Defining the minimal important change in headache after surgery for degenerative cervical radiculopathy: a population-based study from the Norwegian Registry for Spine Surgery.

Abstract

Previous studies reported that 58%-88% of patients undergoing operations for degenerative cervical radiculopathy (DCR) have concomitant headache, but the prospects of experiencing a minimal important change (MIC) in the headache after surgery are unknown. This study aimed to assess the prevalence of concomitant headache prior to DCR surgery, establish the MIC for headache, and determine the proportion of patients achieving this level of improvement at 12 months follow-up. In this population-based study, 6234 cases operated on for DCR were prospectively enrolled in the Norwegian Registry for Spine Surgery and followed for 12 months. The Global Perceived Effect scale was used as an external criterion and receiver operating characteristic (ROC) curve analyses to assess MIC values of the numeric rating scale for headache (NRS-HA) change score and the corresponding percentage change scores. At admission for surgery, 4689 (75.2%) of 6234 cases reported concomitant headache. A percentage change in the NRS-HA of 23.6% was the most accurate and acceptable MIC cutoff value (area under the ROC curve = 0.75, 95% confidence interval 0.73-0.78). At the 12-month follow-up evaluation, 63% of the cases with headache achieved improvement equal to or greater than the MIC value. Patients undergoing operations for DCR who have concurrent headache can be informed that empirically at least 60% will have a noticeable improvement of their headache 12 months after surgery.