CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy): a neurovascular disease diagnosed by ultrastructural examination of the skin

Notch3 Arg170Cys knock-in mice display pathologic and clinical features of the neurovascular disorder cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy

OBJECTIVE

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an adult-onset neurovascular disorder caused by stereotyped mutations in the NOTCH3 receptor. Elucidation of its pathobiology is still incomplete and remains a challenge, in part because the available preclinical mouse models to date do not reproduce the full spectrum of CADASIL pathology and clinical disease.

METHODS AND RESULTS

Here, we report a novel knock-in mouse with Arg170Cys substitution in murine Notch3, corresponding to the prevalent Arg169Cys substitution in CADASIL. The Notch3(Arg170Cys) mice displayed late-onset, dominant CADASIL arteriopathy with typical granular osmiophilic material deposition and developed brain histopathology including thrombosis, microbleeds, gliosis, and microinfarction. Furthermore, Notch3(Arg170Cys) mice experienced neurological symptoms with motor defects such as staggering gait and limb paresis.

CONCLUSIONS

This model, for the first time, phenocopies the arteriopathy and the histopathologic as well as clinical features of CADASIL and may offer novel opportunities to investigate disease pathogenesis.

The possible roles of brain pericytes in brain ischemia and stroke

Brain pericytes regulate a variety of functions, such as microcirculation, angiogenesis, and the blood brain barrier in the brain. Recent studies have also shown that they are pluripotent in a manner similar to mesenchymal stem cells. Since, brain pericytes actively control these functions, these cells probably play an important role not only during brain ischemia, but also in the post-stroke period.

Notch3 ectodomain is a major component of granular osmiophilic material (GOM) in CADASIL

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited systemic vascular disorder characterized by recurrent subcortical ischemic strokes leading to vascular dementia. The gold standard to confirm the diagnosis is to identify a mutation in the underlying gene NOTCH3, encoding a transmembrane receptor protein. Granular osmiophilic material (GOM) deposition around vascular smooth muscle cells is a specific diagnostic feature of CADASIL and electron microscopic examination of a skin biopsy is another useful method for its diagnosis. Although accumulation of Notch3 ectodomain on the surface of vascular smooth muscle cells has been reported, the composition of GOM has not been elucidated. To elucidate the relationship between Notch3 protein and GOM, we performed postembedding immunogold electron microscopy using cryofixed and freeze substituted skin taken from two CADASIL patients. Our results demonstrate that GOM around vascular smooth muscle cells was specifically labeled with antibodies against the extracellular portion of Notch3 but not with antibodies recognizing the intracellular Notch3 domain. In non-CADASIL skin sections, no antibody binding was detected around the small dermal arteries. From these results, the major component of GOM in CADASIL patients is the ectodomain of the Notch3 gene product. Our results shed light on the relationship between Notch3 gene mutations and morphological deposition of GOM around the vascular smooth muscle cells.

Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephaloapthy (CADASIL)

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited cerebrovascular disease characterized by recurrent subcortical ischemic strokes starting in the third or fourth decade as a result of mutations in the Notch3 gene. Granular osmiophilic material (GOM) deposition around the vascular smooth muscle cells is a specific feature and electron microscopic observations of skin biopsies are useful for this diagnosis. A 39-year-old female with dizziness, abnormal visual fields, and hemiplegia, and a 42-year-old male with tinnitus and dizziness, were suspected of suffering from CADASIL based on MRI findings. Both cases were shown to have characteristic deposits of GOM, 200 to 800 nm in diameter, around the vascular smooth muscle cells of small arteries in the deep dermis, and thus the diagnoses of CADASIL were made, although there was no family history of cerebrovascular disorders or dementia. Dermatologists should be aware of these ultra-structural findings because this disease may occur sporadically and might be more common than initially thought.

CADASIL-an unusual manifestation with prominent cutaneous involvement

Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leucencephalopathy (CADASIL) is a rare vascular disorder affecting mainly the central nervous system with transient ischaemic attacks, strokes, psychiatric symptoms and dementia. It is a progressive familial disease owing to mutations in the Notch3 gene. Clinically apparent skin involvement is usually absent. Electron microscopy of seemingly uninvolved skin reveals characteristic granular deposits in the basal lamina of vessels and adnexals. We report on a case of CADASIL with generalized haemorrhagic macules and patches. Typical neurological symptoms as well as classical findings in histopathology and electron microscopy confirmed the diagnosis. Immunofluorescence showed an increased number of vessels with walls markedly thickened by deposits of fibrin, complement and immunoglobulins. This method could serve as an additional method for accurate diagnosis of CADASIL.

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.