Clinical Features According to the Histological Types of the Outer Membrane of Chronic Subdural Hematoma

OBJECTIVE: The aim of our study was to classify the outer membrane of chronic subdural hematoma (CSDH) histologically and to determine the clinical and radiological meaning of the classified membranes. METHODS: The outer membrane specimen of 31 patients who underwent surgery for CSDH were acquired in this study. The specimen was classified into four types and each were analyzed of the symptoms on the admission day and during the period from trauma to surgery. The radiological features such as subdural fluid density, Hounsfield number, thickness of the hematoma, and midline shift were analyzed. RESULTS: There were 6% of type I, 29% of type II, 39% of type III, and 26% of type IV neomembranes. The cases of CSDH accompanied by neurologic deficit were highest from type IV of 63%, followed by type II with 56%. On the radiological findings such as Hounsfield unit, hematoma thickness and midline shift, only hematoma thickness between type II and III were statistically significant (p=0.021). The hematoma thickness and midline shift were greatest in type II. On computed tomography scans, the isodense, hyperdense and laminar type that shows the high recurrence rate formed 75% of type II and 67% of type IV while type III had the low possibility of recurrence rate (33%). CONCLUSION: We have identified that the outer membrane have the tendency to develop from type I to IV in time while type II and type IV may have more risk of neurologic deficit and the high possibility of recurrence.