Imaging Diagnosis—degenerative Intraspinal Cyst Associated With an Intervertebral Disc

Abstract

A 6-year-old neutered male Rottweiler had chronic episodic signs of thoracolumbar pain and inability to stand that did not improve after rest and nonsteroidal antiinflammatory medication. In magnetic resonance images, an extradural mass was identified between the spinal cord and the T13/L1 intervertebral disc; the mass was compressing the cord in a dorsoventral direction. The lesion had a low signal intensity rim that enhanced slightly after gadolinium administration, and contents with similar signal intensity to cerebrospinal fluid. The lesion was removed surgically by severing its attachments to the annulus fibrosus. The histologic diagnosis was degenerative intraspinal cyst. The origin of such cysts, and their relationship to synovial and ganglion cysts is discussed.

Extramedullary Spinal Cysts in Dogs

“…As with meningeal cysts, histopathology should remain the gold standard in defining these lesions, and this classification provides a robust scheme to classify extramedullary spinal cysts in the clinic. We found complete reports on 60 such intraspinal cysts in 24 dogs …”

“…Intraspinal cysts may arise from either the annulus fibrosus or dorsal longitudinal ligament, although they remain uncommon compared to intraspinal synovial cysts of the intervertebral joints Penning et al reported an intraspinal cyst arising from the annulus fibrosus in a dog with features similar to those reported in people. The pathophysiology is considered similar to that which results in intraspinal cyst formation of the vertebral joints .…”

“…Indeed, it is now well accepted that synovial and ganglion cysts may represent the same entity at different stages of development . In rarer cases, cystic structures may form from the annulus fibrosus of the intervertebral disc or dorsal longitudinal ligament . These intraspinal cysts are present in the epidural space either adjacent to the facet joint, ligamentum flavum, or intervertebral disk.…”

“…Long‐term results suggest a 50–100% relapse rate, though not all intraspinal cysts are amenable to aspiration given the gelatinous nature of the contents of some. In contrast, most dogs reported to have intraspinal cysts underwent surgery . All 22 veterinary reports of surgical intraspinal cyst removal report good outcomes with a median follow‐up of 9 months (range, 2 weeks–36 months) .…”

“…The recurrence of intraspinal cysts after surgery in people is low . Surgery would therefore appear an appropriate option given all reported dogs had progressive neurologic signs that resolved after surgery . Furthermore, most intraspinal cysts in dogs are accompanied by other stenotic degenerative disease of the vertebral column, making surgical decompression more desirable.…”