Chiari Type I Revision Decompressive Surgery Indications and Operative Technique: Experience in A Large Adult Cohort.

INTRODUCTION: Chiari Malformation is characterized by inferior displacement of the cerebellar tonsils through the foramen magnum, frequently resulting in strain related headaches, and motor/sensory dysfunction. Chiari decompression technique varies significantly, possibly contributing to frequent revisions. We reviewed revision Chiari decompressions at our institution to determine the primary indications for revision and outcomes after revision.

METHOD: We retrospectively reviewed patients who underwent revision of Chiari decompression at our institution from 2005-2020. Demographics, indications for revision surgery, operative techniques, imaging findings, and pre-/post-operative symptoms were collected. Chi-squared test was performed to determine statistical significance using a p<0.05. Independent predictors of operative outcomes were identified.

RESULT: A total of 46 patients (91% female, mean age 38.8 years) were included for analysis. The median time to revision surgery was 69.1 months (range 0-364 months) with headache (n=37, 80%) being the most commonly recurring symptom. Large craniectomy (n=28, 61%) was the most frequent indication for revision surgery. Thirty-two (70%) patients underwent cranioplasty, 20 (43%) required duraplasty, 15 (33%) required arachnoid dissection, and 15 (33%) required tonsillar reduction during revision surgery. Post-revision follow-up (at 8.9 ± 5.2 months average, range 1-18 months), revealed an average reduction in all Chiari-related symptoms relative to symptoms before the revision.

CONCLUSION: The most common indication for revision Chiari decompression was a large craniectomy resulting in cerebellar ptosis. We found that tonsillar reduction paired with modest craniectomy achieved near-complete resolution of symptoms with minimal complications. For patients with recurrent or persistent sequelae of Chiari malformation after decompression, revision may reduce symptom severity.