Altered Brain Functional Connectome in Migraine with and without Restless Legs Syndrome: A Resting-State Functional MRI Study

Meso-scale reorganization of local-global brain networks under mild sedation of propofol anesthesia

The fragmentation of the functional brain network has been identified through the functional connectivity (FC) analysis in studies investigating anesthesia-induced loss of consciousness (LOC). However, it remains unclear whether mild sedation of anesthesia can cause similar effects. This paper aims to explore the changes in local-global brain network topology during mild anesthesia, to better understand the macroscopic neural mechanism underlying anesthesia sedation. We analyzed high-density EEG from 20 participants undergoing mild and moderate sedation of propofol anesthesia. By employing a local-global brain parcellation in EEG source analysis, we established binary functional brain networks for each participant. Furthermore, we investigated the global-scale properties of brain networks by estimating global efficiency and modularity, and examined the changes in meso-scale properties of brain networks by quantifying the distribution of high-degree and high-betweenness hubs and their corresponding rich-club coefficients. It is evident from the results that the mild sedation of anesthesia does not cause a significant change in the global-scale properties of brain networks. However, network components centered on SomMot L show a significant decrease, while those centered on Default L, Vis L and Limbic L exhibit a significant increase during the transition from wakefulness to mild sedation (p<0.05). Compared to the baseline state, mild sedation almost doubled the number of high-degree hubs in Vis L, DorsAttn L, Limbic L, Cont L, and reduced by half the number of high-degree hubs in SomMot R, DorsAttn R, SalVentAttn R. Further, mild sedation almost doubled the number of high-betweenness hubs in Vis L, Vis R, Limbic R, Cont R, and reduced by half the number of high-betweenness hubs in SomMot L, SalVentAttn L, Default L, and SomMot R. Our results indicate that mild anesthesia cannot affect the global integration and segregation of brain networks, but influence meso-scale function for integrating different resting-state systems involved in various segregation processes. Our findings suggest that the meso-scale brain network reorganization, situated between global integration and local segregation, could reflect the autonomic compensation of the brain for drug effects. As a direct response and adjustment of the brain network system to drug administration, this spontaneous reorganization of the brain network aims at maintaining consciousness in the case of sedation.

Functional magnetic resonance imaging in migraine: A systematic review

BACKGROUND

Migraine is a highly prevalent primary headache disorder. Despite a high burden of disease, key disease mechanisms are not entirely understood. Functional magnetic resonance imaging is an imaging method using the blood-oxygen-level-dependent signal, which has been increasingly used in migraine research over recent years. This systematic review summarizes recent findings employing functional magnetic resonance imaging for the investigation of migraine.

METHODS

We conducted a systematic search and selection of functional magnetic resonance imaging applications in migraine from April 2014 to December 2021 (PubMed and references of identified articles according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines). Methodological details and main findings were extracted and synthesized.

RESULTS

Out of 224 articles identified, 114 were included after selection. Repeatedly emerging structures of interest included the insula, brainstem, limbic system, hypothalamus, thalamus, and functional networks. Assessment of functional brain changes in response to treatment is emerging, and machine learning has been used to investigate potential functional magnetic resonance imaging-based markers of migraine.

CONCLUSIONS

A wide variety of functional magnetic resonance imaging-based metrics were found altered across the brain for heterogeneous migraine cohorts, partially correlating with clinical parameters and supporting the concept to conceive migraine as a brain state. However, a majority of findings from previous studies have not been replicated, and studies varied considerably regarding image acquisition and analyses techniques. Thus, while functional magnetic resonance imaging appears to have the potential to advance our understanding of migraine pathophysiology, replication of findings in large representative datasets and precise, standardized reporting of clinical data would likely benefit the field and further increase the value of observations.

Microstructural changes of basal ganglia in migraine with restless legs syndrome: findings from a neuroimaging study

In this study, it is planned to investigate the integrity of the basal ganglia structures in migraineurs with restless legs syndrome (RLS) to explore this relationship. In this study, 58 patients who were diagnosed migraine and 51 healthy controls (HCs) were included. Patients diagnosed with migraine were divided into two groups: Group I (migraine without RLS) and Group II (migraine with RLS). The integrity of basal ganglia was evaluated with region of interest diffusion tensor imaging method which allows us to assess microstructural changes of the tissue. The mean age of the patients was 35.98 ± 7.92 years, and the mean age of the HCs was 33.84 ± 11.06. 84.5% (n = 49) of the patients were female and 15.5% (n = 9) were male. 82.4% (n = 42) of the HCs were female, 17.6% (n = 9) were male. The number of  the patients without RLS was 41 (Group I), and the number of the patients with RLS was 17 (Group II). When basal ganglia structures were compared between groups of the patients with and without RLS, the fractional anisotropy (FA) value of the left putamen differed (Group I: 0.30 ± 0.06 vs. Group II: 0.25 ± 0.7, p = 0.01). The significant relationship was found attack frequency and presence of RLS with left putamen FA values according to multiple regression analysis. It was determined in this study that the changes in the microstructure of putamen, one of the basal ganglia structures, may be associated with the presence of RLS in migraineurs.

Alterations of Functional Connectivity in Patients With Restless Legs Syndrome

Restless legs syndrome (RLS) is a common neurological illness marked by a strong desire to move one’s legs, usually in association with uncomfortable sensations. Recent studies have investigated brain networks and connectivity in RLS. The advent of network analysis has greatly improved our understanding of the brain and various neurological disorders. A few studies have investigated alterations in functional connectivity in patients with RLS. This article reviews functional connectivity studies of patients with RLS, which have identified significant alterations relative to healthy controls in several brain networks including thalamic, salience, default-mode, and small-world networks. In addition, network changes related to RLS treatment have been found, including to repetitive transcranial magnetic stimulation, transcutaneous spinal cord direct-current stimulation, and dopaminergic drugs. These findings suggest that the underlying pathogenesis of RLS includes alterations in the functional connectivity in the brain and that RLS is a network disorder.

[Comorbidity in migraine]

Migraine is a common and often disabling disease with a prominent genetic basis. There are many comorbidities associated with migraine which have been identified as risk factors for progression to chronic migraine. Each of these has its own genetic load and shares some common characteristics with migraine. The identification of migraine comorbidities may help clarify common underlying genetic and biological mechanisms of diseases. The treatment of migraine should involve a multifaceted approach, aimed at identifying and reducing possible risk and comorbidity factors. This may prevent the evolution toward a chronic form and then toward pharmacological resistance.

Hypothalamic structural integrity and temporal complexity of cortical information processing at rest in migraine without aura patients between attacks

The hypothalamus has been attributed an important role during the premonitory phase of a migraine attack. Less is known about the role played by the hypothalamus in the interictal period and its relationship with the putative neurocognitive networks previously identified in the pathophysiology of migraine. Our aim was to test whether the hypothalamic microstructure would be altered during the interictal period and whether this co-existed with aberrant connectivity at cortical level. We collected multimodal MRI data from 20 untreated patients with migraine without aura between attacks (MO) and 20 healthy controls (HC) and studied fractional anisotropy, mean (MD), radial (RD), and axial diffusivity of the hypothalamus ROI as a whole from diffusion tensor imaging (DTI). Moreover, we performed an exploratory analysis of the same DTI metrics separately for the anterior and posterior hypothalamic ROIs bilaterally. From resting-state functional MRI, we estimated the Higuchi's fractal dimension (FD), an index of temporal complexity sensible to describe non-periodic patterns characterizing BOLD signature. Finally, we correlated neuroimaging findings with migraine clinical features. In comparison to HC, MO had significantly higher MD, AD, and RD values within the hypothalamus. These findings were confirmed also in the exploratory analysis on the sub-regions of the hypothalamus bilaterally, with the addition of lower FA values on the posterior ROIs. Patients showed higher FD values within the salience network (SN) and the cerebellum, and lower FD values within the primary visual (PV) network compared to HC. We found a positive correlation between cerebellar and SN FD values and severity of migraine. Our findings of hypothalamic abnormalities between migraine attacks may form part of the neuroanatomical substrate that predisposes the onset of the prodromal phase and, therefore, the initiation of an attack. The peculiar fractal dimensionality we found in PV, SN, and cerebellum may be interpreted as an expression of abnormal efficiency demand of brain networks devoted to the integration of sensory, emotional, and cognitive information related to the severity of migraine.

Comorbidities of primary headache disorders: a literature review with meta-analysis

Background

Primary headache disorders are common and burdensome conditions. They are associated to several comorbidities, such as cardiovascular or psychiatric ones, which, in turn, contribute to the global burden of headache. The aim of this study is to provide a comprehensive description of the pooled prevalence of comorbidities of primary headache disorders using a meta-analytical approach based on studies published between 2000 and 2020.

Methods

Scopus was searched for primary research (clinical and population studies) in which medical comorbidities were described in adults with primary headache disorders. Comorbidities were extracted using a taxonomy derived from the Global Burden of Disease (GBD) study. We compared prevalence of comorbidities among headache sufferers against general population using GBD-2019 estimates, and compared comorbidities’ proportions in clinical vs. population studies, and by age and gender.

Results

A total of 139 studies reporting information on 4.19 million subjects with primary headaches were included: in total 2.75 million comorbidities were reported (median per subject 0.64, interquartile range 0.32–1.07). The most frequently addressed comorbidities were: depressive disorders, addressed in 51 studies (pooled proportion 23 %, 95 % CI 20–26 %); hypertension, addressed in 48 studies (pooled proportion 24 %, 95 % CI 22–26 %); anxiety disorders addressed in 40 studies (pooled proportion 25 %, 95 % CI 22–28 %). For conditions such as anxiety, depression and back pain, prevalence among headache sufferers was higher than in GBD-2109 estimates. Associations with average age and female prevalence within studies showed that hypertension was more frequent in studies with higher age and less females, whereas fibromyalgia, restless leg syndrome, and depressive disorders were more frequent in studies with younger age and more female.

Conclusions

Some of the most relevant comorbidities of primary headache disorders – back pain, anxiety and depression, diabetes, ischemic heart disease and stroke – are among the most burdensome conditions, together with headache themselves, according to the GBD study. A joint treatment of headaches and of these comorbidities may positively impact on headache sufferers’ health status and contribute to reduce the impact of a group of highly burdensome diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10194-021-01281-z.

Cerebral blood flow alterations in hemodialysis patients with and without restless legs syndrome: an arterial spin labeling study

Hemodialysis with restless legs syndrome (HD-RLS) is associated with alterations in neuronal function, the blood-brain barrier and iron deposition, thus affecting cerebral metabolism and perfusion. This study utilized three-dimensional arterial spin labeling (ASL) to identify HD-RLS-related perfusion patterns and potential relationships with disease severity. Twenty-six HD-RLS patients, 30 hemodialysis patients without restless legs syndrome (HD-nRLS) and 30 age-, sex-, and education-matched healthy controls were included in this study. One-way analysis of covariance and post hoc analyses were used to assess differences in cerebral blood flow (CBF) values, demographics and clinical data among the three groups. Pearson's correlation analysis was conducted between altered CBF values in the HD-RLS group and clinical data. Compared with HD-nRLS patients, HD-RLS patients showed increased CBF in the right primary motor cortex (false discovery rate [FDR]-corrected P < 0.05). Compared with the normal controls, both HD subgroups (i.e., those with and without RLS) exhibited consistent CBF changes, including increased CBF in the left medial superior frontal gyrus and bilateral thalamus and decreased CBF in the left insular cortices (FDR-corrected P < 0.05). This abnormal hyperperfusion in the sensorimotor cortex and basal ganglia provides evidence for a sensory processing disorder in RLS that may be involved in the pathogenesis of RLS in HD patients.

Identifying neuroanatomical signatures in insomnia and migraine comorbidity

STUDY OBJECTIVES

While insomnia and migraine are often comorbid, the shared and distinct neuroanatomical substrates underlying these disorders and the brain structures associated with the comorbidity are unknown. We aimed to identify patterns of neuroanatomical substrate alterations associated with migraine and insomnia comorbidity.

METHODS

High-resolution T1-weighted images were acquired from subjects with insomnia, migraine, and comorbid migraine and insomnia, respectively, and healthy controls (HC). Direct group comparisons with HC followed by conjunction analyses identified shared regional gray matter volume (GMV) alterations between the disorders. To further examine large-scale anatomical network changes, a seed-based structural covariance network (SCN) analysis was applied. Conjunction analyses also identified common SCN alterations in two disease groups, and we further evaluated these shared regional and global neuroanatomical signatures in the comorbid group.

RESULTS

Compared with controls, patients with migraine and insomnia showed GMV changes in the cerebellum and the lingual, precentral, and postcentral gyri (PCG). The bilateral PCG were common GMV alteration sites in both groups, with decreased structural covariance integrity observed in the cerebellum. In patients with comorbid migraine and insomnia, shared regional GMV and global SCN changes were consistently observed. The GMV of the right PCG also correlated with sleep quality in these patients.

CONCLUSION

These findings highlight the specific role of the PCG in the shared pathophysiology of insomnia and migraine from a regional and global brain network perspective. These multilevel neuroanatomical changes could be used as potential image markers to decipher the comorbidity of the two disorders.

Pathophysiological Bases of Comorbidity in Migraine

Despite that it is commonly accepted that migraine is a disorder of the nervous system with a prominent genetic basis, it is comorbid with a plethora of medical conditions. Several studies have found bidirectional comorbidity between migraine and different disorders including neurological, psychiatric, cardio- and cerebrovascular, gastrointestinal, metaboloendocrine, and immunological conditions. Each of these has its own genetic load and shares some common characteristics with migraine. The bidirectional mechanisms that are likely to underlie this extensive comorbidity between migraine and other diseases are manifold. Comorbid pathologies can induce and promote thalamocortical network dysexcitability, multi-organ transient or persistent pro-inflammatory state, and disproportionate energetic needs in a variable combination, which in turn may be causative mechanisms of the activation of an ample defensive system with includes the trigeminovascular system in conjunction with the neuroendocrine hypothalamic system. This strategy is designed to maintain brain homeostasis by regulating homeostatic needs, such as normal subcortico-cortical excitability, energy balance, osmoregulation, and emotional response. In this light, the treatment of migraine should always involves a multidisciplinary approach, aimed at identifying and, if necessary, eliminating possible risk and comorbidity factors.

Individual pain sensitivity is associated with resting-state cortical activities in healthy individuals but not in patients with migraine: a magnetoencephalography study

Background

Pain sensitivity may determine the risk, severity, prognosis, and efficacy of treatment of clinical pain. Magnetic resonance imaging studies have linked thermal pain sensitivity to changes in brain structure. However, the neural correlates of mechanical pain sensitivity remain to be clarified through investigation of direct neural activities on the resting-state cortical oscillation and synchrony.

Methods

We recorded the resting-state magnetoencephalographic (MEG) activities of 27 healthy individuals and 30 patients with episodic migraine (EM) and analyzed the source-based oscillatory powers and functional connectivity at 2 to 59 Hz in pain-related cortical regions, which are the bilateral anterior cingulate cortex (ACC), medial orbitofrontal (MOF) cortex, lateral orbitofrontal (LOF) cortex, insula cortex, primary somatosensory cortex (SI), primary motor cortex (MI), and posterior cingulate cortex (PCC). The mechanical punctate pain threshold (MPPT) was obtained at the supraorbital area (the first branch of the trigeminal nerve dermatome, V1) and the forearm (the first thoracic nerve dermatome, T1) and further correlated with MEG measures.

Results

The MPPT is inversely correlated with the resting-state relative powers of gamma oscillation in healthy individuals (all corrected P < 0.05). Specifically, inverse correlation was noted between the MPPT at V1 and gamma powers in the bilateral insula (r = − 0.592 [left] and − 0.529 [right]), PCC (r = − 0.619 and − 0.541) and MI (r = − 0.497 and − 0.549) and between the MPPT at T1 and powers in the left PCC (r = − 0.561) and bilateral MI (r = − 0.509 and − 0.520). Furthermore, resting-state functional connectivity at the delta to beta bands, especially between frontal (MOF, ACC, LOF, and MI), parietal (PCC), and sensorimotor (bilateral SI and MI) regions, showed a positive correlation with the MPPT at V1 and T1 (all corrected P < 0.05). By contrast, in patients with EM, the MPPT was not associated with resting-state cortical activities.

Conclusions

Pain sensitivity in healthy individuals is associated with the resting-state gamma oscillation and functional connectivity in pain-related cortical regions. Further studies must be conducted in a large population to confirm whether resting-state cortical activities can be an objective measurement of pain sensitivity in individuals without clinical pain.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10194-020-01200-8.

Blast-induced hearing loss suppresses hippocampal neurogenesis and disrupts long term spatial memory

Acoustic information transduced by cochlear hair cells is continuously relayed from the auditory pathway to other sensory, motor, emotional and cognitive centers in the central nervous system. Human epidemiological studies have suggested that hearing loss is a risk factor for dementia and cognitive decline, but the mechanisms contributing to these memory and cognitive impairments are poorly understood. To explore these issues in a controlled experimental setting, we exposed adult rats to a series of intense blast wave exposures that significantly reduced the neural output of the cochlea. Several weeks later, we used the Morris Water Maze test, a hippocampal-dependent memory task, to assess the ability of Blast Wave and Control rats to learn a spatial navigation task (memory acquisition) and to remember what they had learned (spatial memory retention) several weeks earlier. The elevated plus maze and open field arena were used to test for anxiety-like behaviors. Afterwards, hippocampal cell proliferation and neurogenesis were evaluated using bromodeoxyuridine (BrdU), doublecortin (DCX), and Neuronal Nuclei (NeuN) immunolabeling. The Blast Wave and Control rats learned the spatial navigation task equally well and showed no differences on tests of anxiety. However, the Blast Wave rats performed significantly worse on the spatial memory retention task, i.e., remembering where they had been two weeks earlier. Deficits on the spatial memory retention task were associated with significant decreases in hippocampal cell proliferation and neurogenesis. Our blast wave results are consistent with other experimental manipulations that link spatial memory retention deficits (long term memory) with decreased cell proliferation and neurogenesis in the hippocampus. These results add to the growing body of knowledge linking blast-induced cochlear hearing loss with the cognitive deficits often seen in combat personnel and provide mechanistic insights into these extra auditory disorders that could lead to therapeutic interventions.

Haemodynamic activity characterization of resting state networks by fractal analysis and thalamocortical morphofunctional integrity in chronic migraine

BACKGROUND

Chronic migraine (CM) can be associated with aberrant long-range connectivity of MRI-derived resting-state networks (RSNs). Here, we investigated how the fractal dimension (FD) of blood oxygenation level dependent (BOLD) activity may be used to estimate the complexity of RSNs, reflecting flexibility and/or efficiency in information processing in CM patients respect to healthy controls (HC).

METHODS

Resting-state MRI data were collected from 20 untreated CM without history of medication overuse and 20 HC. On both groups, we estimated the Higuchi's FD. On the same subjects, fractional anisotropy (FA) and mean diffusivity (MD) values of bilateral thalami were retrieved from diffusion tensor imaging and correlated with the FD values.

RESULTS

CM showed higher FD values within dorsal attention system (DAS) and the anterior part of default-mode network (DMN), and lower FD values within the posterior DMN compared to HC. Although FA and MD were within the range of normality, both correlated with the FD values of DAS.

CONCLUSIONS

FD of DAS and DMN may reflect disruption of cognitive control of pain in CM. Since the normal microstructure of the thalamus and its positive connectivity with the cortical networking found in our CM patients reminds similar results obtained assessing the same structures but with the methods of neurophysiology, in episodic migraine during an attack, this may be yet another evidence in supporting CM as a never-ending migraine attack.

Migraine and Sleep in Children: A Bidirectional Relationship

Migraine and sleep disorders in children exhibit a bidirectional relationship. This relationship is based on shared pathophysiology. Migraine involves activation of the trigeminal vascular system. Nociceptive neurons that innervate the dura release various vasoactive peptides. Calcitonin gene-related peptide is the most active of these peptides. Neural pathways that are involved in sleep generation are divided into those responsible for circadian rhythm, wake promotion, non-rapid eye movement, and rapid eye movement sleep activation. Sleep state switches are a critical component of these systems. The cerebral structures, networks, and neurochemical systems that are involved in migraine align closely with those responsible for the regulation of sleep. Neurochemical systems that are involved with both the pathogenesis of migraine and regulation of sleep include adenosine, melatonin, orexin, and calcitonin gene-related peptide. Sleep disorders represent the most common comorbidity with migraine in childhood. The prevalence of parasomnias, obstructive sleep apnea, and sleep-related movement disorders is significantly greater in children migraineurs. Infantile colic is a precursor of childhood migraine. Treatment of comorbid sleep disorders is important for the appropriate management of children with migraine. Sleep-based behavioral interventions can be of substantial benefit. These interventions are particularly important in children due to limited evidence for effective migraine pharmacotherapy.

Altered resting-state functional connectivity between subregions in the thalamus and cortex in migraine without aura

BACKGROUND AND PURPOSE

Migraine is a complex and disabling neurological disorder, the exact neurological mechanisms of which remain unclear. The thalamus is considered to be the hub of the central processing and integration of nociceptive information, as well as the modulation of these processes.

METHODS

A total of 48 migraineurs without aura (MWoAs) during the interictal phase and 48 age- and sex-matched healthy controls underwent resting-state functional magnetic resonance imaging scans. We utilized masked independent component analysis and seed-based functional connectivity (FC) to investigate whether MWoAs exhibited abnormal FC between subregions in the thalamus and the cortex regions.

RESULTS

The MWoAs showed significantly weaker FC between the anterior dorsal thalamic nucleus and left precuneus. Additionally, MWoAs exhibited significantly reduced FC between the ventral posterior nucleus (VPN) and left precuneus, right inferior parietal lobule (R-IPL) and right middle frontal gyrus. Furthermore, the FC Z-scores between the VPN and R-IPL were negatively correlated with pain intensity in MWoAs. The disease duration of patients was negatively correlated with the FC Z-scores between the VPN and R-IPL.

CONCLUSION

These altered thalamocortical connectivity patterns may contribute to multisensory integration abnormalities, deficits in pain attention, cognitive evaluation and pain modulation. Pain sensitivity and disease duration are closely tied to abnormal FC between the VPN and R-IPL. Remarkably, recurrent headache attacks might contribute to this maladaptive functional plasticity closely related to pain intensity.

Structural neuroimaging findings in migraine patients with restless legs syndrome

PURPOSE

One out of three migraine patients might have accompanying restless legs syndrome (RLS). In our study, we aimed to compare the volumes of the brain structures of migraineurs with and without RLS.

METHODS

We had 37 female patients with migraine and 17 females as the control group. Nineteen migraineurs had no RLS (RLS₀) and 18 migraineurs had comorbidity of RLS (RLS₁). The volumes of the brain structures were obtained by manual measurements, volBrain, and voxel-based morphometry (VBM). Manually, we measured caudate and putamen volumes. We used age, years of education, depression, anxiety scores, and total intracranial volume as covariates.

RESULTS

According to VBM analyses, the volumes of the left superior occipital gyrus and precuneus were increased, and the substantia nigra and cuneus were decreased in the RLS₁ group compared with the RLS₀ group. RLS₁ patients had larger superior temporal gyrus, Brodmann area 38, and left insula, and RLS₀ patients had larger Brodmann area 22, right superior temporal gyrus, and Heschl gyrus compared with controls. Migraine and RLS₀ patients had a smaller corpus callosum anteriorly, whereas RLS₁ patients had a smaller splenium. Caudate volumes were larger in migraine patients via the three techniques. There was a positive relation between the caudate and putamen volumes and attack frequency.

CONCLUSIONS

Comorbidity of RLS might be a confounding factor in structural neuroimaging studies in migraine. Deficits in the visual network seem to be related to accompanying RLS; deficits in the auditory network are particularly related to migraine.

Neuroimaging investigation of memory changes in migraine: a systematic review

BACKGROUND

Individuals with migraine usually complain about lower memory performance. Diagnostic methods such as neuroimaging may help in the understanding of possible morphologic and functional changes related to the memory of those individuals. Therefore, the aim of this review is to analyze the available literature on neuroimaging changes related to memory processing in migraine.

METHODS

We searched the following databases: Pubmed/Medline, Psycinfo, Science Direct, Cochrane and Web of Science. We used articles without restriction of year of publication. The combination of descriptors used for this systematic review of literature were Neuroimaging OR Imaging OR Brain AND Migraine OR Chronic Migraine AND Memory.

RESULTS

Of the 306 articles found, nine were selected and all used magnetic resonance imaging (MRI). The studies used structural and functional MRI techniques with a predominance of 3 Tesla equipment and T1-weighted images. According to the results obtained reported by these studies, migraine would alter the activity of memory-related structures, such as the hippocampus, insula and frontal, parietal and temporal cortices, thereby suggesting a possible mechanism by which migraine would influence memory, especially in relation to the memory of pain.

CONCLUSIONS

Migraine is associated to global dysfunction of multisensory integration and memory processing. This condition changes the activity of structures in various regions related to memory of pain, prospective memory, as well as in short- and long-term verbal and visuospatial memories. However, it is necessary to perform studies with larger samples in association with cognitive tests, and without the interference of medications to verify possible alterations and to draw more concrete conclusions.

Tracking the Migraine Cycle Using Visual Tasks

There are a number of reports that perceptual, electrophysiological and imaging measures can track migraine periodicity. As the electrophysiological and imaging research requires specialist equipment, it has few practical applications. This study sought to track changes in performance on four visual tasks over the migraine cycle. Coherence thresholds were measured for two motion and two orientation tasks. The first part of the study confirmed that the data obtained from an online study produced comparable results to those obtained under controlled laboratory conditions. Thirteen migraine with aura, 12 without aura, and 12 healthy controls participated. The second part of the study showed that thresholds for discriminating vertical coherent motion varied with the migraine cycle for a majority of the participants who tested themselves multiple times (four with aura, seven without). Performance improved two days prior to a migraine attack and remained improved for two days afterwards. This outcome is as expected from an extrapolation of earlier electrophysiological research. This research points to the possibility of developing sensitive visual tests that patients can use at home to predict an impending migraine attack and so take steps to try to abort it or, if it is inevitable, to plan their lives around it.

Short-latency afferent inhibition and somato-sensory evoked potentials during the migraine cycle: surrogate markers of a cycling cholinergic thalamo-cortical drive?

Background

Short-latency afferent inhibition (SAI) consists of motor cortex inhibition induced by sensory afferents and depends on the excitatory effect of cholinergic thalamocortical projections on inhibitory GABAergic cortical networks. Given the electrophysiological evidence for thalamo-cortical dysrhythmia in migraine, we studied SAI in migraineurs during and between attacks and searched for correlations with somatosensory habituation, thalamocortical activation, and clinical features.

Methods

SAI was obtained by conditioning the transcranial magnetic stimulation-induced motor evoked potential (MEP) with an electric stimulus on the median nerve at the wrist with random stimulus intervals corresponding to the latency of individual somatosensory evoked potentials (SSEP) N20 plus 2, 4, 6, or 8 ms. We recruited 30 migraine without aura patients, 16 between (MO), 14 during an attack (MI), and 16 healthy volunteers (HV). We calculated the slope of the linear regression between the unconditioned MEP amplitude and the 4-conditioned MEPs as a measure of SAI. We also measured SSEP amplitude habituation, and high-frequency oscillations (HFO) as an index of thalamo-cortical activation.

Results

Compared to HV, SAI, SSEP habituation and early SSEP HFOs were significantly reduced in MO patients between attacks, but enhanced during an attack. There was a positive correlation between degree of SAI and amplitude of early HFOs in HV, but not in MO or MI.

Conclusions

The migraine cycle-dependent variations of SAI and SSEP HFOs are further evidence that facilitatory thalamocortical activation (of GABAergic networks in the motor cortex for SAI), likely to be cholinergic, is reduced in migraine between attacks, but increased ictally.

Different iron deposition patterns in hemodialysis patients with and without restless legs syndrome: a quantitative susceptibility mapping study

OBJECTIVE

Brain iron deposition in hemodialysis (HD) patients increases over time. Iron deficiency in gray matter nuclei has been reported to lead to idiopathic restless legs syndrome (RLS) symptoms. Regardless of unpleasant RLS sensations, the patterns of iron deposition between hemodialysis patients with RLS (HD-RLS) and hemodialysis patients without RLS (HD-nRLS) are still unclear. To evaluate the differences in iron deposition patterns between HD-RLS and HD-nRLS patients, we utilized quantitative susceptibility mapping (QSM).

METHODS

In sum, 24 HD-RLS patients, 25 HD-nRLS patients and 30 age- and sex-matched healthy controls (HCs) were enrolled. The QSM was used to assess susceptibility values of the regions of interest (ROIs), including the caudate nucleus (CN), putamen (PUT), globus pallidus (GP), thalamus (THA), substantia nigra (SN), red nucleus (RN) and dentate nucleus (DN).

RESULTS

HD duration was significantly longer in HD-RLS patients than in HD-nRLS patients (P < 0.05). The susceptibility of HD-RLS and HD-nRLS patients in PUT was higher than that in HCs (P < 0.05), illustrating elevated iron content in the nucleus. Compared with HD-nRLS patients, HD-RLS patients demonstrated reduced susceptibility in CN and PUT (both P < 0.05). Compared with HCs, HD-RLS patients displayed decreased susceptibility in DN (P < 0.05).

CONCLUSIONS

Different iron deposition patterns between HD-RLS and HD-nRLS patients in PUT and DN, which further support disturbed sensory processing in RLS, may be involved in RLS pathogenesis in HD patients.

Functional Network-Based Statistics Reveal Abnormal Resting-State Functional Connectivity in Minimal Hepatic Encephalopathy

Purpose: Whole-brain functional network analysis is an emerging methodology for exploring the mechanisms underlying hepatic encephalopathy (HE). This study aimed to identify the brain subnetwork that is significantly altered within the functional connectome in minimal HE (MHE), the earliest stage of HE. Materials and Methods: The study enrolled 19 cirrhotic patients with MHE and 19 controls who underwent the resting-state functional magnetic resonance imaging and cognitive assessment based on the Psychometric Hepatic Encephalopathy Score (PHES). A whole-brain functional connectivity (FC) matrix was calculated for each subject. Then, network-based statistical analyses of the functional connectome were used to perform group comparisons, and correlation analyses were conducted to identify the relationships between FC alterations and cognitive performance. Results: MHE patients showed significant reduction of positive FC within a subnetwork that predominantly involved the regions of the default-mode network, such as the bilateral posterior cingulate gyrus, bilateral medial prefrontal cortex, bilateral hippocampus and parahippocampal gyrus, bilateral angular gyrus, and left lateral temporal cortex. Meanwhile, MHE patients showed significant reduction of negative FC between default-mode network regions (such as the bilateral posterior cingulate gyrus, medial prefrontal cortex, and angular gyrus) and the regions involved in the somatosensory network (i.e., bilateral precentral and postcentral gyri) and the language network (i.e., the bilateral Rolandic operculum). The correlations of FC within the default-mode subnetwork and PHES results were noted. Conclusion: Default-mode network dysfunction may be one of the core issues in the pathophysiology of MHE. Our findings support the notion that HE is a neurological disease related to intrinsic brain network disruption.

Patterns of gray matter alterations in migraine and restless legs syndrome

Objectives

Migraine and restless legs syndrome (RLS) are often comorbid and share elements of pathology; however, their neuroanatomical underpinnings are poorly understood. This study aimed to identify patterns of gray matter volume (GMV) alteration specific to and common among patients with RLS, migraine, and comorbid migraine and RLS.

Methods

High‐resolution T1‐weighted images were acquired from 116 subjects: 27 RLS patients, 22 migraine patients, 22 patients with comorbid migraine and RLS, and 45 healthy controls. Direct group comparisons and conjunction analysis were first used to localize the distinct and shared neural signatures of migraine and RLS. We also investigated whether the shared neural signature could be replicated in an additional comorbid migraine/RLS group.

Results

Compared with healthy controls, migraine patients showed GMV changes in the lateral occipital cortex, cerebellum, frontal pole, and middle frontal gyrus (MFG), and RLS patients showed GMV changes in the thalamus, middle temporal gyrus, anterior cingulate cortex, insular cortex, and MFG. In migraine, compared with RLS, GMV differences were found in the precuneus, lateral occipital and occipital fusiform cortex, superior frontal and precentral gyri, and cerebellum. Conjunction analyses for these disorders showed altered GMV in the MFG, also found in patients with comorbid migraine and RLS. The GMV of the MFG also correlated with sleep quality in patients with comorbid migraine and RLS.

Interpretation

Migraine and RLS are characterized by shared and distinctive neuroanatomical characteristics, with a specific role of the MFG. These findings may be related to shared pathophysiology of these two distinct disorders.

Restless legs syndrome is associated with headache-related disabilities in patients with migraine: a prospective 7-year follow-up study

BACKGROUND AND PURPOSE

No prospective study has evaluated the impact of restless legs syndrome (RLS) on clinical factors in patients with migraine. We planned a prospective study to assess the impact of RLS comorbid status on clinical factors in patients with migraine.

METHODS

A total of 101 patients with migraine who were evaluated for RLS twice at 7-year intervals in a university hospital setting were included in this study. The RLS group was defined as positive for RLS at either baseline or follow-up and the non-RLS group was defined as negative for RLS at both baseline and follow-up. The Migraine Disability Assessment (MIDAS) questionnaire, Beck Depression Inventory-II (BDI-II), Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale were administered to all patients.

RESULTS

The RLS prevalence was 16.8% at baseline and 20.8% at follow-up. Compared with the non-RLS group (n = 27), the RLS group (n = 74) showed a significantly higher rate of smoking and higher MIDAS and BDI-II scores at 7-year follow-up. A significant reduction in MIDAS and BDI-II scores at 7-year follow-up compared with those at baseline was observed in the non-RLS group, but not in the RLS group. The non-RLS group showed a significantly lower MIDAS score at 7-year follow-up than the RLS group after adjusting for confounding variables such as age, gender, smoking status, Epworth Sleepiness Scale and PSQI scores using analysis of covariance. The persistent RLS group (n = 11) (positive for RLS at both baseline and follow-up) showed a significantly higher rate of smoking and increased MIDAS, BDI-II and PSQI scores compared with the non-RLS group (n = 74) at 7-year follow-up.

CONCLUSION

Our prospective study showed that RLS had a significant impact on headache-related disability in patients with migraine.