Magnetic resonance imaging features and clinical signs associated with presumptive and confirmed progressive myelomalacia in dogs: 12 cases (1997-2008)

Objective-To characterize clinical signs and findings from magnetic resonance imaging (MRI) and CSF analysis for dogs with progressive myelomalacia (PM) diagnosed on the basis of clinical and histologic features. Design-Retrospective case series. Animals-5 dogs with confirmed PM and 7 with presumptive PM evaluated from 1997 through 2008. Procedures-Medical records of study dogs were reviewed, and clinical signs and MRI and CSF findings were evaluated. A clinical diagnosis of PM was made on the basis of detection of disk-associated spinal cord compression via MRI and progression of clinical signs from initial paraparesis or paraplegia to thoracic limb lower motor neuron paresis to tetraplegia associated with cranial migration of the extent of cutaneous trunci reflex extinction and analgesia, terminating in death due to respiratory paralysis. Results-All dogs were paraplegic and had signs of lower motor neuron lesions. As revealed by MRI of the vertebral column, the length of abnormal signal intensity was more than 6-fold, compared with the body length of L2. In some dogs, these abnormal MRI findings were observed before PM was clinically diagnosed. The CSF examination revealed hemorrhagic xanthochromia. Conclusions and Clinical Relevance-A hyperintense region of the spinal cord > 6 times the length of L2 on T2-weighted imaging might be a characteristic MRI finding of PM. In some dogs, such MRI findings were observed before PM was clinically diagnosed. Progressive myelomalacia may thus be diagnosable at the early stage through MRI and CSF examination before signs of PM develop. (J Am Vet Med Assoc 2010;237:1160-1165)