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Supplemental: Chiari I Malformation (CM)

To date, there has been no study to comprehensively assess the effectiveness of SOC for Chiari I malformation using validated patient-reported outcome measures.

 

"Fifty patients undergoing first-time SOC and C1 laminectomy for Chiari I malformation 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" (Parker et al., 2013).

 

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 Chiari I malformation 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 (Parker et al., 2013)

A recognized shortcoming of symptom questionnaires is that their numerical scores lack a direct, clinically significant meaning. The HTI along with the North American spine Society (NASS) Satisfaction Questionnnaire used to determine a patient's satisfaction with surgery can be used to define a MCID.

 

MCID Threshold Calculation The MCID threshold is defined as the lower limit of the 95% confidence interval (CI) for the median change score of each other outcome metrics for the patients classified as responders based on each anchor (NASS Satisfaction Questionnaire and HTI). Additionally, the probability that scores will correctly discriminate between responders and nonresponders (accuracy) can be depicted by the area under the receiver-operating characteristic (ROC) curve. This value ranges from 0.5 (discrimination is no better than pure chance) to 1.0 (all patients are able to be correctly discriminated). An area of 0.7 to 0.8 is considered adequate; an area of 0.8 to 0.9 is considered excellent (Copay et al., 2007).

 

The HTI is a patient reported assessment of how the patient feels after surgery compared to before surgery. Treatment "responders" are considered to be patients that are markedly better or slightly better after surgery. "Non-responders" are the same, slightly worse, or markedly worse after surgery. In the Parker study (2013), 33 patients (66%) were responders and 17 (34%) were non-responders to standard treatment. The HTI can provide a standard and replicable way to compare the response rates of different surgical procedures for Chiari I malformation. The HTI is an item in the SF-36 and does not need to be assessed separately if the study includes the SF-36.