ABSTRACT
Extramedullary cyst-like spinal conditions are fluid-filled collections associated with the spinal structures outside of the spinal cord, and they can be clinically silent or produce clinical signs through compression of the spinal cord or nerve roots. Extramedullary cyst-like lesions can be divided into meningeal and non-meningeal lesions. Non-meningeal cysts most commonly originate from the articular process joints (synovial and ganglion cysts), while the existence of cysts of ligamentous or discal origin is controversial in dogs and cats. Spinal non-meningeal cyst-like conditions are degenerative intraspinal fluid-filled structures arising from the vertebral articulations, ligamentous or discal structures of the vertebral column. Almost all such cystic structures reported thus far in veterinary medicine have been associated with the articular process joints. Magnetic resonance imaging is considered the modality of choice to image arachnoid diverticula because unlike other techniques it allows assessment of the spinal cord parenchyma and detection of comorbidities such as syringomyelia.
