Atlanto-axial subluxation

Classification according to ICD-10
M43.3	Habitual atlanto-axial subluxation with myelopathy
M43.4	Other habitual atlanto-axial subluxation
ICD-10 online (WHO version 2019)

An atlanto-axial subluxation ( AASL ) is an incomplete dislocation ( subluxation ) of the joint between the first and second cervical vertebrae ( second head joint , atlantoaxial joint). The cause is a change in position (dislocation) and instability of the joint construction. Atlanto-axial subluxation can damage the spinal cord .

Etiology and Occurrence

The disease can have various causes:

a congenital malformation in which the dens axis (“tooth” of the second cervical vertebra) is not ( densaplasia ) or is only imperfectly developed. This malformation occurs mainly in humans and in small breeds of dogs . Significantly less often, malformations of the holding straps of the dens axis can also be a triggering factor.
abnormal looseness or slackness of the straps, e.g. B. Down syndrome , Marfan syndrome , Ehlers-Danlos syndrome , Larsen syndrome , Kniest dysplasia .
Traumatic due to a fracture of the dens axis or a torn bony ligament.
in rheumatoid arthritis , as well as juvenile idiopathic arthritis are at increased risk of AASL.

Clinical picture

The symptoms vary according to the degree of spinal cord injury. In addition to pain in the neck area, especially when bending the neck, paralysis of the limbs ( tetraparesis ), severe gait disorders ( ataxia , wobbler syndrome ) and disorders of proprioception occur.

With congenital AASL, the symptoms usually appear gradually, within the first year of life. In the case of traumatic AASL, on the other hand, a sudden (peracute) appearance can be observed and complete paralysis of all limbs ( tetraplegia ) can occur.

In patients at risk of such instability, the extent of anesthesia must be clarified in order to avoid possible spinal cord damage caused by overstretching the head.

diagnosis

The extent of the bony malalignment, the atlantoaxial dislocation , is determined on the basis of an X-ray . Malformations, the consequences of trauma or rheumatic changes can be recorded well. In high-risk patients, functional recordings in (careful) flexion and extension allow the extent of the instability to be estimated.

Any damage to the spinal cord and its extent is determined on the basis of the clinical-neurological examination and can be visualized using magnetic resonance imaging (MRT).

Therapy and prognosis

Pure instability without a fixed subluxation usually does not require treatment. The indication and success of a treatment depend on the extent of the damage to the spinal cord.

One possible therapy is the surgical stabilization of the joint using various osteosynthesis procedures.

While the prognosis is good for the congenital form with symptoms that are not yet too strong , it is poor for traumatic damage with tetraplegia.

A recent study shows that conservative therapy with a neck brace is often sufficient for young dogs.

Literature and Sources

Andre Jaggy: Atlas and textbook of small animal neurology . Schlütersche, Hannover 2005, ISBN 3-87706-739-5 , p. 305 .
F. Hefti: Children's orthopedics in practice . Springer, Berlin 1998, ISBN 3-540-61480-X .
D. von Torklus, W. Gehle: The upper cervical spine. Regional morphology. Pathology and traumatology. Practical X-ray atlas and systematics . 3. Edition. Thieme, Stuttgart 1977, ISBN 3-13-453303-0 .

Individual evidence

↑ ME Havig, KK Cornell, JC Hawthorne, JJ McDonnell, BA Selcer: Evaluation of nonsurgical treatment of atlantoaxial subluxation in dogs: 19 cases (1992-2001). In: J Am Vet Med Assoc. Volume 227, No. 2, Jul 15, 2005, pp. 257-262.

[1] ME Havig, KK Cornell, JC Hawthorne, JJ McDonnell, BA Selcer: Evaluation of nonsurgical treatment of atlantoaxial subluxation in dogs: 19 cases (1992-2001). In: J Am Vet Med Assoc. Volume 227, No. 2, Jul 15, 2005, pp. 257-262.