Aneurysmal subarachnoid haemorrhage is a complex pathology, the pathophysiology of which is still imperfectly understood. Its morbidity and mortality remain significant. In addition to the damage sustained by the brain in the immediate aftermath of aneurysmal rupture, which is inaccessible to life-saving treatment, a significant proportion of lesions occur at a distance from the initial event. Delayed cerebral ischaemia is one of the most morbid complications. It combines an inflammatory pattern with vascular dysfunction and neuronal excitotoxicity, leading to avoidable secondary neuronal loss.

Vascular dysfunction is mediated by a loss of homeostasis between endothelial cells and figurative blood cells, including platelets. However, the interrelationship between these elements and the precise chronology of the dysfunction remain imperfectly described to date.

It therefore seems appropriate to propose temporal monitoring of platelet activation kinetics over time, combined with concomitant collection of markers of endothelial damage, in order to clarify the vascular chronobiology of this pathology.

Inclusion Criteria:

• Male and Female Adults ≤18 years of age.
• Hospitalised in the neurological intensive care unit of the Pierre Wertheimer Hospital of the Hospices Civils de Lyon following an aneurysmal meningeal haemorrhage of any modified Fischer score, previously diagnosed by cerebral CT scan.
• Patients admitted to the neurological intensive care unit or the NICU of the Pierre Wertheimer Hospital of the Hospices Civils de Lyon for an intra-parenchymal haematoma.
• Patient who has been informed and has formulated his/her non-opposition, or close relative of the patient who has been informed and has formulated his/her non-opposition.
• Affiliated to a social security scheme.

Exclusion Criteria:

• Non-aneurysmal SAH
• Ischaemic stroke
• Patients with previously known platelet function disorders
• Pregnant or breast-feeding women
• Patients under legal protection (guardianship, curatorship, safeguard of justice)
• Patients under compulsory psychiatric care
• Patients taking part in a study which may interfere with the present study

We therefore chose to carry out an exhaustive recruitment of the active file of consecutive patients eligible for the study selection criteria. In the Medical ICA and Neurovascular ICU Department of the Pierre Wertheimer Hospital of the Hospices Civils de Lyon, treating patients with sub-aneurysmal meningeal haemorrhage or intraparenchymal haemorrhage. 40 patients in each group