Back aches – Atlantoaxial Instability

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One of the causes of neck pain is AAI or Atlantoaxial instability. Find out more about this condition caused by excessive movement between vertebrae. 

[caption id="attachment_4093" align="alignleft" width="196" caption="AAI can cause neck pain"]Neck/back pain caused by AAI[/caption]

What is AAI?

Atlantoaxial instability (AAI) is the excessive movement between the first two vertebrae of the neck known as atlas (C1) and axis (C2). It sometimes results in dislocation, termed as atlantoaxial dislocation.

Causes of AAI

AAI occurs due to a bone or ligament (tissue holding the vertebrae steady) defect in the first two cervical vertebrae of the neck, viz. the atlas and axis. It can affect people of any race, sex and age.

  • Trauma: It can occur due to trauma after an accident, like a car accident.
  • Infection: It is possible after an upper respiratory tract infection or infection after head and neck surgery.
  • In certain medical conditions: Rheumatoid arthritis or RA commonly affects the upper cervical spine.
  • Congenital anomalies: Congenital scoliosis (curvature of the spine), osteogenesis imperfect (extremely fragile bones) and neurofibromatosis (genetic disorder of the nervous system), among others can cause AAI.
  • Syndromes: children with Down syndrome may have AAI but in the majority of the cases, it is asymptomatic and can be left alone.
  • Tumours: Cancerous growths can cause weakening of the vertebrae, resulting in AAI.

Symptoms and signs of AAI

  • Many cases of AAI are asymptomatic and need no intervention.
  • Neurologic symptoms may manifest and include neck pain, limited neck movement, wry neck or torticollis, abnormal gait, clumsiness, easy fatiguability and difficulty in walking. Severe symptoms include bladder problems, hemiplegia (paralysis on one side of the body), paraplegia(paralysis of both lower limbs) and quadriplegia(paralysis of all four limbs).
  • In patients with RA, the lowermost part of the brainstem called medulla is compressed. The medulla oblongata is a vital centre of respiration. Additionally, they may have vertebra-basilar insufficiency or VBI. In this case the vertebral artery which supplies blood to the portion of the brain behind is compressed which causes lack of blood supply to the brain. This condition can be fatal if undiagnosed or left untreated.
  • Some patients also have pain at the back of the head, vertigo, and affection of some cranial nerves.

Diagnosis of AAI

A complete history and thorough nervous system examination by a neurologist is a must. AAI may be confused with ankylosing spondylitis, osteogenesis imperfecta and neurofibromatosis.

Investigation of AAI

X- rays of the cervical spine are diagnostic. In certain cases when tumours are suspected or when unable to view the exact dislocation, CT scans or MRI may be advised.

Treatment of AAI

The objective of treatment is to stabilise the spine, protect the spinal cord, decompress the adjoining nerves and reduce any deformity.

Medication: Medication is not really useful in AAI except for occasional anti-inflammatory drugs to reduce inflammation. Conservative methods like traction or use of a brace may be tried.

Family members should be made aware of symptoms which may appear and need medical attention promptly.

Surgery: Surgery is of value to stabilise the spine and decompress the nerves. A procedure called posterior fusion is used to fuse the axis and atlas. It is successful to relieve pain and minimise neurological symptoms.

Children with this condition should be allowed to participate in sports only after consulting their physician, as sports may worsen the condition.


If the surgery is successful, then the pain and progression of symptoms is arrested. Rarely do paralysis and death occur due to AAI.

Written by Dr Nisreen Nakhoda, General Physician