De novo mutation in the NOTCH3 gene causing CADASIL

Diagnosis and Management of Cerebral Small Vessel Disease

OBJECTIVE

Cerebral small vessel disease (CSVD) is a common neurologic condition that contributes to considerable mortality and disability because of its impact on ischemic and hemorrhagic stroke risk and dementia. While attributes of the disease have been recognized for over two centuries, gaps in knowledge remain related to its prevention and management. The purpose of this review is to provide an overview of the current state of knowledge for CSVD.

LATEST DEVELOPMENTS

CSVD can be recognized by well-defined radiographic criteria, but the pathogenic mechanism behind the disease is unclear. Hypertension control remains the best-known strategy for stroke prevention in patients with CSVD, and recent guidelines provide a long-term blood pressure target of less than 130/80 mm Hg for patients with ischemic and hemorrhagic stroke, including those with stroke related to CSVD. Cerebral amyloid angiopathy is the second leading cause of intracerebral hemorrhage and may be increasingly recognized because of newer, more sensitive imaging modalities. Transient focal neurologic episodes is a relatively new term used to describe "amyloid spells." Guidance on distinguishing these events from seizures and transient ischemic attacks has been published.

ESSENTIAL POINTS

CSVD is prevalent and will likely be encountered by all neurologists in clinical practice. It is important for neurologists to be able to recognize CSVD, both radiographically and clinically, and to counsel patients on the prevention of disease progression. Blood pressure control is especially relevant, and strategies are needed to improve blood pressure control for primary and secondary stroke prevention in patients with CSVD.

First patient with mosaic NOTCH3 gene pathogenic variant. Unrevealed mosaicisms and importance of their detection

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited small vessel disease caused predominantly by pathogenic variants in NOTCH3 gene. Neither germline nor somatic mosaicism has been previously published in NOTCH3 gene. CADASIL is inherited in an autosomal dominant manner; only rare cases have been associated with de novo pathogenic variants. Mosaicism is more common than previously thought because mosaic variants often stay unrevealed. An apparently de novo variant might actually be a consequence of a parental mosaicism undetectable with Sanger sequencing, especially in the case of low grade mosaicism. Parental testing by sensitive tools like deep targeted next-generation sequencing (NGS) analysis could detect cases of unrevealed medium or low level mosaicism in patients tested by Sanger sequencing. Here, we report the first patient with mosaic NOTCH3 gene pathogenic variant to our knowledge; the allelic fraction in the leucocyte DNA was low (13%); the pathogenic variant was inhered by his two daughters. The patient was diagnosed by deep targeted NGS analysis after studying his two affected daughters. This report highlights the importance of parental testing by sensitive tools like deep targeted NGS analysis. Detection of mosaicism is of great importance for diagnosis and adequate family genetic counseling.

NOTCH3 signaling is essential for NF-κB activation in TLR-activated macrophages

Macrophage activation by Toll receptors is an essential event in the development of the response against pathogens. NOTCH signaling pathway is involved in the control of macrophage activation and the inflammatory processes. In this work, we have characterized NOTCH signaling in macrophages activated by Toll-like receptor (TLR) triggering and determined that DLL1 and DLL4 are the main ligands responsible for NOTCH signaling. We have identified ADAM10 as the main protease implicated in NOTCH processing and activation. We have also observed that furin, which processes NOTCH receptors, is induced by TLR signaling in a NOTCH-dependent manner. NOTCH3 is the only NOTCH receptor expressed in resting macrophages. Its expression increased rapidly in the first hours after TLR4 activation, followed by a gradual decrease, which was coincident with an elevation of the expression of the other NOTCH receptors. All NOTCH1, 2 and 3 contribute to the increased NOTCH signaling detected in activated macrophages. We also observed a crosstalk between NOTCH3 and NOTCH1 during macrophage activation. Finally, our results highlight the relevance of NOTCH3 in the activation of NF-κB, increasing p65 phosphorylation by p38 MAP kinase. Our data identify, for the first time, NOTCH3 as a relevant player in the control of inflammation.

CADASIL vs. Multiple Sclerosis: Is It Misdiagnosis or Concomitant? A Case Series

Introduction: Cerebral autosomal dominant arteriopathy and subcortical infarct leukoencephalopathy (CADASIL) is the most common form of hereditary stroke caused by a mutation in the NOTCH3 gene located on the short arm of chromosome 19. A small number of published reports describe CADASIL patients who were initially diagnosed as multiple sclerosis. Although it was previously indicated that there was no association between NOTCH3 mutations and multiple sclerosis, the involvement of autoimmune mechanisms among patients with CADASIL has been hypothesized.

Case Presentation: Case 1 is a middle-aged woman with initial diagnoses of multiple sclerosis (MS) and myelitis that continued to progress despite treatment with disease-modifying agents. She had occasional migraines, transient blurred vision, and multiple lacunar infarcts. She continued treatment for about 15 years with no significant alleviation and progressive changes on brain MRI; genetic testing was ordered which showed NOTCH3 mutation, and diagnosis was changed to CADASIL with subsequent revision of treatment course. However, the presence of myelitis in this patient is unusual and may raise the question of a concurrent autoimmune process. Case 2 is a woman presenting with vertigo and paresthesia and diagnosed with MS based on an initial brain MRI showing biventricular white matter hyperintensities; however, she was not started on any disease-modifying agents. Her symptoms were reevaluated by a neurologist, and genetic testing was performed for NOTCH 3. Case 3 is a young woman with a history of migraines who initially presented with numbness and gait ataxia which later progressed to speech difficulty and memory loss. A diagnosis of MS was established which was later changed to CADASIL.

Conclusion: Since CADASIL is a rare disease, it is imperative to raise awareness of its unique clinical condition as well as variation in its clinical presentations. It is crucial that the overlapping symptoms between MS and CADASIL be thoroughly examined to avoid misdiagnosis and treatment complications. The involvement of autoimmune mechanisms in CADASIL and the role of NOTCH3 gene mutations in provoking an autoimmune process should be further investigated.

Genetic architecture of common non-Alzheimer's disease dementias

Frontotemporal dementia (FTD), dementia with Lewy bodies (DLB) and vascular dementia (VaD) are the most common forms of dementia after Alzheimer's disease (AD). The heterogeneity of these disorders and/or the clinical overlap with other diseases hinder the study of their genetic components. Even though Mendelian dementias are rare, the study of these forms of disease can have a significant impact in the lives of patients and families and have successfully brought to the fore many of the genes currently known to be involved in FTD and VaD, starting to give us a glimpse of the molecular mechanisms underlying these phenotypes. More recently, genome-wide association studies have also pointed to disease risk-associated loci. This has been particularly important for DLB where familial forms of disease are very rarely described. In this review we systematically describe the Mendelian and risk genes involved in these non-AD dementias in an effort to contribute to a better understanding of their genetic architecture, find differences and commonalities between different dementia phenotypes, and uncover areas that would benefit from more intense research endeavors.

Speech-language disorders in CADASIL: a case report

ABSTRACT The purpose of this study was to report the main speech-language disorders in a patient with CADASIL diagnosis, attending the Speech Therapy School Clinic of a Higher Education Institution from 2008 to 2013. Clinical evaluation of the speech organs was carried out, verifying reduced mobility and tonus of lips, tongue and cheeks, with major repercussions on deglutition in the last two years of care. Multiple swallowing were observed for pasty consistency, and coughing, for the liquid one, with "wet" vocal quality and cervical auscultation without alterations, after multiple swallowing. A hoarse vocal quality with asthenia, weak loudness, hypernasal resonance and imprecise articulation were observed regarding the patient’s voice. The speech therapy aimed at maintaining food intake and communication, improving the patient’s quality of life.

Genetic Factors of Cerebral Small Vessel Disease and Their Potential Clinical Outcome

Cerebral small vessel diseases (SVD) have been causally correlated with ischemic strokes, leading to cognitive decline and vascular dementia. Neuroimaging and molecular genetic tests could improve diagnostic accuracy in patients with potential SVD. Several types of monogenic, hereditary cerebral SVD have been identified: cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL), cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), cathepsin A-related arteriopathy with strokes and leukoencephalopathy (CARASAL), hereditary diffuse leukoencephalopathy with spheroids (HDLS), COL4A1/2-related disorders, and Fabry disease. These disorders can be distinguished based on their genetics, pathological and imaging findings, clinical manifestation, and diagnosis. Genetic studies of sporadic cerebral SVD have demonstrated a high degree of heritability, particularly among patients with young-onset stroke. Common genetic variants in monogenic disease may contribute to pathological progress in several cerebral SVD subtypes, revealing distinct genetic mechanisms in different subtype of SVD. Hence, genetic molecular analysis should be used as the final gold standard of diagnosis. The purpose of this review was to summarize the recent discoveries made surrounding the genetics of cerebral SVD and their clinical significance, to provide new insights into the pathogenesis of cerebral SVD, and to highlight the possible convergence of disease mechanisms in monogenic and sporadic cerebral SVD.

CADASIL

Cerebral small-vessel disease is a prevalent condition that is strongly associated with ischemic stroke and dementia. The most prevalent inherited cause of cerebral small-vessel disease is CADASIL, cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy, a disorder linked to mutations in NOTCH3. The most common symptoms of CADASIL are small ischemic strokes and/or transient ischemic attacks and cognitive impairment, appearing in middle age, that may progress to frank vascular dementia. However, it is increasingly recognized that individual symptom types, onset, and disease severity span a wide spectrum, even among individuals in the same family. Magnetic resonance imaging in CADASIL reveals severe white-matter hyperintensities, evidence of prior subcortical strokes, and, in some cases, microhemorrhages. Several hundred mutations in NOTCH3 have been described worldwide in CADASIL, and virtually all of these mutations alter the cysteine content of the extracellular NOTCH3 gene product. This molecular genetic signature of CADASIL has led to the hypothesis that structural abnormalities in the vascular smooth-muscle protein NOTCH3 trigger arterial degeneration, vascular protein accumulation, and cerebrovascular failure.

Genotype-phenotype correlations of cysteine replacement in CADASIL

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is characterized by cerebral infarction related to mutations in the notch homolog protein 3 (NOTCH3). We enrolled 10 patients whose brain magnetic resonance imaging (MRI) fluid-attenuated inversion recovery images showed hyperintensities (HIs) in the deep white matter and the external capsule. We then investigated the mutations in NOTCH3 using direct sequencing within the region of intron-exon boundaries in exons 2-24 of NOTCH3. Eight patients harboring NOTCH3 mutations (8 of 10) were identified, including a novel mutation, p.C162Y, and 3 cases with a sporadic form. Seven patients with cysteine replacement showed HI in the anterior part of the temporal lobes (ATLs), whereas these changes were not detected in 1 patient without cysteine replacement, p.R75P. Reviewing previous reports, we conclude that the patients can clearly be divided in 2 groups: those with cysteine replacement who showed HI in the ATL and those without cysteine replacement who showed no HI in the ATL. Our findings expand the understanding of genotype-phenotype correlations in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy.

Inherited neurovascular diseases affecting cerebral blood vessels and smooth muscle

Neurovascular diseases are among the leading causes of mortality and permanent disability due to stroke, aneurysm, and other cardiovascular complications. Cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) and Marfan syndrome are two neurovascular disorders that affect smooth muscle cells through accumulation of granule and osmiophilic materials and defective elastic fiber formations respectively. Moyamoya disease, hereditary hemorrhagic telangiectasia (HHT), microcephalic osteodysplastic primordial dwarfism type II (MOPD II), and Fabry's disease are disorders that affect the endothelium cells of blood vessels through occlusion or abnormal development. While much research has been done on mapping out mutations in these diseases, the exact mechanisms are still largely unknown. This paper briefly introduces the pathogenesis, genetics, clinical symptoms, and current methods of treatment of the diseases in the hope that it can help us better understand the mechanism of these diseases and work on ways to develop better diagnosis and treatment.

Neoplastic lesions in CADASIL syndrome: report of an autopsied Japanese case

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL) is one of the most common heritable causes of stroke and dementia in adults. The gene involved in the pathogenesis of CADASIL is Notch3; in which mutations affect the number of cysteine residues in its extracellular domain, causing its accumulation in small arteries and arterioles of the affected individuals. Besides the usual neurological and vascular findings that have been well-documented in CADASIL patients, this paper additionally reports multiple neoplastic lesions that were observed in an autopsy case of CADASIL patient; that could be related to Notch3 mutation. The patient was a 62 years old male, presented with a past history of neurological manifestations, including gait disturbance and frequent convulsive attacks. He was diagnosed as CADASIL syndrome with Notch3 Arg133Cys mutation. He eventually developed hemiplegia and died of systemic convulsions. Autopsy examination revealed-besides the vascular and neurological lesions characteristic of CADASIL- multiple neoplastic lesions in the body; carcinoid tumorlet and diffuse idiopathic pulmonary neuro-endocrine cell hyperplasia (DIPNECH) in the lungs, renal cell carcinoma (RCC), prostatic adenocarcinoma (ADC) and adenomatoid tumor of the epididymis. This report describes a spectrum of neoplastic lesions that were found in a case of CADASIL patient that could be related to Notch3 gene mutations.

Imaging characteristics of cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL)

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL) is an autosomal dominant vascular disorder. Diagnosis and follow-up in patients with CADASIL are based mainly on magnetic resonance imaging (MRI). MRI shows white matter hyperintensities (WMHs), lacunar infarcts and cerebral microbleeds (CMBs). WMHs lesions tend to be symmetrical and bilateral, distributed in the periventricular and deep white matter. The anterior temporal lobe and external capsules are predilection sites for WMHs, with higher specificity and sensitivity of anterior temporal lobe involvement compared to an external capsule involvement. Lacunar infarcts are presented by an imaging signal that has intensity of cerebrospinal fluid in all MRI sequences. They are localized within the semioval center, thalamus, basal ganglia and pons. CMBs are depicted as focal areas of signal loss on T2 images which increases in size on the T2*-weighted gradient echo planar images ("blooming effect").