Should Motor Function Determine the Timing of Scoliosis Surgery in Spinal Muscular Atrophy (SMA)? (P5.006)

Objective: To assess the impact of scoliosis surgery on motor function in SMA types 2 and 3. Background: Weakness affects motor performance and can lead to spinal deformities in SMA. Scoliosis surgery decision-making is based on curve progression, pulmonary function, and skeletal maturity. Reported benefits include quality of life, sitting balance, endurance, and cosmesis. Postoperative functional decline has been described, but the impact of scoliosis surgery on motor function has not been formally assessed. Design/Methods: Data was acquired prospectively as part of an IRB-approved multicenter natural history study. Eighteen participants (type 2=13, type 3=5, 1 ambulatory) who underwent scoliosis surgery had motor function assessed pre-operatively and at least 3 months post-operatively. Age, SMA type, and Hammersmith Functional Motor Scale Expanded (HFMSE) were collected before and after surgery. Independent t-tests were performed to determine group differences. Results: Four of 18 participants had minimal HFMSE changes between -2 and +2 points (mean values: age=8.6 years, SD=3.3; baseline score=6.8; change=-0.25, SD=2.1). The remaining 14 participants lost >3 points on the HFMSE, representing a clinically meaningful change (mean values: age=10.0 years, SD=3.9; baseline score=19.4; change=-11.9, SD=9.0). No participant had improvement greater than 2 points. There was no age difference between stable and progressive groups (p=0.474), but there were significant differences in baseline HFMSE score (p=0.002) and change scores (p<0.001). Conclusions: Scoliosis surgery often has a negative impact on function. Baseline HFMSE score anticipates functional decline post-operatively. Patients with higher motor function scores have more to lose and are at greater risk of a clinically meaningful post-operative loss. These observations should alert clinicians to the risk and provide anticipatory guidance to the family and child. Longer follow-up is necessary to determine if changes are permanent, continue to progress, or diminish. Evaluating the relative vulnerabilities of individually measured motor functions to surgical intervention should be informative. Disclosure: Dr. Dunaway has received personal compensation for activities with ISIS Pharmaceuticals, Inc. as a consultant. Dr. Montes has received personal compensation for activities with Isis Pharmeceuticals as a consultant. Dr. Salazar has nothing to disclose. Dr. Glanzman has nothing to disclose. Dr. Pasternak has nothing to disclose. Dr. Quigley has nothing to disclose. Dr. Ciurylo has nothing to disclose. Dr. Riley has nothing to disclose. Dr. Martens has nothing to disclose. Dr. Gee has nothing to disclose. Dr. Duong has nothing to disclose. Dr. Civitello has nothing to disclose. Dr. Chiriboga has received personal compensation for activities with Up To Date, ISIS pharmaceuticals/Biogen, and Roche pharmaceuticals. Dr. Tennekoon has nothing to disclose. Dr. Day has received personal compensation for activities with Sarepta Therapeutics and PTC Therapeutics as a consultant. Dr. Finkel has received personal compensation for activities with Isis Pharmaceuticals and Voyager Therapeutics as a consultant and/or speaker. Dr. Darras has received personal compensation for activities with UpToDate, Inc., Isis Pharmaceuticals, Inc., and Athena Diagnostics as a consultant. Dr. De Vivo has received personal compensation for activities with Isis Pharmaceuticals as a consultant.