Merck Manual

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Atlantoaxial Subluxation

(C1–C2 Subluxation)


Peter J. Moley

, MD, Hospital for Special Surgery

Reviewed/Revised Oct 2022
Topic Resources

Atlantoaxial subluxation is misalignment of the 1st and 2nd cervical vertebrae, which may occur only with neck flexion.

Atlantoaxial subluxation is usually asymptomatic but may cause vague neck pain, occipital headache, or occasionally intermittent (and potentially fatal) cervical spinal cord compression.

Diagnosis of Atlantoaxial Subluxation

  • Plain x-rays

  • MRI to assess the integrity of the ligaments

Atlantoaxial subluxation is usually diagnosed with plain cervical x-rays; however, flexion views may be required to show intermittent subluxation. Views during flexion, as tolerated by the patient, show dynamic instability of the entire cervical spine. If x-rays are abnormal or if they are normal but subluxation is still suspected, MRI, which is more sensitive, should be done. MRI also provides the most sensitive evaluation of spinal cord compression Diagnosis Various lesions can compress the spinal cord, causing segmental sensory, motor, reflex, and sphincter deficits. Diagnosis is by MRI. Treatment is directed at relieving compression. (See also... read more Diagnosis and is done immediately if cord compression is suspected.

Treatment of Atlantoaxial Subluxation

  • Treatment of symptoms

  • Cervical immobilization

  • Surgery

Indications for treatment of atlantoaxial subluxation include pain, neurologic deficits, and potential spinal instability. Treatment includes symptomatic measures and cervical immobilization, usually beginning with a rigid cervical collar. Urgency of treatment is generally based on symptoms or presence of cord abnormalities on MRI in susceptible patients. In cases where symptoms increase or in acute traumatic injuries, surgery may be needed to stabilize the spine.

NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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