Sergio A. Gomes ^1,2,3 Rui Alvites ^1,2,4 Bruna Lopes ^1,2 André Filipe Monteiro Coelho ^1,2 Mike Targett ⁵ Jorge Ribeiro ^1,2 Débora Gouveia ^2,6,7 Ângela Paula Martins ^2,6,7 Artur Varejão ^2,8 Ana Colette Maurício ^1,2* Ana Lúcia Luís ^1,2

• ¹ Center for the Study of Animal Science, Abel Salazar Institute of Biomedical Sciences, University of Porto, Porto, Portugal
• ² AL4Animals, Lisbon, Portugal
• ³ Dovecote Veterinary Hospital, Castle Donington, England, United Kingdom
• ⁴ Cooperativa de Ensino Superior Politécnico e Universitário, Gandra, Porto, Portugal
• ⁵ School of Veterinary Medicine and Science, Faculty of Medicine and Health Sciences, University of Nottingham, Nottingham, England, United Kingdom
• ⁶ Lusofona University, Lisbon, Portugal
• ⁷ Arrábida Veterinary Hospital, Arrábida Animal Rehabilitation Center, Azeitão, Portugal
• ⁸ University of Trás-os-Montes and Alto Douro, Vila Real, Portugal

Background: Current literature warrants surgical decompression in paraplegic dogs with absent pain perception (APP), but it is unknown the rate of ambulatory dogs with APP following thoracolumbar (TL) IVDE surgery, in a clinical setting. Also, the outcome of paraplegic APP French bulldogs (FB) is anecdotally considered poor. The aims of this study were three-fold within a large population of TL-IVDE paraplegic dogs with APP undergoing decompressive surgery: (1) characterise early spontaneous pelvic limb movement and ambulation following surgery; (2) identify risk-factors for recovery of ambulation; (3) compare the outcome of FB and Dachshunds presenting with APP.Single centre retrospective case-series of dogs with paraplegia with APP with a diagnosis of TL-IVDE on CT or MRI, undergoing surgical decompression (hemilaminectomy+/-durotomy). Two main groups were defined: ambulatory, non-ambulatory. These were further characterised depending on the presence of pain perception and spontaneous movement. Outcome was obtained at 4-8 weeks postoperatively. Statistical analysis was performed comparing ambulatory and non-ambulatory dogs, and comparing rates of ambulation on FB vs. Dachshunds.Results: 127 included cases, 77/127 (60.6%) ambulatory at recheck, 9/127 (7.1%) ambulatory with APP. Remaining case distribution of non-ambulatory cases was: with APP (32/127;25.2%), with pain perception (5/127;3.9%), with spontaneous movement (5/127;3.9%). Multivariate analysis revealed 2 negative-factors for recovery of ambulation: dogs undergoing hemilaminectomy alongside durotomy (p=0.003) and dogs presenting with spinal shock (lower motor-neuron signs with a lesion higher than the L3-L4 intervertebral disc) alongside reduced/absent withdrawal-reflex (p=0.008). No difference was found between Dachshunds (n=41, 73.2% ambulatory) and FB (n=33, 63.6% ambulatory) in terms of recovery of ambulation, with only 2/33 (6.1%) FB developing myelomalacia.Early recovery of ambulation alone (60.6%) and ambulation alongside pain perception (53.5%) occurred in the majority of surgically managed TL-IVDE affected dogs with APP. Negative prognostic factors for recovery of ambulation were durotomy performed alongside hemilaminectomy, and dogs presenting with spinal shock with reduced/absent withdrawal-reflexes, the later translating to a reduced/absent withdrawal reflexes with a lesion higher than L3-L4 intervertebral disc. Finally, no indications of a worse prognosis for recovery of ambulation or a higher rate of development of myelomalacia in FB when compared with Dachshunds were found.