N01 - Case-control investigation of clinician-determined variables in progressive myelomalacia after disc herniation in dogs

Background – Progressive myelomalacia after disc herniation in dogs is frequently fatal, and there is no proven effective treatment. More information regarding potential causes, including replication studies, is required as a first step in reducing its incidence.
Hypothesis/Objectives – To investigate the association of progressive myelomalacia with i) variables under veterinary control; and ii) patient characteristics.
Animals – 233 dogs presenting to a university neurology clinic with absent hindquarter pain perception following acute thoracolumbar disc herniation over a 10-year period.
Methods – Case-control analysis of association between progressive myelomalacia and putative causal factors using univariable and multivariable logistic regression. Pre-specified sample size appropriate to replicate previously implicated associations.
Results – 45 (19%) dogs were diagnosed with progressive myelomalacia. None of the exposure factors under veterinary control, including pre-operative administration of corticosteroids or non-steroidal anti-inflammatory drugs, time from presentation to completion of surgery, high or low blood pressure events during anesthesia, 4-vertebral length durotomy, surgery time and extent of decompressive surgery appeared to be associated with progressive myelomalacia. The analysis supports the previously suggested higher risk for progressive myelomalacia associated with lesions affecting the lumbosacral intumescence versus T3-L3 lesions (OR=3.96; 95%CI:1.35-11.63).
Conclusions and clinical importance – Veterinarians currently do not have reliable means to influence the incidence of progressive myelomalacia in a susceptible population of dogs, emphasizing the need for further therapeutic investigations (including formal trials of extensive durotomy). The replication of a high incidence of progressive myelomalacia with lesions of the lumbar intumescence suggests that it is a robust association.