Expanding the Distinctive Neuroimaging Phenotype of ACTA2 Mutations

Imaging Review of Pediatric Monogenic CNS Vasculopathy with Genetic Correlation

Monogenic cerebral vasculopathy is a rare but progressively recognizable cause of pediatric cerebral vasculopathy manifesting as early as fetal life. These monogenic cerebral vasculopathies can be silent or manifest variably as fetal or neonatal distress, neurologic deficit, developmental delay, cerebral palsy, seizures, or stroke. The radiologic findings can be nonspecific, but the presence of disease-specific cerebral and extracerebral imaging features can point to a diagnosis and guide genetic testing, allowing targeted treatment. The authors review the existing literature describing the frequently encountered and rare monogenic cerebral vascular disorders affecting young patients and describe the relevant pathogenesis, with an attempt to categorize them based on the defective step in vascular homeostasis and/or signaling pathways and characteristic cerebrovascular imaging findings. The authors also highlight the role of imaging and a dedicated imaging protocol in identification of distinct cerebral and extracerebral findings crucial in the diagnostic algorithm and selection of genetic testing. Early and precise recognition of these entities allows timely intervention, preventing or delaying complications and thereby improving quality of life. It is also imperative to identify the specific pathogenic variant and pattern of inheritance for satisfactory genetic counseling and care of at-risk family members. Last, the authors present an image-based approach to these young-onset monogenic cerebral vasculopathies that is guided by the size and predominant radiologic characteristics of the affected vessel with reasonable overlap. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

A familial missense ACTA2 variant p.Arg198Cys leading to Moyamoya-like arteriopathy with straight course of the intracranial arteries, aortic aneurysm and lethal aortic dissection

BACKGROUND

Cerebral vasculopathies frequently lead to severe medical conditions such as stroke or intracranial hemorrhage and have a broad range of possible etiologies that require different therapeutic regimens. However, vasculopathies sometimes present with characteristic angiographic findings, that - if recognized - can guide a more specific diagnostic work-up. Certain ACTA2 variants are associated with a distinctive cerebrovascular phenotype characterized by an anomalously straight course of intracranial arteries, dilatation of proximal ICA and stenosis of distal ICA, in the absence of a compensatory basal collateral network found in Moyamoya disease. Until recently, this ACTA2 cerebral arteriopathy has been reported only in ACTA2 variants impairing Arg179.

METHODS AND MATERIALS

We report a familial case of a missense ACTA2 variant p.Arg198Cys with angiographic features of an ACTA2 cerebral arteriopathy. We analyzed the neuroimaging features of all four variant carrying family members and discussed the cerebrovascular abnormalities we found on the background of the current literature on ACTA2 arteriopathies.

RESULTS

Neuroimaging of the variant carriers revealed angiographic abnormalities characteristic for ACTA2 cerebral arteriopathy such as stenoses of the terminal internal carotid artery, occlusion of the proximal middle cerebral artery and an anomalously straight course of the intracranial arteries. In our index patient catheter angiography showed a Moyamoya-like basal collateral network alongside with the above-mentioned features of an ACTA2 cerebral arteriopathy. The detected missense ACTA2 variant p.Arg198Cys was not known to be associated a cerebral arteriopathy, so far. One of the patients later died from aortic dissection - a common vascular complication of ACTA2 variants.

CONCLUSION

The familial case expands the phenotype of the detected ACTA2 variant p.Arg198Cys and hereby broadens the range of ACTA2 variants associated with a cerebral arteriopathy. Further, it emphasizes the importance of an interdisciplinary approach of vasculopathies.

Neonatal diagnosis of ACTA2-related disease: A case report and review of literature

Multisystemic smooth muscle dysfunction syndrome (MSMDS, OMIM # 613834) is a rare autosomal dominant condition caused by pathogenetic variants of ACTA2 gene that result in impaired muscle contraction. MSMDS is characterized by an increased susceptibility to aneurismal dilatations and dissections, patent ductus arteriosus, early onset coronary artery disease, congenital mydriasis, chronic interstitial lung disease, hypoperistalsis, hydrops of gall bladder, and hypotonic bladder. Here, we report an early diagnosis of a MSMDS related to ACTA2 p.Arg179His (R179H) mutation in a newborn and performed a review of the literature. An early diagnosis of MSMDS is extremely important, because of the severe involvement of cardiovascular system in the MSMDS. Multidisciplinary care and surveillance and timely management of symptoms are important to reduce the risk of complications.

Childhood Cerebral Vasculitis : A Multidisciplinary Approach

Cerebral vasculitis is increasingly recognized as a common cause of pediatric arterial stroke. It can present with focal neurological deficits, psychiatric manifestations, seizures, and encephalopathy. The etiopathogenesis of childhood cerebral vasculitis (CCV) is multifactorial, making an inclusive classification challenging. In this review, we describe the common and uncommon CCV with a comprehensive discussion of etiopathogenesis, the role of various imaging modalities, and advanced techniques in diagnosing CCV. We also highlight the implications of relevant clinical, laboratory, and genetic findings to reach the final diagnosis. Based on the clinicoradiological findings, a stepwise diagnostic approach is proposed to facilitate CCV diagnosis and rule out potential mimics. Identification of key clinical manifestations, pertinent blood and cerebrospinal fluid results, and evaluation of central nervous system vessels for common and disease-specific findings will be emphasized. We discuss the role of magnetic resonance imaging, MR angiography, and vessel wall imaging as the imaging investigation of choice, and reservation of catheter angiography as a problem-solving tool. We emphasize the utility of brain and leptomeningeal biopsy for diagnosis and exclusion of imitators and masqueraders.

Imaging of Suspected Stroke in Children, From the AJR Special Series on Emergency Radiology

Pediatric stroke encompasses different causes, clinical presentations, and associated conditions across ages. Although it is relatively uncommon, pediatric stroke presents with poor short- and long-term outcomes in many cases. Because of a wide range of overlapping presenting symptoms between pediatric stroke and other more common conditions, such as migraine and seizures, stroke diagnosis can be challenging or delayed in children. When combined with a comprehensive medical history and physical examination, neuroimaging plays a crucial role in diagnosing stroke and differentiating stroke mimics. This review highlights the current neuroimaging workup for diagnosing pediatric stroke in the emergency department, describes advantages and disadvantages of different imaging modalities, highlights disorders that predispose children to infarct or hemorrhage, and presents an overview of stroke mimics. Key differences in the initial approach to suspected stroke between children and adults are also discussed.

Cerebral arteriopathy and ischemic stroke in a pediatric MYH11 patient

OBJECTIVES

Mutations in the MYH11 gene result in smooth muscle cell dysfunction and are associated with familial thoracic aortic aneurysms and dissection. We describe a pediatric patient with a stroke and a pathogenic MYH11 IVS32G>A mutation, and a phenotype similar to ACTA2.

METHODS

A proband girl with an acute ischemic stroke underwent genetic analysis and 7T high-resolution MRI.

RESULTS

A 12-year-old girl presented with a right middle cerebral artery occlusion. She received thrombolysis and underwent mechanical thrombectomy. An extensive stroke work-up was negative. A three-generation pedigree showed a splice site mutation of MYH11 IVS32G>A of the proband and three more family members. A 7T-MRI showed "broomstick-like" straightening of distal arterial segments, a V-shaped anterior corpus callosum and a post-stroke cystic area of encephalomalacia. This vascular appearance and parenchymal abnormalities typically present in patients with an ACTA2 phenotype. 7T-MRI also demonstrated thickening of the right middle cerebral arterial wall.

DISCUSSION

This case suggests that MYH11 patients may have a similar angiographic and brain parenchymal phenotype to patients with ACTA2 mutations. This is the first report of arterial wall thickening in a MYH11 stroke patient using 7T-MRI. Patients with MYH11 mutations may display a focal cerebral steno-occlusive arteriopathy that may lead to stroke.

Clinical and neuroimaging features of a familial pathogenic ACTA2 variant as a model of a vascular neurocristopathy

The clinical and neuroimaging findings of a family with a variant ACTA2 gene (c351C > G), presenting with smooth muscle dysfunction in structures of neural crest derivation, are discussed. The combination of aortic abnormalities, patent ductus arteriosus, congenital mydriasis and distinctive cerebrovascular and brain morphological abnormalities characterise this disorder. Two sisters, heterozygous for the variant, and their mother, a mosaic, are presented. Brain parenchymal changes are detailed for the first time in a non-Arg179His variant. Radiological features of the petrous canal and external carotid are highlighted. We explore the potential underlying biological and embryological mechanisms.

Triple bypass for multisystem smooth muscle dysfunction syndrome due to Arg179His ACTA2 mutation

Missense mutations in the smooth muscle-specific isoform of the alpha-actin (ACTA2) gene, which encodes smooth muscle actin, congenitally cause systemic smooth muscle dysfunction, leading to multiple systemic smooth muscle dysfunction syndrome. This disease is often diagnosed through the development of congenital mydriasis, patent ductus arteriosus, or thoracic aortic aneurysm at a young age. Some patients develop cerebrovascular lesions, also known as ACTA2 cerebral arteriopathy, which cause ischemic stroke and require surgical revascularization. However, an effective and safe treatment has not yet been established owing to the rarity of the disease. Furthermore, most reports of this disease involve children, with only a few reports on adults and few detailed reports on treatment outcomes published to date. We report a 46-year-old woman with ACTA2 cerebral arteriopathy caused by Arg179His, the most common mutation in this disease; she is the oldest patient reported with this disease to the best of our knowledge. The patient was diagnosed with multiple systemic smooth muscle dysfunction syndrome and ACTA2 cerebral arteriopathy after experiencing a stroke in the right cingulate gyrus. She underwent direct triple bypass with three anastomoses of the right superficial temporal artery to the middle and anterior cerebral arteries. She developed an ischemic stroke as a postoperative complication.The efficacy and safety of this procedure have not been clearly confirmed owing to the frailty of the donor superficial temporal artery and the poor development of collateral circulation; however, direct bypass should be considered a treatment option for patients experiencing progressive multiple strokes.

ACTA2-Related Dysgyria: An Under-Recognized Malformation of Cortical Development

BACKGROUND AND PURPOSE

Pathogenic variants in the ACTA2 gene cause a distinctive arterial phenotype that has recently been described to be associated with brain malformation. Our objective was to further characterize gyral abnormalities in patients with ACTA2 pathogenic variants as per the 2020 consensus recommendations for the definition and classification of malformations of cortical development.

MATERIALS AND METHODS

We performed a retrospective, multicentric review of patients with proved ACTA2 pathogenic variants, searching for the presence of malformations of cortical development. A consensus read was performed for all patients, and the type and location of cortical malformation were noted in each. The presence of the typical ACTA2 arterial phenotype as well as demographic and relevant clinical data was obtained.

RESULTS

We included 13 patients with ACTA2 pathogenic variants (Arg179His mutation, n = 11, and Arg179Cys mutation, n = 2). Ninety-two percent (12/13) of patients had peri-Sylvian dysgyria, 77% (10/13) had frontal dysgyria, and 15% (2/13) had generalized dysgyria. The peri-Sylvian location was involved in all patients with dysgyria (12/12). All patients with dysgyria had a characteristic arterial phenotype described in ACTA2 pathogenic variants. One patient did not have dysgyria or the characteristic arterial phenotype.

CONCLUSIONS

Dysgyria is common in patients with ACTA2 pathogenic variants, with a peri-Sylvian and frontal predominance, and was seen in all our patients who also had the typical ACTA2 arterial phenotype.

Refractory cerebral infarction in a child with an ACTA2 mutation

INTRODUCTIONS

A specific mutation in the ACTA2 gene is known to cause multisystemic smooth muscle dysfunction syndrome, which is associated with cerebrovascular diseases and various organ disorders. Cerebral infarctions resulting from severe vasculopathy can be refractory; however, there are no previous reports describing the detailed clinical course of recurrent cerebral infarctions due to an ACTA2 mutation. Herein, we report a patient with an ACTA2 mutation who experienced multiple refractory cerebral infarctions in early childhood.

PATIENT DESCRIPTION

The patient was aged 1 year and 5 months at her first episode of cerebral infarction. Arteriopathy due to an ACTA2 mutation was diagnosed based on the characteristic cerebrovascular findings and abnormal physical findings, such as bilateral dilated pupils. Bilateral encephaloduroarteriosynangiosis and encephalogaleosynangiosis were performed after the first episode. Because the cerebral infarctions recurred postoperatively, administration of cilostazol followed by bosentan was started. However, despite these treatments she experienced seven cerebral infarctions by age 2 years and 6 months.

INTERPRETATION

Cerebral infarctions in patients with a specific ACTA2 mutation can occur even in early childhood, recur frequently, and cause severe motor and cognitive impairment. Physicians should be highly aware of this disease and be ready to provide the medical and surgical interventions necessary to minimize the disabling sequelae.

Definitions and classification of malformations of cortical development: practical guidelines

Malformations of cortical development are a group of rare disorders commonly manifesting with developmental delay, cerebral palsy or seizures. The neurological outcome is extremely variable depending on the type, extent and severity of the malformation and the involved genetic pathways of brain development. Neuroimaging plays an essential role in the diagnosis of these malformations, but several issues regarding malformations of cortical development definitions and classification remain unclear. The purpose of this consensus statement is to provide standardized malformations of cortical development terminology and classification for neuroradiological pattern interpretation. A committee of international experts in paediatric neuroradiology prepared systematic literature reviews and formulated neuroimaging recommendations in collaboration with geneticists, paediatric neurologists and pathologists during consensus meetings in the context of the European Network Neuro-MIG initiative on Brain Malformations (https://www.neuro-mig.org/). Malformations of cortical development neuroimaging features and practical recommendations are provided to aid both expert and non-expert radiologists and neurologists who may encounter patients with malformations of cortical development in their practice, with the aim of improving malformations of cortical development diagnosis and imaging interpretation worldwide.

Cerebrovascular Disease Progression in Patients With ACTA2 Arg179 Pathogenic Variants

OBJECTIVE

To establish progression of imaging biomarkers of stroke, arterial steno-occlusive disease, and white matter injury in patients with smooth muscle dysfunction syndrome caused by mutations in the ACTA2 gene, we analyzed 113 cerebral MRI scans from a retrospective cohort of 27 patients with ACTA2 Arg179 pathogenic variants.

METHODS

Systematic quantifications of arterial ischemic strokes and white matter lesions were performed on baseline and follow-up scans using planimetric methods. Critical stenosis and arterial vessel diameters were quantified applying manual and semiautomated methods to cerebral magnetic resonance angiograms. We then assessed correlations between arterial abnormalities and parenchymal injury.

RESULTS

We found characteristic patterns of acute white matter ischemic injury and progressive internal carotid artery stenosis during infancy. Longitudinal analysis of patients older than 1.2 years showed stable white matter hyperintensities but increased number of cystic-like lesions over time. Progressive narrowing of the terminal internal carotid artery occurred in 80% of patients and correlated with the number of critical stenoses in cerebral arteries and arterial ischemic infarctions. Arterial ischemic strokes occurred in same territories affected by critical stenosis.

CONCLUSIONS

We found characteristic, early, and progressive cerebrovascular abnormalities in patients with ACTA2 Arg179 pathogenic variants. Our longitudinal data suggest that while steno-occlusive disease progresses over time and is associated with arterial ischemic infarctions and cystic-like white matter lesions, white matter hyperintensities can remain stable over long periods. The evaluated metrics will enable diagnosis in early infancy and be used to monitor disease progression, guide timing of stroke preventive interventions, and assess response to current and future therapies.

Expanding the cerebrovascular phenotype of the p.R258H variant in ACTA2 related hereditary thoracic aortic disease (HTAD)

Heterozygous variants in smooth muscle alpha-actin gene (ACTA2) are the most frequent cause of autosomal dominant hereditary thoracic aortic disease (HTAD). Several genotype-phenotype associations have been described, including a severe multisystemic smooth muscle disorder associated with de novo ACTA2 p.R179 variants, characterized by highly penetrant and early onset vascular disease, involvement of smooth muscle cell (SMC)-dependent organs and a distinct cerebrovascular phenotype. Missense variants at position 258 (p.R258C and p.R258H) have also been reported to have a more severe presentation including an increased risk for aortic dissection and a high risk of stroke. It has previously been suggested that the cerebrovascular phenotype of patients with p.R258 variants could represent a mild presentation of the cerebrovascular phenotype associated with p.R179 variants. Here we report on a five generation HTAD family with the p.R258H variant and describe the cerebrovascular findings seen in three family members, to expand on the previously reported phenotype associated with variants at this codon.

ACTA2 leukovasculopathy: A rare pediatric white matter disorder

A 3-year-old girl presented with ataxia, dilated pupils, and behavioral change prompting work up for stroke. Her medical history included chronic mydriasis and patent ductus arteriosus requiring aortoplasty. Magnetic resonance imaging of the brain demonstrated confluent white matter signal abnormality concerning for leukodystrophy. Magnetic resonance angiography revealed a cerebral vessel arteriopathy with a "broomstick appearance" and other neuroradiographic findings consistent with ACTA2 mutation. Pathogenic Arg179His ACTA2 mutation was confirmed in the patient. ACTA2-related leukovasculopathy should be considered during workup of patients with abnormal white matter (eg, leukodystrophies), childhood stroke, and arteriopathies. Recognizing the combination of commonly associated physical and medical conditions associated with radiographic features of this neurogenetic condition will prompt appropriate care and screening for comorbidities associated with this disorder.

Genome-Wide Analysis Identifies NURR1-Controlled Network of New Synapse Formation and Cell Cycle Arrest in Human Neural Stem Cells

Nuclear receptor-related 1 (Nurr1) protein has been identified as an obligatory transcription factor in midbrain dopaminergic neurogenesis, but the global set of human NURR1 target genes remains unexplored. Here, we identified direct gene targets of NURR1 by analyzing genome-wide differential expression of NURR1 together with NURR1 consensus sites in three human neural stem cell (hNSC) lines. Microarray data were validated by quantitative PCR in hNSCs and mouse embryonic brains and through comparison to published human data, including genome-wide association study hits and the BioGPS gene expression atlas. Our analysis identified ~40 NURR1 direct target genes, many of them involved in essential protein modules such as synapse formation, neuronal cell migration during brain development, and cell cycle progression and DNA replication. Specifically, expression of genes related to synapse formation and neuronal cell migration correlated tightly with NURR1 expression, whereas cell cycle progression correlated negatively with it, precisely recapitulating midbrain dopaminergic development. Overall, this systematic examination of NURR1-controlled regulatory networks provides important insights into this protein's biological functions in dopamine-based neurogenesis.

Genomics and Radiogenomics in Inherited Neurometabolic Disorders - A Practical Primer for Pediatricians

Advances in genetics has revolutionised the way we understand, diagnose and manage neurological disorders. Notwithstanding the fact that genetic confirmation has already become standard of care in routine clinical practice, radiological and clinical phenotyping has not diminished in value; in fact it has found an enhanced role in guiding and interpreting genetic test results. Inherited neurometabolic disorders are a prominent group of disorders which are seen commonly in clinical practice and many are potentially treatable. The concept of Radiogenomics is the bridge from phenotype to genotype and the strength of association varies widely across different inherited metabolic diseases. Understanding the strengths and limitations of these correlations forms the basis of success of multidisciplinary approach to diagnose these disorders. In this article authors give a brief overview of the genetic basis of a disease, available genetic tests and the prominent role of radiology in contemplating a diagnostic suspicion and guiding further confirmatory tests.