مسلم عباس عبد الحسين الحجامي

Migraine, a recurrent neurological disorder, was characterized by significant changes in brain morphology and function, particularly in response to repetitive external stimuli during the interictal phase. This study aimed to elucidate the differential impacts of these changes on brain function by focusing on migraine subtypes with aura (MWA) and without aura (MWoA), as distinguishing between these subtypes is clinically significant for achieving accurate diagnosis, understanding the underlying pathophysiology, and tailoring treatment strategies. Recognized as a critical mechanism in the onset of migraine aura, cortical spreading depression (CSD) was investigated for its complex role in both MWA and MWoA. However, its relationship with clinical features such as sensory hypersensitivity, impaired habituation, and altered functional connectivity remained to be fully understood. Using a high-density EEG (HD-EEG) system with 128 electrodes, both taskbased and resting-state data were analyzed to investigate cortical dynamics. Steadystate visual evoked potentials (SSVEP) examined neural responses to visual stimuli at 4 Hz and 6 Hz, revealing patterns of cortical excitability and habituation deficits. Resting-state EEG analysis further explored baseline connectivity, providing a comprehensive framework for assessing functional changes in migraine.

Abstract: This investigation explores cortical connectivity in individuals diagnosed with migraine, employing high-density electroencephalography (HD-EEG) and steady-state visual evoked potentials (SSVEP) to discern distinctions between migraine with aura (MWA) and migraine without aura (MWoA). The cohort comprised 22 participants suffering from migraines, categorized into MWA (13 participants, including 7 females) and MWoA (9 participants, with 5 females), alongside a control group of 19 healthy individuals (8 females), exhibiting no history of migraines. The ages of the migraine and control groups were 29±1 and 27±1 years, respectively. The methodology involved exposing subjects to visual stimuli at frequencies of four Hz and six Hz, each for a duration of 2 seconds, interspersed with inter-stimulus intervals of 1 to 1.5 seconds. The frequencies were presented in a randomized sequence, with each being delivered 100 times. Through the acquisition of EEG data from 128 custom electrode positions, inter- and intra-hemispheric coherence during the interictal phase was meticulously analyzed. It was observed that individuals with migraines exhibited a pronounced reduction in alpha-wave pattern uniformity across both intra- and inter-hemispheric connections, a phenomenon markedly accentuated in the MWA group. Further, a unique functional connectivity metric derived from HD-EEG data during repeated SSVEP stimulation emerged as a potential biomarker capable of differentiating between MWA and MWoA subjects. Notably, a significant discrepancy in the slope between Block 1 and Block 6 was observed in MWA subjects, highlighting a distinct response irrespective of stimulation frequency. These findings underscore the clinical significance of cortical connectivity measures in understanding migraine pathophysiology and developing targeted treatments. The variation in alpha-band coherence could reflect differential sensory processing and neural communication mechanisms, potentially linked to Cortical Spreading Depression (CSD). Despite the promising insights, the limited sample size underscores the need for cautious interpretation of the results and further research. This study contributes to the body of knowledge on migraine-induced alterations in brain function, paving the way for refined diagnostic and therapeutic strategies.

Abstract Migraine is a periodic disorder in which a patient experiences changes in the morphological and functional brain, leading to the abnormal processing of repeated external stimuli in the inter-ictal phase, known as the habituation deficit. This is a significant feature clinically of migraine in both two types with aura or without aura and plays an essential role in studying pathophysiological differences between these two groups. Several studies indicated that the reason for migraine aura is cortical spreading depression (CSD) but did not clarify its impact on migraine without aura and lack of habituation. In this study, 22 migraine patients (MWA, N = 13), (MWoA, N = 9), and healthy controls (HC, N = 19) were the participants. Participants were exposed to the steady state of visual evoked potentials also known as (SSVEP), which are the signals for a natural response to the visual motivation at four Hz or six Hz for 2 s followed by the inter-stimulus interval that varies between 1 and 1.5 s. The order of the temporal frequencies was randomized, and each temporal frequency was shown 100 times. We recorded from 128 customized electrode locations using high-density electroencephalography (HD-EEG) and measured amplitude and habituation for the N1–P1 and P1–N2 from the first to the sixth blocks of 100 sweep features in patients and healthy controls. Using the entropy, a decrease in amplitude and SSVEP N1-P1 habituation between the first and the sixth block appeared in both MWA and MWoA (p = 0.0001, Slope = −0.4643), (p = 0.065, Slope = 0.1483), respectively, compared to HC. For SSVEP P1–N2 between the first and sixth block, it is varied in both MWA (p = 0.0029, Slope = −0.3597) and MWoA (p = 0.027, Slope = 0.2010) compared to HC. Therefore, migraine patients appear amplitude decrease and habituation deficit but with different rates between MWA, and MWoA compared to HCs. Our findings suggest this disparity between MWoA and MWA in the lack of habituation and amplitude decrease in the inter-ictal phase has a close relationship with CSD. In light of the fact that CSD manifests during the inter-ictal phase of migraine with aura, which is when migraine seizures are most likely to occur, multiple researchers have lately reached this conclusion. This investigation led us to the conclusion that CSD during the inter-ictal phase and migraine without aura are associated. In other words, even if previous research has not demonstrated it, CSD is the main contributor to both types of migraine (those with and without aura)

Abstract Inability of habituation is a phenomenon whereby droop responses of cortical responses to repetitive sensory stimulation where the amplitude is persistently increased, which results in an increase in the stimulation time in migraineurs. In contrast, in healthy subjects, the cortical responses to repeated sensory stimuli become progressively lower with respect to the start of the stimulation. This abnormal responsivity to painful or painless stimuli, which becomes visible in the N2P2 in EEG rhythms with repeated stimuli, is a significant feature of migraine patients, so it plays an important role in classifying the phases of migraine (interictal, pre-ictal). The main role of genetics in migraine and its significance in the mechanisms is that it causes altered habits and abnormalities in cortical excitability in both adults and children who are closely related to parent and first-degree relative migraineurs[140-144]. Moreover, habituation and abnormality of cortical excitability increased during the period of hormones in a female who suffers from migraines. In this review, we have tried to outline and discuss the most important research findings over the past twenty years with regard to the habituation deficit in many aspects, such as migraine, its causes, and the role of EEG rhythms in the diagnosis and rehabilitation of migraine patients[144]. The findings of the review indicate that future research may need to create a new classification dependent on EEG recordings which can be used to distinguish between the two types of migraine: with aura (MWA) and without aura (MWoA