The aim of this pilot phase trial is to assess the safety and tolerability, and estimate the efficacy of sirolimus in reducing the incidence of ICH during high-risk periods for rebleeding, compared to placebo. This pilot trial will inform the design of a future definitive clinical trial on sirolimus treatment for CCM.
Inclusion Criteria: 1. Age 18-65 years, any gender; 2. Patients who have experienced their first symptomatic BSCM ICH within the six months before randomisation; 3. Diagnosed with solitary BSCM through T2, GRE/T2\*, or SWI MR imaging; 4. ICH within or around the BSCM confirmed by CT /MR; 5. Capable of signing an informed consent form with the accompaniment and understanding of a guardian. Exclusion Criteria: 1. Cancer history; 2. Pregnancy or lactation; 3. Sirolimus/starch allergy; 4. Modified Rankin Scale (mRS) score 5, respiratory failure or currently severe bleeding requiring life support treatment; 5. Abnormal liver and/or kidney function (transaminase levels greater than 50, creatinine greater than 110), abnormal white blood cell/platelet counts (white blood cell count below 3.5 or above 9.5 x 109/L or exceeding normal values, platelet count below 100 or above 300); 6. History of previous immunosuppressive therapy; 7. History of prior surgical intervention for CCM ; 8. History of prior cranial radiation therapy ; 9. Familial CCM or people with multiple CCM; 10. Patients with concurrent acute active infections (e.g., severe bacterial, viral, or fungal infections); 11. Uncontrolled diabetes mellitus; 12. Currently participating in another clinical trial; 13. Patient unwilling/unable to undergo MRI. 14. Co-administration of drugs affecting CYP3A4 enzymes (ketoconazole, voriconazole, itraconazole, telithromycin, clarithromycin).