Mechanical Intracranial Artery DilAtation Using Stent-retriever for Cerebral Vasospasm

Inclusion Criteria: * 1\. Patients≥ 19 years 2. Radiologic confirmed refractory intracranial vasospasm or due to subarachnoid hemorrhage (caused by trauma, aneurysmal rupture, spontaneous, etc.) or suspected recurrent intracrania vasospasm with the following radiological/clinical evidence (\* refractory intracranial vasospasm: despite of standard treatment ≥ 50% decrease in vessel diameter compared to first angiography) * recurrent intracrania vasospasm: Even though chemical angioplasty was performed, radiologically cerebral vasospasm worsens (severe cerebral vasospasm(70-99%)) with worsening clinical symptoms. 3\. Individuals who voluntarily signed the informed consent form to participate in this study. Exclusion Criteria: * 1\. Pre-existing intracranial stenosis ≥ 50% 2. Patients whose condition makes further evaluation and procedures difficult * Exclude if Hunt and Hess grade is 4 or higher. 3. Difficult vascular access * History of vascular malformation, vascular anastomosis, or stent placement. 4. Distal location: Middle cerebral artery (MCA) segment M3 or below, anterior cerebral artery (ACA) segment A3 or below, posterior cerebral artery (PCA) segments P3 or P4 or below. 5\. Cerebral vasospasm caused by vasculitis or dissection. 6. Hypersensitivity to medications to be used (contrast agents, vasodilators..). 7\. Pregnancy or breastfeeding. 8. History of connective tissue disease or blood coagulation disorders. 9. Patients with untreated areas of subarachnoid hemorrhage. 10. Patients with symptoms due to other causes (e.g., hydrocephalus, infection, etc.). 11\. Irreversible cerebral infarction in the entire vascular territory where vasospasm occurred. 12\. Known allergy to medical device materials (Nitinol, Platinum, Iridium). 13. Bleeding or coagulation disorders (Platelet count \< 20,000 or INR \> 1.7). 14. In case of rapid worsening of cerebral hemorrhage symptoms , cerebral edema, surgery, or other urgent treatment required. 15\. Subject with uncontrolled blood pressure (SBP \< 100 mmHg). 16. Subject with liver dysfunction (AST/ALT \> x2 upper normal limit ). 17. Subject with renal dysfunction (eGFR \< 60 mL/min/1.73㎡). 18. Subject with clinically significant cardiac complications such as arrhythmia, heart failure, or myocardial infarction. 19\. Subject with brain edema or elevated intracranial pressure. 20. Known current or past use of illicit drugs or alcohol abuse. 21. Requiring the administration of medications contraindicated with nimodipine. 22\. Subject with systemic complications such as infection, fever, inflammation, edema, hypersensitivity, foreign body reaction, toxicity, or shock. 23\. Subject with visual impairment or ocular complications. 24. Any other cases where the investigator determines that participation in the clinical trial is not possible.