[Causative factors of recurrence of chronic subdural hematoma].

Burr hole opening and irrigation of hematoma is now a widespread simple technique for the treatment of chronic subdural hematoma (CSH). However, recurrence of hematoma has been sometimes experienced after initial treatment. The purpose of this report is to analyze the causative factors in recurrence of the hematoma after the burr hole opening and irrigation. Out of 68 adult cases of CSH treated by burr hole opening and irrigation technique at Toranomon Hospital during the past nine years, 11 cases (16.2%) showed recurrence of symptoms due to reaccumulation of hematoma after the 1st operation. They were compared with non-recurrence cases from the viewpoint of clinical signs, symptoms and course and serial CT findings. But there was no statistically significant difference between them. The causative factors of recurrence of CSH were analyzed and divided into four categories. Type 1 (3 cases): specific promoting factors--Primary intracranial hypotension (2 cases) and anticoagulant therapy (1 case). Type 2 (1 cases): immature timing of operation. Type 3 (4 cases): other causes probably due to operative procedure--Insufficient postoperative external drainage. Type 4 (3 cases): unknown cause. Several authors have reported causative factors of recurrence of CSH so far, but they are still controversial. An additive treatment in the cases involving specific factors, and planning the timing and some procedures of operation are proposed in order to avoid recurrence of CSH.