Natural history of brain capillary vascular malformations in hereditary hemorrhagic telangiectasia patients

Longitudinal Assessment of Curaçao Criteria in Children with Hereditary Hemorrhagic Telangiectasia

OBJECTIVE

To assess the utility of the Curaçao criteria by age over time in children with hereditary hemorrhagic telangiectasia (HHT).

STUDY DESIGN

This was a single-center, retrospective analysis of patients attending the HHT clinic at the Hospital for Sick Children (Toronto, Canada) between 2000 and 2019. The evaluation of the Curaçao criteria was completed during initial and follow-up visits. Screening for pulmonary and brain arteriovenous malformations was completed at 5 yearly intervals.

RESULTS

A total of 116 patients with genetic confirmation of HHT were included in the analysis. At initial screening at a median (IQR) age of 8.4 (2.8, 12.9) years, 41% met criteria for a definite clinical diagnosis (≥3 criteria). In children <6 years at presentation, only 23% fulfilled at least 3 criteria initially. In longitudinal follow-up, 63% reached a definite clinical diagnosis, with a median (IQR) follow-up duration of 5.2 (3.2, 7.9) years (P = .005). Specifically, more patients met the epistaxis and telangiectasia criteria at last visit compared with initial (79% vs 60%; P = .006; 47% vs 30%; P = .02) but not for the arteriovenous malformation criterion (59% vs 57%; P = .65).

CONCLUSIONS

In the pediatric population, most patients do not meet definite clinical criteria of HHT at initial presentation. Although the number of diagnostic criteria met increased over time, mainly due to new onset of epistaxis and telangiectasia, accuracy remained low during follow-up visits. Relying solely on clinical criteria may lead to underdiagnosis of HHT in children.

Brain arteriovenous malformation in hereditary hemorrhagic telangiectasia: Recent advances in cellular and molecular mechanisms

Hereditary hemorrhagic telangiectasia (HHT) is a genetic disorder characterized by vessel dilatation, such as telangiectasia in skin and mucosa and arteriovenous malformations (AVM) in internal organs such as the gastrointestinal tract, lungs, and brain. AVMs are fragile and tortuous vascular anomalies that directly connect arteries and veins, bypassing healthy capillaries. Mutations in transforming growth factor β (TGFβ) signaling pathway components, such as ENG (ENDOGLIN), ACVRL1 (ALK1), and SMAD4 (SMAD4) genes, account for most of HHT cases. 10-20% of HHT patients develop brain AVMs (bAVMs), which can lead to vessel wall rupture and intracranial hemorrhages. Though the main mutations are known, mechanisms leading to AVM formation are unclear, partially due to lack of animal models. Recent mouse models allowed significant advances in our understanding of AVMs. Endothelial-specific deletion of either Acvrl1, Eng or Smad4 is sufficient to induce AVMs, identifying endothelial cells (ECs) as primary targets of BMP signaling to promote vascular integrity. Loss of ALK1/ENG/SMAD4 signaling is associated with NOTCH signaling defects and abnormal arteriovenous EC differentiation. Moreover, cumulative evidence suggests that AVMs originate from venous ECs with defective flow-migration coupling and excessive proliferation. Mutant ECs show an increase of PI3K/AKT signaling and inhibitors of this signaling pathway rescue AVMs in HHT mouse models, revealing new therapeutic avenues. In this review, we will summarize recent advances and current knowledge of mechanisms controlling the pathogenesis of bAVMs, and discuss unresolved questions.

Imaging to intervention: a review of what the Interventionalist needs to Know about Hereditary Hemorrhagic Telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) is a disorder that affects 1 in 5000-10,000 people worldwide and can result in devastating complications such as cerebral abscess, stroke, massive hemorrhage, and even death. HHT is an autosomal dominant disorder that leads to the formation of abnormal communication between the arteries and veins with a resultant spectrum of vascular anomalies. The disorder affects many organ systems and thus requires a dedicated multidisciplinary approach. Interventional radiologists are vital members of this team providing expertise not only in disease management, but in complex embolotherapy, helping to maintain the health of these patients. This article reviews clinical manifestations, screening guidelines, diagnostic criteria, and endovascular management of HHT.

Hereditary Hemorrhagic Telangiectasia: The Convergence of Genotype, Phenotype, and Imaging in Modern Diagnosis and Management of a Multisystem Disease

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disease that manifests as vascular malformations in the brain, lung, liver, gastrointestinal tract, nasal mucosa, and skin. Diagnosis and management of HHT is guided in large part by imaging studies, making it a condition with which the radiology community needs familiarity. Proper screening and care lead to improved morbidity and mortality in patients with HHT. International guidelines were recently updated and form the basis for a detailed discussion of the role of imaging and image-guided therapy in HHT. © RSNA, 2021 Online supplemental material is available for this article.

Systemic and CNS manifestations of inherited cerebrovascular malformations

Cerebrovascular malformations occur in both sporadic and inherited patterns. This paper reviews imaging and clinical features of cerebrovascular malformations with a genetic basis. Genetic diseases such as familial cerebral cavernous malformations and hereditary hemorrhagic telangiectasia often have manifestations in bone, skin, eyes, and visceral organs, which should be recognized. Genetic and molecular mechanisms underlying the inherited disorders are becoming better understood, and treatments are likely to follow. An interaction between the intestinal microbiome and formation of cerebral cavernous malformations has emerged, with possible treatment implications. Two-hit mechanisms are involved in these disorders, and additional triggering mechanisms are part of the development of malformations. Hereditary hemorrhagic telangiectasia encompasses a variety of vascular malformations, with widely varying risks, and a more recently recognized association with cortical malformations. Somatic mutations are implicated in the genesis of some sporadic malformations, which means that discoveries related to inherited disorders may aid treatment of sporadic cases. This paper summarizes the current state of knowledge of these conditions, salient features regarding mechanisms of development, and treatment prospects.

Neurovascular disease and syndromes: Diagnosis and therapy in children

The pediatric neurovascular disease runs the chronologic spectrum with dramatic changes in the presentation, evaluation, and treatment from the prenatal, perinatal, and infant periods through childhood and adolescence. These diseases are often dynamic throughout this period and the dynamic continues throughout life. There are four major categories: high-flow arteriovenous shunting lesions, arterial aneurysms, low-flow vascular lesions, and vascular occlusive disease. The high-flow lesions can be subdivided into a vein of Galen malformation, non-Galenic arteriovenous fistula, dural sinus malformations and fistula, and arteriovenous malformation. Low-flow vascular lesions include cerebral cavernous malformation, developmental venous anomaly, and capillary telangiectasia. The cerebrovascular occlusive disease can be divided between arterial occlusive disease and cerebral venous sinus thrombosis. The presentation of each of these entities can be very similar, especially in younger children; however, imaging and laboratory analysis can establish the diagnosis leading to the most appropriate therapy. A multidisciplinary team, dedicated to treating pediatric cerebrovascular disease, is important in delivering the best outcomes in these complex diseases. Given the relative rarity of pediatric presentation of cerebrovascular disease, many apply adult concepts to children. A better understanding of the diseases and their difference from adults makes a critical difference in selecting the correct approach.

The Roles of TGF-β Signaling in Cerebrovascular Diseases

Cerebrovascular diseases are one of the leading causes of death worldwide, however, little progress has been made in preventing or treating these diseases to date. The transforming growth factor-β (TGF-β) signaling pathway plays crucial and highly complicated roles in cerebrovascular development and homeostasis, and dysregulated TGF-β signaling contributes to cerebrovascular diseases. In this review, we provide an updated overview of the functional role of TGF-β signaling in the cerebrovascular system under physiological and pathological conditions. We discuss the current understanding of TGF-β signaling in cerebral angiogenesis and the maintenance of brain vessel homeostasis. We also review the mechanisms by which disruption of TGF-β signaling triggers or promotes the progression of cerebrovascular diseases. Finally, we briefly discuss the potential of targeting TGF-β signaling to treat cerebrovascular diseases.

European Reference Network for Rare Vascular Diseases (VASCERN) position statement on cerebral screening in adults and children with hereditary haemorrhagic telangiectasia (HHT)

Hereditary haemorrhagic telangiectasia (HHT) is a multisystemic vascular dysplasia inherited as an autosomal dominant trait. Approximately 10 % of patients have cerebral vascular malformations, a proportion being cerebral arteriovenous malformations (AVMs) and fistulae that may lead to potentially devastating consequences in case of rupture. On the other hand, detection and treatment related-risks are not negligible, and immediate. While successful treatment can be undertaken in individual cases, current data do not support the treatment of unruptured AVMs, which also present a low risk of bleeding in HHT patients. Screening for these AVMs is therefore controversial.

Structured discussions, distinctions of different cerebrovascular abnormalities commonly grouped into an “AVM” bracket, and clear guidance by neurosurgical and neurointerventional radiology colleagues enabled the European Reference Network for Rare Vascular Disorders (VASCERN-HHT) to develop the following agreed Position Statement on cerebral screening:

1) First, we emphasise that neurological symptoms suggestive of cerebral AVMs in HHT patients should be investigated as in general neurological and emergency care practice. Similarly, if an AVM is found accidentally, management approaches should rely on expert discussions on a case-by-case basis and individual risk-benefit evaluation of all therapeutic possibilities for a specific lesion.

2) The current evidence base does not favour the treatment of unruptured cerebral AVMs, and therefore cannot be used to support widespread screening of asymptomatic HHT patients.

3) Individual situations encompass a wide range of personal, cultural and clinical states. In order to enable informed patient choice, and avoid conflicting advice, particularly arising from non-neurovascular interpretations of the evidence base, we suggest that all HHT patients should have the opportunity to discuss knowingly brain screening issues with their healthcare provider.

4) Any screening discussions in asymptomatic individuals should be preceded by informed pre-test review of the latest evidence regarding preventative and therapeutic efficacies of any interventions. The possibility of harm due to detection of, or intervention on, a vascular malformation that would not have necessarily caused any consequence in later life should be stated explicitly.

We consider this nuanced Position Statement provides a helpful, evidence-based framework for informed discussions between healthcare providers and patients in an emotionally charged area.

Comparison of MRI, MRA, and DSA for Detection of Cerebral Arteriovenous Malformations in Hereditary Hemorrhagic Telangiectasia

BACKGROUND AND PURPOSE

Patients with hereditary hemorrhagic telangiectasia (HHT) have a high prevalence of brain vascular malformations, putting them at risk for brain hemorrhage and other complications. Our aim was to evaluate the relative utility of MR imaging and MRA compared with DSA in detecting cerebral AVMs in the HHT population.

MATERIALS AND METHODS

Of 343 consecutive patients evaluated at the University of California, San Francisco HTT Center of Excellence, 63 met the study inclusion criteria: definite or probable hereditary hemorrhagic telangiectasia defined by meeting at least 2 Curacao criteria or positive genetic testing, as well as having at least 1 brain MR imaging and 1 DSA. MRIs were retrospectively reviewed, and the number of AVMs identified was compared with the number of AVMs identified on DSA.

RESULTS

Of 63 patients, 45 (71%) had AVMs on DSA with a total of 92 AVMs identified. Of those, 24 (26%) were seen only on DSA; 68 (74%), on both DSA and MR imaging; and 5 additional lesions were seen only on MR imaging. Of the 92 lesions confirmed on DSA, 49 (53.3%) were seen on the 3D-T1 postgadolinium sequence, 52 (56.5%) were seen on the 2D-T1 postgadolinium sequence, 35 (38.0%) were seen on the SWI sequence, 24 (26.1%) were seen on T2 sequence, and 25 (27.2%) were seen on MRA. The sensitivity and specificity of MR imaging as a whole in detecting AVMs then confirmed on DSA were 80.0% and 94.4%, respectively, and the positive and negative predictive values were 97.3% and 65.4%, respectively.

CONCLUSIONS

This study reinforces the use of MR imaging as a primary screening tool for cerebral AVMs in patients with hereditary hemorrhagic telangiectasia and suggests that 3D-T1 postgadolinium and 2D-T1 postgadolinium performed at 3T are the highest yield sequences.