Incipient CADASIL

Progress to Clarify How NOTCH3 Mutations Lead to CADASIL, a Hereditary Cerebral Small Vessel Disease

Notch signaling is conserved in C. elegans, Drosophila, and mammals. Among the four NOTCH genes in humans, NOTCH1, NOTCH2, and NOTCH3 are known to cause monogenic hereditary disorders. Most NOTCH-related disorders are congenital and caused by a gain or loss of Notch signaling activity. In contrast, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) caused by NOTCH3 is adult-onset and considered to be caused by accumulation of the mutant NOTCH3 extracellular domain (N3ECD) and, possibly, by an impairment in Notch signaling. Pathophysiological processes following mutant N3ECD accumulation have been intensively investigated; however, the process leading to N3ECD accumulation and its association with canonical NOTCH3 signaling remain unknown. We reviewed the progress in clarifying the pathophysiological process involving mutant NOTCH3.

Four Novel Disease-Causing Variants in the NOTCH3 Gene in Russian Patients with CADASIL

BACKGROUND

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited disease with unknown mechanisms and a broad phenotypic spectrum. It is caused by pathogenic variants in the NOTCH3 gene. The symptoms of the disease mainly include recurrent strokes with vascular risk factors, migraine with aura, dementia, and mood disturbances.

CASE PRESENTATION

Peripheral blood samples were collected from five patients from four unrelated families to extract genomic DNA. In four patients, analysis of exons 2, 3, 4, 5, 6 and adjacent intronic regions of the NOTCH3 gene was made via Sanger sequencing. Two previously undescribed nucleotide variants were identified in two patients: missense variant c.208G>T, (p.Gly70Cys) in exon 1 and splice-site variant c.341-1G>C in intron 3. Further DNA of two other patients were analyzed using a next-generation sequencing-based custom AmpliSeq™ panel for 59 genes associated with leukodystrophies. Two novel missense variants in the NOTCH3 gene were identified, c.1136G>A, (p.Cys379Tyr) in exon 7 and c.1547G>A, (p.Cys516Tyr) in exon 10. The pathogenic variant c.1547G>A, (p.Cys516Tyr) was confirmed in the fifth patient (family case) by Sanger sequencing. All patients had a history of headaches, transient ischemic attacks, memory impairment, and characteristics of MRI results. Three patients had strokes and two patients had psychiatric symptoms.

CONCLUSION

We found four previously undescribed pathogenic variants in the NOTCH3 gene in five patients with CADASIL and described their clinical and genetic characteristics. These results expand the mutational spectrum of CADASIL.

NOTCH3 mutations in a cohort of Portuguese patients within CADASIL spectrum phenotype

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common inherited cerebral small vessel disease. It is caused by mutations in the NOTCH3 gene, which encodes a membranebound receptor protein with three main distinct functional domains. Thus far, several different NOTCH3 mutations, most of them cysteine altering variants, have been described and although they tend to cluster in certain exons, their distribution varies in different geographically populations. Therefore, in this study, we describe the mutation analysis of NOTCH3 gene in 24 Portuguese families with small vessel disease suspected to have CADASIL from the central region of Portugal. The genetic analysis revealed 15 different heterozygous variants, eight pathogenic cysteine altering variants, six cysteine sparing variants and one nonsense variant, located mainly in the exons 4, 8 and 11. Thus, in our population, the genetic testing should initially be focused on these exons. In addition, the genetic findings broaden the mutational and clinical spectrum of CADASIL related phenotype and provide additional evidences for genetic counseling and clinical management.

Archetypal NOTCH3 mutations frequent in public exome: implications for CADASIL

Objective

To determine the frequency of distinctive EGFr cysteine altering NOTCH3 mutations in the 60,706 exomes of the exome aggregation consortium (ExAC) database.

Methods

ExAC was queried for mutations distinctive for cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), namely mutations leading to a cysteine amino acid change in one of the 34 EGFr domains of NOTCH3. The genotype‐phenotype correlation predicted by the ExAC data was tested in an independent cohort of Dutch CADASIL patients using quantified MRI lesions. The Dutch CADASIL registry was probed for paucisymptomatic individuals older than 70 years.

Results

We identified 206 EGFr cysteine altering NOTCH3 mutations in ExAC, with a total prevalence of 3.4/1000. More than half of the distinct mutations have been previously reported in CADASIL patients. Despite the clear overlap, the mutation distribution in ExAC differs from that in reported CADASIL patients, as mutations in ExAC are predominantly located outside of EGFr domains 1–6. In an independent Dutch CADASIL cohort, we found that patients with a mutation in EGFr domains 7–34 have a significantly lower MRI lesion load than patients with a mutation in EGFr domains 1–6.

Interpretation

The frequency of EGFr cysteine altering NOTCH3 mutations is 100‐fold higher than expected based on estimates of CADASIL prevalence. This challenges the current CADASIL disease paradigm, and suggests that certain mutations may more frequently cause a much milder phenotype, which may even go clinically unrecognized. Our data suggest that individuals with a mutation located in EGFr domains 1–6 are predisposed to the more severe “classical” CADASIL phenotype, whereas individuals with a mutation outside of EGFr domains 1–6 can remain paucisymptomatic well into their eighth decade.

Intelligence Impairment, Personality Features and Psychopathology Disturbances in a Family Affected with CADASIL

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a small-vessel disease of the brain that is characterized by headache, recurring lacunar strokes, mood changes and progressive cognitive deterioration. The disease is transmitted with an autosomal dominant pattern and usually starts during midadulthood (at 30–50 years of age). Cognitive deficits in patients with CADASIL develop slowly. The dementia causes frontal-like symptoms and it typically develops after a history of recurrent stroke. We describe three patients from one Spanish family affected by this disease. All three cases underwent comprehensive clinical and neuropsychological examination, and were monitored for seven years. The results obtained in this study describe a) a significant loss of the intelligence quotient (IQ) and noticeable damage to abstract ability (g factor), b) mood and psychopathological disturbances (major depression and dysthymia), and c) a personality with neurotic features.

Emerging genomic biomarkers in migraine

Migraine is a debilitating neurovascular condition classified as either migraine with aura or migraine without aura. A significant genetic basis has been implicated in migraine and has probed the role of neurotransmitters, hormones and vascular genes in this disorder. The aim of this review is to highlight the recent genetic discoveries contributing to our understanding of the complex pathogenesis of migraine. The current review will discuss the role of neurotransmitter-related genes in migraine, including the recently identified TRESK and variants of the KCNN3 gene, as well as outlining studies investigating hormone receptor genes, such as ESR1 and PGR, and vascular-related genes, including the MTHFR and NOTCH 3 genes.

Genetically confirmed CADASIL in a pediatric patient

A 17-year-old girl presented with migraine with prolonged aura and aura without headache. Neurologic examination was normal. Her mother, who did not have a history of migraine, developed right-face and -arm numbness at the age of 45. Evaluation revealed white matter changes consistent with CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy), and genetic testing showed a Notch3 gene mutation consistent with CADASIL. Our patient's MRI revealed white matter changes and the same Notch3 gene mutation. Low-dose aspirin was started in an attempt to prevent stroke. CADASIL is considered a degenerative disease of adult onset that leads to progressive neurologic deterioration. Onset of symptoms is in the third decade. Migraine, one of its most common manifestations, can develop in childhood. Evaluation for secondary causes is warranted in select pediatric patients who present with atypical migraine, when there is a family history of CADASIL or atypical patterns such as aura without headache, or in the presence of white matter abnormalities. The pathophysiology of CADASIL is poorly understood, and there is no proven effective therapy. Patients require genetic counseling and close follow-up. It is not known if interventions such as antiplatelet therapy are beneficial if instituted early in the course of the disease. Screening of family members at risk for CADASIL, even in the pediatric population, should be considered and offered to patients with CADASIL and their families. CADASIL has rarely been described in the pediatric population. This case report expands our current understanding of the disorder in children.

Association of a Notch 3 gene polymorphism with migraine susceptibility

Introduction: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL) shares common symptoms with migraine. Most CADASIL causative mutations occur in exons 3 and 4 of the Notch 3 gene. This study investigated the role of C381T (rs 3815188) and G684A (rs 1043994) single nucleotide polymorphisms (SNP) in exons 3 and 4, respectively, of the Notch 3 gene in migraine.

Results: The first part of the study, in a population of 275 migraineurs and 275 control individuals, found a significant association between the C381T variant and migraine, specifically in migraine without aura (MO) sufferers. The G684A variant was also found to be significantly associated with migraine, specifically in migraine with aura (MA) sufferers. A follow-up study in 300 migraineurs and 300 control individuals did not show replicated association of the C381T variant with migraineurs. However, the G684A variant was again shown to be significantly associated with migraine, specifically with MA.

Conclusion: Further investigation of the G684A variant and the Notch 3 gene is warranted to understand their role in migraine.

The genetics of white matter lesions

White matter lesions (WMLs), commonly seen as hyperintensities on T2-weighted MRI scans of healthy elderly individuals, are considered to be related to small vessel disease in the brain, and are often associated with subtle cognitive and functional impairments. WMLs also show a strong correlation with a wide range of neurodegenerative and neuropsychiatric disorders. Although a number of vascular risk factors for WMLs have been identified, genetic factors are also important with twin and family studies reporting high heritability. Mutations in several genes have been described that lead to monogenic disorders manifesting WMLs, such as Fabry disease and CADASIL. Because most individuals with WMLs do not have Mendelian disorders, most of the focus has been on single nucleotide polymorphisms as genetic risk markers for WMLs, either directly or through their interactions with other genes or medical risk factors. Candidate genes examined to date include those involved in cholesterol regulation and atherosclerosis, hypertension, neuronal repair, homocysteine levels, and oxidative stress pathways. In addition, although there have been a few genome-wide linkage studies, only one genome-wide association study has been performed. The majority of the genetic findings need independent replication, and studies need to be extended to other candidate genes. Collaborative efforts to examine genome-wide associations in large samples of both sexes of a broad age range using longitudinal studies are necessary. The identification of individuals genetically at risk of developing white matter lesions will have important implications for recognizing the etiology of WMLs and thereby developing clinical intervention strategies for their prevention.

Diagnostic criteria for CADASIL in the International Classification of Headache Disorders (ICHD-II): are they appropriate?

We reviewed the characteristics of headache in patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), to verify the appropriateness of the International Classification of Headache Disorders, second edition (ICHD-II) criteria. Available data were found through Medline/PubMed using the keyword “cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL)”. The search was restricted to studies published in English in the years between 1993 and 2008. We excluded studies that did not report original data on CADASIL and information regarding the presence of headache. We found 34 studies reporting data on 749 patients overall; 387 (51.7%) patients had headache. According to the authors’ definition, 356 (92%) patients were reported as having migraine and 31 (8%) as having headache. Of the 356 patients who were defined as migraineurs, 125 (35.1%) had migraine with aura, 7 (2%) migraine without aura, 156 (43.8%) unspecified migraine and 68 (19.1%) had more than one type of migraine. Among the 31 patients reported as suffering from headache, the headache was not further detailed in 18 (58.1%) patients; it was defined as chronic in 6 (19.3%), as resembling migraine with aura in 4 (12.9%), as resembling migraine without aura in 2 (6.5%) and as tension type in 1 (3.2%) patient. In patients with CADASIL, the headache was usually referred to as migraine and mostly as migraine with aura. However, this referral is formally incorrect since the diagnostic criteria for any type of migraine in the ICHD-II require that the disturbance is not attributed to another disorder. For this reason, we suggest updating the ICHD-II in relation to CADASIL. Our suggestion is to insert a new category referred to as Headache attributed to genetic disorder including Headache attributed to CADASIL.

Migraine and Genetic and Acquired Vasculopathies

It is remarkable that migraine is a prominent part of the phenotype of several genetic vasculopathies, including cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL), retinal vasculopathy with cerebral leukodystrophy (RVCL) and hereditary infantile hemiparessis, retinal arteriolar tortuosity and leukoencephalopahty (HIHRATL). The mechanisms by which these genetic vasculopathies give rise to migraine are still unclear. Common genetic susceptibility, increased susceptibility to cortical spreading depression (CSD) and vascular endothelial dysfunction are among the possible explanations. The relation between migraine and acquired vasculopathies such as ischaemic stroke and coronary heart disease has long been established, further supporting a role of the (cerebral) blood vessels in migraine. This review focuses on genetic and acquired vasculopathies associated with migraine. We speculate how genetic and acquired vascular mechanisms might be involved in migraine.

Brain lesions and cerebral functional impairment in migraine patients

Migraine is an independent risk factor for ischemic stroke, mainly in the subpopulation of women with migraine with aura who are younger than 45 years, particularly those that use estrogen containing oral contraceptives. Migraine however should be considered a benign condition as the absolute increase of stroke risk is small. Migraine is also associated with a high prevalence of cerebral white matter hyperintensities, occurring in the deep and periventricular white matter as well as infratentorial, mainly pontine. The pathogenesis and clinical significance of these hyperintensities is unclear. We do not know whether migraine may be considered a progressive disorder in a subset of patients because of accumulation of these hyperintensities over time. Studies on the relationship between migraine and cognitive functioning yielded conflicting results. Two recent studies have provided reassuring news for the migraine patient. A population-based twin study showed that a lifetime migraine diagnosis was not associated with cognitive deficits in middle-aged subjects. A long-term prospective study, assessing cognitive and memory changes in ageing individuals with and without a history of migraine, showed that migraineurs do not exhibit more decline on cognitive tests over time versus controls. Migraine is certainly not a recognized risk factor for (vascular) dementia.

Psychiatric disturbances in CADASIL: a brief review

BACKGROUND

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited cerebrovascular disease, clinically characterized by a variable combination of migraine, recurrent transient ischemic attack (TIA) or lacunar strokes, cognitive decline, and mood disturbances. However, the assessment of psychiatric disturbances in this disease has never been carried out systematically.

METHODS

This paper presents a brief review of the literature regarding the occurrence of psychiatric disorders in CADASIL patients.

RESULTS

The prevalence of psychiatric disorders in CADASIL patients is reported to range from 20% to 41%. The psychiatric disturbances reported with the highest frequency are mood disturbances (9-41%). Pooling together the studies and considering a total of 454 CADASIL patients reported in the literature, 106 of these were affected by mood disturbances (24%). The majority of studies however did not use any defined criteria to assess the presence of psychiatric disorders and diagnoses were mainly based on history or review of clinical records.

CONCLUSIONS

The review of CADASIL literature suggests the need for a more structured approach to the investigation of these disturbances that are highly prevalent and may greatly impact quality of life in these patients.

CADASIL: the most common hereditary subcortical vascular dementia

Cerebral autosomal dominant arteriopathy with subcortical infarct and leukoencephalopathy (CADASIL) is the most common hereditary subcortical vascular dementia. It is caused by the defective NOTCH3 gene, which encodes a transmembrane receptor; over 170 different mutations are known. The main clinical features are migraine with aura (often atypical or isolated), strokes, cognitive decline/dementia and psychiatric symptoms. Executive and organizing cognitive functions are impaired first, memory is affected late. Typical MRI findings are T2 weighted hyperintensities in temporopolar white matter and the capsula externa. Smooth muscle cells in small arteries throughout the body degenerate and vessel walls become fibrotic. In the brain, this results in circulatory disturbances and lacunar infarcts, mainly in cerebral white matter and deep gray matter. The exact pathogenesis is still open: a dominant-negative toxic effect is suggested, possibly related to Notch3 misfolding. Diagnosis is reached either by identifying a pathogenic NOTCH3 mutation or by electron microscopic demonstration of granular osmiophilic material in a (skin) biopsy. Only symptomatic treatment is available at present.

Autosomal dominant leukoencephalopathy with mild clinical symptoms due to cerebrovascular dysfunctions: a new disease entity?

A family with cerebrovascular dysfunctions and extensive white matter lesions was presented. The proband had suffered migraine. His brother showed syncopal episodes and migraine. His mother also suffered severe migraine with aura, and had transient hemiparesis during pregnancy. Their brain MRIs, being quite similar to each other, revealed diffuse bilateral deep white matter lesions, with no changes in serial follow-up. His grandmother showed similar white matter changes on CT, consistent with autosomal dominant inheritance. Lesions were considered to be due to chronic vasogenic edema based upon increased apparent diffusion coefficient (ADC) values on diffusion-weighted imaging, normal spectrum ratio of metabolites on (1)H MR spectroscopy, and decreased regional cerebral blood flows on single-photon emission CT (SPECT). A deficiency of genetically determined factors contributing to the autoregulation of small blood vessels might possibly lead to both clinical symptoms and white matter lesions through the breakdown of the blood-brain barrier and resultant vasogenic edema. Although cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) was suspected, neither NOTCH3 mutation nor granular osmiphilic material (GOM) in the arteriole walls were detected. Further accumulation of similar cases is necessary to establish the possibility of a new familial leukoencephalopathy.

Neuropsychiatric manifestations in CADASIL

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited small-artery disease of mid-adulthood caused by mutations of the NOTCH3 gene. The disease is responsible for widespread white-matter lesions associated with lacunar infarctions in various subcortical areas. The disease is responsible for migraine with aura and ischemic strokes, and is associated with various degrees of cognitive impairment and with mood disturbances. CADASIL is considered as a unique model to investigate what is known as "subcortical ischemic vascular dementia." Recent data suggest that the number of lacunar infarctions and severity of cerebral atrophy are the main magnetic resonance imaging markers associated with cognitive and motor disabilities in this disorder. Mood disturbances are reported in 10% to 20% of patients, most often in association with cognitive alterations. Their exact origin remains unknown; the presence of ischemic lesions within the basal ganglia or the frontal white matter may promote the occurrence of these symptoms. Further studies are needed to better understand the relationships between cerebral lesions and both cognitive and psychiatric symptoms in this small-vessel disease of the brain.

A review of genetic causes of ischemic and hemorrhagic stroke

Genetic predisposition to stroke has been proven in animal models and in humans. Unraveling the genetic factors that play a role in common stroke is very difficult, as the causation of stroke is multifactorial (a combination of environmental and genetic risk factors) and the genetic part is very complex (polygenic, multiple genes play a role). Many common risk factors for stroke like diabetes and arterial hypertension are partly inherited, so many genetic loci contribute more or less to the stroke phenotype. Recent knowledge is increased for monogenic forms of stroke, such as cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy and the amyloid angiopathies. These disorders can serve as models to study environmental or genetic factors that contribute also to the common forms of stroke. Animal model of stroke can also provide valuable information on genetic factors involved in stroke predisposition. In this review, the focus lies on monogenic forms of stroke that can serve as models to study the more common phenotypes.

Skin biopsy findings and results of neuropsychological testing in the first confirmed cases of CADASIL in Norway

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is characterized by mutations in the notch3 gene. The mutation can be demonstrated by a gene test. The first group of Norwegian patients with CADASIL confirmed by gene testing was recently described. The present study includes six of the original nine patients with demonstrated notch3 mutation plus one patient with symptoms, who had been unwilling to go through gene testing. These seven patients underwent skin biopsy for electron microscopy. One patient was cognitively too impaired, but six went through neuropsychological testing. By electron microscopy characteristic granular osmiophilic material (GOM) was detected in all skin biopsies. The material is seen as granular deposits in the basal lamina of the smooth muscle layer, often making impressions upon adjacent smooth muscle cells. It seems important that blood vessels over a certain size (diameter >20 microm) are examined. A varying extent of cognitive decline was noted amongst all by neuropsychological testing. In cases with multiple infarctions reduction of perceptual speed, visuospatial skills and working memory could be demonstrated. Four patients showed executive dysfunction.

Migraine and stroke - why do we talk about it?

Data from observational studies suggest that migraine may be a risk factor for stroke. Furthermore, a significant association between migraine and ischemic stroke (IS) has been demonstrated in population and case-control studies. The risk of IS appears to be higher for migraine with aura than for migraine without aura. The pathogenesis is not known but several studies report some common biochemical mechanisms in the two diseases. Meta-analysis also demonstrates that subjects with migraine are at higher risk of showing white matter abnormalities on magnetic resonance images than are those without migraine.

Migraine and Cerebral White Matter Lesions

BACKGROUND

Patients with migraine are at an increased risk for white matter lesions, typically multiple, small, punctate hyperintensities in the deep or periventricular white matter, best observed on magnetic resonance imaging utilizing T2-weighted or FLAIR sequences. The underlying pathogenesis of white matter lesions in migraineurs is unknown, and the lesions are usually nonspecific and of unclear clinical significance.

REVIEW SUMMARY

Often the presence of white matter lesions causes uncertainty for physicians and anxiety for patients and may lead to a variety of diagnostic tests and treatments. Occasionally, white matter lesions may represent a secondary cause for headaches such as CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy). CADASIL is underrecognized and underdiagnosed; it should be suggested by (i) 1 or more of recurrent subcortical ischemic strokes (especially before age 60 and in the absence of vascular risk factors), migraine (especially with aura, including atypical or prolonged auras) and/or early cognitive decline or subcortical dementia; (ii) bilateral, multifocal, T2/FLAIR hyperintensities in the deep white matter and periventricular white matter with lesions involving the anterior temporal pole, external capsule, basal ganglia, and/or pons; and (iii) an autosomal-dominant family history of migraine, early-onset stroke, or dementia. The clinical spectrum of CADASIL is broad, and there is a poor genotype-phenotype correlation. In certain individuals or families, migraine may be the only clinical manifestation.

CONCLUSIONS

While the prevalence of nonspecific white matter lesions in migraineurs is increased, the white matter lesions may occasionally represent a secondary cause for headache such as CADASIL. Greater awareness of the unique clinical, neuroimaging, and pathologic features, as well as the availability of diagnostic genetic testing, should enhance the recognition and diagnosis of this fascinating condition.

Investigation of the low-density lipoprotein receptor gene and cholesterol as a risk factor for migraine

The Low-Density Lipoprotein Receptor (LDLR) gene is a cell surface receptor that plays an important role in cholesterol homeostasis. We investigated the (TA)n polymorphism in exon 18 of the LDLR gene on chromosome 19p13.2 performing an association analysis in 244 typical migraine-affected patients, 151 suffering from migraine with aura (MA), 96 with migraine without aura (MO) and 244 unaffected controls. The populations consisted of Caucasians only, and controls were age- and sex-matched. The results showed no significant difference between groups for allele frequency distributions of the (TA)n polymorphism even after separation of the migraine-affected individuals into subgroups of MA and MO affected patients. This is in contradiction to Mochi et al. who found a positive association of this variant with MO. Our study discusses possible differences between the two studies and extends this research by investigating circulating cholesterol levels in a migraine-affected population.

Migraine: an ophthalmologist's perspective

PURPOSE OF REVIEW

Migraine is a common disorder with visual and neurologic manifestations. Many patients present to ophthalmologists without a previous diagnosis of migraine. It is therefore essential for the ophthalmologist to have a good understanding of migraine to appropriately help these patients. Neurologic syndromes with migraine and retinopathy are well known. Here again, the ophthalmologist may play a role in establishing the correct diagnosis.

RECENT FINDINGS

For long the initial changes during a migraine attack have been shown to occur in the occipital cortex. In the recent years, the understanding of migraine has advanced with the availability of functional neuroimaging. A possible role of brainstem structures in the initiation of migraine attacks has been proposed based on functional magnetic resonance imaging blood oxygenation level-dependent signals. Activation of brainstem structures preceded activation of occipital cortex. Our understanding of cortical spreading depression is also advancing. Using multiwavelength optical intrinsic imaging, cortical spreading depression has been shown to have a triphasic response in rats. For the first time it has been shown that the cortical spreading depression activated the trigeminovascular system, which is followed by a series of cortical meningeal and brainstem events that cause the migraine headache. Sildenafil has been shown to induce migraine attack without dilation of cerebral blood vessels, further confirming that Wolf's vasogenic theory may not be true. Several loci for migraine have been identified in recent years. A new locus for migraine with and without aura has been identified on chromosome 6, a locus for migraine without aura to chromosome 14, and a locus for migraine with aura on chromosome 4.

SUMMARY

Our understanding of migraine is rapidly evolving with functional neuroimaging. There are several unanswered questions. In this article, we will review the epidemiology, genetics, and clinical features of various forms of migraine with emphasis on ocular migraine, pathogenesis, and briefly the management of migraine.