Foramen magnum decompression with cranioplasty for treatment of caudal occipital malformation syndrome in dogs

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Dewey CW, Marino DJ, Bailey KS, et al. 

Vet Surg 2007;36:406-415.

OBJECTIVES: To describe a cranioplasty procedure used in conjunction with foramen magnum decompression (FMD) for the treatment of canine caudal occipital malformation syndrome (COMS), and to evaluate the clinical outcome. STUDY DESIGN: Prospective clinical study. ANIMALS: Dogs (n=21) with COMS diagnosed by magnetic resonance imaging (MRI). METHODS: After FMD, titanium screws were placed around the perimeter of the foramen magnum defect and a skull plate fashioned from titanium mesh and polymethylmethacrylate was attached to the back of the skull, using the titanium screws as anchor posts. Follow-up was obtained by direct examination by the authors, telephone interviews with owners and referring veterinarians, and a questionnaire sent to owners of surviving dogs designed to assign objective measures of response to surgical intervention. Surgical success was defined as improvement in >or=1 aspects of clinical dysfunction (e.g. scratching, pain) postoperatively. Owner-assigned pre- and postoperative quality-of-life (QOL) scores (1-5) for surviving dogs were compared using a Wilcoxon’s signed rank test for paired data (P<or=.05). RESULTS: No intraoperative complications occurred and postoperative complications were limited to transient worsening of a pre-existing head tilt and ataxia in 1 dog, and the need for oral pain medication for 1-4 weeks in 3 dogs. Seventeen dogs (81%) had clinical improvement after surgery. Although clinical signs resolved in 1 dog, it died after being hit by a car, 5 months after surgery. One dog had no change in clinical signs; this patient’s clinical signs were not severe and the owners had opted for surgery primarily to prevent progression of disease. Two dogs were euthanatized; 1 because of no improvement of severe clinical signs, and 1 because of sustained recurrence of apparent head and neck pain 7 months later. One dog required a dorsal laminectomy at a second site (C1/C2 vertebral level), 2 months later. Four dogs has transient “flare-ups” of apparent head/neck pain 2-13 months later; all resolved with transient re-institution of oral analgesic therapy. Further surgery at the FMD was not needed. Based on the returned questionnaires, there was an overall significant improvement in QOL scores. CONCLUSIONS: FMD with cranioplasty was well tolerated, with no intraoperative complications, and minor postoperative complications. Most dogs improved clinically, and none required further surgery at the original FMD site. CLINICAL RELEVANCE: FMD with cranioplasty may be an effective surgical method of treating dogs with COMS and is well tolerated. Based on prior reports of FMD for this disorder, it appears that cranioplasty may reduce the rate of surgical failure caused by formation of compressive scar tissue at the FMD site in the short term. Results of this preliminary study support further evaluation of the cranioplasty procedure in a larger group of dogs over a more extended follow-up period.