Dura mater marsupialization for spinal arachnoid diverticulum in dogs: 19 cases

Introduction and aim of the study. The spinal arachnoid diverticulum (SAD) is an intradural, extramedullary lesion that consists of an abnormal accumulation of the cerebrospinal fluid, causing a compressive and progressive myelopathy and gait abnormalities. Surgery is the treatment of choice of SAD but it is unclear which technique gives the best results. The aim of the study was to evaluate the outcome in the affected dogs treated with dura mater marsupialization. Materials and methods. Dogs diagnosed with SAD and surgically treated with dura mater marsupialization were included in the study. The postoperative outcome was considered at 15 days (T1) and 1 year after surgery (T2) and factors impacting on outcome were evaluated. When available, information regarding the neurological condition after the first 12 months post-operatively, were evaluated. Results. Nineteen dogs met the inclusion criteria, eight having cervical localisation of SAD and eleven caudal thoracic one. Main represented breeds were Pug, Rottweiler, French Bulldog. In dogs with cervical localisation, clinical condition was stable in 5/9 and worse in 3/9 at T1; 7/9 dogs improved at T2. For caudal thoracic patients, neurological condition remained stable in 9/11 cases and worsened in 2 dogs 15 days after surgery, with improvement of 9/11 dogs one year after surgery. There were 2 recurrences within one year. Overall, the improvement one year after surgery was detected in 16/19 dogs, with mild improvement in 12 cases, from moderate paresis to mild paresis and/or ataxia, and 4 dogs completely recovered. Body weight in dogs with cervical SAD was significantly associated with short-term outcome. Discussion. Most dogs achieved neurological improvement one year after surgery, demonstrating that this type of chronic lesion requires an adequate period of time for functional recovery. Initial post-operative worsening can occur in heavy dogs with cervical SAD. Marsupialization of the dura mater appears to be effective; however, in acquired SAD in the caudal thoracic region with concomitant underlying vertebral or disc pathology, it may not lead to recovery of the neurological condition in the long term.