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The Cornell veterinarian1991; 81(1); 67-75;

Atlantoaxial malformation in a half-Arabian colt.

Abstract: A 1-year-old half-Arabian colt was referred for evaluation of a cranial cervical abnormality. Physical examination revealed the left wing of the atlas to be more ventral than the right wing. A head tilt, with the pole deviated to the left, was present because of the malpositioned atlas. Neurologic examination identified symmetrical weakness, ataxia, and proprioceptive deficits in all four limbs. Radiographs of the cranial cervical region revealed fusion of the atlas and axis, and deviation of the atlantoaxial joint to the left of the median plane. Euthanasia was elected. Necropsy confirmed the radiographic findings. The atlas was rotated 20 degrees counterclockwise when viewed from the caudal aspect. Multifocal myelomalacia was present in the first and second cervical spinal cord segments. The malformation was believed to be due to a degenerative process or abnormal embryological development.
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Publication Date: 1991-01-11 PubMed ID: 1993394
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This study looked at a case of atlantoaxial malformation in a 1-year-old half-Arabian colt that was causing it to have severe physical and neurological symptoms. It was determined that the colt’s abnormal condition may have been caused by either a degenerative process or issues during its embryological development.

Investigation and Examination

The half-Arabian colt, aged just one year, was brought in due to an observed cranial cervical abnormality. Here is a rundown of the examination process:

  • The physical examination showed that the left side of the colt’s first vertebra in the neck (the atlas) was lower than the right, leading to a tilt of the head with a deviation towards the left.
  • A neurological examination identified symptoms of symmetrical weakness, unsteady movement (ataxia), and deficits in sense of position and movement of the body (proprioceptive deficits) in all four limbs.

Radiographic Findings

Further medical investigations were conducted to verify the nature of the orthopedic condition, notably:

  • Radiographs of the cranial cervical region, the top part of the neck, indicated fusion of the first two vertebrae in the neck, the atlas and axis, and deviation of the joint between these (the atlantoaxial joint) to the left of the midline.

Outcome and Necropsy Findings

Due to the severity of symptoms and prognosis, euthanasia was decided on for the animal. A necropsy or post-mortem examination led to the following findings:

  • As seen in the radiographs, it was confirmed that the colt’s atlas was indeed rotated about 20 degrees counterclockwise.
  • Areas of softening or necrosis within the spinal cord (myelomalacia) were noted in the first two cervical spinal cord segments. This suggests that the malformation caused severe damage to the colt’s spinal cord leading to its symptoms.

Possible Causes of Malformation

The examination and necropsy results suggested that the abnormal union and deviation in the top two neck bones, along with the asymmetrical positioning of the atlas, were due to either:

  • A degenerative process where the colt’s vertebrae had degraded over time, or
  • Abnormalities during the embryological development of the animal, causing the malformation to occur before its birth.

Cite This Article

APA
Blikslager AT, Wilson DA, Constantinescu GM, Miller MA, Corwin LA. (1991). Atlantoaxial malformation in a half-Arabian colt. Cornell Vet, 81(1), 67-75.

Publication

The Cornell veterinarian
ISSN: 0010-8901
NlmUniqueID: 0074245
Country: United States
Language: English
Volume: 81
Issue: 1
Pages: 67-75

Researcher Affiliations

Blikslager, A T
  • Department of Veterinary Medicine and Surgery, College of Veterinary Medicine, University of Missouri, Columbia 65211.
Wilson, D A
    Constantinescu, G M
      Miller, M A
        Corwin, L A

          MeSH Terms

          • Animals
          • Atlanto-Axial Joint / abnormalities
          • Atlanto-Axial Joint / diagnostic imaging
          • Axis, Cervical Vertebra / abnormalities
          • Cervical Atlas / abnormalities
          • Horses / abnormalities
          • Male
          • Radiography

          Citations

          This article has been cited 4 times.
          1. Cole R, Taintor J, Hanson R. Atlanto-axial malformation in an adult Quarter horse gelding. Can Vet J 2017 Sep;58(9):923-925.
            pubmed: 28878414
          2. Bordbari MH, Penedo MCT, Aleman M, Valberg SJ, Mickelson J, Finno CJ. Deletion of 2.7 kb near HOXD3 in an Arabian horse with occipitoatlantoaxial malformation. Anim Genet 2017 Jun;48(3):287-294.
            doi: 10.1111/age.12531pubmed: 28111759google scholar: lookup
          3. Hülsmeyer VI, Flatz K, Putschbach K, Bechter MR, Weiler S, Fischer A, Feist M. Traumatic odontoid process synchondrosis fracture with atlantoaxial instability in a calf: clinical presentation and imaging findings. Ir Vet J 2015;68(1):6.
            doi: 10.1186/s13620-015-0034-5pubmed: 25937919google scholar: lookup
          4. Aleman M, Dimock AN, Wisner ER, Prutton JW, Madigan JE. Atlanto-axial approach for cervical myelography in a Thoroughbred horse with complete fusion of the atlanto-occipital bones. Can Vet J 2014 Nov;55(11):1069-73.
            pubmed: 25392550
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