Case Study

CT – Atlanto-axial subluxation with secondary compressive myelopathy, congenital, in a 7 month old F Yorkshire terrier

This 7 month old F Yorkshire Terrier presented with neurological signs. Rads show focal scoliosis at approximate level of T5. Hyper-reflexia pelvic limbs, 2-3+ in thoracic limbs. Uable to stand normally; when recumbent, voluntary movement all 4 limbs. Pain present. WBC 20,800, increased platelets, Total protein 7.8

DX

congenital malformation of the atlanto-occipital junction and additional atlanto-axial subluxation with secondary compressive myelopathy.

Image Interpretation

CT of the skull, neck , thorax –

The lateral ventricles and their respective olfactory recesses present moderately asymmetric dilation. In the region of the quadrigeminal cistern a moderate fluid accumulation with subtentorial extension and mild mass effect on the adjacent brain parenchyma is noted. The axis presents marked subluxation in respect to the atlas. Marked compression and dorsal kinking of the dural tube and upper cervical spinal cord is caused by the malpositioning of the atlas with dorsal subluxation of the odontoid process. A focal mineral opacity is present dorsal to the body of the atlas, consistent with center of the proatlas. The dorsal arch of the atlas is displaced cranially and overlaps the caudoventral tip of the supraooccipital bone. A mass effect on the caudal contour of the cerebellum is assumed. A mid thoracic spinal malformation was not identified.

Outcome

The findings explain neurological deficits in all four limbs. Surgical therapy by caudal
cranioplasty and stabilization of the atlanto-axial subluxation will improve long-term
prognosis of the patient. Potent pain-medication may be considered as palliative
treatment option.
The hydrocephalus and supracollicular fluid accumulation are considered incidental.
Although they may be influenced/enhanced to some degree by altered flow of the CSF
due to the craniocervical malformation.