Outcomes of non-limited versus cranial-limited extensive hemilaminectomy and durotomy in dogs with thoracolumbar intervertebral disc extrusion and presumptive progressive myelomalacia.

Abstract

Background: Progressive myelomalacia (PMM) can occur secondary to thoracolumbar intervertebral disc extrusion (TL-IVDE) and is typically fatal. A recent study suggested that compared with dogs undergoing standard hemilaminectomy, the survival rate of dogs with presumptive PMM improved with non-limited extensive hemilaminectomy and durotomy (EHLD) conducted on the region with a hyperintense intramedullary signal on T2-weighted magnetic resonance imaging (MRI). Applying EHLD results in a large wound and entails prolonged surgical duration. The current study aimed to retrospectively compare the outcomes between an EHLD group and a limited EHLD group (EHLD-L) with TL-IVDE and presumptive PMM. EHLD-L was performed from one additional vertebral body cranial to the spinal cord parenchyma with the T2-weighted hyperintense region identified on MRI, extending caudally until spinal cord swelling and/or softening was visually confirmed during hemilaminectomy and durotomy. Twelve dogs diagnosed with TL-IVDE and presumptive PMM based on clinical features and MRI findings were retrospectively recruited. After diagnosis, seven and five dogs immediately underwent EHLD-L and EHLD, respectively. Medical records of all dogs were retrospectively reviewed, and the postoperative survival outcome, length of the hemilaminectomy window, and surgical operating time between the two groups were compared.

Results: One month after the surgery, the survival rates of the EHLD-L and EHLD groups were 6/7 and 5/5, respectively. The median length of the hemilaminectomy window was 4 (range, 4-6) for the EHLD-L group and 10 (range, 6-14) for the EHLD group (p = 0.076). The mean surgical operating times were 106 (range, 80-168) minutes in the EHLD-L group and 192 (range, 128-207) minutes in the EHLD group (p = 0.030). There was no improvement in any surviving dogs' urinary continence or pelvic limb function.

Conclusions: Compared with EHLD, EHLD-L can be associated with a smaller surgical wound and a shorter anesthesia time. EHLD-L did not affect the recovery of pelvic limb function or urinary continence. However, it can be an alternative to EHLD for preserving the life of dogs with presumed PMM.