Endoscopically Observed Outer Membrane Color of Chronic Subdural Hematoma and Histopathological Staging: White as a Risk Factor for Recurrence

Endoscopic treatment for chronic subdural hematoma (CSDH) has been reported, but endoscopic findings of CSDH have not been thoroughly investigated. This study aimed to elucidate the relationship between endoscopic findings and CSDH recurrence. Furthermore, it examined the association between Nagahori's histopathological staging of CSDH and outer membrane color. Here, we retrospectively analyzed the operative videos of 70 patients with CSDH. The endoscopic findings were investigated, and their correlations with CSDH recurrence, the reduction ratio of the midline shift, and hematoma thickness on day 30 after the operation were analyzed. The outer membrane was white in 21 cases, yellow in 25 cases, and red in 24 cases. CSDH recurred in three (4.2%) patients, all of whom had a white outer membrane (adjusted odds ratio, 18; 95% confidence interval, 1.6-20.6; P = 0.007). The other endoscopic findings were not significantly related to CSDH recurrence, extent of the reduction ratio of the midline shift, or hematoma thickness. The outer membrane colors of white, red, yellow, and white almost corresponded to the histopathological staging from type I to IV in order. Our findings suggest that a white outer membrane is a risk factor for recurrence; these colors may represent the extent of inflammation related to the evolution of CSDH estimated from the histopathological findings.