17.Mar 2023

Case of the month: 4-year-old yorkshire terrier, presented due to cervical pain

 

Signalment and anamnesis

  • Yorkshire terrier, 4 years, male intact
  • Presented due to cervical pain

For further clarification the following radiographs were taken:

 

 

Radiographic description

  • Mediolateral images of the cervical spine in neutral and gently flexed positions
  • The angle between the dorsal lamina of the vertebral bodies of C1 and C2 is different in the neutral and flexed images, and the atlantoaxial overlap is shortened in the flexed images (atlantoaxial overlap is approximately -1.4 mm in the flexed images and +1,5 in neutral position):

  • The dens axis is displaced dorsally in the lateral images but is otherwise intact and without evidence of dysplasia

Diagnosis

  • Atlantoaxial subluxation/atlantoaxial instability

Outcome

  • MRI examination with thin-slice T1w and T2w sequences did not reveal a transverse ligament in the area of the dens axis
  • Due to the dorsal displacement of the dens axis, there is focal dorsal displacement and ventral compression of the myelon
  • In addition, the myelon dorsal to the dens axis shows focal T2W hyperintensity, which may indicate edema, hemorrhage, or chronic gliosis and Waller's degeneration

Comparative image:

  • Normal course of the cranial cervical myelon and normal location of the dens axis using an unremarkable dog as an example


Discussion

  • Congenital atlantoaxial instability/subluxation is more common in small breed dogs such as the Yorkshire Terrier, Toy Poodle, and Chihuahua, but can also occasionally occur in large dog breeds and cats
  • Symptoms occur on average at 21.3 months of age and are caused by excessive flexion of the atlantoaxial joint, resulting in dorsal subluxation of the axis in relation to the atlas, which can cause ventral compression of the spinal cord
  • Symptoms may be acute or gradual and range from pain on movement with or without ataxia to quadriplegia, respiratory failure, and death in the most severe cases
  • The most common causes of instability are abnormally developed bones and ligaments in the atlantoaxial joint, transverse ligament, and dens axis

Therapy

  • Conservative therapy usually involves splinting, stabilization of the cervical spine, rest, and medication. Conservative therapy is successful in about 62% of cases
  • If there is no improvement, surgical treatment is recommended. There are several surgical methods, all aimed at stabilizing the atlantoaxial joint. Surgical therapy is successful in about 60-90% of cases

Many thanks to Dr. ECVDI Thorsten Rick for this case report

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