PROJECT SUMMARY Clinical Core: Abstract The Clinical Core (CC) supports the Park-Reeves Chiari & Syringomyelia Center (PRCSC) by leading participant screening, enrollment, and consenting processes as well as the acquisition of clinical data, neurobehavioral assessments (NIH Toolbox), and patient-reported outcome measures (PROM), including health-related quality of life (hrQOL) instruments. This will include patients with CM recruited for participation through the clinical practices at Washington University/St. Louis Children’s Hospital/Barnes-Jewish Hospital but also through the multicenter Park-Reeves Chiari Genetics Group. The CC will maintain the 5 key datasets to support the aims and scientific initiatives all four proposed P01 Projects: 1) PRCSC multicenter registry; 2) PRCSC’s 42-center PCORI-supported randomized clinical trial Posterior Fossa Decompression With or Without Duraplasty for Chiari Type I Malformation with Syringomyelia (the PFD/D Trial); 3) Chiari Comorbidites database; 4) Park-Reeves Chiari Genetics database; and 5) P01 Prospective Cohort 1 (aged 9-18 years) and Cohort 2 (aged ≥19 years). All data will be coded, anonymized, uploaded, and stored using existing Standing Operating Procedures. Through these and related rigorous processes, the CC will support the PRCSC’s overarching mission to redefine CM using leading-edge, high quality genetic, radiological, and clinical data, and to determine the effect of CM on brain development, neurological outcomes, and PROM. The functions of the CC are to: 1. Recruit and maintain the study cohorts for all aspects of PRCSC. 2. Coordinate all clinical follow-up, neurobehavioral assessments, and PROM across all Projects and Cores. 3. Provide clinical data, developmental assessments, and PROM to all PRCSC Cores and Projects to facilitate their scientific initiatives. 4. Conduct long-term, longitudinal clinical follow-up with neurobehavioral assessment, and PROM and hrQOL scoring to determine disease natural history and treatment durability in CM and SM. 5. Manage the workflow of all PRCSC-wide clinical databases, including the design of forms, data entry, quality control, and the distribution of analyzed clinical data sets to investigators, Projects, and Cores. 6. Engage the CM community to contribute to PRCSC studies and support its research priorities. 7. Support the PRCSC mission by nurturing early-stage investigators so that they develop into independent, effective CM scientists.