A Dorsal Intramedullary T2-Weighted Hypointense Signal Suggests Haemorrhagic Necrotic Material Indicating Ascending-Descending Myelomalacia in Dogs.

Abstract

BACKGROUND: Ascending-descending myelomalacia (ADMM) is a progressive softening of the spinal cord observed in dogs after spinal cord injury (SCI). On histopathology, areas of hemorrhagic necrotic material are found in the central canal and dorsal funiculi. HYPOTHESIS/OBJECTIVES: We investigated if hemorrhagic necrotic material dorsal to the central canal can be identified on magnetic resonance imaging (MRI). We hypothesized that signal changes are seen in dogs with ADMM, but not in those without ADMM. ANIMALS: Twenty-six dogs with pathologically confirmed ADMM, focal myelomalacia (FM) and 10 control dogs. METHODS: Retrospective case-control study comparing intramedullary signal dorsal to the central canal in dogs with ADMM, FM, and control dogs. RESULTS: A hypointense signal dorsal to the central canal on transverse T2-weighted fast spin echo and gradient echo images was observed. If present in both T2-d T2*-weighted sequences, it was significantly associated with ADMM (p = 0.004; specificity, 81%; sensitivity, 100%). If the T2-weighted hypointense focus was identified at a distance ≥ 3 vertebral bodies from the initial site of spinal cord injury, it was strongly associated with ADMM (p = 0.01) with a specificity of 100% and sensitivity of 78%. CONCLUSION AND CLINICAL IMPORTANCE: A dorsal intramedullary T2-weighted hypointense focus likely represents hemorrhagic necrotic material in the dorsal funiculi. If present at a distance of ≥ 3 vertebral bodies away from the initial site of SCI, it might aid in the diagnosis of ADMM in dogs by MRI.