Establishment of a CSF Bank for the Development of Biomarkers of Smooth Muscle Cell (SMC) Damage in Monogenic Cerebral Small Vessel Disease

For patients woth monogenic cSVD : Inclusion Criteria: * Patients aged between 18 and 80 years at the time of inclusion * Diagnosis confirmed by detection of a pathogenic mutation in the NOTCH3 gene characteristic of CADASIL, or in another gene responsible for other forms of monogenic cSVD (such as COL4A1, COL4A2, HTRA1). * Beneficiary of a social security system * Having given their written consent Non inclusion Criteria: * Contraindication to lumbar puncture: * Haemostasis disorder (severe thrombocytopenia \<60,000/mm3, PT abnormalities, INR\>1.5 and/or aPTT\>1.5) or anticoagulant use. * Spinal plaque in or near the lumbar region (surgery) that may interfere with CSF collection * Behavioural disorder that may interfere with the sampling process * Intracranial process, intracranial hypertension or risk of involvement on imaging * Skin lesions (inflammation or infection of any kind) or developmental abnormality (myelomeningocele) adjacent to the puncture site * Person referred to in articles L. 1121-5 to L. 1121-8 and L. 1122-12 of the public health code, defined as : * Pregnant, parturient or breastfeeding woman * Person deprived of liberty by judicial or administrative decision * Person hospitalised without consent and not subject to a legal protection measure, and person admitted to a health or social establishment for purposes other than research * Minor * Person of full age subject to a legal protection measure (guardianship, curators or safeguard of justice), person…