Atlantoaxial Instability Clinical Presentation
- Author: Daniel P Leas, MD; Chief Editor: Jeffrey A Goldstein, MD more...
Usually, persons with congenital anomalies do not become symptomatic before the third decade of life. The spine is assumed to be able to accommodate differing regions of hypermobility and fusions. With time, the degenerative changes occurring in the lower cervical spine increase rigidity and alter the balance. This gradual loss of motion places increasing loads on the atlantoaxial articulation.
The cervical spine is involved more frequently in patients with rheumatoid arthritis (RA). Cervical involvement tends to be asymptomatic in the scenario of systemic rheumatoid manifestations. In addition, the severity of the systemic manifestations should serve as a marker of the degree of cervical involvement.
In cases associated with trauma, head and facial injuries may be present. The flexion-extension moment exerted on the spine can cause ligamentous disruption with subsequent atlantoaxial instability (AAI).
In some persons with Grisel syndrome, an antecedent illness or infection occurs.
For patients with genetic or metabolic syndromes with higher rates of AAI or AAS as compared with a normal population, there are multiple additional details that are relevant to the clinician. A thorough cervical spine examination is warranted for patients presenting with the following conditions:
Down syndrome - Approximately 13% of patients with DS will have asymptomatic AAI, and 1.5% will have neurologic symptoms stemming from this instability 
Spondyloepiphyseal dysplasia (SED) - SED congenita is associated with a 40% risk of AAI; SED tarda usually does not manifest AAI 
Morquio syndrome - AAI is usually secondary to odontoid hypoplasia or aplasia; patients tend to present later in childhood and usually later than those with SED congenita; nearly all patients with Morquio syndrome will develop AAI, and some surgeons recommend prophylactic stabilization to combat the morbidity associated with spinal cord compression 
Chondrodysplasia punctata - AAI is the primary cause of disability and death in these patients; about 20% will present with weakness, and 20% will present with hyperreflexia; spinal cord compression can occur at an early age 
Metatropic dysplasia - Patients with this rare syndrome patients survive into young adulthood but develop AAI early; nearly all appear to have odontoid hypoplasia, and in a small series, 75% of these patients had associated instability 
A careful neurologic examination should be conducted, especially for children at risk. Assess sensory, motor, and other neurologic functions. Upper motor neuron signs, including hyperreflexia, clonus, and extensor plantar reflexes, may be indicative of symptomatic AAI. Somatosensory evoked response may reveal information regarding neurologic involvement.
In individuals with rotatory displacement, a cock-robin deformity or torticollis can be the presenting symptom.
Many patients with RA present with occipital pain. Others develop myelopathy, vertigo, brainstem signs, or lower cranial nerve palsies. The brainstem findings occur either with basilar invaginations or with the alteration of the path of the vertebral artery with changing of normal anatomy. Rana reported the subtle association of involvement of the fifth cranial nerve, which has a descending tract that extends to C2. Pyramidal signs, including hyperactive reflexes, a positive Babinski sign, and proprioceptive loss, should alert the physician for developing myelopathy.
The most specific physical findings in patients with symptomatic AAI secondary to infections of the head and neck are torticollis, tenderness over the spinous process of the axis with palpation, and the Sudeck sign (displacement of spine of the axis in the direction of head tilt).
A reduction in size of the nasopharynx and increased nasal resonance also may be present due to forward displacement of the arch of the atlas.
Persons with atlantoaxial subluxation (AAS) due to inflammatory processes less frequently exhibit signs of root or cord involvement.
Spinal cord compression can arise or worsen if susceptible patients are subjected to extreme ranges of motion. Symptoms of progressive neurologic dysfunction can include upper motor neuron signs, including the following:
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