Canine acute cervical myelopathy: Hydrated nucleus pulposus extrusion or intraspinal discal cysts?

Objective: To differentiate between hydrated nucleus pulposus extrusion and ventral intraspinal discal cysts in dogs.

Study Design: Prospective case series.

Animals: Twenty dogs with acute onset of cervical myelopathy due to hydrated nucleus pulposus extrusion or ventral intraspinal discal cysts.

Methods: Clinical and magnetic resonance (MR) imaging findings, outcome after surgical treatment, cytologic and histologic findings of compressive material were taken into account. Comparisons and considerations were done between findings reported herein and what was previously described as suspected hydrated nucleus pulposus extrusion and intraspinal cysts.

Results: All dogs were presented with acute onset of cervical myelopathy. MR imaging showed compressive cervical myelopathy at C2-C3 (n = 1), C3-C4 (n = 6), C4-C5 (n = 8), and C5-C6 (n = 5) intervertebral disc spaces, due to extradural material suggestive of either partially hydrated nucleus pulposus extrusion or intraspinal discal cyst, with T2 hyperintense and T1 iso-hypointense signal and variable contrast enhancement after gadolinium injection. All dogs were treated surgically by ventral slot (n = 15) or dorsolateral hemilaminectomy (n = 5). All dogs had a favorable outcome and regained a normal gait. The extradural material collected at surgery varied from liquid to more obvious gelatinous material. Cytologic or histologic examination of the material revealed similar findings for all dogs, compatible with partially degenerated nucleus pulposus.

Conclusions: Dogs with acute onset of compressive cervical myelopathy due to extradural material resembling human intraspinal cysts on MR images are most likely to have extrusion of partially degenerated nucleus pulposus and should be treated accordingly.