First Report of a pCys194Arg Notch 3 Mutation in a Romanian CADASIL Patient with Transient Ischemic Attacks and Patent Foramen Ovale – Case Report and Brief Review

Abstract

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a hereditary disease caused by mutations in NOTCH3 gene, characterized by accumulation of a toxic protein in the small and medium size arterioles. Clinical manifestations of CADASIL include lacunar infarcts or, less frequently, large artery ischemic strokes, transient ischemic attacks, dementia, migraine and psychiatric disorders. Brain magnetic resonance imaging (MRI) usually shows multiple lacunar infarcts, diffuse leukoencephalopathy and cerebral microbleeds. The authors report the case of a 39-year-old Romanian woman who presented two transient ischemic attacks manifested with aphasia, headache and mild cognitive impairment. Brain MRI showed multiple isolated and confluent bilateral supratentorial hyperintense fluid-attenuated inversion recovery (FLAIR) and apparent diffusion coefficient (ADC) areas involving the subcortical and deep white matter, but also lenticular and caudate regions and normal aspects of the brain arteries on magnetic resonance angiography (MR-angiography). Differential diagnosis with other disorders affecting small cerebral vessels was performed. Transesophageal echocardiography showed presence of patent foramen ovale (PFO), with right-to-left shunt and contrast passage at Valsalva maneuver. Genetic testing revealed a pCys194Arg heterozygous mutation with C580T>C nucleotide’s change on exon 4 of NOTCH 3 gene. The authors discuss the association of CADASIL to PFO and mild cognitive impairment as well as ongoing research for a therapeutic strategy.

Keywords:CADASIL, patent foramen ovale, lacunar infarct, migraine, dementia.

INTRODUCTION

Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL) is a hereditary small vessel disease caused by mutations in the NOTCH3 gene, leading to toxic NOTCH3 protein accumulation in the small- to medium sized arterioles. The accumulation is systemic, but most pronounced in brain vessels, which leads to clinical symptoms of recurrent stroke and dementia starting at a mean age of 45-50 years. In patients with CADASIL, arteries are markedly thickened (1) and there is a significant loss of smooth muscle cells that are replaced by amorphous material, which includes excessive NOTCH3 ectodomain protein (2). These changes are present in leptomeningeal and penetrating small arteries of the grey and white matter (3), inducing altered vasoreactivity and reduction of cerebral blood flow.

The clinical manifestations of CADASIL include cerebral ischemic events (single or multiple lacunar infarcts and, less frequently, large artery infarctions and transient ischemic attacks), but also dementia, psychiatric disorders and migraine with aura. Multiple lacunar infarcts, diffuse leukoencephalopathy, which frequently involves the external capsule and anterior temporal regions, and cerebral microbleeds are the characteristic features of brain MRI in CADASIL. At genetic testing, almost all CADASIL patients carry cysteine-involving mutations in NOTCH3; however, cysteine-sparing mutations were also reported in the literature (4) such as the Arg75Pro mutation, which has been frequently found in Japan (5).

CASE REPORT

We report the case of a 39-year-old woman, non-smoker, non-alcohol consumer, with a family history of migraine affecting her mother, who died at the age of 65 due to an ischemic stroke. The patient reported six miscarriages during the first and second trimesters of pregnancy and two episodes of expressive aphasia without disturbance of consciousness, lasting for several minutes and associated with occipital headache. She also reported memory impairment and attention deficit. Neurologic examination revealed bilateral pyramidal syndrome with increased deep tendon reflexes, mild attention and memory deficits with a MMSE (Mini-Mental State Examination) score of 26, blood pressure of 146/102 mm Hg and heart rate of 126/min (sinus rhythm). Psychiatric evaluation revealed attention deficit, depression and sleep induction disorder.

Brain MRI showed multiple white matter hyperintensities on T2 and fluid-attenuated inversion recovery (FLAIR) sequences, hypointense on T1, without gadolinium enhancement and localized in the subcortical white matter of the fronto-parieto-temporo-occipital lobes bilaterally, in the internal and external capsules and in the pons, with a confluent appearance and no microbleeds (Figure 1). Electroencephalography and visual evoked potentials were normal. Doppler ultrasound of cervical vessels was also normal. Transesophageal echocardiography showed patent foramen ovale, with right-to-left shunt and contrast passage at Valsalva maneuver.

Laboratory workup revealed normal biochemistry, complete blood count and coagulation, including protein C, protein S, antithrombin III, Leyden factor and homocysteine. Immunological markers were also within normal range, including anti-Sm, anti-Ro, antinuclear antibodies, antineutrophil cytoplasmic antibodies, anti-double stranded DNA antibodies, circulating immune complexes, antiphospholipid antibodies and rheumatoid factor. Serology for human immunodeficiency virus, hepatitis B and C, syphilis and Borrelia Burgdorferi was negative. Oligoclonal bands were absent in the cerebrospinal fluid and the immunoglobulin index was normal.

Angiotensin-converting enzyme and alphagalactosidase were within normal range. Genetic testing for MTHFR (methylenetetrahydrofolate reductase) mutation revealed heterozygous mutation of A1298C. Since our patient had a score of 17 on the CADASIL scale (6), we decided to test for NOTCH3 mutations. Sequencing of exons 3 and 4 of NOTCH3, using Sanger sequencing technique, showed heterozygous mutation of exon 4 with C580T>C nucleotide’s change and pVys194Arg amino-acids change.

Diagnosis of CADASIL was made based on clinical signs, brain MRI findings and genetic testing. The episodes of language impairment were interpreted as left carotid artery transient ischemic attacks. The hypothesis of a migraine with aura could not be excluded, as the ICHD-3 criteria for aura were also fulfilled, i.e., (A) two attacks, (B) with fully reversible language disorder, (C) that can be considered as unilateral symptoms (left carotid territory), lasting under 60 minutes and accompanied by headache (7).

DISCUSSIONS

To date, there is no treatment available for CADASIL, and NOTCH3 targeting therapies are in a preclinical phase of development (8). Several therapies were tested in clinical trials, but none of them showed efficiency for treatment of CADASIL. Starting from the hypothesis of influencing vasomotor function to stop disease progression, a randomized controlled trial was designed to test the safety and effect on endothelium dependent vasodilation of sapropterin, a synthetic tetrahydrobiopterin analogue. Tetrahydrobiopterin, essential cofactor for nitric oxide synthesis in endothelial cells, ameliorates endothelial function. However, sapropterin at the average dose of 5 mg/kg/day, although safe and well tolerated, did not affect endothelium-dependent vasodilation in CADASIL patients (9).

Another phase II randomized double-blind controlled safety trial, comparing dabigatran with aspirin for preventing ischemic brain lesions in CADASIL patients (10), was completed, but the results have not been published yet.

Since this patient did not present cerebral microbleeds and there was no evidence of an additional benefit of anticoagulation versus antiplatelet therapy for CADASIL, we chose aspirin due to its lower risk of brain hemorrhage, knowing the increased prevalence of microbleeds in CADASIL patients (11). The patient received aspirin 75 mg qd, metoprolol 50 mg qd, gabapentin 300 mg qd and clonazepam 0.5 mg qd. We have also administered deproteinized hemoderivative of calf blood 200 mg tid for improvement of cerebral circulation. Under this scheme, there was no additional TIA, blood pressure and cardiac rhythm normalized, but a low intensity headache persisted. Recommendation for PFO surgical closure was debated, given the possible recurrence of ischemic strokes or new silent infarcts on follow-up brain MRI. Recent studies have concluded that PFO alone may not be an independent risk factor for cerebrovascular events in the general popu- lation (12, 13).

The association of PFO with CADASIL is not a coincidence. CADASIL patients have a high prevalence of right-to-left shunt attributable to patent foramen ovale (PFO), twice more that it was found in cerebrovascular non-CADASIL patients (14). This association suggests a common genetic origin of CADASIL and PFO. Indeed, it was proven that NOTCH signaling regulates cell differentiation during cardiovascular system development (15). NOTCH3 mutations may have a role in abnormal development of endocardium, as suggested by an experimental report showing that NOTCH3 was also expressed in heart precursors during embryogenesis and that NOTCH pathway regulated atrioventricular morphogenesis, including cardiac valves and septum (15). In our patient, the transient ischemic attacks may be related to the presence of PFO with right-to-left shunt revealed by transesophageal echocardiography.

Our patient already had mild cognitive impairment, probably due to extensive white matter lesions. In CADASIL patients, cognitive impairment may be explained by vascular damage, but recent research suggests that NOTCH3 dysfunction may induce an aberrant precursor cell proliferation and differentiation during adult hippocampal neurogenesis, an essential process for integration of new spatial memory (16). This partly explains why the specific therapies for vascular dementia associated with subcortical infarcts yielded disappointing results in CADASIL patients. Although a cholinergic neuronal deficit was found, by measuring cortical choline acetyltransferase (ChAT) enzyme activity and assessing immunocytochemical distribution of ChAT and p75 neurotrophin receptor (P75NTR) in postmortem brain tissue from genetically confirmed CADASIL patients, the randomized double-blind clinical trial using donepezil for cognitive impairment in CADASIL patients did not reach the primary end-points, showing no improvement from baseline in the vascular Alzheimer disease assessment scale cognitive subscale (V-ADAS-cog) (17).

Genetic testing of NOTCH3 mutation is essential in differentiating CADASIL from CADASIL-like cases, but NOTCH3 gene mutation analysis is still expensive and time consuming. Therefore, it is reasonable to pre-screen the suspected patients using the CADASIL scale established by Francesca Pescini and reported to have 96.7% sensitivity and 74.2% specificity in a pooled analysis of patients from different populations (6). However, due to extensive variability of genomic characteristics of CADASIL patients in different regions and populations, it is necessary to further refine the pre-genetic screening tool and to better define the genetic testing panel (18, 19).

CONCLUSIONS

This is the first report of a pCys194Arg heterozygous mutation on exon 4 of NOTCH3 gene in a Romanian CADASIL patient. CADASIL is a pathology that should be considered in every young patient with multiple ischemic strokes or silent brain infarcts involving mainly, but not only, the small and medium-sized cerebral arteries, associating memory impairment and right-to-left cardiac shunt. Brain imaging and genetic testing are essential for establishing diagnosis, and pre-genetic screening tools may be useful to better identify patients who need to be genetically tested. Genetic testing by encephalopathy gene panel is expected to improve accuracy of CADASIL differential diagnosis and increase the knowledge on this disease.

Conflict of interests: none declared

Financial support: none declared.

Aknowledgments: The authors wish to thank Mr. Dan Eftenie (Gentest International SRL), who was involved in performing the genetic testing of this patient.

FIGURE 1.

Multiple isolated and confluent bilateral supratentorial hyperintense. Flair and ADC areas involving the subcortical and profound white matter(arrows), but also the lenticulo-caudat regions. Normal aspects of the brain arteries on MR-angiography