Increasing precision in the management of pediatric neurosurgical cerebrovascular diseases with molecular genetics

Introduction: Neurovascular Diseases across the Pediatric Age Spectrum

Pediatric cerebrovascular diseases have distinct clinical presentations, pathophysiology, and management compared to the adult counterparts. This introductory article discusses the imaging techniques and neurovascular conditions unique to each age group from the fetal stages through childhood, including vascular malformations, arteriopathy, and strokes. The article also underscores the importance of genetic factors and the need for a multidisciplinary approach in the diagnosis and treatment of pediatric neurovascular disorders.

Lectin-type oxidized LDL receptor-1 as a potential therapeutic target for cerebral cavernous malformations treatment

Introduction

Cerebral cavernous malformations (CCMs) are pathologic lesions comprised of clusters of thin-walled capillaries characterized by abnormal proliferation, angiogenesis, and bleeding secondary to somatic or germline mutations in endothelial cells. CCMs can cause headaches, seizures and/or neurological defects. There is a clinical need to develop better tools to detect CCMs and follow their progression in conjunction with the current use of neuroimaging techniques. Here we present data supporting the utility of LOX-1 (lectin-type oxidized LDL receptor 1), a 50 kDa transmembrane protein implicated in endothelial cell dysfunction and ischemia, as a putative biomarker for CCM.

Methods

CCM urine samples (n = 23) were collected from pediatric CCM patients. Matched healthy controls (n = 24) were collected from pediatric patients with either Chiari I malformation or fatty filum terminale, and otherwise normal findings. All samples were collected with patient/family consent and institutional review board approval.Samples were analyzed with Olink Proteomic Proximity Extension Assay (PEA). Differences in expression for 2,925 unique proteins were quantified between healthy control urine samples and CCM urine samples. The results were normalized, validated, and analyzed for demographic bias. In addition to urine samples, CCM tissue from patients was harvested and used to create primary cell lines for in vitro analysis of LOX-1 expression, in addition to immunofluorescence of lesional tissue excised at surgery.

Results

ANOVA analysis of the CCM urine samples showed a statistically significant increase in LOX-1 compared to the control samples, with CCM patients exhibiting a > 5-fold increase in urinary expression. Corroborating these elevated levels of circulating marker, analysis of source tissue from surgically resected CCMs revealed that LOX-1 is increased in both CCM patient cavernoma primary cell lines and operative specimens.

Conclusion

LOX-1 is involved with pathways implicated in CCM pathogenesis and our data here reveals that LOX-1 expression is significantly elevated in CCM patients as compared to matched healthy control individuals, including both source tissue from surgically excised CCMs and in analysis of samples collected from outside of the central nervous system, particularly urine. This proof-of-principle data suggests that LOX-1 may have potential utility as a target for CCM treatment and supports further investigation related to its potential mechanistic impact on CCM pathogenesis.

Pediatric non-galenic pial arteriovenous fistula's characteristics and outcomes: a systematic review

INTRODUCTION

Pediatric non-galenic pial arteriovenous fistulas (pAVFs) are rare vascular malformations that are characterized by a pial arterial-venous connection without an intervening capillary bed. Outcomes and treatment strategies for pAVFs are highly individualized, owing to the rarity of the disease and lack of large-scale data guiding optimal treatment approaches.

METHODS

We performed a systematic review of pediatric patients (< 18 years at diagnosis) diagnosed with a pAVF by digital subtraction angiogram (DSA). The demographics, treatment modalities, and outcomes were documented for each patient and clinical outcome data was collected. Descriptive information stratified by outcome scores were classified as follows: 1 = excellent (no deficit and full premorbid activity), 2 = good (mild deficit and full premorbid activity), 3 = fair (moderate deficit and impaired activity), 4 = poor (severe deficit and dependent on others), 5 = death.

RESULTS

A total of 87 studies involving 231 patients were identified. Median age at diagnosis was 3 years (neonates to 18 years). There was slight male preponderance (55.4%), and 150 subjects (81.1%*) experienced excellent outcomes after treatment. Of the 189 patients treated using endovascular approaches, 80.3% experienced excellent outcomes and of the 15 patients surgically treated subjects 75% had an excellent outcome. The highest rate of excellent outcomes was achieved in patients treated with Onyx (95.2%) and other forms of EvOH (100%). High output heart failure and comorbid vascular lesions tended to result in worse outcomes, with only 54.2% and 68% of subjects experiencing an excellent outcome, respectively. *Outcomes were reported in only 185 patients.

CONCLUSION

pAVFs are rare lesions, necessitating aggregation of patient data to inform natural history and optimal treatment strategies. This review summarizes the current literature on pAVF in children, where children presenting with heart failure as a result of high flow through the lesion were less likely to experience an excellent outcome. Prospective, large-scale studies would further characterize pediatric pAVFs and enable quantitative analysis of outcomes to inform best treatment practices.

Management of Pediatric Intracranial Arteriovenous Malformations

Pediatric intracranial arteriovenous malformations (AVMs) are challenging lesions managed by pediatric neurosurgeons. The high risk of hemorrhage and neurologic injury is compounded by the unique anatomy of each malformation that requires individualizing treatment options. This article reviews the current status of pediatric AVM epidemiology, pathophysiology and clinical care, with a specific focus on the rationale and methodology of surgical resection.

Pediatric Cerebral Vascular Malformations : Current and Future Perspectives

Intracranial vascular malformations typically encountered by pediatric neurosurgeons include arteriovenous malformations, vein of Galen malformations and cavernous malformations. While these remain amongst some of the most challenging lesions faced by patients and caregivers, the past decade has produced marked advances in the understanding of the pathophysiology of these conditions, with concomitant innovations in treatment. This article will highlight present and future perspectives relevant to these diseases, with a focus on an emerging approach utilizing disease-specific mutations to develop a novel taxonomy for these conditions.

Discovery and Characterization of Ephrin B2 and EphB4 Dysregulation and Novel Mutations in Cerebral Cavernous Malformations: In Vitro and Patient-Derived Evidence of Ephrin-Mediated Endothelial Cell Pathophysiology

Intracranial vascular malformations manifest on a continuum ranging from predominantly arterial to predominantly venous in pathology. Cerebral cavernous malformations (CCMs) are capillary malformations that exist at the midpoint of this continuum. The axon guidance factor Ephrin B2 and its receptor EphB4 are critical regulators of vasculogenesis in the developing central nervous system. Ephrin B2/EphB4 dysregulation has been implicated in the pathogenesis of arterial-derived arteriovenous malformations and vein-based vein of Galen malformations. Increasing evidence supports the hypothesis that aberrant Ephrin B2/EphB4 signaling may contribute to developing vascular malformations, but their role in CCMs remains largely uncharacterized. Evidence of Ephrin dysregulation in CCMs would be important to establish a common link in the pathogenic spectrum of EphrinB2/Ephb4 dysregulation. By studying patient-derived primary CCM endothelial cells (CCMECs), we established that CCMECs are functionally distinct from healthy endothelial cell controls; CCMECs demonstrated altered patterns of migration, motility, and impaired tube formation. In addition to the altered phenotype, the CCMECs also displayed an increased ratio of EphrinB2/EphB4 compared to the healthy endothelial control cells. Furthermore, whole exome sequencing identified mutations in both EphrinB2 and EphB4 in the CCMECs. These findings identify functional alterations in the EphrinB2/EphB4 ratio as a feature linking pathophysiology across the spectrum of arterial, capillary, and venous structural malformations in the central nervous system while revealing a putative therapeutic target.

Monogenic Causes of Cerebrovascular Disease in Childhood: A Case Series

BACKGROUND

Despite an increase in the number of genes associated with pediatric stroke, imaging phenotypes in children have not been well reported. Guidelines are needed to facilitate the identification and treatment of patients with monogenic causes of cerebrovascular disorders.

METHODS

We performed a retrospective review of imaging and medical records of patients aged zero to 21 years with monogenic causes of vascular malformations, small or large vessel disease, transient ischemic attacks, and/or ischemic or hemorrhagic stroke. We classified patients according to their imaging phenotype and reviewed neurological and systemic features and management strategies. We reviewed the literature to identify genes associated with cerebrovascular disorders presenting in childhood.

RESULTS

We identified 18 patients with monogenic causes of cerebrovascular disorders and classified each patient as belonging to one or more of three cerebrovascular phenotypes according to predominant imaging characteristics: small vessel disease, large vessel disease, and/or vascular malformations. Preventative treatments included aspirin, N-acetylcysteine, tocilizumab, therapeutic low-molecular-weight heparin, and resection of vascular malformations.

CONCLUSIONS

Classifying pediatric patients with cerebrovascular disorders by imaging phenotype can aid in determining the next steps in genetic testing and treatment.

Etiologies of Brain Arteriovenous Malformation Recurrence: A Focus on Pediatric Disease

Pediatric brain arteriovenous malformations are a major cause of morbidity and mortality, with the harmful effects of this disease compounded by the additional disability-years experienced by children with ruptured or other symptomatic arteriovenous malformations. In addition to the risks shared with their adult counterparts, pediatric patients frequently experience recurrence following radiographic cure, which presents an additional source of morbidity and mortality. Therefore, there is a need to synthesize potential mechanisms contributing to the elevated recurrence risk in the pediatric population and discuss how these translate to practical considerations for managing these patients.

Technical evolution of pediatric neurosurgery: moyamoya disease

Moyamoya disease (MMD) is a rare steno-occlusive disease of the bilateral internal carotid arteries that predominantly occurs in East Asia. Since the first description of the MMD by Suzuki and Takaku in 1969, significant advances have been made in both basic and clinical understanding of the disease. The incidence and prevalence of pediatric MMD have increased, potentially due to improved detection rates. The advancement of neuroimaging techniques has enabled MRI-based diagnostics and detailed visualization of the vessel wall. Various methods of surgical treatments are successful in pediatric MMD patients, and recent studies emphasize the importance of reducing postoperative complications since the goal of MMD surgery is to prevent future cerebral infarction and hemorrhage. Long-term outcomes following appropriate surgical treatment in pediatric MMD patients have shown promising results, including favorable outcomes in very young patients. Further studies with a large patient cohort are needed to establish individualized risk group stratification for determining the optimal timing of surgical treatment and to conduct multidisciplinary outcome assessments.

Evolution of clinical and translational advances in the management of pediatric arteriovenous malformations

Arteriovenous malformations (AVMs) represent one of the most challenging diagnoses in pediatric neurosurgery. Until recently, the majority of AVMs was only identified after hemorrhage and primarily treated with surgery. However, recent advances in a wide range of fields-imaging, surgery, interventional radiology, radiation therapy, and molecular biology-have profoundly advanced the understanding and therapy of these complex lesions. Here we review the progress made in pediatric AVMs with a specific focus on innovations relevant to clinical care.

Rare variants in ANO1, encoding a calcium-activated chloride channel, predispose to moyamoya disease

Moyamoya disease, a cerebrovascular disease leading to strokes in children and young adults, is characterized by progressive occlusion of the distal internal carotid arteries and the formation of collateral vessels. Altered genes play a prominent role in the aetiology of moyamoya disease, but a causative gene is not identified in the majority of cases. Exome sequencing data from 151 individuals from 84 unsolved families were analysed to identify further genes for moyamoya disease, then candidate genes assessed in additional cases (150 probands). Two families had the same rare variant in ANO1, which encodes a calcium-activated chloride channel, anoctamin-1. Haplotype analyses found the families were related, and ANO1 p.Met658Val segregated with moyamoya disease in the family with an LOD score of 3.3. Six additional ANO1 rare variants were identified in moyamoya disease families. The ANO1 rare variants were assessed using patch-clamp recordings, and the majority of variants, including ANO1 p.Met658Val, displayed increased sensitivity to intracellular Ca2+. Patients harbouring these gain-of-function ANO1 variants had classic features of moyamoya disease, but also had aneurysm, stenosis and/or occlusion in the posterior circulation. Our studies support that ANO1 gain-of-function pathogenic variants predispose to moyamoya disease and are associated with unique involvement of the posterior circulation.