Background: Outcome assessment for the management of Chiari Malformation Type 1 (CM1) is difficult due to the lack of a reliable and specific surgical outcome assessment scale. Such a scale could reliably correlate postoperative outcomes with preoperative symptoms.

Objective: We developed a novel scoring system and applied it retrospectively to 146 patients treated at our institution in order to create and verify a simple and quantifiable assessment of Chiari outcomes.

Methods: The Chicago Chiari Outcome Scale (CCOS) uses four postoperative outcome categories (pain, non-pain symptoms, functionality, and complications) graded 1 – 4 for a total possible score of 16. As a comparison to current Chiari outcome methodology, each patient was also placed into a gestalt outcome group of “improved,” “unchanged” or “worse” (I/U/W). Patients were stratified by CCOS scores and by I/U/W group.

Results: Stratifying patients by total CCOS scores showed that patients who achieved CCOS scores between 13-16 were predominantly in the I/U/W improved group (n=101, 69%); scores between 9-12 were predominantly I/U/W unchanged (n=39, 27%), and scores between 4-8 were I/U/W worse (n=6, 4%). Symptom sub-score results provided insight into the specifics of the overall outcome in addition to the more quantitative nature of the 16-point scale.

Conclusion: We describe a CCOS that assigns higher scores to patients judged improved by gestalt I/U/W ratings and lower scores to those who were unchanged or worse while defining outcome in four specific subcategories. As such, this CCOS should allow for a more unified and quantifiable outcome assessment after Chiari surgery.

From: A Novel Scoring System for Assessing Chiari Malformation Type I Treatment Outcomes by Aliaga et al

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