Focal gray matter decrease in the cerebral pain network of migraine patients

Introduction Migraine is considered a frequent, primary headache disorder due to transient abnormal brain function. According to the current classification of the International Headache Society, structural brain lesions are absent in primary headaches. However, recent studies with voxel-based morphometry (VBM) demonstrated selective brain alterations in both cluster headache (bilateral increase of gray matter in postero-lateral hypothalamus) and chronic tension-type headache (gray matter decrease in orbifrontal cortex, insula, and anterior cingulate cortex). The purpose of this study was to investigate the presence of structural abnormalities in patients with migraine using the optimized voxel-based morphometry method, a highly sensitive technique to detect focal gray and white brain matter abnormalities. Methods A group of 27 right-handed migraine patients, diagnosed according to ICHD-II criteria, and 27 right-handed healthy controls underwent high resolution structural magnetic resonance imaging (MRI). Data was analyzed using MATLAB 6.5 and Statistical Parametric Mapping 2 (SPM2). Covariance analysis was used to detect local gray matter changes in migraine patients and between episodic and chronic migraine. Regression analysis was performed to search for a relationship between local gray matter changes with the clinical characteristics of migraine. Results Significant gray matter volume reduction was found in the right superior temporal gyrus, right parietal operculum, right inferior frontal gyrus, left angular gyrus, left inferior parietal lobule and left precentral gyrus of migraine patients. In comparison with episodic migraine, patients with chronic migraine showed a significant bilateral reduction of gray matter concentration in the anterior cingulate cortex (AAC), right angular gyrus and right inferior frontal gyrus. Finally, we found a significant correlation between the frequency of migraine attacks and the reduction of gray matter concentration in AAC of migraine patients. Discussion Our study shows a significant gray matter reduction in migraine patients of several cortical areas involved in pain processing and a selective alteration of AAC related to frequency of migraine attacks. Functional neuroimaging shows that several brain regions are activated by pain, including frontal and pre-frontal cortices, operculoinsular cortex, primary and secondary somatosensory cortices, AAC, thalamus and regions within the parietal and temporal cortices. In addition, AAC plays a key role in the affective and attentive processing of pain sensations. Our data supports the results of previous studies suggesting that migraine may be considered a progressive brain disorder and highlights the importance of prophylactic antimigraine therapy in order to avoid the progression of the disease.