The objective of the NEUTROSURGERY study is to describe the local and locoregional immuno-inflammatory activity in patients suffering from malignant sylvian ischaemic cerebral accident and treated with decompressive hemicraniectomy compared to a control population of patients to be operated on in neurosurgery for another neurosurgical pathology.

Inclusion Criteria Patients:

• Collegial indication given by a neurologist, a neuroreanimator and a neurosurgeon for HD in the context of a malignant sylvian AIC.

Inclusion Criteria Control:

- For neurosurgical operations in which cranial, meningeal, vascular (branch of the middle meningeal artery) or cerebral bone tissue is not preserved during the surgical approach.

Non-inclusion Criteria Patients:

• HD carried out in a context of acute cerebral haemorrhage
• Pre-existing neurological disability: modified Rankin score > 2
• Patient benefiting from a legal protection measure

Non-inclusion Criteria Controls:

• Patient to be operated on for an acute vascular condition: meningeal haemorrhage, subdural or extradural haemorrhage, intra parenchymal haemorrhage.
• Patient operated on for an osteomeningeal pathology present at the approach site.
• Patient operated on for an infectious cranial or neuro-meningeal pathology.
• Patient to be operated on as a result of an intracranial traumatic condition

The target population concerns patients suffering from malignant sylvian ischaemic cerebral accident and treated with decompressive hemicraniectomy. Eligibility will be assessed as soon as the first results of the MRI or brain scan carried out as part of the thrombolysis alert by the interventional neurologist or neuroradiologist triggering the treatment, in front of a large ischaemic cerebral accident (>145 ml).