiency
• Chronic nitrous oxide abuse
• Spinal cord neoplasm (involving conus medullaris)
• Lyme disease
• HIV myelopathy and neuropathy

Workup

Thorough neurologic history and examination

Laboratory Tests

• Lumbar puncture: The diagnosis of neurosyphilis requires a CSF mononuclear pleocytosis of 20 WBC/μL or a reactive Venereal Disease Research Laboratory (VDRL) or a positive intrathecal T. pallidum antibody index. Pleocytosis is less specific in patients with HIV due to HIV-related meningitis.
• The CSF VDRL test is specific for neurosyphilis but is only 30% to 70% sensitive. If there is a high suspicion, CSF treponemal tests should be pursued.
• False-positive serum RPR may occur in Lyme disease, nonvenereal treponematoses, genital herpes simplex, pregnancy, systemic lupus erythematosus, alcoholic cirrhosis, scleroderma, and mixed connective tissue disease.
• All patients with syphilis should be tested for HIV. Persons who are HIV positive are at increased risk of developing neurosyphilis.

Imaging Studies

Not necessary if diagnosis confirmed clinically and serologically

How is this condition treated?

Acute General Treatment

• CDC guidelines: Aqueous crystalline penicillin G 18 to 24 million units per day, administered as 3 to 4 million units IV every 4 hr, or continuous infusion for 10 to 14 days; or if adherence can be ensured, penicillin G procaine, 2.4 million units IM daily, plus probenecid 500 mg orally four times a day for 10 to 14 days ^.
• If patient is penicillin allergic, either desensitize to penicillin or obtain an infectious disease (ID) consultation. Limited data exist for ceftriaxone, but penicillin is strongly preferred.
• Otosyphilis or syphilitic uveitis may occur in isolation or associated with other neurosyphilis symptoms and should be treated similarly to neurosyphilis even with normal CSF results.
• Many of the symptoms—degenerative neuropathic joint disease, lightning pains—persist after treatment.

Chronic Treatment

• Physical therapy
• Analgesics, carbamazepine, gabapentin, or steroids may help lightning pain
• Supportive care (wheelchair, toileting issues, etc.)

Disposition

• Normalization or eightfold improvement in serum RPR titer predicts normalization of abnormal CSF studies after appropriate neurosyphilis treatment. Repeat lumbar puncture is recommended every 6 mo if HIV coinfection without effective viral suppression or if there is not the expected improvement in serum RPR titers.
• Further indication for retreatment: If there is a fourfold increase in titers or a failure of titers >1:32 to decrease at least fourfold by 6 to 12 mo.

Referral

• Joint replacement in moderate cases
• ID consult for patients with penicillin allergy

Pearls & Considerations

• Diagnosis should be considered in all patients with a progressive neuropsychiatric disorder with signs of spinal cord dysfunction and peripheral neuropathy.
• Penicillin does not improve late neurosyphilitic syndromes but usually halts their progression.