The presentation by Prof. Dominique Hervé (Service de Neurologie, Centre de Référence des Maladies Vasculaires Rares du Cerveau et de l’Œil, Hopital Lariboisière, Paris, France) titled “Handling Genetic Cerebral Small Vessel Disease Care Organization in France and Collaboration at the European Level” aimed to highlight the French model for managing the healthcare organization for genetic small vessel diseases (SVD). The Lariboisière Hospital in Paris is the reference centre for vascular diseases of the brain. It boasts the capability of having a multifunctional team, bringing together all experts involved in these diseases, thus enabling close interaction between a vascular neurologist, an ophthalmologist, a surgeon, a neuroradiologist, a team of psychologists, a social worker when necessary, the neurovascular genetics laboratory, and the patient association. Nationally, France has a network of expert centres that provide appropriate care as close as possible to patients’ residences, with a dedicated pediatric reference centre. All centres focus on monogenic cerebral small vessel diseases, including COL4A1/A2 angiopathy due to mutations in the COL4A1 and COL4A2 genes, glycine or stop codon mutations; PADMAL (pontine autosomal dominant microangiopathy and leukoencephalopathy) due to a COL4A1 mutation; CADASIL, the most frequent hereditary small vessel disease of the brain caused by mutations in the NOTCH3 gene, and other autosomal dominant forms of cerebral vascular diseases.

Most patients who come to Prof. Hervé’s centre do so with the suspicion of a small vessel disease of the brain before a precise diagnosis is made. In these situations, there are two main questions: Do we confirm that this is a rare small vessel disease of the brain? Which of the monogenic small vessel diseases is it? To answer the latter question, there are clinical and imaging clues to identify the different genetic small vessel diseases. For example, COL4A1 angiopathy due to glycine mutations can be suggested by the onset of the disease during childhood or in the fetus, a more hemorrhagic than an ischemic presentation, or multisystem involvement, including skin and muscles. Imaging clues can include the observation of anomalies in the retinal capillaries. However, some patients arrive without these relatively specific points, only with some non-specific markers of small vessel disease, making it difficult to give a specific disease definition.

In France, Prof. Hervé’s genetic laboratory uses a gene panel strategy daily, reducing the risk of error due to phenotype overlap. The frequency of small vessel diseases identified in the genetic laboratory varies, with NOTCH3 mutations in CADASIL patients being by far the most frequent, followed by COL4A1 and A2 glycine mutations.

When a precise diagnosis of a small vessel disease of the brain is made, the only option is to propose preventive and symptomatic measures, mainly based on mechanistic aspects and expert consensus. Due to the small number of patients, limited clinical evidence, and the absence of clinical trials, there are no official recommendations.

At Prof. Hervé’s center, it is recommended to introduce antihypertensive treatment in hypertensive patients with COL4A1 glycine mutations if systolic blood pressure exceeds 130 mmHg, especially after a cerebral hemorrhage. Antiplatelet treatment is not recommended, but in patients with ischemic stroke without prior hemorrhagic stroke, antiplatelets are introduced after carefully evaluating the risk-benefit ratio. Anticoagulants are avoided, except in specific situations such as a high risk of thrombosis or atrial fibrillation, and in the case of COL4A1/A2 angiopathy only under strict blood pressure control. Lifestyle interventions are also addressed, such as avoiding high-intensity physical exercise that could favor cerebral hemorrhages, and close monitoring of women during pregnancy, considering a cesarean section for fetuses with COL4A1/A2 mutations.

In addition to these measures, Prof. Hervé’s center offers comprehensive support to patients, including psychological support and support for at-risk relatives. They also organize annual clinical and imaging follow-ups during a one-day hospitalization, during which brain and visceral artery imaging is performed to detect aneurysms, and they provide information about the disease. Specifically, for patients’ relatives, they offer presymptomatic genetic testing according to local ethical rules and multidisciplinary genetic counseling to help individuals prepare psychologically, professionally, and socially.