[Studies of the factors affecting the reduction of chronic subdural hematoma: effect of preoperative factors with special reference to cerebral atrophy].

The authors examined the preoperative factors affecting the reduction of chronic subdural hematoma (CSDH). A new method was developed to calculate the reduction rate of CSDH using CT volumetry technique. Postoperative serial CT films were examined and each hematoma volume was calculated by microcomputer. A postoperative exponential decrease of hematoma volume was observed, and the log-transformation of the hematoma volume turned the curve to a linear decrease. The least square method was used to fit an exponential curve, and the half reduction date (HRD) was calculated from the fitting curve. This HRD represents a mathematical indicator of the reduction rate of CSDH. Using this technique, the relationships between this HRD and the following parameters were examined in 61 patients. The preoperative factors examined are as follows; 1) patient's age, 2) preoperative hematoma volume, 3) CT number of the hematoma, 4) time interval between the head injury and the onset of symptom, and 5) the degree of cerebral atrophy. The degree of cerebral atrophy was calculated by means of a simple approximate formula as described by one of the authors (K.N.). Patient's age and the hematoma volume were correlated with HRD, and the correlation coefficients were 0.346 (p less than 0.01) and 0.298 (p less than 0.05) respectively. On the other hand, preoperative CT findings and the duration from the trauma had no correlation with HRD. Cerebral atrophy has hitherto been thought to affect the reduction of hematoma. However, our quantitative study revealed no correlation between cerebral atrophy and the reduction of hematoma rate. This unexpected result may be attributed to the difference between cerebral atrophy and cerebral elasticity.(ABSTRACT TRUNCATED AT 250 WORDS)