Extradural decompression versus duraplasty in Chiari malformation type I with syrinx: outcomes on scoliosis from the Park-Reeves Syringomyelia Research Consortium
Authors: Sadler Brooke , Skidmore Alex , Gewirtz Jordan , Anderson Richard C. E. , Haller Gabe , Ackerman Laurie L. , Adelson P. David , Ahmed Raheel , Albert Gregory W. , Aldana Philipp R. , Alden Tord D. , Averill Christine , Baird Lissa C. , Bauer David F. , Bethel-Anderson Tammy , Bierbrauer Karin S. , Bonfield Christopher M. , Brockmeyer Douglas L. , Chern Joshua J. , Couture Daniel E. , Daniels David J. , Dlouhy Brian J. , Durham Susan R. , Ellenbogen Richard G. , Eskandari Ramin , Fuchs Herbert E. , George Timothy M. , Grant Gerald A. , Graupman Patrick C. , Greene Stephanie , Greenfield Jeffrey P. , Gross Naina L. , Guillaume Daniel J. , Hankinson Todd C. , Heuer Gregory G. , Iantosca Mark , Iskandar Bermans J. , Jackson Eric M. , Jea Andrew H. , Johnston James M. , Keating Robert F. , Khan Nickalus , Krieger Mark D. , Leonard Jeffrey R. , Maher Cormac O. , Mangano Francesco T. , Mapstone Timothy B. , McComb J. Gordon , McEvoy Sean D. , Meehan Thanda , Menezes Arnold H. , Muhlbauer Michael , Oakes W. Jerry , Olavarria Greg , O’Neill Brent R. , Ragheb John , Selden Nathan R. , Shah Manish N. , Shannon Chevis N. , Smith Jodi , Smyth Matthew D. , Stone Scellig S. D. , Tuite Gerald F. , Wait Scott D. , Wellons John C. , Whitehead William E. , Park Tae Sung , Limbrick David D. , Strahle Jennifer M. 
Published: June 2021

OBJECTIVE
Scoliosis is common in patients with Chiari malformation type I (CM-I)–associated syringomyelia. While it is known that treatment with posterior fossa decompression (PFD) may reduce the progression of scoliosis, it is unknown if decompression with duraplasty is superior to extradural decompression.

METHODS
A large multicenter retrospective and prospective registry of 1257 pediatric patients with CM-I (tonsils ≥ 5 mm below the foramen magnum) and syrinx (≥ 3 mm in axial width) was reviewed for patients with scoliosis who underwent PFD with or without duraplasty.

RESULTS
In total, 422 patients who underwent PFD had a clinical diagnosis of scoliosis. Of these patients, 346 underwent duraplasty, 51 received extradural decompression alone, and 25 were excluded because no data were available on the type of PFD. The mean clinical follow-up was 2.6 years. Overall, there was no difference in subsequent occurrence of fusion or proportion of patients with curve progression between those with and those without a duraplasty. However, after controlling for age, sex, preoperative curve magnitude, syrinx length, syrinx width, and holocord syrinx, extradural decompression was associated with curve progression > 10°, but not increased occurrence of fusion. Older age at PFD and larger preoperative curve magnitude were independently associated with subsequent occurrence of fusion. Greater syrinx reduction after PFD of either type was associated with decreased occurrence of fusion.

CONCLUSIONS
In patients with CM-I, syrinx, and scoliosis undergoing PFD, there was no difference in subsequent occurrence of surgical correction of scoliosis between those receiving a duraplasty and those with an extradural decompression. However, after controlling for preoperative factors including age, syrinx characteristics, and curve magnitude, patients treated with duraplasty were less likely to have curve progression than patients treated with extradural decompression. Further study is needed to evaluate the role of duraplasty in curve stabilization after PFD.