Atlantoaxial instability

A small number of people with Down syndrome are at risk of subluxation of the cervical spine and subsequent spinal compression due to joint laxity and anatomical differences in the cervical vertebrae. The most common place for this to occur is C1 to C2, or the atlantoaxial joint. If spinal cord compression is untreated, permanent paralysis may result.

While about 15% of people with Down syndrome have ligamentous laxity of the atlantoaxial joint on X-ray, only 1 to 2% of this group develop symptoms of spinal cord compression. The value of routine radiography is controversial because there is poor correlation between radiographic findings and clinical signs and symptoms; routine radiographic screening is not recommended.

Neurological surveillance is vital for early detection of spinal cord compression. Encourage people with Down syndrome and their families and carers to be alert to signs of cervical degeneration or cord compression including:

  • difficulty walking or abnormal gait
  • neck pain, torticollis or head tilt
  • fatigue or coordination problems
  • peripheral sensory deficits
  • hyperreflexia (eg spasticity, clonus, extensor plantar reflex)
  • incontinence.

If compression is suspected, immobilise the patient’s spine and arrange a same-day cervical spine X-ray, magnetic resonance imaging (MRI) and neurosurgical consult.

Risk of subluxation is assessed with a lateral cervical X-ray in neutral, flexed and extended positions. Examine people with increased atlantoaxial intervals (more than 5 mm on X-ray), but without symptoms, annually. Refer people with atlantoaxial intervals of more than 7 mm to a neurosurgeon.

Clinicians should carefully consider, and take great care with, any procedures that put stress on the neck of a child or adult with Down syndrome (eg intubation, neck manipulation).

Ensure people with Down syndrome who have increased atlantoaxial intervals and those who support them are aware of and avoid activities that are likely to put pressure on the cervical spine (eg contact or high-speed sports, gymnastic exercises involving extreme neck flexion or extension). Some sporting organisations (eg Special Olympics) require information on the person’s atlantoaxial interval measurements prior to them participating.