CLINICAL ARTICLE J Neurosurg Pediatr 25:21–29, 2020 Outcomes in children undergoing posterior fossa decompression and duraplasty with and without tonsillar reduction for Chiari malformation type I and syringomyelia: a pilot prospective multicenter cohort study *Joyce Koueik, MD, MS,1 Carolina Sandoval-Garcia, MD,1 John R. W. Kestle, MD,2 Brandon G. Rocque, MD, MS,3 David M. Frim, MD, PhD,4 Gerald A. Grant, MD,5 Robert F. Keating, MD,6 Carrie R. Muh, MD,7 W. Jerry Oakes, MD,3 Ian F. Pollack, MD,8 Nathan R. Selden, MD, PhD,9 R. Shane Tubbs, PhD, PA-C,3 Gerald F. Tuite, MD,10 Benjamin Warf, MD,11 Victoria Rajamanickam, MS,12 Aimee Teo Broman, MA,12 Victor Haughton, MD,13 Susan Rebsamen, MD,13 Timothy M. George, MD,14 and Bermans J. Iskandar, MD1 1Department of Neurological Surgery, University of Wisconsin, Madison, Wisconsin; 2Department of Neurosurgery, University of Utah, Salt Lake City, Utah; 3Department of Neurosurgery, Children’s of Alabama, Birmingham, Alabama; 4Section of Neurosurgery, Department of Surgery, University of Chicago, Chicago, Illinois; 5Department of Pediatric Neurosurgery, Stanford Health Care, Palo Alto, California; 6Department of Neurosurgery, Children’s National Health System, Washington, DC; 7Department of Neurosurgery, Duke University Medical Center, Durham, North Carolina; 8Department of Neurosurgery, UPMC Children’s Hospital of Pittsburgh, Pennsylvania; 9Department of Neurological Surgery, Oregon Health and Science University, Portland, Oregon; 10Department of Neurosurgery, Johns Hopkins All Children’s Hospital, Tampa, Florida; 11Department of Neurosurgery, Boston Children’s Hospital, Boston, Massachusetts; Departments of 12Biostatistics and Medical Informatics and 13Radiology, University of Wisconsin–Madison, Wisconsin; and 14Department of Neurosurgery, Dell Medical School, Austin, Texas OBJECTIVE Despite significant advances in diagnostic and surgical techniques, the surgical management of Chiari malformation type I (CM-I) with associated syringomyelia remains controversial, and the type of surgery performed is surgeon dependent. This study’s goal was to determine the feasibility of a prospective, multicenter, cohort study for CM-I/syringomyelia patients and to provide pilot data that compare posterior fossa decompression and duraplasty (PFDD) with and without tonsillar reduction. METHODS Participating centers prospectively enrolled children suffering from both CM-I and syringomyelia who were scheduled to undergo surgical decompression. Clinical data were entered into a database preoperatively and at 1–2 weeks, 3–6 months, and 1 year postoperatively. MR images were evaluated by 3 independent, blinded teams of neuro- surgeons and neuroradiologists. The primary endpoint was improvement or resolution of the syrinx. RESULTS Eight clinical sites were chosen based on the results of a published questionnaire intended to remove geo- graphic and surgeon bias. Data from 68 patients were analyzed after exclusions, and complete clinical and imaging re- cords were obtained for 55 and 58 individuals, respectively. There was strong agreement among the 3 radiology teams, and there was no difference in patient demographics among sites, surgeons, or surgery types. Tonsillar reduction was not associated with > 50% syrinx improvement (RR = 1.22, p = 0.39) or any syrinx improvement (RR = 1.00, p = 0.99). There were no surgical complications. CONCLUSIONS This study demonstrated the feasibility of a prospective, multicenter surgical trial in CM-I/syringomyelia ABBREVIATIONS ASAP = American Syringomyelia and Chiari Alliance Project; CM-I = Chiari malformation type I; PFD = posterior fossa decompression; PFDD = PFD and duraplasty; PFDD-T = PFDD with tonsillar reduction. SUBMITTED April 10, 2019. ACCEPTED August 1, 2019. INCLUDE WHEN CITING Published online October 18, 2019; DOI: 10.3171/2019.8.PEDS19154. * J.K. and C.S.G share first authorship, and T.M.G. and B.J.I. share senior authorship of this work. ©AANS 2020, except where prohibited by US copyright law J Neurosurg Pediatr Volume 25 • January 2020 21 Unauthenticated | Downloaded 09/29/21 01:25 AM UTC Koueik et al. and provides pilot data indicating no discernible difference in 1-year outcomes between PFDD with and without tonsillar reduction, with power calculations for larger future studies. In addition, the study revealed important technical factors to consider when setting up future trials. The long-term sequelae of tonsillar reduction have not been addressed and would be an important consideration in future investigations. https://thejns.org/doi/abs/10.3171/2019.8.PEDS19154 KEYWORDS Chiari malformation decompression; tonsillar resection; syrinx improvement; surgical outcomes HIARI malformation type I (CM-I) consists of a cau- that compared the outcomes of PFDD with and without dal position of the cerebellar tonsils in the upper tonsillar resection/reduction. The primary hypothesis was cervical spinal canal. The accessibility of MRI has that the two procedures were equivalent, with syrinx im- Cled to an increase in CM-I diagnosis, which is detected at provement as the primary outcome and symptomatic im- an average age of 24.9 ± 15.8 years.19 While acquired ton- provement as the secondary outcome. sillar ectopia has been reported as a consequence of hy- The study concept and design originated from the fol- drocephalus, trauma, brain tumors,22 and other etiologies lowing: 1) a survey of the membership of the American (e.g., lumboperitoneal shunting),29 true CM-I is thought to Syringomyelia and Chiari Alliance Project (ASAP), the be congenital. largest patient-support network in North America, which Syringomyelia is a fluid-filled cavity within the spinal indicated that the surgical approach used to decompress a cord that occurs secondary to a variety of etiologies, in- CM-I is the most critical clinical question to answer (un- cluding tumor, trauma, tethered cord, arachnoiditis, or, published), and 2) a survey of the American Society of as in the present study, CM-I. While surgical series of Pediatric Neurosurgeons, which revealed important trends CM-I decompression have reported a 65%–80% rate of and differences in treatment practices across the US and co-occurrence of syringomyelia,8,19,26 imaging and epide- highlighted the relevance of establishing outcome com- miological CM-I studies have shown only a 23% rate of parisons across centers to make appropriate management co-occurrence.24 recommendations.21 If warranted, the surgical treatment for CM-I consists of enlargement of the posterior cranial fossa. The decision Patient Recruitment and Clinical Data to treat CM-I surgically is based on the severity and pro- After obtaining IRB approval for the study from all gression of symptoms and signs, in conjunction with MRI participating centers, pediatric patients diagnosed with and CSF flow findings. Most, though not all, pediatric neu- both CM-I and syringomyelia were recruited. Inclusion rosurgeons agree that the presence of significant syringo- criteria included: children aged 0 to 17 years; a CM-I with myelia in association with CM-I is an indication for pos- tonsil position at least 5 mm below the foramen magnum; terior fossa decompression (PFD), even in the absence of 21,25 a syrinx with a width > 50% of the cross-sectional diam- symptoms. However, there is major controversy about eter of the spinal cord, and a length of at least 2 cervi- the surgical technique that is used. While some advocate cal and/or thoracic vertebral segments. Exclusion criteria bone-only craniocervical decompression (typically cra- included one or more of the following preexisting condi- niectomy and C1 posterior arch removal), others recom- tions: hydrocephalus; tumor; brain trauma; stroke; men- mend bone decompression and duraplasty, and still others ingitis; abscess; other congenital anomalies of the brain recommend bone decompression and duraplasty with ton- 21 or skull base; vertebral anomalies (i.e., Klippel-Feil, atlas sillar reduction. While it is agreed generally that avoid- assimilation, etc.); degenerative or demyelinating disease; ing a dural opening leads to a lower complication rate, a CM-I without syringomyelia; syringomyelia with cerebel- rigorous comparison of the outcomes of various surgical lar tonsils in a normal position; fibromyalgia; chronic fa- techniques is unavailable, as most studies to date have ex- 5,7,17 tigue syndrome; and prior posterior fossa surgery. Patients amined small, single-center, retrospective cohorts. unable to provide consent were also excluded. Standard- The goals of this pilot trial were to demonstrate the ized forms were used for patient demographics, radiologi- feasibility of conducting a prospective, multicenter, surgi- cal assessments, surgical details, and clinical follow-ups. cal cohort comparison study of CM-I and syringomyelia Data collected included pre- and postoperative signs and patients by establishing a cooperative group of centers to symptoms, pre- and postoperative MR images of the brain work toward the goal of a future randomized trial, allow and entire spine, details of the surgical intervention, and the sample size and power for such a trial to be estimated, postoperative complications. The Office of Clinical Trials and provide 1-year outcome data that compare two stand- in the University of Wisconsin Institute for Clinical and ard CM-I decompression procedures: craniectomy, C1 posterior arch removal, and duraplasty without tonsillar Translational Research managed the study. De-identified, reduction (PFDD) and craniectomy,