Subdural Tension on the Brain in Patients with Chronic Subdural Hematoma Is Related to Hemiparesis but Not to Headache or Recurrence

Hemiparesis is a major symptom of chronic subdural hematoma (CSDH). Its severity does not always correlate with hematoma size. The authors analyzed hematoma thickness, pressure, and tension to clarify the mechanism of hemiparesis in CSDH patients.A burr-hole surgery was performed on 124 CSDHs in 102 patients. Hematoma thickness and midline shift were measured by computed tomography, and hematoma pressure was measured in surgery. According to Laplace law, tension was calculated as follows: (half the hematoma thickness × hematoma pressure)/2. Student t test and Pearson correlation coefficient (r) were applied in statistical analysis of findings.Motor weakness was identified in 76.5% of our cases. Tension was strongly related to hemiparesis (r = -0.747, P0.01), whereas hematoma thickness (r = -0.458, P0.01) and pressure (r = -0.596, P0.01) were moderately correlated. Mean age of 14 patients (13.7%) with headache was much younger than those without headache (P0.01). Stronger midline shift (P0.01) and greater ratio of midline shift to hematoma thickness (P0.01) were statistically correlated with headache. Recurrence was recognized in 8 patients (7.8%), and stronger midline shift (P0.05) and greater ratio of midline shift to hematoma thickness (P0.05) were statistically associated with recurrence.Tension is the most influencing factor to hemiparesis in CSDH patients. This study also elucidates the mechanism for quick recovery from hemiparesis after surgery in that tension on the motor cortex is decreased immediately by drainage.