Neuroimaging Studies of Chronic Migraine and Medication Overuse Headache

Extensive research has been conducted, and there is still a need for further investigation to gain a comprehensive understanding of the underlying mechanisms of chronic migraine, regardless of whether it is caused by excessive use of medication. In this chapter, we have examined multiple neuroimaging investigations conducted on individuals suffering from chronic migraine, which have unveiled numerous structural and functional abnormalities inside the brain. Upon reviewing the studies, it is evident that the brain undergoes structural changes that are likely associated with chronic pain processing and multisensory integration. These changes include variations in the thickness of gray matter and modifications in the shape and depth of brain scissurae. Additionally, patients who excessively use acute medication experience a decrease in the volume of the orbitofrontal cortex. Furthermore, there are widespread modifications in the microstructure of white matter fiber bundles. The hypothalamus exhibits modified connections with the brainstem and other cortical areas/networks. There are diverse changes in functional connectivity, as observed through ROI-to-ROI analysis and independent component analysis of large-scale brain networks. The exploration of the functionality of the glymphatic system has yielded inconsistent findings. Additionally, there is a significant decrease in blood flow in cortical structures and white fiber bundles. Additional research is essential to strengthen the capacity to compare and replicate results across studies by implementing standardized methods for data collection and analysis. This research will aim to enhance our comprehension of the pathophysiology of migraine chronification.