A 55-year-old man with longstanding seropositive RA develops bilateral hand deformity and now presents with neck pain and sudden onset of gait ataxia. X-ray of the cervical spine (lateral in flexion) shows an atlanto-dens interval of 7 mm. What complication is most likely?

• A Cervical spondylosis at C5–C6
• B Vertebral artery dissection
• C Demyelinating myelopathy secondary to DMARDs
• D Atlanto-axial subluxation causing cervical cord compression ✓

Explanation

Atlanto-axial subluxation (AAS) is a well-recognised complication of seropositive RA due to erosion of the transverse ligament by pannus. An atlanto-dens interval (ADI) greater than 3 mm in adults (normal ≤3 mm; >9 mm indicates high risk of cord compression) with neurological signs requires urgent MRI and surgical referral for posterior cervical fusion. AAS in RA may present with sudden neurological deterioration, occipital neuralgia, or Lhermitte sign. Cervical spondylosis at C5–C6 does not explain an elevated ADI.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.