Cerebral Arteriovenous Malformations

Cerebral arteriovenous malformations (CAVMs) are abnormal vessels located on the surface of the brain or within the cerebral parenchyma, causing abnormal communication between the arterial and venous networks, without the interposition of the capillary bed. The main risk associated with these malformations is rupture, which causes intracranial bleeding and can lead to serious sequelae or even death. CAVMs (except those of clearly identified genetic origin \[\< 5%\], such as mutations associated with Rendu-Osler disease) have long been considered to be of non-genetic origin. However, somatic genetic mutations that activate the RAS/RAF/MEK/ERK (MAPK) signalling pathway have recently been identified in surgical specimens of cAVMs. Furthermore, targeted inhibition of this pathway is effective in treating these malformations in animals and appears to be effective in extracranial arteriovenous malformations, particularly superficial ones.

The cerebral arteriovenous malformations correspond to the formation of an entanglement of morphologically abnormal vessels called nidus, which shunt the blood circulation directly from the arterial circulation to the venous circulation. The cerebral arteriovenous malformations are an important cause of hemorrhagic stroke. The hypothesis is that cerebral haemorrhage associated with a cerebral arteriovenous malformations would come from peri-nidal micro-vessels, in connection with infiltration of leucocytes and / or defective maintenance of microvascular integrity by platelets.

The Comprehensive HHT Outcomes Registry of the United States (CHORUS) is an observational registry of patients diagnosed with Hereditary Hemorrhagic Telangiectasia (HHT). The purpose of this study is to better understand HHT, the symptoms and complications it causes, and the impact the disease has on people's lives. The investigators will collect long-term information about the participant, allowing us to understand how the disease changes over time, and what factors can influence those changes. Ultimately, this should help improve treatments for the disease. Another important goal of the study is to provide a way to contact people to participate in future clinical trials and other research. The registry will be a centralized resource for recruitment for clinical trials. People in the registry will not be obligated to join any of these additional studies, but if interested, can agree to be contacted if they may be eligible for a study. Participants will: * Be asked to provide permission to collect information from their medical records, including things like demographic information, diagnosis information, family history, test results, treatment information, symptoms, complications, lifestyle and other relevant medical information. * Be asked study-related questions by phone or at a clinic visit. * Be asked study-related questions every year after enrollment for up to 10 years or until the study ends. A member of the study team will communicate with participants by phone or at clinic visits to collect information regarding any changes to their health over the previous year/s including new test results, treatment information, symptoms, and complications from HHT.