Clinical, magnetic resonance imaging and histologic findings of canine thoracolumbar discal pseudocyst: 8 cases (2014‐2019)

Abstract

To report the clinical and MRI features, and histologic findings of thoracolumbar discal pseudocyst in dogs. The records of eight dogs with thoracolumbar discal cyst-like structures were retrospectively collected to record their clinical signs, MRI features and surgical and histologic findings. Eight dogs with surgically and histologically confirmed thoracolumbar discal pseudocysts were included in the case series. Six dogs presented with acute onset and two dogs presented with subacute onset of thoracolumbar myelopathy. MRI showed compressive thoracolumbar myelopathy due to a round to oval-shaped epidural mass lesion communicating with the intervertebral disc, iso/hypointense on T1WI and mostly hyperintense on T2WI, associated with a variable contrast-enhancing wall, compatible with a cyst-like structure. These structures were surgically visualised and removed through a mini-hemilaminectomy or hemilaminectomy and submitted for histologic investigation. One dog also underwent cytologic examination of the cystic content. Similar to that in humans, histology revealed a cyst-like nature with a wall consisting of dense fibrous connective tissue containing clusters of chondroid cells accompanied by groups of notochordal cells and occasional erythrocytes; however, a real epithelial lining was missing and the term pseudocyst seemed more appropriate. This report describes clinical signs, and MRI and histologic findings of discal pseudocysts in dogs with thoracolumbar myelopathy. Despite being rare, discal pseudocysts should be considered as a differential diagnosis in dogs with acute onset thoracolumbar myelopathy.