Ascending haemorrhagic myelomalacia associated with systemic hypertension in a hyperthyroid cat

CASE SUMMARY: An 8-year-old domestic shorthair neutered male cat was presented with acute onset of paraplegia, absent nociception on the pelvic limbs, tail and perianal area, and a previous history of uncontrolled hyperthyroidism (even after thyroidectomy) and chronic hypertension. The magnetic resonance findings (heterogeneous intramedullary ill-defined area, isointense on T1-weighted and hyperintense on short tau inversion recovery and T2-weighted scans between T12 and L5 spinal cord segments) were consistent with ascending haemorrhagic myelomalacia, which was confirmed by histopathology. It also revealed myelomalacia associated with diffuse arteriolar hyalinosis, similar to the reports found with hypertensive encephalopathy. RELEVANCE AND NOVEL INFORMATION: Myelomalacia should be considered as a possible outcome in cats with hypertension. Considering that hypertension is a common consequence of hyperthyroidism, emphasis should be given to blood pressure monitoring, especially after treatment of this condition. We describe the histopathological changes occurring in the spinal cord associated with a state of hypertension.