Makindo Medical Notes

Related Subjects: |Dementias |Abbreviated Mental Test Score (AMTS) |Syphilis |Treponema

About

• Tabes dorsalis typically develops 10-35 years after a primary syphilis infection.
• It is a rare neurological form of tertiary syphilis and occurs less frequently in the post-antibiotic era.

Aetiology

• Neurosyphilis: Tabes dorsalis results from neurosyphilitic damage to the dorsal (sensory) nerve roots and degeneration of the posterior columns of the spinal cord, leading to ataxia and sensory loss.
• General Paresis: Syphilitic infection of the brain can result in cortical atrophy, delusions of grandeur, dementia-like symptoms, and epilepsy.
• Meningovascular Syphilis: Causes endarteritis and fibrosis, affecting cranial nerves II, III, and IV, leading to stroke-like episodes.

Clinical Features

• Shooting lancinating pains: Due to irritation of the sensory nerve roots.
• Positive Romberg’s sign: Patients experience a loss of balance when standing with their eyes closed due to posterior column degeneration.
• Ataxic gait: Characterized by a broad-based, unsteady walk caused by sensory ataxia.
• Argyll Robertson pupil: Small, irregular pupils that do not react to light but constrict with accommodation.
• Charcot joints: Destruction of joints due to the loss of protective pain sensation, leading to painless damage to weight-bearing joints.
• Neurosyphilis features: May include optic atrophy, loss of deep pain sensation, and mental changes associated with the general paresis of the insane.

Differential Diagnosis

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

Investigations

• CSF analysis: May show elevated protein levels, raised WCC, and the presence of oligoclonal bands.
• TPHA and FTA-ABS: Positive syphilis-specific serological tests (TPHA, FTA-ABS). VDRL may turn negative following treatment.
• Motor nerve conduction velocity: Usually normal.
• MRI spine: May show a high T2 signal in the dorsal cord, along with spinal cord atrophy.

Management

• Benzylpenicillin IV: The primary treatment for neurosyphilis.
• Herxheimer Reaction: A reaction to the treatment caused by the rapid release of toxins from dying spirochaetes, often manifesting as fever, chills, and worsening symptoms. This reaction may be managed with steroids.