Ultrastructural pathological features of cerebrovascular malformations: a preliminary report

Mapping cell diversity in human sporadic cerebral cavernous malformations

BACKGROUND

Cerebral cavernous malformation (CCM) is a low-flow, bleeding-prone vascular disease that can cause cerebral hemorrhage, seizure and neurological deficits. Its inheritance mode includes sporadic or autosomal dominant inheritance with incomplete penetrance, namely sporadic CCM (SCCM) and familial CCM. SCCM is featured by single lesion and single affection in a family. Among CCM patients especially SCCM, the pathogenesis of the corresponding phenotypes and pathological features or candidate genes have not been fully elucidated yet.

METHODS

Here, we performed in-depth single-cell RNA sequencing (scRNA-Seq) and bulk assay for transposase-accessible chromatin sequencing (ATAC-Seq) in SCCM and control patients. Further validation was conducted for the gene of interest using qPCR and RNA in situ hybridization (RNA FISH) techniques to provide further atlas and evidence for SCCM generative process.

RESULTS

We identified six cell types in the SCCM and control vessels and found that the expression of NEK1, RNPC3, FBRSL1, IQGAP2, MCUB, AP3B1, ESCO1, MYO9B and PVT1 were up-regulated in SCCM tissues. Among the six cell types, we found that compared with control conditions, PVT1 showed a rising peak which followed the pseudo-time axis in endothelial cell clusters of SCCM samples, while showed an increasing trend in smooth muscle cell clusters of SCCM samples. Further experiments indicated that, compared with the control vessels, PVT1 exhibited significantly elevated expression in SCCM samples.

CONCLUSION

In SCCM conditions, We found that in the process of development from control to lesion conditions, PVT1 showed a rising peak in endothelial cells and showed an increasing trend in smooth muscle cells at the same time. Overall, there was a significantly elevated expression of NEK1, RNPC3, FBRSL1, IQGAP2, MCUB, AP3B1, ESCO1, MYO9B and PVT1 in SCCM specimens compared to control samples.

Defining the Functional Influence of Endothelial Cell-Expressed Oncogenic Activating Mutations on Vascular Morphogenesis and Capillary Assembly

This study sought to define key molecules and signals controlling major steps in vascular morphogenesis, and how these signals regulate pericyte recruitment and pericyte-induced basement membrane deposition. The morphogenic impact of endothelial cell (EC) expression of activating mutants of Kirsten rat sarcoma virus (kRas), mitogen-activated protein kinase 1 (Mek1), phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), Akt serine/threonine kinase 1 (Akt1), Ras homolog enriched in brain (Rheb) Janus kinase 2 (Jak2), or signal transducer and activator of transcription 3 (Stat3) expression versus controls was evaluated, along with EC signaling events, pharmacologic inhibitor assays, and siRNA suppression experiments. Primary stimulators of EC lumen formation included kRas, Akt1, and Mek1, whereas PIK3CA and Akt1 stimulated a specialized type of cystic lumen formation. In contrast, the key drivers of EC sprouting behavior were Jak2, Stat3, Mek1, PIK3CA, and mammalian target of rapamycin (mTor). These conclusions are further supported by pharmacologic inhibitor and siRNA suppression experiments. EC expression of active Akt1, kRas, and PIK3CA led to markedly dysregulated lumen formation coupled to strongly inhibited pericyte recruitment and basement membrane deposition. For example, activated Akt1 expression in ECs excessively stimulated lumen formation, decreased EC sprouting behavior, and showed minimal pericyte recruitment with reduced mRNA expression of platelet-derived growth factor-BB, platelet-derived growth factor-DD, and endothelin-1, critical EC-derived factors known to stimulate pericyte invasion. The study identified key signals controlling fundamental steps in capillary morphogenesis and maturation and provided mechanistic details on why EC activating mutations induced a capillary deficiency state with abnormal lumens, impaired pericyte recruitment, and basement deposition: predisposing stimuli for the development of vascular malformations.

Hyaluronic acid turnover controls the severity of cerebral cavernous malformations in bioengineered human micro-vessels

Cerebral cavernous malformations (CCMs) are vascular lesions that predominantly form in blood vessels of the central nervous system upon loss of the CCM multimeric protein complex. The endothelial cells within CCM lesions are characterized by overactive MEKK3 kinase and KLF2/4 transcription factor signaling, leading to pathological changes such as increased endothelial cell spreading and reduced junctional integrity. Concomitant to aberrant endothelial cell signaling, non-autonomous signals from the extracellular matrix (ECM) have also been implicated in CCM lesion growth and these factors might explain why CCM lesions mainly develop in the central nervous system. Here, we adapted a three-dimensional microfluidic system to examine CCM1 deficient human micro-vessels in distinctive extracellular matrices. We validate that pathological hallmarks are maintained in this model. We further show that key genes responsible for homeostasis of hyaluronic acid, a major extracellular matrix component of the central nervous system, are dysregulated in CCM. Supplementing the matrix in our model with distinct forms of hyaluronic acid inhibits pathological cell spreading and rescues barrier function. Hyaluronic acid acts by dampening cell-matrix adhesion signaling in CCM, either downstream or in parallel of KLF2/4. This study provides a proof-of-principle that ECM embedded 3D microfluidic models are ideally suited to identify how changes in ECM structure and signaling impact vascular malformations.

The rare case of optic nerve cavernoma: A case report depicting the diagnostic challenge

The manuscript describes a case of Cavernous Malformation in the optic pathway which is extremely rare, accounting for less than 1% of central nervous system cavernomas. This case report highlights a patient initially diagnosed with a glioma, but subsequent MRI changes and extensive analysis ruled in favor of a hemorrhagic optic neuropathy caused by an optic nerve cavernoma. The patient experienced temporary vision loss but fully regained her vision within a week. Based on clinical, biochemical, and radiological findings, it was confirmed as a rare case of optic nerve cavernoma, and the patient was managed expectantly due to her complete recovery of vision. Follow-up imaging after 1 year indicated a stable lesion with evolving characteristics consistent with a cavernoma. This study provides an informative review of the condition and highlights the key radiologic features of this disease.

Radiation-Induced Cerebral Cavernous Malformations: A Single-Center Experience and Systematic Literature Review

OBJECTIVE

Radiation was first demonstrated to be associated with cavernomagenesis in 1992. Since then, a growing body of literature has shown the unique course and presentation of radiation-induced cavernous malformations (RICMs). This study summarizes the literature on RICMs and presents a single-center experience.

METHODS

A prospectively maintained single institution vascular malformation database was searched for all cases of intracranial cavernous malformation (January 1, 1997-December 31, 2021). For patients with a diagnosis of RICM, information on demographic characteristics, surgical treatments, radiation, and surgical outcomes was obtained and analyzed. A comprehensive literature search was conducted using PubMed, Embase, Cochrane, and Web of Science databases for all reported cases of RICM.

RESULTS

A retrospective review of 1662 patients treated at a single institution yielded 10 patients with prior radiation treatment in the neck or head region and a subsequent diagnosis of intracranial RICM. The median (interquartile range) latency between radiation and presentation was 144 (108-192) months. Nine of 10 patients underwent surgery; symptoms improved for 5 patients, worsened for 3, and were stable for 1. The systematic literature review yielded 64 publications describing 248 patients with RICMs. Of the 248 literature review cases, 71 (28.6%) involved surgical resection. Of 39 patients with reported surgical outcomes, 32 (82%) experienced improvement.

CONCLUSIONS

RICMs have a unique course and epidemiology. RICMs should be considered when patients with a history of radiation present with neurologic impairment. When RICMs are identified, symptomatic patients can be treated effectively with surgical excision and close follow-up.

Significance of perilesional T1 hyperintense areas in the differential diagnosis of primary adult-type diffuse glioma: A case report

Perilesional T1 hyperintensity on magnetic resonance imaging (MRI) of intra-axial brain masses is an unusual feature of the perilesional area, characteristic of cavernous malformations (CMs) and metastatic brain tumors (METs). Here, we report a case of primary diffuse glioma with a perilesional T1 hyperintense area (HIA) on MRI. A 61-year-old woman with transient aphasia visited our hospital. Radiological examination revealed an intra-axial mass with acute/subacute hemorrhaging and calcification in the left frontal lobe. It was presumed to be a CM because of the perilesional T1 HIA. Gross total resection of the tumor was performed, and the pathological diagnosis was anaplastic oligodendroglioma, not otherwise specified by World Health Organization 2016 classification. Histopathological findings in the perilesional T1 HIA indicated hemorrhage involvement in the surrounding white matter. No recurrence appeared after radio-chemotherapy. Perilesional T1 HIAs, characteristic of CMs and METs, are also seen in primary diffuse gliomas. Therefore, caution should be taken when using this sign for the differential diagnosis of intracranial masses.

A novel KRIT1/CCM1 mutation accompanied by a NOTCH3 mutation in a Chinese family with multiple cerebral cavernous malformations

Family cerebral cavernous malformations (FCCMs) are mainly inherited through the mutation of classical CCM genes, including CCM1/KRIT1, CCM2/MGC4607, and CCM3/PDCD10. FCCMs can cause severe clinical symptoms, including epileptic seizures, intracranial hemorrhage (ICH), or functional neurological deficits (FNDs). In this study, we reported a novel mutation in KRIT1 accompanied by a NOTCH3 mutation in a Chinese family. This family consists of 8 members, 4 of whom had been diagnosed with CCMs using cerebral MRI (T1WI, T2WI, SWI). The proband (II-2) and her daughter (III-4) had intracerebral hemorrhage and refractory epilepsy, respectively. Based on whole-exome sequencing (WES) data and bioinformatics analysis from 4 patients with multiple CCMs and 2 normal first-degree relatives, a novel KRIT1 mutation, NG_012964.1 (NM_194456.1): c.1255-1G > T (splice-3), in intron 13 was considered a pathogenic gene in this family. Furthermore, based on 2 severe and 2 mild CCM patients, we found an SNV missense mutation, NG_009819.1 (NM_000435.2): c.1630C > T (p.R544C), in NOTCH3. Finally, the KRIT1 and NOTCH3 mutations were validated in 8 members using Sanger sequencing. This study revealed a novel KRIT1 mutation, NG_012964.1 (NM_194456.1): c.1255-1G > T (splice-3), in a Chinese CCM family, which had not been reported previously. Moreover, the NOTCH3 mutation NG_009819.1 (NM_000435.2): c.1630C > T (p.R544C) might be a second hit and associated with the progression of CCM lesions and severe clinical symptoms.

Cellular loci involved in the development of brain arteriovenous malformations

Brain arteriovenous malformations (bAVMs) are abnormal vessels that are prone to rupture, causing life-threatening intracranial bleeding. The mechanism of bAVM formation is poorly understood. Nevertheless, animal studies revealed that gene mutation in endothelial cells (ECs) and angiogenic stimulation are necessary for bAVM initiation. Evidence collected through analyzing bAVM specimens of human and mouse models indicate that cells other than ECs also are involved in bAVM pathogenesis. Both human and mouse bAVMs vessels showed lower mural cell-coverage, suggesting a role of pericytes and vascular smooth muscle cells (vSMCs) in bAVM pathogenesis. Perivascular astrocytes also are important in maintaining cerebral vascular function and take part in bAVM development. Furthermore, higher inflammatory cytokines in bAVM tissue and blood demonstrate the contribution of inflammatory cells in bAVM progression, and rupture. The goal of this paper is to provide our current understanding of the roles of different cellular loci in bAVM pathogenesis.

Emerging pathogenic mechanisms in human brain arteriovenous malformations: a contemporary review in the multiomics era

A variety of pathogenic mechanisms have been described in the formation, maturation, and rupture of brain arteriovenous malformations (bAVMs). While the understanding of bAVMs has largely been formulated based on animal models of rare hereditary diseases in which AVMs form, a new era of “omics” has permitted large-scale examinations of contributory genetic variations in human sporadic bAVMs. New findings regarding the pathogenesis of bAVMs implicate changes to endothelial and mural cells that result in increased angiogenesis, proinflammatory recruitment, and breakdown of vascular barrier properties that may result in hemorrhage; a greater diversity of cell populations that compose the bAVM microenvironment may also be implicated and complicate traditional models. Genomic sequencing of human bAVMs has uncovered inherited, de novo, and somatic activating mutations, such as KRAS, which contribute to the pathogenesis of bAVMs. New droplet-based, single-cell sequencing technologies have generated atlases of cell-specific molecular derangements. Herein, the authors review emerging genomic and transcriptomic findings underlying pathologic cell transformations in bAVMs derived from human tissues. The application of multiple sequencing modalities to bAVM tissues is a natural next step for researchers, although the potential therapeutic benefits or clinical applications remain unknown.

NOGOB receptor deficiency increases cerebrovascular permeability and hemorrhage via impairing histone acetylation-mediated CCM1/2 expression

The loss function of cerebral cavernous malformation (CCM) genes leads to most CCM lesions characterized by enlarged leaking vascular lesions in the brain. Although we previously showed that NOGOB receptor (NGBR) knockout in endothelial cells (ECs) results in cerebrovascular lesions in the mouse embryo, the molecular mechanism by which NGBR regulates CCM1/2 expression has not been elucidated. Here, we show that genetic depletion of Ngbr in ECs at both postnatal and adult stages results in CCM1/2 expression deficiency and cerebrovascular lesions such as enlarged vessels, blood-brain-barrier hyperpermeability, and cerebral hemorrhage. To reveal the molecular mechanism, we used RNA-sequencing analysis to examine changes in the transcriptome. Surprisingly, we found that the acetyltransferase HBO1 and histone acetylation were downregulated in NGBR-deficient ECs. The mechanistic studies elucidated that NGBR is required for maintaining the expression of CCM1/2 in ECs via HBO1-mediated histone acetylation. ChIP-qPCR data further demonstrated that loss of NGBR impairs the binding of HBO1 and acetylated histone H4K5 and H4K12 on the promotor of the CCM1 and CCM2 genes. Our findings on epigenetic regulation of CCM1 and CCM2 that is modulated by NGBR and HBO1-mediated histone H4 acetylation provide a perspective on the pathogenesis of sporadic CCMs.

Cervical intradural extramedullary cavernous malformation as a rare cause of subarachnoid hemorrhage without spinal dysfunction: illustrative case

BACKGROUND

Intradural extramedullary cavernoma is a very rare lesion of the spinal cord, especially of the cervical spine. Its clinical presentation can vary with symptoms of sensory or motor deficits and even with symptoms of subarachnoid hemorrhage (SAH).

OBSERVATIONS

The authors present a case of a 45-year-old man with SAH with prolonged neck pain and increasing headache confirmed by lumbar puncture. Head computed tomography revealed only discrete blood deposits in the right frontal and biparietal lobes. The finding of pan-cerebral angiography was negative for the cause of bleeding. Spinal magnetic resonance imaging revealed an intradural extramedullary mass lesion at cervical level C5–6. The finding of subsequent cervical angiography was negative. The diagnosis of a cavernous malformation was confirmed histopathologically after surgery. The cavernoma was completely removed, and full recovery of the initial symptoms was achieved.

LESSONS

Spinal lesions should be considered in the diagnostic work-up for SAH with excluded origin of bleeding in cranial neuroimaging. An intradural extramedullary cavernous malformation is an extremely rare entity in the differential diagnosis of SAH, and surgical resection is the treatment of choice to prevent further bleeding and neurological deficits.

Cavernous malformations

Cavernous malformations are relatively common intracerebral malformations of which we only became properly aware after the introduction of MRI. They may be sporadic or familial. Familial CMs may be multiple and new lesions appear over time requiring intermittent MR control. Many sporadic CMs have no symptoms. The commonest location is in the supratentorial cerebral parenchyma presenting with epilepsy. The best treatment is microsurgery. A small proportion are in the brainstem and may rebleed and even be lethal. Treatment includes microsurgery and radiosurgery. Microsurgery cures the patient but has substantial problems with complications, deterioration and partial removal. Radiosurgery has taken time to demonstrate that it can over 2 years substantially reduce the risk of rebleeds without the risks of microsurgery. Both methods have a part to play in the treatment.

The multifaceted PDCD10/CCM3 gene

The programmed cell death 10 (PDCD10) gene was originally identified as an apoptosis-related gene, although it is now usually known as CCM3, as the third causative gene of cerebral cavernous malformation (CCM). CCM is a neurovascular disease that is characterized by vascular malformations and is associated with headaches, seizures, focal neurological deficits, and cerebral hemorrhage. The PDCD10/CCM3 protein has multiple subcellular localizations and interacts with several multi-protein complexes and signaling pathways. Thus PDCD10/CCM3 governs many cellular functions, which include cell-to-cell junctions and cytoskeleton organization, cell proliferation and apoptosis, and exocytosis and angiogenesis. Given its central role in the maintenance of homeostasis of the cell, dysregulation of PDCD10/CCM3 can result in a wide range of altered cell functions. This can lead to severe diseases, including CCM, cognitive disability, and several types of cancers. Here, we review the multifaceted roles of PDCD10/CCM3 in physiology and pathology, with a focus on its functions beyond CCM.

Intracerebral and subarachnoid hemorrhage in pregnancy

Maternal stroke occurs in around 34 out of every 100,000 deliveries and is responsible for around 5%-12% of all maternal deaths. It is most commonly hemorrhagic, and women are at highest risk for developing pregnancy-related hemorrhage during the early postpartum period through 6 weeks following the delivery. The most common causes of hemorrhagic stroke in pregnant patients are arteriovenous malformations and cerebral aneurysms. Management is similar to that for acute hemorrhagic stroke in the nonpregnant population with standard use of computed tomography and judicious utilization of intracranial vessel imaging and contrast. The optimal delivery method is evaluated on a case-by-case basis, and cesarean delivery is not always required. As most current studies are limited by retrospective design, relatively small sample sizes, and heterogeneous study term definitions, strong and comprehensive evidence-based guidelines on the management of acute hemorrhagic stroke in pregnant patients are still lacking. In the future, multicenter registries and prospective studies with uniform definitions will help improve management strategies in this complex patient population.

CCM2L (Cerebral Cavernous Malformation 2 Like) Deletion Aggravates Cerebral Cavernous Malformation Through Map3k3-KLF Signaling Pathway

[Figure: see text].

Propranolol Reduces the Development of Lesions and Rescues Barrier Function in Cerebral Cavernous Malformations: A Preclinical Study

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A Review of Proliferative Vascular Disorders of the Central Nervous System of Animals

In disease, blood vessel proliferation has many salient roles including in inflammation, when granulation tissue fills superficial defects, or in the recanalization of an occluded blood vessel. Sometimes angiogenesis goes awry-granulation can be exuberant, and plexiform proliferation of vascular components can contribute to pulmonary hypertension. This review focuses on the diverse manifestations of pathologic vascular overgrowth that occur in the brain, spinal cord, and meninges of animals from birth until old age. Entities discussed include systemic reactive angioendotheliomatosis in which glomeruloid vascular proliferations are encountered in various organs including the central nervous system (CNS). The triad of CNS vascular malformations, hamartomas, and benign vascular proliferations are an especially fraught category in which terminology overlap and the microscopic similarity of various disorders makes diagnostic classification incredibly challenging. Pathologists commonly take refuge in "CNS vascular hamartoma" despite the lack of any unique histopathologic features and we recommend that this diagnostic category be abandoned. Malformative lesions that are often confusing and have similar features; the conditions include arteriovenous malformation, cavernous angioma, venous angioma, and capillary telangiectases. Meningioangiomatosis, a benign meningovascular proliferation with dual components, is a unique entity seen most commonly in young dogs. Last, accepted neoplastic conditions range from lower-grade locally acquired growths like hemangioblastoma (a tumor of mysterious interstitial stromal cells encountered in the setting of abundant capillary vasculature proliferation), the rare hemangioendothelioma, and the highly malignant and invariably multifocal metastatic hemangiosarcoma. Additionally, this review draws on the comparative medical literature for further insights into this problematic topic in pathology.

Signalling through cerebral cavernous malformation protein networks

Cerebral cavernous malformations (CCMs) are neurovascular abnormalities characterized by thin, leaky blood vessels resulting in lesions that predispose to haemorrhages, stroke, epilepsy and focal neurological deficits. CCMs arise due to loss-of-function mutations in genes encoding one of three CCM complex proteins, KRIT1, CCM2 or CCM3. These widely expressed, multi-functional adaptor proteins can assemble into a CCM protein complex and (either alone or in complex) modulate signalling pathways that influence cell adhesion, cell contractility, cytoskeletal reorganization and gene expression. Recent advances, including analysis of the structures and interactions of CCM proteins, have allowed substantial progress towards understanding the molecular bases for CCM protein function and how their disruption leads to disease. Here, we review current knowledge of CCM protein signalling with a focus on three pathways which have generated the most interest—the RhoA–ROCK, MEKK3–MEK5–ERK5–KLF2/4 and cell junctional signalling pathways—but also consider ICAP1-β1 integrin and cdc42 signalling. We discuss emerging links between these pathways and the processes that drive disease pathology and highlight important open questions—key among them is the role of subcellular localization in the control of CCM protein activity.

Mapping endothelial-cell diversity in cerebral cavernous malformations at single-cell resolution

Cerebral cavernous malformation (CCM) is a rare neurovascular disease that is characterized by enlarged and irregular blood vessels that often lead to cerebral hemorrhage. Loss-of-function mutations to any of three genes results in CCM lesion formation; namely, KRIT1, CCM2, and PDCD10 (CCM3). Here, we report for the first time in-depth single-cell RNA sequencing, combined with spatial transcriptomics and immunohistochemistry, to comprehensively characterize subclasses of brain endothelial cells (ECs) under both normal conditions and after deletion of Pdcd10 (Ccm3) in a mouse model of CCM. Integrated single-cell analysis identifies arterial ECs as refractory to CCM transformation. Conversely, a subset of angiogenic venous capillary ECs and respective resident endothelial progenitors appear to be at the origin of CCM lesions. These data are relevant for the understanding of the plasticity of the brain vascular system and provide novel insights into the molecular basis of CCM disease at the single cell level.

Targeting miR-27a/VE-cadherin interactions rescues cerebral cavernous malformations in mice

Cerebral cavernous malformations (CCMs) are vascular lesions predominantly developing in the central nervous system (CNS), with no effective treatments other than surgery. Loss-of-function mutation in CCM1/krev interaction trapped 1 (KRIT1), CCM2, or CCM3/programmed cell death 10 (PDCD10) causes lesions that are characterized by abnormal vascular integrity. Vascular endothelial cadherin (VE-cadherin), a major regulator of endothelial cell (EC) junctional integrity is strongly disorganized in ECs lining the CCM lesions. We report here that microRNA-27a (miR-27a), a negative regulator of VE-cadherin, is elevated in ECs isolated from mouse brains developing early CCM lesions and in cultured ECs with CCM1 or CCM2 depletion. Furthermore, we show miR-27a acts downstream of kruppel-like factor (KLF)2 and KLF4, two known key transcription factors involved in CCM lesion development. Using CD5-2 (a target site blocker [TSB]) to prevent the miR-27a/VE-cadherin mRNA interaction, we present a potential therapy to increase VE-cadherin expression and thus rescue the abnormal vascular integrity. In CCM1- or CCM2-depleted ECs, CD5-2 reduces monolayer permeability, and in Ccm1 heterozygous mice, it restores dermal vessel barrier function. In a neonatal mouse model of CCM disease, CD5-2 normalizes vasculature and reduces vascular leakage in the lesions, inhibits the development of large lesions, and significantly reduces the size of established lesions in the hindbrain. Furthermore, CD5-2 limits the accumulation of inflammatory cells in the lesion area. Our work has established that VE-cadherin is a potential therapeutic target for normalization of the vasculature and highlights that targeting miR-27a/VE-cadherin interaction by CD5-2 is a potential novel therapy for the devastating disease, CCM.

Cerebral cavernous malformation (CCM) is a disease for which, hitherto, surgery has been the only option. This study shows that a potential therapeutic, CD5-2, inhibits lesion development and vascular leak in the brains of CCM neonatal mice by targeting the endothelial cell–specific adhesion molecule VE-cadherin and restoring the vascular integrity of CCM lesions.

Cavernous Hemangioma of the Chiasm and Left Optic Nerve

Cavernous malformations (CMs) of the optic nerves, chiasm, and optic tract are very rare. This report describes a 26-year-old man who presented with recurring headaches, loss of vision in his left eye, and elevated blood pressure. After being diagnosed with glioma of the chiasm, he was referred to our department. Magnetic resonance imaging revealed signs of a mass lesion of the left chiasmal area, a finding confirmed after transcranial biopsy. In February 2015, he underwent gross total resection of the cavernous angioma of the chiasm and the left optic nerve. Three months later, the patient's vision returned to normal. The absence of a typical clinical picture and the lack of radiological visualization can hinder pathologic diagnosis. Total microsurgical resection is the optimal treatment strategy for patients with CMs of the chiasm and optic nerve because it usually results in improved vision and long-term benefits. The results in this patient demonstrate the importance of rapid diagnosis and gross total surgical resection of CMs of the chiasm and left optic nerve.

Emerging Pharmacologic Targets in Cerebral Cavernous Malformation and Potential Strategies to Alter the Natural History of a Difficult Disease: A Review

Importance

Cerebral cavernous malformations (CCMs) are vascular lesions of the brain that may lead to hemorrhage, seizures, and neurologic deficits. Most are linked to loss-of-function mutations in 1 of 3 genes, namely CCM1 (originally called KRIT1), CCM2 (MGC4607), or CCM3 (PDCD10), that can either occur as sporadic events or are inherited in an autosomal dominant pattern with incomplete penetrance. Familial forms originate from germline mutations, often have multiple intracranial lesions that grow in size and number over time, and cause an earlier and more severe presentation. Despite active preclinical research on a few pharmacologic agents, clinical translation has been slow. Open surgery and, in some cases, stereotactic radiosurgery remain the only effective treatments, but these options are limited by lesion accessibility and are associated with nonnegligible rates of morbidity and mortality.

Observations

We discuss the limits of CCM management and introduce findings from in vitro and in vivo studies that provide insight into CCM pathogenesis and indicate molecular mechanisms as potential therapeutic targets. These studies report dysregulated cellular pathways shared between CCM, cardiovascular diseases, and cancer. They also suggest the potential effectiveness of proper drug repurposing in association with, or as an alternative to, targeted interventions.

Conclusions and Relevance

We propose methods to exploit specific molecular pathways to design patient-tailored therapeutic approaches in CCM, with the aim to alter its natural progression. In this scenario, the lack of effective pharmacologic options remains a critical barrier that poses an unfulfilled and urgent medical need.

Serine phosphorylation of the small phosphoprotein ICAP1 inhibits its nuclear accumulation

Nuclear accumulation of the small phosphoprotein integrin cytoplasmic domain-associated protein-1 (ICAP1) results in recruitment of its binding partner, Krev/Rap1 interaction trapped-1 (KRIT1), to the nucleus. KRIT1 loss is the most common cause of cerebral cavernous malformation, a neurovascular dysplasia resulting in dilated, thin-walled vessels that tend to rupture, increasing the risk for hemorrhagic stroke. KRIT1's nuclear roles are unknown, but it is known to function as a scaffolding or adaptor protein at cell-cell junctions and in the cytosol, supporting normal blood vessel integrity and development. As ICAP1 controls KRIT1 subcellular localization, presumably influencing KRIT1 function, in this work, we investigated the signals that regulate ICAP1 and, hence, KRIT1 nuclear localization. ICAP1 contains a nuclear localization signal within an unstructured, N-terminal region that is rich in serine and threonine residues, several of which are reportedly phosphorylated. Using quantitative microscopy, we revealed that phosphorylation-mimicking substitutions at Ser-10, or to a lesser extent at Ser-25, within this N-terminal region inhibit ICAP1 nuclear accumulation. Conversely, phosphorylation-blocking substitutions at these sites enhanced ICAP1 nuclear accumulation. We further demonstrate that p21-activated kinase 4 (PAK4) can phosphorylate ICAP1 at Ser-10 both in vitro and in cultured cells and that active PAK4 inhibits ICAP1 nuclear accumulation in a Ser-10-dependent manner. Finally, we show that ICAP1 phosphorylation controls nuclear localization of the ICAP1-KRIT1 complex. We conclude that serine phosphorylation within the ICAP1 N-terminal region can prevent nuclear ICAP1 accumulation, providing a mechanism that regulates KRIT1 localization and signaling, potentially influencing vascular development.

Cerebral Cavernous Malformation Proteins in Barrier Maintenance and Regulation

Cerebral cavernous malformation (CCM) is a disease characterized by mulberry shaped clusters of dilated microvessels, primarily in the central nervous system. Such lesions can cause seizures, headaches, and stroke from brain bleeding. Loss-of-function germline and somatic mutations of a group of genes, called CCM genes, have been attributed to disease pathogenesis. In this review, we discuss the impact of CCM gene encoded proteins on cellular signaling, barrier function of endothelium and epithelium, and their contribution to CCM and potentially other diseases.

Immunofluorescence of Cell-Cell and Cell-Extracellular Matrix Adhesive Defects in In Vitro Endothelial CCM Model: Juxtacrine Role of Mutant Extracellular Matrix on Wild-Type Endothelial Cells

Endothelial cells lining cerebral cavernous malformations (CCM) present strong adhesive and mechanical defects. Increased cell contractility is a driver to the onset and the expansion of the CCM lesions. 2D in vitro endothelial models have been developed from either endothelial cells isolated from ccm1-3 knock-out mice or CCM1-3-silenced primary endothelial cells. These in vitro models faithfully recapitulate the adhesive and contractile defects of the CCM-deficient endothelial cells such as increased cell-extracellular matrix (ECM) adhesion through β1 integrin-anchored actin stress fibers, abnormal remodeling of the ECM, and destabilized VE-cadherin-dependent cell-cell junctions. Using such 2D in vitro CCM models, we have shown that the ECM remodeled by CCM-depleted endothelial cells can propagate CCM-like adhesive defects to wild-type endothelial cells, a process potentially pertinent to CCM lesion expansion. Here, we detail methods for studying the morphology of focal adhesions, actomyosin cytoskeleton, and VE-cadherin-dependent Adherens junctions by immunofluorescence and morphometric analyses. Moreover, we detail the protocols to produce and purify remodeled ECM and to test its effect on endothelial cell adhesion.

RNA-Sequencing Highlights Inflammation and Impaired Integrity of the Vascular Wall in Brain Arteriovenous Malformations

Background and Purpose—

Interventional treatment of unruptured brain arteriovenous malformations (BAVMs) has become increasingly controversial. Because medical therapy is still lacking, we aimed to obtain insight into the disease mechanisms implicated in BAVMs and to identify potential targets for medical treatment to prevent rupture of a BAVM.

Methods—

We used next-generation RNA sequencing to identify differential expression on a transcriptome-wide level comparing tissue samples of 12 BAVMs to 16 intracranial control arteries. We identified differentially expressed genes by negative binominal generalized log-linear regression (false discovery rate corrected P <0.05). We selected 10 genes for validation using droplet digital polymerase chain reaction. We performed functional pathway analysis accounting for potential gene-length bias, to establish enhancement of biological pathways involved in BAVMs. We further assessed which Gene Ontology terms were enriched.

Results—

We found 736 upregulated genes in BAVMs including genes implicated in the cytoskeletal machinery and cell-migration and genes encoding for inflammatory cytokines and secretory products of neutrophils and macrophages. Furthermore, we found 498 genes downregulated including genes implicated in extracellular matrix composition, the binary angiopoietin-TIE system, and TGF (transforming growth factor)-β signaling. We confirmed the differential expression of top 10 ranked genes. Functional pathway analysis showed enrichment of the protein digestion and absorption pathway (false discovery rate-adjusted P =1.70×10 −2 ). We identified 47 enriched Gene Ontology terms (false discovery rate-adjusted P <0.05) implicated in cytoskeleton network, cell-migration, endoplasmic reticulum, transmembrane transport, and extracellular matrix composition.

Conclusions—

Our genome-wide RNA-sequencing study points to involvement of inflammatory mediators, loss of cerebrovascular quiescence, and impaired integrity of the vascular wall in the pathophysiology of BAVMs. Our study may lend support to potential receptivity of BAVMs to medical therapeutics, including those promoting vessel maturation, and anti-inflammatory and immune-modifying drugs.

Risk factors for hemorrhage of brain arteriovenous malformation

Patients with brain arteriovenous malformation (bAVM) are at risk of intracranial hemorrhage (ICH). Overall, bAVM accounts for 25% of hemorrhagic strokes in adults <50 years of age. The treatment of unruptured bAVMs has become controversial, because the natural history of these patients may be less morbid than invasive therapies. Available treatments include observation, surgical resection, endovascular embolization, stereotactic radiosurgery, or combination thereof. Knowing the risk factors for bAVM hemorrhage is crucial for selecting appropriate therapeutic strategies. In this review, we discussed several biological risk factors, which may contribute to bAVM hemorrhage.

Cavernous angiomas: deconstructing a neurosurgical disease

Cavernous angioma (CA) is also known as cavernoma, cavernous hemangioma, and cerebral cavernous malformation (CCM) (National Library of Medicine Medical Subject heading unique ID D006392). In its sporadic form, CA occurs as a solitary hemorrhagic vascular lesion or as clustered lesions associated with a developmental venous anomaly. In its autosomal dominant familial form (Online Mendelian Inheritance in Man #116860), CA is caused by a heterozygous germline loss-of-function mutation in one of three genes-CCM1/KRIT1, CCM2/Malcavernin, and CCM3/PDCD10-causing multifocal lesions throughout the brain and spinal cord.In this paper, the authors review the cardinal features of CA's disease pathology and clinical radiological features. They summarize key aspects of CA's natural history and broad elements of evidence-based management guidelines, including surgery. The authors also discuss evidence of similar genetic defects in sporadic and familial lesions, consequences of CCM gene loss in different tissues at various stages of development, and implications regarding the pathobiology of CAs.The concept of CA with symptomatic hemorrhage (CASH) is presented as well as its relevance to clinical care and research in the field. Pathobiological mechanisms related to CA include inflammation and immune-mediated processes, angiogenesis and vascular permeability, microbiome driven factors, and lesional anticoagulant domains. These mechanisms have motivated the development of imaging and plasma biomarkers of relevant disease behavior and promising therapeutic targets.The spectrum of discoveries about CA and their implications endorse CA as a paradigm for deconstructing a neurosurgical disease.

Endothelial cell clonal expansion in the development of cerebral cavernous malformations

Cerebral cavernous malformation (CCM) is a neurovascular familial or sporadic disease that is characterised by capillary-venous cavernomas, and is due to loss-of-function mutations to any one of three CCM genes. Familial CCM follows a two-hit mechanism similar to that of tumour suppressor genes, while in sporadic cavernomas only a small fraction of endothelial cells shows mutated CCM genes. We reported that in mouse models and in human patients, endothelial cells lining the lesions have different features from the surrounding endothelium, as they express mesenchymal/stem-cell markers. Here we show that cavernomas originate from clonal expansion of few Ccm3-null endothelial cells that express mesenchymal/stem-cell markers. These cells then attract surrounding wild-type endothelial cells, inducing them to express mesenchymal/stem-cell markers and to contribute to cavernoma growth. These characteristics of Ccm3-null cells are reminiscent of the tumour-initiating cells that are responsible for tumour growth. Our data support the concept that CCM has benign tumour characteristics.

Cerebral cavernous malformation is a vascular disease characterized by capillary-venous cavernomas in the central nervous system. Here the authors show that cavernomas display benign tumor characteristics and originate from the clonal expansion of mutated endothelial progenitors which can attract surrounding wild-type cells, inducing their mesenchymal transition and leading to growth of the cavernoma.

Defective vascular signaling & prospective therapeutic targets in brain arteriovenous malformations

The neurovascular unit is composed of endothelial cells, vascular smooth muscle cells, pericytes, astrocytes and neurons. Through tightly regulated multi-directional cell signaling, the neurovascular unit is responsible for the numerous functionalities of the cerebrovasculature - including the regulation of molecular and cellular transport across the blood-brain barrier, angiogenesis, blood flow responses to brain activation and neuroinflammation. Historically, the study of the brain vasculature focused on endothelial cells; however, recent work has demonstrated that pericytes and vascular smooth muscle cells - collectively known as mural cells - play critical roles in many of these functions. Given this emerging data, a more complete mechanistic understanding of the cellular basis of brain vascular malformations is needed. In this review, we examine the integrated functions and signaling within the neurovascular unit necessary for normal cerebrovascular structure and function. We then describe the role of aberrant cell signaling within the neurovascular unit in brain arteriovenous malformations and identify how these pathways may be targeted therapeutically to eradicate or stabilize these lesions.

Enhancing vascular visualization in laser speckle contrast imaging of blood flow using multi-focus image fusion

Laser speckle contrast imaging (LSCI) is a full-field optical imaging method for monitoring blood flow and vascular morphology with high spatiotemporal resolution. However, due to the limited depth of field of optical system, it is difficult to capture a clear blood flow image with all blood vessels focused, especially for the non-planar biological tissues. In this study, a multi-focus image fusion method based on contourlet transform is introduced to reduce the misfocus effects in LSCI. The experimental results suggest that this method can provide an all-in-focus blood flow image, which is convenient to observe the blood vessels.

Usefulness of Ultrasound-Guided Microsurgery in Cavernous Angioma Removal

BACKGROUND

Primary elements of surgical treatment of cavernous angiomas (CAs) are precise lesion identification and optimal trajectory determination. Navigation techniques allow for better results compared to microsurgery alone. In this study, we examined the benefits of intraoperative ultrasound (IOUS) use as an adjunct to standard localization systems.

METHODS

We retrospectively analyzed 59 CAs, comparing outcomes in 2 groups of patients: 34 who underwent frame-based or frameless navigation-assisted microsurgery (no-IOUS group) and 25 who underwent IOUS-guided microsurgery associated with these techniques (IOUS group).

RESULTS

The use of IOUS did not significantly increase the surgery time (mean, 172 ± 1.7 minutes in the IOUS group and 192.6 ± 11.5 in no-IOUS group; P = 0.08). In all 25 patients in the IOUS group, IOUS allowed for ready identification of CA as a hyperechoic mass. At the last follow-up (mean, 41.7 ± 3.5 months postsurgery), 95.2% of the IOUS group and 80.8% of the no-IOUS group had a modified Rankin Scale score of 0-1 and an Extended Glasgow Outcome Scale score of 7-8 (P = 0.2), with 100% and 64%, respectively, included in Engel outcome scale class IA (P = 0.006). Complete removal, as confirmed on postoperative magnetic resonance imaging, was achieved in all patients in the IOUS group and in almost all (97.1%; P = 0.4) patients in the no-IOUS group.

CONCLUSIONS

IOUS is a valid tool for the intraoperative identification of CAs. Implementation of standard localization methods with IOUS guidance was associated with complete resection in all cases, without increasing surgical time. Compared with microsurgery without IOUS guidance, long-term functional outcomes showed better trends, and the epilepsy-free rate was significantly higher.

Supratentorial cavernous malformations adjacent to the corticospinal tract: surgical outcomes and predictive value of diffusion tensor imaging findings

OBJECTIVE

Diffusion tensor imaging (DTI) findings may facilitate clinical decision making in patients with supratentorial cavernous malformations adjacent to the corticospinal tract (CST-CMs). The objective of this study was to determine the predictive value of preoperative DTI findings for surgical outcomes in patients with CST-CMs.

METHODS

A prospectively maintained database of patients with CM referred to the authors' hospital between September 2012 and October 2015 was reviewed to identify all consecutive surgically treated patients with CST-CM. All patients had undergone sagittal T1-weighted anatomical imaging and DTI before surgery. Both DTI findings and clinical characteristics of the patients and lesions were analyzed with respect to surgery-related motor deficits. DTI findings included lesion-to-CST distance (LCD) and the alteration (i.e., deviation, interruption, or degeneration due to the CM) of CST on preoperative DTI images. Surgery-related motor deficits at 1 week and the last clinic visit (≥ 3 months) after surgery were defined as short-term and long-term deficits, respectively. Preoperative and final modified Rankin Scale scores were also analyzed to identify the surgical outcomes in these patients.

RESULTS

A total of 56 patients with 56 CST-CMs were included in this study. The mean LCD was 3.9 ± 3.2 mm, and alterations of the CST were detected in 20 (36.7%) patients. One week after surgery, 21 (37.5%) patients had short-term surgery-related motor deficits, but only 14 (25.0%) patients had long term deficits at the last clinical visit. The mean patient follow-up was 14.7 ± 10.1 months. The difference between preoperative and final modified Rankin Scale scores was not statistically significant (p = 0.490). Multivariate analysis showed that both short-term (p < 0.001) and long-term (p = 0.002) surgery-related motor deficits were significantly associated with LCD. Receiver operating characteristic (ROC) curve results were as follows: for short-term surgery-related motor deficits, the area under the ROC curve (AUC) was 0.860, and the cutoff point was LCD = 2.55 mm; for long-term deficits, the AUC was 0.894, and the cutoff point was LCD = 2.30 mm. Both univariate (p = 0.012) and multivariate (p = 0.049) analyses revealed that CST alteration on preoperative DTI was significantly correlated with short-term surgery-related motor deficits. On univariate analysis, deep location of the CST-CMs was significantly correlated with long-term motor deficits (p = 0.016). Deep location of the CST-CMs had a trend toward significance with long-term motor deficits on the multivariate analysis (p = 0.060).

CONCLUSIONS

To facilitate clinical practice, the authors propose that 3.00 mm (2.55 to ∼3.00 mm) may be the safe LCD for surgery in patients with CST-CMs. A CST alteration on preoperative DTI and a deep location of the CST-CM may be risk factors for short- and long-term surgery-related motor deficits, respectively. A randomized controlled trial is needed to demonstrate the predictive value of preoperative DTI findings on surgical outcomes in patients with CST-CMs in future studies.

Ascending Spinal Cord Infarction Secondary to Recurrent Spinal Cord Cavernous Malformation Hemorrhage

We report a case of a 58-year-old Hispanic man who developed ascending paraparesis over several weeks secondary to recurrent hemorrhages and resulting in spinal cord ischemia from a low thoracic spinal cord cavernous malformation. The patient's deterioration was attributed to recurrent hemorrhage of a thoracic intramedullary cavernous malformation at T11 resulting in vascular congestion and spinal cord ischemia. The patient was found to have a heterozygous mutation on exon 13 of gene KRIT1, which was consistent with autosomal dominant familial cerebral cavernous malformations. Expedited surgical intervention potentially could have prevented this patient's progressive paraplegia.

Epidemiology of cavernous malformations

Cavernous malformations, accounting for approximately 5-15% of all vascular abnormalities in the central nervous system, are angiographically occult lesions which most often present with seizures, rather than acute hemorrhage. Widely variable across populations, the incidence of cavernous malformations has been reported to be 0.15-0.56 per 100 000 persons per year, with an annual hemorrhage rate of 0.6-11% per patient-year. Seen in 0.17-0.9% of the population, up to one-half are familial, and at least three gene loci have been associated with a familial form, more common among Hispanic Americans. Most cavernous malformations are supratentorial, with 10-23% in the posterior fossa, and approximately 5% found in the spine.

Pathology of cavernous malformations

Cavernous malformations (CMs) are low-pressure angiographically occult lesions, composed of blood-filled sinusoidal locules known as "caverns." Although these lesions were once believed to be congenital in nature, there is compelling evidence to support de novo formation of CMs as well. They can occur as sporadic lesions or be inherited in an autosomal-dominant phenotype in familial forms of the disease. The pathophysiology of CMs is commonly believed to be due to abnormal vascular pathology. Three genes, CCM1, CCM2, and CCM3, have been extensively studied for their role in vascular pathology, resulting in abnormal angiogenesis and compromising the structural integrity of vessel endothelial cell. The expression of growth factors has been researched to gain insight into the dynamic behavior of CM lesions. Gross and microscopic images are utilized in this chapter to illustrate the pathologic findings of these lesions. Ultrastructural analysis demonstrates the aberrations in CM endothelial cells and structural integrity that may provide better understanding into how and why these lesions have a propensity to hemorrhage.

B-Cell Depletion Reduces the Maturation of Cerebral Cavernous Malformations in Murine Models

Cerebral cavernous malformations (CCMs) are relatively common vascular malformations, characterized by increased Rho kinase (ROCK) activity, vascular hyper-permeability and the presence of blood degradation products including non-heme iron. Previous studies revealed robust inflammatory cell infiltration, selective synthesis of IgG, in situ antigen driven B-cell clonal expansion, and deposition of immune complexes and complement proteins within CCM lesions. We aimed to evaluate the impact of suppressing the immune response on the formation and maturation of CCM lesions, as well as lesional iron deposition and ROCK activity. Two murine models of heterozygous Ccm3 (Pdcd10), which spontaneously develop CCM lesions with severe and milder phenotypes, were either untreated or received anti-mouse BR3 to deplete B cells. Brains from anti-mouse BR3-treated mice exhibited significantly fewer mature CCM lesions and smaller lesions compared to untreated mice. B cell depletion halted the progression of lesions into mature stage 2 lesions but did not prevent their genesis. Non-heme iron deposition and ROCK activity was decreased in lesions of B cell depleted mice. This represents the first report of the therapeutic benefit of B-cell depletion in the development and progression of CCMs, and provides a proof of principle that B cells play a critical role in CCM lesion genesis and maturation. These findings add biologics to the list of potential therapeutic agents for CCM disease. Future studies would characterize the putative antigenic trigger and further define the mechanism of immune response in the lesions.

PDCD10 (CCM3) regulates brain endothelial barrier integrity in cerebral cavernous malformation type 3: role of CCM3-ERK1/2-cortactin cross-talk

Impairment of brain endothelial barrier integrity is critical for cerebral cavernous malformation (CCM) lesion development. The current study investigates changes in tight junction (TJ) complex organization when PDCD10 (CCM3) is mutated/depleted in human brain endothelial cells. Analysis of lesions with CCM3 mutation and brain endothelial cells transfected with CCM3 siRNA (CCM3-knockdown) showed little or no increase in TJ transmembrane and scaffolding proteins mRNA expression, but proteins levels were generally decreased. CCM3-knockdown cells had a redistribution of claudin-5 and occludin from the membrane to the cytosol with no alterations in protein turnover but with diminished protein-protein interactions with ZO-1 and ZO-1 interaction with the actin cytoskeleton. The most profound effect of CCM3 mutation/depletion was on an actin-binding protein, cortactin. CCM3 depletion caused cortactin Ser-phosphorylation, dissociation from ZO-1 and actin, redistribution to the cytosol and degradation. This affected cortical actin ring organization, TJ complex stability and consequently barrier integrity, with constant hyperpermeability to inulin. A potential link between CCM3 depletion and altered cortactin was tonic activation of MAP kinase ERK1/2. ERK1/2 inhibition increased cortactin expression and incorporation into the TJ complex and improved barrier integrity. This study highlights the potential role of CCM3 in regulating TJ complex organization and brain endothelial barrier permeability.

Vascular permeability in cerebral cavernous malformations

Patients with the familial form of cerebral cavernous malformations (CCMs) are haploinsufficient for the CCM1, CCM2, or CCM3 gene. Loss of corresponding CCM proteins increases RhoA kinase-mediated endothelial permeability in vitro, and in mouse brains in vivo. A prospective case-controlled observational study investigated whether the brains of human subjects with familial CCM show vascular hyperpermeability by dynamic contrast-enhanced quantitative perfusion magnetic resonance imaging, in comparison with CCM cases without familial disease, and whether lesional or brain vascular permeability correlates with CCM disease activity. Permeability in white matter far (WMF) from lesions was significantly greater in familial than in sporadic cases, but was similar in CCM lesions. Permeability in WMF increased with age in sporadic patients, but not in familial cases. Patients with more aggressive familial CCM disease had greater WMF permeability compared to those with milder disease phenotype, but similar lesion permeability. Subjects receiving statin medications for routine cardiovascular indications had a trend of lower WMF, but not lesion, permeability. This is the first demonstration of brain vascular hyperpermeability in humans with an autosomal dominant disease, as predicted mechanistically. Brain permeability, more than lesion permeability, may serve as a biomarker of CCM disease activity, and help calibrate potential drug therapy.

Role of intraoperative indocyanine green video-angiography to identify small, posterior fossa arteriovenous malformations mimicking cavernous angiomas. Technical report and review of the literature on common features of these cerebral vascular malformations

OBJECTIVE

To illustrate the usefulness of intraoperative indocyanine green videoangiography (ICG-VA) to identify the nidus and feeders of a small cerebellar AVM resembling a cavernous hemangioma. To review the unique features regarding the overlay between these two vascular malformations and to highlight the importance to identify with ICG-VA, and treat accordingly, the arterial and venous vessels of the AVM.

METHODS

A 36-year old man presented with bilateral cerebellar hemorrhage. MRI was equivocal in showing an underlying vascular malformation but angiography demonstrated a small, Spetzler-Martin grade I AVM. Surgical resection of the AVM with the aid of intraoperative ICG-VA was performed. After hematoma evacuation, pre-resection ICG-VA did not reveal tortuous arterial and venous vessels in keeping with a typical AVM but rather an unusual blackberry-like image resembling a cavernous hemangioma, with tiny surrounding vessels. Such intraoperative appearance, which could also be the consequence of a "leakage" of fluorescent dye from the nidal pathological vessels, with absent blood-brain barrier, into the surrounding parenchymal pathological capillary network, is important to be recognized as an unusual AVM appearance.

RESULTS

Post-resection ICG-VA confirmed the AVM removal, as also shown by postoperative and 3-month follow-up DSAs.

CONCLUSIONS

Despite technical limitations associated with ICG-VA in post-hemorrhage AVMs, this case together with the intraoperative video, demonstrates the useful role of ICG-VA in identifying small AVMs with peculiar features.

CCM1 and the second life of proteins in adhesion complexes

It is well recognized that a number of proteins present within adhesion complexes perform discrete signaling functions outside these adhesion complexes, including transcriptional control. In this respect, β-catenin is a well-known example of an adhesion protein present both in cadherin complexes and in the nucleus where it regulates the TCF transcription factor. Here we discuss nuclear functions of adhesion complex proteins with a special focus on the CCM-1/KRIT-1 protein, which may turn out to be yet another adhesion complex protein with a second life.

Non-schwannomatosis lesions of the internal acoustic meatus-a diagnostic challenge and management: a series report of nine cases

Vestibular schwannomas (VS) are the most common lesions of cerebellopontine angle (CPA) corresponding to 76-91 % of the cases. Usually, these lesions present typical CT and MRI findings. Non-schwannomatous tumors restricted to the internal auditory meatus (IAM) are rare and their preoperative radiological diagnosis may be difficult. This article describes nine surgically treated intrameatal non-schwannomatous lesions (NSL) and reviews the literature. In the last 16 years, a total of 471 patients with diagnosis of VS were operated on in our department. Preoperatively, 42 patients had diagnosis of intrameatal schwannomas, but surgery revealed in nine cases NSL (3 meningiomas, 3 arachnoiditis/neuritis, 1 cavernoma, 1 vascular loop, and 1 arachnoid cyst). Most frequent symptoms presented by patients with NSL were hearing loss 89 % (8/9) of patients, tinnitus 78 % (7/9), and vertigo 33 % (3/9). Almost all lesions (8/9) presented MRI findings of isointense signal in T1W with contrast enhancement. The only exception was the arachnoid cyst with intracystic bleeding, which was hyperintense in T1W that is not enhanced with contrast. This series shows an occurrence of 21.4 % of non-schwannomatous tumors in 42 cases of lesions restricted to the IAM. Whenever a solely intrameatal enhanced tumor is detected, it is necessary to think about other diagnostic possibilities rather than VS. Therapeutic management may be changed, specially if radiosurgical treatment is considered.

Cerebral Cavernous Malformation-1 Protein Controls DLL4-Notch3 Signaling Between the Endothelium and Pericytes

BACKGROUND AND PURPOSE

Cerebral cavernous malformation (CCM) is a neurovascular dysplasia characterized by conglomerates of enlarged endothelial channels in the central nervous system, which are almost devoid of pericytes or smooth muscle cells. This disease is caused by loss-of-function mutations in CCM1, CCM2, or CCM3 genes in endothelial cells, making blood vessels highly susceptible to angiogenic stimuli. CCM1- and CCM3-silenced endothelial cells have a reduced expression of the Notch ligand Delta-like 4 (DLL4) resulting in impaired Notch signaling and irregular sprouting angiogenesis. This study aimed to address if DLL4, which is exclusively expressed on endothelial cells, may influence interactions of endothelial cells with pericytes, which express Notch3 as the predominant Notch receptor.

METHODS

Genetic manipulation of primary human endothelial cells and brain pericytes. Transgenic mouse models were also used.

RESULTS

Endothelial cell-specific ablation of Ccm1 and Ccm2 in different mouse models led to the formation of CCM-like lesions, which were poorly covered by periendothelial cells. CCM1 silencing in endothelial cells caused decreased Notch3 activity in cocultured pericytes. DLL4 proteins stimulated Notch3 receptors on human brain pericytes. Active Notch3 induced expression of PDGFRB2, N-Cadherin, HBEGF, TGFB1, NG2, and S1P genes. Notch3 signaling in pericytes enhanced the adhesion strength of pericytes to endothelial cells, limited their migratory and invasive behavior, and enhanced their antiangiogenic function. Pericytes silenced for Notch3 expression were more motile and could not efficiently repress angiogenesis.

CONCLUSIONS

The data suggest that Notch signaling in pericytes is important to maintain the quiescent vascular phenotype. Deregulated Notch signaling may, therefore, contribute to the pathogenesis of CCM.

Rho kinase as a target for cerebral vascular disorders

The development of novel pharmaceutical treatments for disorders of the cerebral vasculature is a serious unmet medical need. These vascular disorders are typified by a disruption in the delicate Rho signaling equilibrium within the blood vessel wall. In particular, Rho kinase overactivation in the smooth muscle and endothelial layers of the vessel wall results in cytoskeletal modifications that lead to reduced vascular integrity and abnormal vascular growth. Rho kinase is thus a promising target for the treatment of cerebral vascular disorders. Indeed, preclinical studies indicate that Rho kinase inhibition may reduce the formation/growth/rupture of both intracranial aneurysms and cerebral cavernous malformations.

Surgical management of cavernous malformation of the optic nerve with canalicular extension

Background:

Cavernous malformations arising in a single optic nerves paring the chiasm (intracranial prechiasmatic optic nerve) and expanding into the optic canal are extremely rare lesions. Published series or case reports regarding the surgical removal of these vascular malformations within this specific location are scarce.

Case Description:

We present the first case to be published, of an intracranial optic nerve cavernous malformation with a contiguous canalicular component that was totally and successfully removed through a microsurgical pterional approach with excellent clinical outcome.

Conclusion:

This pathology should always be considered in the differential diagnosis of optic neuropathy and visual loss. Early detection and surgical proposal are mandatory, warranting the prevention of permanent damage to visual pathways. Radical resection is challenging, but usually curative and associated with favorable visual outcomes.

Surgical outcomes and natural history of intramedullary spinal cord cavernous malformations: a single-center series and meta-analysis of individual patient data

Object

Information pertaining to the natural history of intramedullary spinal cord cavernous malformations (ISCCMs) and patient outcomes after surgery is scarce. To evaluate factors associated with favorable outcomes for patients with surgically and conservatively managed ISCCMs, the authors performed a systematic review and metaanalysis of the literature. In addition, they included their single-center series of ISCCMs.

Methods

The authors searched MEDLINE, EMBASE, CINAHL, Google Scholar, and The Cochrane Library for studies published through June 2013 that reported cases of ISCCMs. Data from all eligible studies were used to examine the epidemiology, clinical features, and neurological outcomes of patients with surgically managed and conservatively treated ISCCMs. To evaluate several variables as predictors of favorable neurological outcomes, the authors conducted a meta-analysis of individual patient data and performed univariate and multivariate logistic regression analyses. Variables included patient age, patient sex, lesion spinal level, lesion size, cerebral cavernomas, family history of cavernous malformations, clinical course, presenting symptoms, treatment strategy (operative or conservative), symptom duration, surgical approach, spinal location, and extent of resection. In addition, they performed a meta-analysis to determine a pooled estimate of the annual hemorrhage rate of ISCCMs.

Results

Eligibility criteria were met by 40 studies, totaling 632 patients, including the authors' institutional series of 24 patients. Mean patient age was 39.1 years (range 2–80 years), and the male-to-female ratio was 1.1:1. Spinal levels of cavernomas were cervical (38%), cervicothoracic (2.4%), thoracic (55.2%), thoracolumbar (0.6%), lumbar (2.1%), and conus medullaris (1.7%). Average cavernoma size was 9.2 mm. Associated cerebral cavernomas occurred in 16.5% of patients, and a family history of cavernous malformation was found for 11.9% of evaluated patients. Clinical course was acute with stepwise progression for 45.4% of patients and slowly progressive for 54.6%. Symptoms were motor (60.5%), sensory (57.8%), pain (33.8%), bladder and/or bowel (23.6%), respiratory distress (0.5%), or absent (asymptomatic; 0.9%). The calculated pooled annual rate of hemorrhage was 2.1% (95% CI 1.3%–3.3%). Most (89.9%) patients underwent resection, and 10.1% underwent conservative management (observation). Outcomes were better for those who underwent resection than for those who underwent conservative management (OR 2.79, 95% CI 1.46–5.33, p = 0.002). A positive correlation with improved neurological outcomes was found for resection within 3 months of symptom onset (OR 2.11, 95% CI 1.31–3.41, p = 0.002), hemilaminectomy approach (OR 3.20, 95% CI 1.16–8.86, p = 0.03), and gross-total resection (OR 3.61, 95% CI 1.24–10.52, p = 0.02). Better outcomes were predicted by an acute clinical course (OR 1.72, 95% CI 1.10–2.68, p = 0.02) and motor symptoms (OR 1.76, 95% CI 1.08–2.86, p = 0.02); poor neurological recovery was predicted by sensory symptoms (OR 0.58, 95% CI 0.35–0.98, p = 0.04). Rates of neurological improvement after resection were no higher for patients with superficial ISCCMs than for those with deep-seated ISCCMs (OR 1.36, 95% CI 0.71–2.60, p = 0.36).

Conclusions

Intramedullary spinal cord cavernous malformations tend to be clinically progressive. The authors' findings support an operative management plan for patients with a symptomatic ISCCM. Surgical goals include gross-total resection through a more minimally invasive hemilaminectomy approach within 3 months of presentation.

Bleeding propensity of cavernous malformations: impact of tight junction alterations on the occurrence of overt hematoma

OBJECT

Endothelial tight junction (TJ) expression is mostly absent in cerebral cavernous malformations (CMs), which causes increased perilesional erythrocyte and fluid oozing. However, in a subset of CM lesions, foci of preserved TJ staining are observed along endothelial cell contacts. The clinical relevance of this finding is unclear. This study investigates the relevance of the focal TJ protein expression and its association with CM bleeding propensity.

METHODS

Immunohistochemical staining for the TJ proteins claudin-5, occludin, and ZO-1 was performed on 32 CM specimens that were resected during 2008-2010. The patients were allocated to 2 groups according to TJ protein expression, and the clinical and radiological parameters of aggressiveness were analyzed and compared. RESULTS Complete absence of TJ expression was identified in 20 specimens, and focal TJ protein expression in 12. CMs without TJ immunoreactivity were significantly larger (p = 0.022) and had a significantly greater propensity for development of frank hematomas (p = 0.028) and perilesional edema (p = 0.013). Symptom severity, multiplicity, developmental venous anomaly (DVA) presence, and CM location did not show a significant difference depending on TJ expression.

CONCLUSIONS

In a univariate analysis the authors observed significantly less propensity for frank hematomas and perilesional edema as well as smaller size in CM lesions with focal TJ expression compared with CMs without TJ expression. The observed difference in TJ protein expression might be the reason for differences in bleeding propensity of the CM lesions. Although this finding cannot be used in predictive manner at this time, it is a basis for further multivariate analyses of possible CM biological predictors.