Update: Cerebral cavernous malformation pathogenesis

Cerebral cavernous malformation pathogenesis

Genes mutated in cerebral cavernous malformation (CCM) encode proteins that modulate junction formation between vascular endothelial cells.

Most cerebral cavernous malformations are linked to loss-of-function mutations in 1 of 3 genes, namely CCM1 (originally called KRIT1), CCM2(MGC4607), or CCM3 (PDCD10).

How disruption of the CCM complex results in disease remains controversial, with numerous signalling pathways (including Rho, SMAD and Wnt/β-catenin) and processes such as endothelial mesenchymal transition (EndMT) proposed to have causal roles. CCM2 binds to MEKK3 1).

Although a role for these three genes in the formation of these intracranial vascular lesions has been established since the 1990s, additional works have further elucidated the molecular mechanisms by which mutations in these genes and the resultant aberrant proteins interact, leading to the formation of CCMs.

Therefore, it is reasonable to assume that a molecular pathway exists that requires all three proteins to function together correctly for proper cellular function. Moreover, research is demonstrating how each component protein is capable of interacting with numerous other signaling and cytoskeletal molecules allowing for a diverse range of functions in molecular signaling pathways via unique protein–protein interactions.

Significant research findings from 2000 to 2015 have further enhanced our understanding of the pathogenesis of CCM formation. The use of advanced sequencing technologies to characterize genomic mutations and the identification of new signaling pathways and protein–protein interactions have led to great strides in understanding the molecular genetics involved in the development of CCMs. However, many unanswered questions remain, and future studies are clearly needed to improve our understanding of CCM pathogenesis. “Gene to protein to disease” mechanisms involved in the pathogenesis of CCMs should shed further light on potential therapeutic targets. 2).

The Phosphoinositide 3 kinase (PI3K)/Akt pathway is known to play a major role in angiogenesis. Studies have shown that the phosphatase and tensin homologue deleted on chromosome ten (PTEN), a tumor suppressor, is an antagonist regulator of the PI3K/Akt pathway and mediates angiogenesis by activating vascular endothelial growth factor (VEGF) expression.

Understanding the biology of these proteins with respect to their signaling counterpart will help to guide future research towards new therapeutic targets applicable for CCM treatment 3).


Studies identify gain of MEKK3 signalling and KLF2/4 function as causal mechanisms for CCM pathogenesis that may be targeted to develop new CCM therapeutics 4).

CCMs arise from the loss of an adaptor complex that negatively regulates MEKK3KLF2/4 signalling in brain endothelial cells, but upstream activators of this disease pathway have yet to be identified.


Tang et al. identify endothelial Toll-like receptor 4 (TLR4) and the gut microbiome as critical stimulants of cerebral cavernous malformationformation. Activation of TLR4 by Gram negative bacteria or lipopolysaccharide accelerates CCM formation, and genetic or pharmacologic blockade of TLR4 signalling prevents CCM formation in mice. Polymorphisms that increase expression of the TLR4 gene or the gene encoding its co-receptor CD14 are associated with higher CCM lesion burden in humans. Germ-free mice are protected from CCM formation, and a single course of antibiotics permanently alters CCM susceptibility in mice. These studies identify unexpected roles for the microbiome and innate immune signalling in the pathogenesis of a cerebrovascular disease, as well as strategies for its treatment 5).


In this scenario, the lack of effective pharmacologic options remains a critical barrier that poses an unfulfilled and urgent medical need 6).

References

1) , 4)

Zhou Z, Tang AT, Wong WY, Bamezai S, Goddard LM, Shenkar R, Zhou S, Yang J, Wright AC, Foley M, Arthur JS, Whitehead KJ, Awad IA, Li DY, Zheng X, Kahn ML. Cerebral cavernous malformations arise from endothelial gain of MEKK3-KLF2/4 signalling. Nature. 2016 Apr 7;532(7597):122-6. doi: 10.1038/nature17178. Epub 2016 Mar 30. Erratum in: Nature. 2016 May 25;536(7617):488. PubMed PMID: 27027284; PubMed Central PMCID: PMC4864035.
2)

Baranoski JF, Kalani MY, Przybylowski CJ, Zabramski JM. Cerebral Cavernous Malformations: Review of the Genetic and Protein-Protein Interactions Resulting in Disease Pathogenesis. Front Surg. 2016 Nov 14;3:60. Review. PubMed PMID: 27896269.
3)

Kar S, Samii A, Bertalanffy H. PTEN/PI3K/Akt/VEGF signaling and the cross talk to KRIT1, CCM2, and PDCD10 proteins in cerebral cavernous malformations. Neurosurg Rev. 2015 Apr;38(2):229-36; discussion 236-7. doi: 10.1007/s10143-014-0597-8. Epub 2014 Nov 19. PubMed PMID: 25403688.
5)

Tang AT, Choi JP, Kotzin JJ, Yang Y, Hong CC, Hobson N, Girard R, Zeineddine HA, Lightle R, Moore T, Cao Y, Shenkar R, Chen M, Mericko P, Yang J, Li L, Tanes C, Kobuley D, Võsa U, Whitehead KJ, Li DY, Franke L, Hart B, Schwaninger M, Henao-Mejia J, Morrison L, Kim H, Awad IA, Zheng X, Kahn ML. Endothelial TLR4 and the microbiome drive cerebral cavernous malformations. Nature. 2017 May 10. doi: 10.1038/nature22075. [Epub ahead of print] PubMed PMID: 28489816.
6)

Chohan MO, Marchiò S, Morrison LA, Sidman RL, Cavenee WK, Dejana E, Yonas H, Pasqualini R, Arap W. Emerging Pharmacologic Targets in Cerebral Cavernous Malformation and Potential Strategies to Alter the Natural History of a Difficult Disease: A Review. JAMA Neurol. 2018 Nov 26. doi: 10.1001/jamaneurol.2018.3634. [Epub ahead of print] PubMed PMID: 30476961.

UptoDate: Medulla Oblongata Cavernous Malformation

Medulla Oblongata Cavernous Malformation

see also Brainstem cavernous malformation.

53 patients underwent surgical treatment for Medulla Oblongata Cavernous Malformations between 2011 and 2017 in the Beijing Tiantan Hospital with a male-to-female ratio of 1.4 and a mean age of 32.6 years. Eighteen patients (34.0%) had respiratory failure, and two patients (3.8%) had cardiac instabilities, preoperatively. The mean mRS score was 2.7 upon admission. Gross total resection was achieved in 52 patients (98.1%). Postoperatively, twenty-three patients (43.4%) had respiratory dysfunction, and sixteen patients (30.2%) had dysphagia or coughing. The mean follow-up duration was 35.7 months. At the last follow-up evaluation, the mean mRS score was 1.7, and 42 patients (84%) had favorable outcomes, with mRS scores ≤ 2. The conditions of the patients improved in 34 cases (68%), remained unchanged in 10 cases (20%), and worsened in 6 cases (12%) relative to the preoperative baseline. The independent adverse factors for long-term outcome were age ≥ 50 years old and increased time of reservation of tracheal intubationafter surgery.

Surgical treatment of CMs involving the medulla oblongata was very challenging, notably, perioperative respiratory dysfunction, with which patients tend to have unfavorable long-term outcomes, especially for elderly patients 1).


A 28-year-old man who was presented with intractable hiccup for 15 days. It developed suddenly, then aggravated progressively and did not respond to any types of medication. On magnetic resonance images, a well-demarcated and non-enhancing mass with hemorrhagic changes was noted in the left medulla oblongata. Intraoperative findings showed that the lesion was fully embedded within the brain stem and pathology confirmed the diagnosis of cavernous hemangioma. The hiccup resolved completely after the operation. Based on the presumption that the medullary cavernoma may trigger intractable hiccup by displacing or compression the hiccup arc of the dorsolateral medulla, surgical excision can eliminate the symptoms, even in the case totally buried in brainstem 2).


A 61-year-old woman presented with vertigo and swallowing disturbance. T1-weighted magnetic resonance image (MRI) showed a low intensity mass in the dorsolateral portion of the medulla oblongata, and T2-weighted imaging revealed a hemosiderin rim surrounding the lesion. Angiography showed no abnormalities. Surgery using far lateral approach achieved complete removal of the mass and hematoma. Histological examination of the surgical specimen disclosed cavernous angioma. This case suggests that direct surgery can be recommended for cavernous angioma located in the dorsal or lateral medulla oblongata to remove the hematoma and angioma if bleeding clearly provokes neurological symptoms 3).

1)

Xie MG, Xiao XR, Li D, Guo FZ, Zhang JT, Wu Z, Zhang LW. Surgical Treatment of Cavernous Malformations Involving the Medulla Oblongata: 53 Cases. World Neurosurg. 2018 Jul 4. pii: S1878-8750(18)31429-3. doi: 10.1016/j.wneu.2018.06.213. [Epub ahead of print] PubMed PMID: 29981463.
2)

Lee KH, Moon KS, Jung MY, Jung S. Intractable hiccup as the presenting symptom of cavernous hemangioma in the medulla oblongata: a case report and literature review. J Korean Neurosurg Soc. 2014 Jun;55(6):379-82. doi: 10.3340/jkns.2014.55.6.379. Epub 2014 Jun 30. PubMed PMID: 25237438; PubMed Central PMCID: PMC4166338.
3)

Abe M, Ogawa A, Yoshida Y, Hidaka T, Suzuki M, Takahashi S. Surgical removal of cavernous angioma in the medulla oblongata. A case report. Neurosurg Rev. 1997;20(2):128-31. Review. PubMed PMID: 9226673.

Update: Familial cerebral cavernous malformation

Familial cerebral cavernous malformation

Familial cerebral cavernous malformations, which account for at least 20% of all cases, can be passed from parent to child. Individuals with familial CCMs typically have multiple lesions. Familial CCMs are passed through families in an autosomal dominant manner, which means one copy of the altered gene in each cell is sufficient to cause the disorder. Each child of an individual with familial CCM has a 50% chance of inheriting the mutation.
It is an autosomal-dominant disease with incomplete penetrance. The pathogenic genes of FCCM have been mapped into three loci: CCM1/KRIT1, CCM2/MGC4607, and CCM3/PDCD10.
see https://www.ncbi.nlm.nih.gov/books/NBK1293/.


Although the clinical course is unpredictable, symptoms typically present during adult life and include headaches, focal neurological deficits, seizures, and potentially fatal stroke. In addition to neural lesions, extraneural cavernous malformations have been described in familial disease in several tissues, in particular the skin 1).


In recent years there has been an increasing amount of publications linking FCCMs with other pathology, predominantly with extracranial and intracranial mesenchymal anomalies.
When faced with an unusual clinical feature in a patient with a Mendelian disorder, the clinician may entertain the possibilities of either the feature representing a novel manifestation of that disorder or the co-existence of a different inherited condition. Here we describe an individual with a submandibular oncocytoma, pulmonary bullae and renal cysts as well as multiple cerebral cavernous malformations and haemangiomas. Genetic investigations revealed constitutional mutations in FLCN, associated with Birt-Hogg-Dubé syndrome (BHD) and CCM2, associated with familial cerebral cavernous malformation. Intracranial vascular pathologies (but not cerebral cavernous malformation) have recently been described in a number of individuals with BHD (Kapoor et al. in Fam Cancer 14:595-597, 10.1007/s10689-015-9807-y , 2015) but it is not yet clear whether they represent a genuine part of that conditions’ phenotypic spectrum. We suggest that in such instances of potentially novel clinical features, more extensive genetic testing to consider co-existing conditions should be considered where available. The increased use of next generation sequencing applications in diagnostic settings is likely to lead more cases such as this being revealed 2).


A study described an unusual association between 2 independent hereditary diseases of confirmed genetic origin-a combination that has not been described previously 3).
Rosário Marques et al. documented a novel mutation on KRIT1 gene, and the second to be reported in a Portuguese family. This mutation consists in a two nucleotide insertion (c.947_948insAC) within the exon 10, resulting in premature protein termination (p.Leu317Argfs*2). These findings will hopefully contribute to a better clinical, imaging and genetic characterisation of this disease, particularly while trying to identify the factors that influence its treatment and prognosis 4).


Yang et al., investigated the genetic mutation in a Chinese family with FCCM.
The proband is a 29-year-old female presenting with a 1-month history of headache. Brain magnetic resonance imaging (MRI) revealed multiple intracranial lesions, the largest one showing a popcorn-like appearance. After a 4-year conservative observation, there was no significant clinical or radiological progression. Family investigation found five of her relatives had multiple CCM lesions. DNA sequencing analysis in the proband disclosed a novel heterozygous deletion mutation (c.1919delT; p.Phe640SerfsX21) in exon 17 of the CCM1/KRIT1 gene. This mutation leads to a frameshift and is predicted to cause a premature termination codon to generate a truncated Krev interaction trapped-1 (Krit1) protein of 659 amino acids. The mutation segregated with the disease in the family. C The current study identified a novel CCM1/KRIT1 heterozygous deletion mutation (c.1919delT) associated with FCCM. The findings expand the CCM gene mutation profiles in the Chinese population, which will be beneficial for genetic counseling 5).


A proband was hospitalized for sudden unconsciousness and underwent surgical treatment. The section of lesions showed classical cavernous-dilated vessels without intervening brain parenchyma, and hemosiderin-laden macrophages were accumulated in the surrounding tissue. In addition, magnetic resonance imaging (MRI) showed severe multiple cerebral cavernous malformation (CCM) lesions in cerebrum, brainstem, and cerebellum in other affected subjects. Especially, for the proband’s mother, hundreds of lesions were presented, and a few lesions were found in the expanded lateral ventricle (Evans’ index =0.33). Moreover, she showed the similar symptoms of hydrocephalus, including headache, dizziness, and diplopia. It was extremely rare in previous reports. To date, the genetic alterations leading to FCCM in Chinese population remain largely unknown. We investigated genetic defects of this family. Sequence analyses disclosed a novel heterozygous insertion mutation (c.1896_1897insT; p.Pro633SerfsTer22) in KRIT1/CCM1. Moreover, our real-time PCR results revealed that the mRNA level of KRIT1/CCM1 were significantly decreased in FCCM subjects (CCM family =0.42 ± 0.20 vs. healthy control =1.01 ± 0.16, P = 0.004). It indicated that this mutation could cause KRIT1/CCM1 functional mRNA deficiency. It may be closely related with the pathogenesis of FCCM. Our findings provided a new gene mutation profile which will be of great significance in early diagnosis and appropriate clinical surveillance of FCCM patients 6).

Case series

Fifty-seven familial CCM type-1 patients were included in this institutional review board-approved study. Baseline SWI (n = 57) and follow-up SWI (n = 17) were performed on a 3T Siemens MR scanner with lesions counted manually by the study neuroradiologist. We modified an algorithm for detecting radiation-induced microbleeds on SWI images in brain tumor patients, using a training set of 22 manually delineated CCM microbleeds from two random scans. Manual and automated counts were compared using linear regression with robust standard errors, intra-class correlation (ICC), and paired t tests. A validation analysis comparing the automated counting algorithm and a consensus read from two neuroradiologists was used to calculate sensitivity, the proportion of microbleeds correctly identified by the automated algorithm. RESULTS: Automated and manual microbleed counts were in strong agreement in both baseline (ICC = 0.95, p < 0.001) and longitudinal (ICC = 0.88, p < 0.001) analyses, with no significant difference between average counts (baseline p = 0.11, longitudinal p = 0.29). In the validation analysis, the algorithm correctly identified 662 of 1325 microbleeds (sensitivity=50%), again with strong agreement between approaches (ICC = 0.77, p < 0.001). CONCLUSION: The automated algorithm is a consistent method for counting microbleeds in familial CCM patients that can facilitate lesion quantification and tracking 7).


The authors retrospectively reviewed abdominal CT scans in 38 patients with fCCM, 38 unaffected age- and sex-matched control subjects, and 13 patients with sporadic, nonfamilial cerebral cavernous malformation (CCM). The size, number, and laterality of calcifications and the morphologic characteristics of the adrenal gland were recorded. Brain lesion count was recorded from brain magnetic resonance (MR) imaging in patients with fCCM. The prevalence of adrenal calcifications in patients with fCCM was compared with that in unaffected control subjects and those with sporadic CCM by using the Fisher exact test. Additional analyses were performed to determine whether age and brain lesion count were associated with adrenal findings in patients with fCCM. Results Small focal calcifications (SFCs) (≤5 mm) were seen in one or both adrenal glands in 19 of the 38 patients with fCCM (50%), compared with 0 of the 38 unaffected control subjects (P < .001) and 0 of the 13 subjects with sporadic CCM (P = .001). Adrenal calcifications in patients with fCCM were more frequently left sided, with 17 of 19 patients having more SFCs in the left adrenal gland than the right adrenal gland and 50 of the 61 observed SFCs (82%) found in the left adrenal gland. No subjects had SFCs on the right side only. In patients with fCCM, the presence of SFCs showed a positive correlation with age (P < .001) and number of brain lesions (P < .001). Conclusion Adrenal calcifications identified on CT scans are common in patients with fCCM and may be a clinically silent manifestation of disease 8).
1)

de Vos IJ, Vreeburg M, Koek GH, van Steensel MA. Review of familial cerebral cavernous malformations and report of seven additional families. Am J Med Genet A. 2017 Feb;173(2):338-351. doi: 10.1002/ajmg.a.38028. Epub 2016 Oct 28. Review. PubMed PMID: 27792856.
2)

Whitworth J, Stausbøl-Grøn B, Skytte AB. Genetically diagnosed Birt-Hogg-Dubé syndrome and familial cerebral cavernous malformations in the same individual: a case report. Fam Cancer. 2017 Jan;16(1):139-142. doi: 10.1007/s10689-016-9928-y. PubMed PMID: 27722904; PubMed Central PMCID: PMC5243871.
3)

Belousova OB, Okishev DN, Ignatova TM, Balashova MS, Boulygina ES. Hereditary Multiple Cerebral Cavernous Malformations Associated with Wilson Disease and Multiple Lipomatosis. World Neurosurg. 2017 Sep;105:1034.e1-1034.e6. doi: 10.1016/j.wneu.2017.06.002. Epub 2017 Jun 8. PubMed PMID: 28602929.
4)

Rosário Marques I, Antunes F, Ferreira N, Grunho M. Familial cerebral cavernous malformation: Report of a novel KRIT1 mutation in a Portuguese family. Seizure. 2017 Nov 10;53:72-74. doi: 10.1016/j.seizure.2017.10.020. [Epub ahead of print] PubMed PMID: 29145060.
5)

Yang C, Wu B, Zhong H, Li Y, Zheng X, Xu Y. A novel CCM1/KRIT1 heterozygous deletion mutation (c.1919delT) in a Chinese family with familial cerebral cavernous malformation. Clin Neurol Neurosurg. 2017 Nov 20;164:44-46. doi: 10.1016/j.clineuro.2017.11.005. [Epub ahead of print] PubMed PMID: 29169046.
6)

Wang H, Pan Y, Zhang Z, Li X, Xu Z, Suo Y, Li W, Wang Y. A Novel KRIT1/CCM1 Gene Insertion Mutation Associated with Cerebral Cavernous Malformations in a Chinese Family. J Mol Neurosci. 2017 Feb;61(2):221-226. doi: 10.1007/s12031-017-0881-5. Epub 2017 Feb 3. PubMed PMID: 28160210.
7)

Zou X, Hart BL, Mabray M, Bartlett MR, Bian W, Nelson J, Morrison LA, McCulloch CE, Hess CP, Lupo JM, Kim H. Automated algorithm for counting microbleeds in patients with familial cerebral cavernous malformations. Neuroradiology. 2017 Jul;59(7):685-690. doi: 10.1007/s00234-017-1845-8. Epub 2017 May 22. PubMed PMID: 28534135; PubMed Central PMCID: PMC5501247.
8)

Strickland CD, Eberhardt SC, Bartlett MR, Nelson J, Kim H, Morrison LA, Hart BL. Familial Cerebral Cavernous Malformations Are Associated with Adrenal Calcifications on CT Scans: An Imaging Biomarker for a Hereditary Cerebrovascular Condition. Radiology. 2017 Aug;284(2):443-450. doi: 10.1148/radiol.2017161127. Epub 2017 Mar 20. PubMed PMID: 28318403; PubMed Central PMCID: PMC5519414.
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