Migraine visual3/3/2024 Interestingly, none of the published studies assessed patients suffering exclusively from migraine with aura, at least with respect to the most common episodic forms of migraine. To better understand aura-related changes in sensory processing, several independent research groups have dedicated to the study of electrocortical signals during different phases of the migraine cycle using different sensory stimuli, or single or repetitive neuromodulatory techniques delivered over the scalp. Although in animal models CSD is able to ignite the trigeminovascular system, which is the condition for a headache to start, less is known about the possible biomarkers of CSD during the interictal migraine that might predispose to the aura and, perhaps, to the attack itself. After the first description of CSD in animals by Leão up-till-now only indirect evidence for CSD in migraine patients derived from functional MRI and magnetoencephalographic studies has been gathered. The electrocortical phenomenon of cortical spreading depression (CSD) has been implicated in the genesis of migraine aura: it is a wave of neuronal hyperactivity followed by a wave of hypoactivity which often spreads postero-anteriorly and can reach the parietal and/or temporal lobes travelling at a speed of approx. However, a significant proportion of auras may last longer than one hour and may configure the diagnosis of persistent aura without infarction. In fact, focal neurological symptoms which precede or accompany the headache phase (when presents), last no more than 60 min with visual - the most common aura symptom - followed by sensory and aphasic auras. This is, by the way, due to its lower prevalence in comparison to the commonest migraine without aura (MO) and because of the short duration of the aura phase. Moreover, even though amongst the migraineurs those who experience aura (MA) exhibit more pronounced clinical manifestations, these patients have been less frequently studied from a neurophysiological point of view. This implies that most of the possible electrophysiological signatures of these subtle underlying factors were detected between migraine attacks, fluctuating depending on the distance from the last or the next attack. ![]() Since most of the electrophysiological abnormalities mentioned above were more frequently present and had a greater amplitude in migraine with aura than in migraine without aura, neurophysiological techniques have been shown to be of great help in the search for the pathophysiological basis of migraine aura.ĭuring the last 50 years, researchers dedicated their projects to the understanding of neurophysiological peculiarities of the migraine brain which might predispose to the recurrence of migraine attacks. Contrary to what has been observed in the most common forms of migraine, patients with familial hemiplegic migraine show greater habituation in response to visual and trigeminal stimuli, as well as a higher motor threshold and a lower MEP amplitude than healthy subjects. ![]() The limited studies that were able to investigate patients during the aura revealed suppression of evoked potentials, desynchronization in extrastriate areas and in the temporal lobe, and large variations in direct current potentials with magnetoelectroencephalography. Studies of the trigeminal system in MA are sparse and the few available showed lack of blink reflex habituation and abnormal findings on SFEMG reflecting subclinical, probably inherited, dysfunctions of neuromuscular transmission. Studies with single-pulse and repetitive transcranial magnetic stimulation (TMS) have reported abnormal cortical responsivity manifesting as greater motor evoked potential (MEP) amplitude, lower threshold for phosphenes production, and paradoxical effects in response to both depressing or enhancing repetitive TMS methodologies. ![]() ![]() Higher grand-average cortical response amplitudes, an increased interhemispheric response asymmetry, and lack of amplitude habituation were less consistently demonstrated in response to any kind of sensory stimulation in MA patients. Main bodyĪbnormalities in alpha rhythm power and symmetry, the presence of slowing, and increased information flow in a wide range of frequency bands often characterize the spontaneous EEG activity of MA. The purpose of this review is to provide a comprehensive overview of the findings of clinical electrophysiology studies aimed to investigate changes in information processing of migraine with aura patients.
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