Functional connectivity of hypothalamus in chronic migraine with medication overuse.

OBJECTIVE: To investigate the functional connectivity of the hypothalamus in chronic migraine compared to interictal episodic migraine in order to improve our understanding of migraine chronification. METHODS: Using task-free fMRI and ROI-to-ROI analysis, we compared anterior hypothalamus intrinsic connectivity with the spinal trigeminal nucleus in patients with chronic migraine (n = 25) to age- and sex-matched patients with episodic migraine in the interictal phase (n = 22). We also conducted a seed-to-voxel analysis with anterior hypothalamus as a seed. RESULTS: All patients with chronic migraine had medication overuse. We found a significant connectivity (T = 2.08, p = 0.024) between anterior hypothalamus and spinal trigeminal nucleus in the chronic group, whereas these two regions were not connected in the episodic group. The strength of connectivity was not correlated with pain intensity (rho: 0.09, p = 0.655). In the seed-to-voxel analysis, three regions were more connected with the anterior hypothalamus in the chronic group: The spinal trigeminal nuclei (MNI coordinate x = 2, y = -44, z = -62), the right dorsal anterior insula (MNI coordinate x = 10, y = 10, z = 18), and the right caudate (MNI coordinate x = 12, y = 28, z = 6). However, these correlations were no longer significant after whole brain FWE correction. CONCLUSION: An increased functional connectivity between the anterior hypothalamus and the spinal trigeminal nucleus, as previously reported in preictal episodic migraine, was demonstrated in chronic migraine with medication overuse. This finding confirms a major role of the anterior hypothalamus in migraine and suggests that chronic migraineurs are locked in the preictal phase.

Transition from rest to movement: brain correlates revealed by functional connectivity.

It is suggested that resting state networks reflecting correlated neural regional activities participate significantly in brain functioning. A fundamental issue is to understand how these networks interact and how their activities change during behavioral transitions. Our aim was to understand better with functional MRI connectivity how the brain switched from a "resting" to a movement-related state by exploring the transitory readiness state for an intended movement of the right hand. Our study does not address movement preparation occurring in a time scale of milliseconds before movement which has been widely studied but movement-readiness which can last longer. At rest, in the absence of overt goal-directed behavior, a "default-mode" network, whose main areas are the posterior cingulate cortex and precuneus (PCC/Pcu), shows high activity interpreted as day dreaming, free association, stream of consciousness, and inner rehearsal. We found that, during rest, the "default-mode" network and the sensorimotor network were not functionally correlated. During movement-readiness, the two networks were functionally correlated through an interaction between the PCC/Pcu and the medial superior parietal cortex in the upper precuneus. The complex PCC/Pcu has been shown to be involved in retrieval and/or setting up spatial attributes for motor imagery, and thus, would be a key region in the movement-readiness phase. It might functionally connect to the medial superior parietal cortex to initiate the movement programming through retrieval of suited movement parameters. The anterior cingulum, functionally correlated to the primary sensorimotor cortex during movement-readiness would have a motivational role or could generate predictions about the movement.

Altered functional connectivity related to white matter changes inside the working memory network at the very early stage of MS.

Functional magnetic resonance imaging (fMRI) using paced auditory serial addition test (PASAT) as paradigm was used to study the functional connectivity in 18 patients at the very early stage of multiple sclerosis (MS) compared with 18 controls, to determine the existence of circuitry disturbance inside the working memory network and its relationship with white matter abnormalities assessed by conventional MRI and magnetization transfer ratio (MTR) imaging. The left BA 45/46 was selected as the seed region to compute correlation maps with other brain regions. After obtaining the correlation map for each subject, between-group comparisons were performed using random effect procedure. Compared with controls, patients did not show any greater functional connectivity between left BA 45/46 and other regions during PASAT. In contrast, decrease in functional connectivity was observed in patients between left BA 45/46 and left BA 9, right BA 3, and the anterior cingulate cortex (BA 24). In patients, no correlations were found between altered functional connectivity and clinical data. However, functional connectivity observed between left BA 45/46 and BA 24 in patients was correlated with the MTR of normal appearing white matter, and with brain T(2) lesion load. Altered functional connectivity is present inside the working memory network of patients at the very early stage of MS and is related to the extent of diffuse white matter changes.