Adults with migraine have abnormal thalamo-cortical networks and dysrhythmia along with migraine-related deficits in brain function, according to a study published in Neurology.
Researchers recruited 100 adults with migraine without aura and 70 demographically matched healthy controls. Migraine was diagnosed by 3 neurologists based on the International Classification of Headache Disorders. Participants were recruited via advertisements and required to stop taking any prophylactic headache medication during the last month of the study. Further, they were required to be migraine-free for at least 72 hours at time of the magnetic resonance imaging (MRI) scan. Migraine frequency (determined by the number of attacks that were separated by pain-free intervals of at least 48 hours) and intensity (on a scale of 0 to 10, with 10 being the worst pain during a month) were used as clinical measures for migraine without aura. Participants recorded these values in a migraine diary. Anxiety and depression levels were also measured using the self-rating anxiety scale and the self-rating depression scale, respectively.
All participants underwent a functional MRI (fMRI) from which researchers examined dynamic functional network connectivity of the migrainous brain by focusing on the temporal properties of thalamo-cortical connectivity using sliding window cross-correlation, clustering state analysis, and graph-theory methods. Relationship between clinical symptoms and abnormal dynamic functional network connectivity were evaluated using a multivariate linear regression model.
Of the 100 adults with migraine, 9 were excluded due to incomplete scans (lack of resting-state fMRI scan or T1 anatomical scan), and 2 were excluded due to excessive head movement (>3 mm). A total of 89 patients with migraine without aura and 70 healthy controls were ultimately included in the study. Five dynamic functional network connectivity brain states were defined to characterize and compare connectivity patterns. Adults with migraine were found to spend more time in a strongly interconnected between-network state but less time in a sparsely connected state.
Further, the posterior-pulvinar thalamic complex was delineated as a functional component that differentiates patients with migraine from healthy controls. Investigators report broad projections from this thalamic complex to regions implicated in clinical features of migraine, specifically the primary visual, secondary visual, auditory, and somatosensory cortices. Adults with migraine had significantly lower efficiency of information transfer in both global and local dynamic functional network connectivity (P <.001 for both). Seeing as a number of participants with migraine had photophobia (n=50) and phonophobia (n=59), a secondary comparative analysis was conducted and found no significant difference between the subgroups.
Limitations of this study included a lack of focus dynamic functional network connectivity abnormalities and its influence on sensory stimulation, as well as the potential effect of varying levels of vigilance in adults with migraine on dynamic functional network connectivity. Researchers recommended future studies include cardiac, respiratory, or eye-tracking data to further characterize the pathophysiology of adults with migraine.
The investigators this study demonstrates the “dynamic properties of abnormal thalamo-cortical networks coupled with clinical symptoms as well as disrupted functional segregation and integration of dynamic [functional network connectivity] in migraine patients.” They believe these results, “extend current findings regarding thalamo-cortical dysrhythmia in the migraine brain and suggest migraine-related deficits of brain functions in the interictal state.”
Tu Y, Fu Z, Zeng F, et al. Abnormal thalamo-cortical network dynamics in migraine [published online May 10, 2019]. Neurology. doi: 10.1212/WNL.0000000000007607