At a plenary session at AAN2015, Todd Schwedt, MD, presented intriguing research that is helping to shape our understanding of the functional connectivity and brain structure of migraineurs.
We know that migraineurs demonstrate abnormal sensory processing—including abnormal pain integration, modulation, and affective processing. Even between attacks, migraineurs exhibit increased sensitivity to light, sound, and smell. They also have increased rates of pain disorders that may have altered central processing, such as irritable bowel syndrome and fibromyalgia. This suggests that abnormal sensory processing in migraine is potentially the result of altered brain function.
Recent research using resting state functional connectivity MRI supports the presence of abnormal functional connections in those with chronic migraine.1 Functional connections between the anterior insula, amygdala, pulvinar, mediodorsal thalamus, middle temporal cortex, and periaqueductal gray have been described: functional connections between the anterior insula and both the mediodorsal thalamus and periaqueductal gray specifically correlate with the length of time a person has experienced chronic migraine. Dr Schwedt presented additional research which demonstrated abnormal functional connectivity in these areas, as well as evidence that cortical thickness of the temporal parietal junction region may be abnormal.2
A study compared 31 adults with episodic migraine with 32 healthy controls utilizing quantitative sensory testing (QST) and regional cortical thickness using 3 Tesla MRI. Each subject’s heat pain threshold was quantified at the left forearm using QST. Cortical thickness was measured next using T1-weighted sequences by general linear model whole-brain vertex-wise analysis. Subjects were grouped by pain threshold and those with migraine were then compared to controls.
Healthy controls with low heat pain thresholds had a thicker cortex in left superior temporal/inferior parietal region. Migraineurs with low pain heat thresholds had thinner cortex in this area (P<.01). There was no change in this area among the migraineur group despite disease-varied severity, which suggests that this may be an underlying trait of those with migraine. This region is involved in the cognitive aspect of pain, specifically directing attention toward or away from environmental or painful stimuli. One could hypothesize that having this trait may explain why someone with migraine may have a difficult time distracting himself or herself from pain and other nonpainful stimuli.3
Take home points
The potential implications of this research may lead us to an imaging biomarker for migraine using volume, surface area, and thickness of specified brain regions on standard MRI. While migraine remains a clinical diagnosis, structural imaging may eventually become a helpful adjunctive clinical tool.
1. Schwedt TJ, Schlaggar BL, Mar S, et al. Atypical resting-state functional connectivity of affective pain regions in chronic migraine. Headache. 2013;53:737-751.
2. Schwedt TJ, Chong CD. Correlations between brain cortical thickness and cutaneous pain thresholds are atypical in adults with migraine. PLoS One. 2014;9(6).
3. Schwedt T, Chong C. Abstract PL1.001. Adults with migraine have atypical correlations between brain cortical thickness and pain thresholds. Presented at: AAN2015 Washington, DC.