A prospective, randomised, double-blind, placebo-controlled, multicentre trial was designed to compare the the incidence of hematoma progression requiring operation or hematoma recurrence requiring re-operation and improves clinical outcomes at 24 weeks in patients with CSDH of treatment in the HXLS and placebo groups.

The CHARM trial is a prospective, randomized, double-blinded, placebo-controlled, multicenter clinical study. The trial aims to investigate the efficacy of the Chinese herbal formula HXLS as an addition to a primary conservative treatment of CSDH in an effort to prevent surgery. The investigators hypothesize that, compared with placebo, the Chinese herbal formula HXLS reduce incidence of hematoma progression requiring operation or hematoma recurrence requiring re-operation and improves clinical outcomes at 24 weeks in patients with CSDH. Consequently, the defined null hypothesis will be that there is no difference between the groups. In total, 160 patients will be randomly assigned to the HXLS group and the placebo group at a 1:1 ratio.

Inclusion Criteria:

1. Age between 18 and 90 years and either gender will be included.
2. Supratentorial, unilateral or bilateral CSDHs will be verified via cranial CT or magnetic resonance imaging (MRI).
3. Primary hematoma or residual hematoma after burr-hole drainage.
4. Stable vital signs and neurological deficits are indicated by a Glassgow Coma Scale (GCS) score ≥ 14 and a modified Rankin scale (mRS) score ≤ 2.
5. No risk of brain herniation or recent immediate need for surgery will be evaluated by 2 attending neurosurgeons.
6. Written informed consent will be obtained from patients or their next of kins according to their cognitive status.

Exclusion Criteria:

1. Unstable vital signs or symptoms of brain herniation, including severe headache, nausea and vomiting, or disturbed consciousness.
2. Progressive or apparent neurological deficit with a GCS score < 14 or mRS score > 2.
3. Midline shift > 10 mm on the radiological image.
4. Previous medication treatment for CSDH.
5. Previous intracranial surgery for any other neurological disorder.
6. Structural causes for secondary CSDH, including arachnoid cysts, intracranial tumors, vascular malformations, spontaneous intracranial hypotension, coagulopathy, and conversion from acute subdural hematoma.
7. Known hypersensitivity or allergy to HXLS or to any of the ingredients.
8. Malignant tumors.
9. Life expectancy of < 1 year.
10. Abnormal liver function or liver diseases, including uncontrolled hepatitis (alanine transaminase > 120 U/L).
11. Severe renal impairment (estimated glomerular filtration rate < 30 ml/min or serum creatinine > 150 μmol/L).
12. Moderate or severe anemia (hemoglobin ≤ 90 g/L).
13. Severe coagulopathy or a high risk of life-threatening bleeding.
14. Poor medication conditions or the presence of severe comorbidities such that treatment cannot be tolerated or follow-up cannot be completed.
15. Routine oral antithrombotic or antifibrinolytic drugs, steroids, statins, angiotensin-converting enzyme inhibitors, or other traditional Chinese medicines before randomization or are expected to take such medications in the next 24 weeks.
16. Difficulty swallowing oral medication.
17. Pregnancy or lactation.
18. Participating in another study.

The investigators in charge of the recruitment and follow-up evaluation and participants will be blinded, along with the outcome assessors and data analysts.