Cortical spreading depression: Its role in migraine pathogenesis and possible therapeutic intervention strategies

The Efficacy of Trigger Site Surgery in the Elimination of Chronic Migraine Headache: An Update in the Rate of Success and Failure

Migraine headache (MH) is a prevalent neurovascular disorder that affects approximately 15% of the global population. They are more common in women and typically affect young and middle-aged individuals. Chronic MH is characterized by headaches occurring on ≥15 days per month for over three months. While only 5% of MHs are refractory, about 20%-50% do not respond to pharmacologic treatments. As a result, surgical interventions have emerged as an alternative method to eliminate MH since 2000 AD. These surgical treatments primarily target the peripheral mechanisms of MH, focusing on common trigger sites. Migraine surgery involves neurolysis of sensory branches of trigeminal and occipital nerves that supply the face and back of the head. Numerous clinical studies conducted between 2000 and 2021 have extensively described surgical interventions and their prognostic outcomes. After surgery, up to 80% of patients reported complete elimination of headaches, while 20%-35% experienced no relief. The failure to achieve complete elimination of MH can be attributed to various factors. The most common reason for a partial clinical response is the failure to identify all trigger sites or inadequate surgery on the trigger sites. In this review, we aim to provide an overview of current surgical interventions for MH at different trigger sites, including recent updates, success and failure rates, and potential causes of failure.

Anabolic effects of vitamin D and magnesium in aging bone

Decreased bone mass and an increased risk of bone fractures become more common with age. This condition is often associated with osteoporosis and is caused by an imbalance of bone resorption and new bone formation. Lifestyle factors that affect the risk of osteoporosis include alcohol, diet, hormones, physical activity, and smoking. Calcium and vitamin D are particularly important for the age-related loss of bone density and skeletal muscle mass, but other minerals, such as magnesium, also have an important role. Here, we summarize how optimal magnesium and vitamin D balance improve health outcomes in the elderly, the role of magnesium and vitamin D on bone formation, and the implications of widespread deficiency of these factors in the United States and worldwide, particularly in the elderly population.

Migraine: New Molecular Mechanisms

Migraine is an episodic headache disorder affecting more than 10% of the general population. Migraine arises from a primary brain dysfunction that leads to activation and sensitization of the trigeminovascular system. A major incompletely understood issue in the neurobiology of migraine concerns the molecular and cellular mechanisms that underlie the primary brain dysfunction and lead to activation and sensitization of the trigeminovascular system, thus generating and maintaining migraine pain. Here the author reviews recent discoveries that have advanced our understanding of these mechanisms toward a unifying pathophysiological hypothesis, in which cortical spreading depression (CSD), the phenomenon underlying migraine aura, assumes a key role. In particular, the author discusses the main recent findings in the genetics and neurobiology of familial hemiplegic migraine and the insights they provide into the molecular and cellular mechanisms that may lead to the increased susceptibility of CSD in migraineurs.

Magnesium in man: implications for health and disease

Magnesium (Mg(2+)) is an essential ion to the human body, playing an instrumental role in supporting and sustaining health and life. As the second most abundant intracellular cation after potassium, it is involved in over 600 enzymatic reactions including energy metabolism and protein synthesis. Although Mg(2+) availability has been proven to be disturbed during several clinical situations, serum Mg(2+) values are not generally determined in patients. This review aims to provide an overview of the function of Mg(2+) in human health and disease. In short, Mg(2+) plays an important physiological role particularly in the brain, heart, and skeletal muscles. Moreover, Mg(2+) supplementation has been shown to be beneficial in treatment of, among others, preeclampsia, migraine, depression, coronary artery disease, and asthma. Over the last decade, several hereditary forms of hypomagnesemia have been deciphered, including mutations in transient receptor potential melastatin type 6 (TRPM6), claudin 16, and cyclin M2 (CNNM2). Recently, mutations in Mg(2+) transporter 1 (MagT1) were linked to T-cell deficiency underlining the important role of Mg(2+) in cell viability. Moreover, hypomagnesemia can be the consequence of the use of certain types of drugs, such as diuretics, epidermal growth factor receptor inhibitors, calcineurin inhibitors, and proton pump inhibitors. This review provides an extensive and comprehensive overview of Mg(2+) research over the last few decades, focusing on the regulation of Mg(2+) homeostasis in the intestine, kidney, and bone and disturbances which may result in hypomagnesemia.

Animal migraine models for drug development: status and future perspectives

Migraine is number seven in WHO's list of all diseases causing disability and the third most costly neurological disorder in Europe. Acute attacks are treatable by highly selective drugs such as the triptans but there is still a huge unmet therapeutic need. Unfortunately, drug development for headache has almost come to a standstill partly because of a lack of valid animal models. Here we review previous models with emphasis on optimal characteristics of a future model. In addition to selection of animal species, the method of induction of migraine-like changes and the method of recording responses elicited by such measures are crucial. The most naturalistic way of inducing attacks is by infusion of endogenous signaling molecules that are known to cause migraine in patients. The most valid response is recording of neural activity in the trigeminal system. The most useful headache related responses are likely to be behavioral, allowing multiple experiments in each individual animal. Distinction is made between acute and prophylactic models and how to validate each of them. Modern insight into neurobiological mechanisms of migraine is so good that it is only a question of resources and efforts that determine when valid models with ability to predict efficacy in migraine will be available.

Recent progress in migraine pathophysiology: role of cortical spreading depression and magnetic resonance imaging

Migraine is characterised by debilitating pain, which affects the quality of life in affected patients in both the western and the eastern worlds. The purpose of this article is to give a detailed outline of the pathophysiology of migraine pain, which is one of the most confounding pathologies among pain disorders in clinical conditions. We critically evaluate the scientific basis of various theories concerning migraine pathophysiology, and draw insights from brain imaging approaches that have unraveled the prevalence of cortical spreading depression (CSD) in migraine. The findings supporting the role of CSD as a physiological substrate in clinical pain are discussed. We also give an exhaustive overview of brain imaging approaches that have been employed to solve the genesis of migraine pain, and its possible links to the brainstem, the neocortex, genetic endophenotypes, and pathogenetic factors (such as dopaminergic hypersensitivity). Furthermore, a roadmap is proposed to provide a better understanding of pain pathophysiology in migraine, to enable the development of strategies using leads from brain imaging studies for the identification of early biomarkers, efficient prognosis, and treatment planning, which eventually may help in alleviating some of the devastating impact of pain morbidity in patients afflicted with migraine.

Migraine surgery: a plastic surgery solution for refractory migraine headache

Migraine headache can be a debilitating condition that confers a substantial burden to the affected individual and to society. Despite significant advancements in the medical management of this challenging disorder, clinical data have revealed a proportion of patients who do not adequately respond to pharmacologic intervention and remain symptomatic. Recent insights into the pathogenesis of migraine headache argue against a central vasogenic cause and substantiate a peripheral mechanism involving compressed craniofacial nerves that contribute to the generation of migraine headache. Botulinum toxin injection is a relatively new treatment approach with demonstrated efficacy and supports a peripheral mechanism. Patients who fail optimal medical management and experience amelioration of headache pain after injection at specific anatomical locations can be considered for subsequent surgery to decompress the entrapped peripheral nerves. Migraine surgery is an exciting prospect for appropriately selected patients suffering from migraine headache and will continue to be a burgeoning field that is replete with investigative opportunities.

Post-angiography headaches

Headache is a common symptom after cerebral angiography, although it has seldom been studied. We aimed to evaluate the frequency of headache at 24 h and 6 months after angiography and to describe its characteristics. We used a cross-sectional survey of consecutive patients submitted to angiography and determined headache presence and its characterization. Headache occurrence was analyzed against headache history, clinical data, technical and demographical variables. Of 107 procedures studied, 51.3% patients experienced headaches within 24 h. Patients more likely to experience headaches were females or had subarachnoid hemorrhage. Six months post-procedure 48.8% of patients had frequent headaches. These patients had a positive headache history before the procedure, migraine in particular. Half of patients undergoing routine angiography experience benign post-procedure headaches within 24 h (especially women), yet it does not seem to predispose to chronic long-term headaches.

ATP release by way of connexin 36 hemichannels mediates ischemic tolerance in vitro

Spreading depression (SD) is a self-propagating wave of neuronal and glial depolarization that may occur in virtually any gray matter region in the brain. One consequence of SD is an increased tolerance to ischemia. It has been shown that during cortical SD ATP is released into the extracellular space and activation of purinergic receptors leads to the induction of ischemic tolerance. In the present study we show that depolarization of cultured neurons induces ischemic tolerance which is mediated by purinergic receptor activation. Depolarization causes the release of ATP into the extracellular medium, which may be prevented by treatment with the connexin hemichannel blockers flufenamic acid and quinine, but not the pannexin hemichannel blocker carbenoxolone. Knockdown of connexin 36 expression by siRNA greatly reduces the amount of ATP released during depolarization and the subsequent degree of ischemic tolerance. We conclude that during depolarization neurons release ATP by way of connexin 36 hemichannels.

Simulating the propagation of spreading cortical depression (SCD) wavefront on human brain surface

Spreading cortical depression (SCD) is a slowly spreading supression of electroencephalogram (EEG) activity that was first observed in anaesthetized rabbits in 1944. Since then, the spatial properties of propagation have been investigated on numerous animal experiments. In the folded and complex human cortex, both the occurrence of SCD and the relationship between SCD and migraine have been discussed controversially. This study proposes a software tool to simulate the possible wavefront motion on the surface of human brain. The SCD wavefront motion has been simulated up to an affected surface region of roughly 150 cm(2) and validated by clinical experts.

Transcranial direct current stimulation reveals inhibitory deficiency in migraine

The issue of interictal excitability of cortical neurons in migraine patients is controversial: some studies have reported hypo-, others hyperexcitability. The aim of the present study was to observe the dynamics of this basic interictal state by further modulating the excitability level of the visual cortex using transcranial direct current stimulation (tDCS) in migraineurs with and without aura. In healthy subjects anodal tDCS decreases, cathodal stimulation increases transcranial magnetic stimulation (TMS)-elicited phosphene thresholds (PT), which is suggested as a representative value of visual cortex excitability. Compared with healthy controls, migraine patients tended to show lower baseline PT values, but this decrease failed to reach statistical significance. Anodal stimulation decreased phosphene threshold in migraineurs similarly to controls, having a larger effect in migraineurs with aura. Cathodal stimulation had no significant effect in the patient groups. This result strengthens the notion of deficient inhibitory processes in the cortex of migraineurs, which is selectively revealed by activity-modulating cortical input.

[Role of P/Q calcium channel in familial hemiplegic migraine]

Voltage-dependent calcium channels constitute one of the main pathways of calcium entry into neurons. They are the principal actors of synaptic transmission by controlling the release of neurotransmitters. They also contribute to numerous other cell functions, such as gene expression or synaptogenesis. These channels, by their essential cell functions, are at the origin of numerous channelopathies resulting from mutations of the genes encoding their different subunits. Familial Hemiplegic Migraine (FHM) represents one such example of these channelopathies. In this human disease, genetic studies have demonstrated the implication of the CACNA1A gene in a type 1 form of FHM. This gene encodes for the Ca(v)2.1 subunit of P/Q calcium channels and is the target of numerous mutations affecting the properties of channel activity. The question on how discrete mutations of this gene are able to alter the activity of the channel and contribute to the physiopathology of FHM remains an open question. The functional characterization of mutated channels in various heterologous expression systems, as well as in vivo in an animal model, provides a molecular scheme of the physiopathology of FHM in which neurons, astrocytes and blood circulation act in concert.

Do Children with Benign Rolandic Epilepsy Have a Higher Prevalence of Migraine than Those with Other Partial Epilepsies or Nonepilepsy Controls?

PURPOSE

Prior studies have given conflicting data concerning the association of benign rolandic epilepsy of childhood (BREC) and migraine but were limited by lack of sensitive, diagnostic criteria for childhood migraine. By using revised International Headache Society (IHS-R) criteria, we compared the prevalence of migraine in children with BREC with that of those (a) with cryptogenic/symptomatic partial epilepsy and (b) without epilepsy.

METHODS

Three cohorts of children, gender and age matched (within 1 year) were identified: (a) BREC, (b) cryptogenic/symptomatic partial epilepsy, and (c) no history of seizures. Parents were queried in a standardized interview about migraine and migraine equivalents in their child, and in either biologic parent. Migraine was defined by using the IHS-R (for children) and IHS criteria (for parents). Children with headache were divided into definite (meeting IHS-R criteria), probable (recurrent, throbbing headaches with nausea, vomiting, photophobia or phonophobia, not meeting IHS-R criteria), possible (recurrent headaches with throbbing character or associated nausea/vomiting), or nonmigraine groups. chi(2) analysis was used to determine whether the cohort with BREC had a higher prevalence of definite, definite or probable, or definite, probable, or possible migraines or migraine equivalents than the other two cohorts.

RESULTS

Each cohort consisted of 53 children (mean age, 9.8-9.9 years, M/F ratio, 35:18). Those with BREC had higher rates of definite and probable (p = 0.05), of definite, probable, and possible migraine (p = 0.05), and of migraine equivalents excluding motion sickness (p < 0.005) than did those without seizures; however, they did not differ significantly from the cryptogenic/symptomatic partial epilepsy cohort.

CONCLUSIONS

Partial epilepsy, regardless of etiology, is associated with higher rates of migraine in children. The pathophysiologic link between epilepsy and migraine is unknown.

Migrainous scintillating scotoma and headache is ocular in origin: A new hypothesis

Brain neuronal dysfunction has been implicated in pathogenesis of migraine but direct evidence is lacking. Scintillating scotoma of migraine is generally believed to originate at the visual cortex. While cortical spreading depression is a relatively late physiological alteration in migraine, its protective role in neuronal ischaemia is increasingly being recognized. Atenolol, nadolol, or verapamil prevent migraine but do not readily cross the blood-brain barrier or critically influence any brain or peripheral neuronal function. Typical migraine headache, aura, or scintillating scotoma has not been reported following enucleation or evisceration of the eye. In humans, pain and temperature fibres from only the ophthalmic division of the trigeminal nerve reach the upper cervical spinal segments. Pain in migraine attacks including occipital and nuchal discomfort reflects selective involvement of the ophthalmic nerve. Photophobia is largely a retinal reflex involving the ophthalmic division of the trigeminal nerve. Key clinical features of the migrainous scintillating scotoma are consistent with retinal origin. Spreading depression in the retina is well-established. A subtle regional ocular sympathetic deficit prevails in migraine patients and possibly impairs regulation of intraocular choroidal blood volume and intraocular pressure. Several first-line migraine prophylactic agents lower the intraocular pressure. The neuro-ophthalmological basis for a monocular origin of migrainous scintillating scotomata due to mechanical deformation of the posterior segment of the corneo-scleral envelope consequent to choroidal venous congestion and rise in intraocular pressure is presented. Study of distribution and displaceability of the migrainous scintillating scotoma can settle its site of origin. Headache of migraine possibly arises from a similar mechanical deformation of the anterior eye segment followed by antidromic discharge in the trigeminovascular system. Lateralizing negative deficits such as homonymous hemianopia probably reflect vasospastic complications of migraine. A rational explanation for the most characteristic clinical features of migraine and a new template to elucidate the pharmacological basis of anti-migraine drugs is offered.

Lasting accelerative effects of 1 Hz and 20 Hz electrical stimulation on cortical spreading depression: relevance for clinical applications of brain stimulation

Clinical applications of brain stimulation have been increasing during the last decade; however, the mechanisms of action remain unknown. One proposed mechanism of action is that repetitive stimulation modulates cortical excitability. Herein, we explore the question of whether repetitive electric stimulation increases cortical excitability as indexed by the cortical spreading depression. Twenty-four Wistar rats were divided into three groups according to the treatment: sham, 1-Hz and 20-Hz stimulation. Stimulation was applied to the left frontal cortex through a pair of epidurally implanted silver-wire electrodes. The cortical spreading depression-features were analysed at three time points (one day before, one day after and 2 weeks after treatment) in both the stimulated and unstimulated hemisphere. A 3 x 2 x 3 factorial anova with repeated measures showed significant differences in the main effect of time (P < 0.0001), hemisphere (P = 0.0002) and stimulation group (P = 0.008). The interaction between time vs. hemisphere vs. stimulation group was also significant (P < 0.0001). Posthoc analysis demonstrated that 1-Hz and 20-Hz repetitive electrical stimulation significantly increased the velocity of cortical spreading depression in the stimulated hemisphere. Furthermore, 20-Hz stimulation showed a greater effect on cortical spreading depression compared to 1-Hz stimulation. The results show that 1-Hz and 20-Hz repetitive electrical stimulation results in an increase in cortical spreading depression velocity that is associated with the frequency and the hemisphere of stimulation. Furthermore, the effects are found to be long lasting. We believe that these findings have strong relevance to support the clinical application of therapies involving electrical stimulation for diseases of reduced cortical excitability.