Effect of Japanese Herbal Kampo Medicine Goreisan on Reoperation Rates after Burr-Hole Surgery for Chronic Subdural Hematoma: Analysis of a National Inpatient Database

Goreisan is a herbal Kampo medicine used for treating chronic subdural hematoma (CSDH) in Japan. Experimental studies have suggested that Goreisan exerts a hydrogogue effect, but clinical evidence for the effectiveness of Goreisan in CSDH is currently lacking. Using a national Japanese inpatient database, we examined the association between Goreisan use and reoperation rates after burr-hole surgery for CSDH. We identified 36,020 patients, including 3,889 Goreisan users and 32,131 nonusers. Propensity scores of receiving Goreisan were calculated based on hospital characteristics and patient backgrounds (age, sex, body mass index, activities of daily living, consciousness level, comorbidities, antithrombotic agent use, mannitol infusion, and corticosteroid infusion). One-to-one propensity-score matching created 3,879 pairs of Goreisan users and nonusers. Propensity-matched analysis revealed that Goreisan use was significantly associated with a lower reoperation rate (4.8%) compared with nonuse (6.2%) (risk difference, −1.4%; 95% confidence interval (CI), −2.4% to −0.38%). The number needed to prevent one reoperation was 72 (95% CI, 41–265). Instrumental-variable analysis showed similar results to the propensity-matched analysis. These results suggest that Goreisan use reduced the need for reoperation after burr-hole surgery for CSDH.