Resting State Functional Connectivity After Sphenopalatine Ganglion Blocks in Chronic Migraine With Medication Overuse Headache: A Pilot Longitudinal fMRI Study
Background: Chronic migraine accompanied by medication overuse headache (CMw/MOH) poses significant treatment challenges. The sphenopalatine ganglion (SPG) has been targeted for therapeutic interventions since the early 1900s, yet the precise mechanisms underlying its efficacy remain unclear. This study explores the impact of repetitive SPG blockades on the functional connectivity of brain networks associated with pain processing in CMw/MOH patients.
Methods: Ten participants diagnosed with CMw/MOH underwent a series of SPG blockade treatments. Functional magnetic resonance imaging (fMRI) was utilized to assess resting-state connectivity within the salience network (27 nodes, 351 connections) and the central executive network (CEN; 17 nodes, 136 connections). Paired samples t-tests, corrected for multiple comparisons, evaluated changes in intranetwork connectivity and overall network strength before and after the treatment series.
Results: Post-treatment analyses revealed significant enhancements in functional connectivity:
- Salience Network: Improved connectivity between the prefrontal cortex and regions including the insula, basal ganglia, motor, and frontal cortices. Additional changes were observed between the temporal cortex, basal ganglia, and supramarginal gyrus.
- Central Executive Network: Enhanced connectivity between the prefrontal cortex and areas such as the anterior thalamus, caudate, and frontal cortex. Overall CEN connectivity strength increased significantly (Baseline: 0.00 ± 0.08; 6 weeks: 0.03 ± 0.09; P = .01).
Clinically, participants experienced a notable reduction in moderate to severe headache days per month (Baseline: 21.1 ± 6.6; 6 weeks: 11.2 ± 6.5; P < .001). Scores on the Headache Impact Test (HIT-6) decreased from 66.1 ± 2.6 to 60.2 ± 3.6 (P < .001), and Patient Health Questionnaire (PHQ-9) scores improved from 12.4 ± 5.7 to 6.1 ± 3.6 (P = .008).
Conclusion: The study indicates that repetitive SPG blockades are associated with enhanced functional connectivity in brain regions critical to pain processing in CMw/MOH patients. These findings suggest that SPG blockades may exert a neuromodulatory effect, potentially offering a therapeutic avenue for individuals suffering from chronic migraines with medication overuse headaches.