A global analysis of craniospinal hemodynamics and hydrodynamics is necessary to better understand the pathophysiology of Chiari malformations. This includes an analysis of intraventricular CSF flow, intracranial subarachnoid spaces, foramen magnum, cervical subarachnoid spaces and within the syringomyelia cavity when present. The investigators will also analyze the pulsatility of the cerebellar tonsils in the foramen magnum. Hemodynamic analysis will be performed at the high cervical level (internal carotid and vertebral arteries, jugular veins) and intracranially (carotid and basilar arteries, right sinus and superior longitudinal sinus). This analysis will be made possible by PCMRI acquisitions with slice planes allowing the analysis of the dynamics of the CSF (mesencephalic aqueduct, prepontic cisterns, foramen magnum, at the level of the C2C3 disc, syringomyelia if present), cerebellar tonsils (foramen magnum). The cross-sectional planes for hemodynamic analysis will be at the level of the C2C3 disc (cervical vascular analysis) and upstream of the polygon of Willis (intracranial vascular analysis).

The goal is to complement the clinical and morphological investigations with quantitative imaging of cerebrospinal fluid (CSF) and blood flow in the craniospinal system. These flows are potentially altered or causes of this Chiari anomaly.

The investigators propose a translational research project of clinical research allowing the analysis of a diagnostic technique by a diagnostic, monocentric, prospective study. After neurosurgical consultation, patients with Chiari malformation will be assigned to a symptomatic Chiari malformation or a non-symptomatic Chiari malformation group. They will be offered to participate in this study after information and informed consent. The allocation between the two groups will be made according to the symptomatic or non-symptomatic nature of the Chiari malformation. After inclusion, the patients will have a morphological MRI and a PCMRI according to the determined slice plans and allowing a global analysis of the craniospinal hemohydrodynamics. Craniospinal hemohydrodynamics in a control population will also be analyzed using the same methodology by PCMRI.

Inclusion Criteria:

• All patients with major symptomatic or nonsymptomatic CMI
• aged 18 to 50 years
• no previous neurosurgical, neurological, or cardiological history.
• Controls should be age-matched to symptomatic CMI group. They should not have a history of neurosurgery, neurology, or cardiology.

Exclusion Criteria:

• Patients who are minors or over 50 years of age
• CMI invalidated by our radiological review
• Neurosurgical, neurological or cardiological history
• MRI contraindication
• pregnant, breast-feeding and parturient women