Resting State Functional Connectivity After Sphenopalatine Ganglion Blocks in Chronic Migraine With Medication Overuse Headache: A Pilot Longitudinal fMRI Study.

OBJECTIVE: In this pilot study, the purpose is to investigate if a series of sphenopalatine ganglion (SPG) blockade treatments modulate the functional connectivity within the salience and central executive network (CEN) in chronic migraine with medication overuse headaches (CMw/MOH ).

BACKGROUND: Using intranasal local anesthesia to block the SPG for the treatment of various headache disorders has been employed in clinical practice since the early 1900s. However, the exact mechanism of how SPG modulate resting state intrinsic functional brain networks connectivity remains to be elucidated. This pilot study seeks to understand the resting state connectivity changes in salience and CENs, with emphasis on the mesocorticolimbic systems, before and after a series of SPG block treatments.

METHODS: Using fMRI, resting state connectivity was derived from predefined networks of nodes (regions of interests) for the salience (27 nodes, 351 connections) and CENs (17 nodes, 136 connections). After treatments, a paired samples t-test (with 10,000 permutations to correct for multiple comparison) was used to evaluate changes in the intranetwork resting state functional connectivity within the salience and executive networks, as well as the overall network connectivity strength.

RESULTS: When comparing connectivity strength at baseline to that at the end of treatment in our cohort of 10 CMw/MOH participants, there were several connections within the salience (n = 9) and executive (n = 8) networks that were significantly improved. Within the salience network, improved connectivity was observed between the prefrontal cortex and various regions of the insula, basal ganglia, motor, and frontal cortex. Additionally, changes in connectivity were observed between regions of the temporal cortex with the basal ganglia and supramarginal gyrus. Within the CEN, improved connectivity was observed between the prefrontal cortex and regions of the anterior thalamus, caudate, and frontal cortex. After treatment, the overall CEN connectivity was significantly improved (Baseline 0.00 ± 0.08; 6 weeks 0.03 ± 0.09, P = .01); however, the overall salience network connectivity was not significantly improved (Baseline -0.01 ± 0.10; 6 weeks 0.01 ± 0.12, P = .26). Additionally, after treatment, there was a significant reduction in the number of moderate/severe headache days per month (Baseline 21.1 ± 6.6; 6 weeks 11.2 ± 6.5, P < .001), HIT-6 (Baseline 66.1 ± 2.6; 6 weeks 60.2 ± 3.6, P < .001), and PHQ-9 (Baseline 12.4 ± 5.7; 6 weeks 6.1 ± 3.6, P = .008) scores.

CONCLUSION: In this longitudinal fMRI study, we observed improved functional connectivity within both networks, primarily involving connectivity between regions of the prefrontal cortex and limbic (cortical-limbic) structures, and between different cortical (cortical-cortical) regions after a series of repetitive SPG blockades. The overall CEN strength was also improved. Our results suggest that recurrent parasympathetic inhibition via SPG is associated with improved functional connectivity in brain regions critical to pain processing in CMw/MOH .