Makindo Medical Notes

Related Subjects: |Syringomyelia |Syringobulbia |Dandy Walker syndrome

🧠 Tabes dorsalis is a rare late manifestation of tertiary syphilis, typically developing 10–35 years after the initial infection. It reflects neurosyphilitic damage to the dorsal roots and posterior columns of the spinal cord. Cases are now uncommon in the post-antibiotic era.

📖 About

• Degeneration of the dorsal (sensory) nerve roots + posterior spinal columns → sensory ataxia and neuropathic pain.
• Represents one form of neurosyphilis, alongside general paresis and meningovascular syphilis.

🧬 Aetiology

• Neurosyphilis: Syphilitic damage to dorsal roots and posterior columns → ataxia + loss of position sense.
• General Paresis: Cortical atrophy → psychiatric features (delusions of grandeur, dementia-like decline, epilepsy).
• Meningovascular Syphilis: Endarteritis and fibrosis affecting cranial nerves (II, III, IV) → stroke-like episodes.

🩺 Clinical Features

• Shooting, lancinating pains: Due to dorsal root irritation.
• Positive Romberg’s sign: Loss of balance with eyes closed (posterior column degeneration).
• Ataxic gait: Broad-based, stamping walk due to sensory ataxia.
• Argyll Robertson pupil: Small, irregular pupils that accommodate but do not react to light (“prostitute’s pupil”).
• Charcot joints: Painless joint destruction from loss of protective sensation.
• Other neurosyphilis signs: Optic atrophy, loss of deep pain, mental changes from general paresis.

🔍 Differential Diagnosis

• Subacute combined degeneration (Vitamin B12 deficiency)
• Multiple sclerosis
• HIV myelopathy
• Nitrous oxide abuse
• Copper deficiency
• Sarcoidosis

🧪 Investigations

• CSF analysis: Elevated protein, raised WCC, sometimes oligoclonal bands.
• Syphilis serology: TPHA & FTA-ABS usually positive. VDRL may become negative post-treatment.
• Motor nerve conduction: Usually normal (sensory tracts affected).
• MRI spine: High T2 signal in dorsal cord, with cord atrophy.

💊 Management

• IV Benzylpenicillin: Mainstay therapy for neurosyphilis.
• Jarisch–Herxheimer reaction: Fever, chills, symptom flare after antibiotics (due to spirochaete lysis). May require steroids to blunt reaction.

📉 Prognosis

• Progression may halt with treatment, but neurological damage is often irreversible.
• Early recognition and antibiotic therapy remain crucial to prevent disability.