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Comprehensive Assessment of 1-Year Outcomes and Determination of Minimum Clinically Important Difference in Pain, Disability, and Quality of Life After Suboccipital Decompression for Chiari Malformation I in Adults

Parker, Scott L. MD; Godil, Saniya S. MD; Zuckerman, Scott L. BS; Mendenhall, Stephen K. BS; Wells, John A. BS; Shau, David N. BS; McGirt, Matthew J. MD

doi: 10.1227/NEU.0000000000000032
Research-Human-Clinical Studies

BACKGROUND: To date, there has been no study to comprehensively assess the effectiveness of suboccipital craniectomy (SOC) for Chiari malformation I (CMI) using validated patient-reported outcome measures.

OBJECTIVE: To determine the effectiveness and minimum clinically important difference thresholds of SOC for the treatment of adult patients with CMI using patient-reported outcome metrics.

METHODS: Fifty patients undergoing first-time SOC and C1 laminectomy for CMI at a single institution were followed up for 1 year. Baseline and 1-year postoperative pain, disability, quality of life, patient satisfaction, and return to work were assessed. Minimum clinically important difference thresholds were calculated with 2 anchors: the Health Transition Index and North American Spine Society satisfaction questionnaire.

RESULTS: The severity of headaches improved in 37 patients (74%). Improvement in syrinx size was seen in 12 patients (63%) and myelopathy in 12 patients (60%). All patient-reported outcomes showed significant improvement 1 year postoperatively (P < .05). Of the 38 patients (76%) employed preoperatively, 29 (76%) returned to work postoperatively at a median time of 6 weeks (interquartile range, 4-12 weeks). Minimum clinically important difference thresholds after SOC for CMI were 4.4 points for numeric rating scale for headache, 0.7 points for numeric rating scale for neck pain, 13.8 percentage points for Headache Disability Index, 14.2 percentage points for Neck Disability Index, 7.0 points for Short Form-12 Physical Component Summary, 6.1 points for Short Form-12 Mental Component Summary, 4.5 points for Zung depression, 1.7 points for modified Japanese Orthopaedic Association, and 0.34 quality-adjusted life-years for Euro-Qol-5D.

CONCLUSION: Surgical management of CMI in adults via SOC provides significant and sustained improvement in pain, disability, general health, and quality of life as assessed by patient-reported outcomes. This patient-centered assessment suggests that suboccipital decompression for CMI in adults is an effective treatment strategy.

ABBREVIATIONS: CI, confidence interval

CMI, Chiari malformation type I

EQ-5D, Euro-Qol-5D; HDI, Head Disability Index

HTI, Health Transition Index

MCID, minimum clinically important difference

MCS, Mental Component Summary

mJOA, modified Japanese Orthopaedic Association

NASS, North American Spine Society

NDI, Neck Disability Index

NRS, numeric rating scale

PCS, Physical Component Summary

PRO, patient-reported outcome

ROC, receiver-operating characteristic

SF-12, Short Form-12-Item Survey

Department of Neurosurgery, Vanderbilt University Medical Center, and Vanderbilt Spinal Column Surgical Outcomes and Quality Research Laboratory, Nashville, Tennessee

Correspondence: Scott L. Parker, MD, 4347 Village at Vanderbilt, Nashville, TN 37232-8618. E-mail:

Received April 22, 2013

Accepted June 4, 2013

Copyright © by the Congress of Neurological Surgeons