Background: Chronic subdural hematoma (CSDH) is common in neurosurgical practice. The exact timing of brain expansion
is still unknown.
Objective: To study prospectively the timing of full brain expansion and timing of recurrence after surgery of CSDH.
Material and Method: After burr hole and closed-system drainage for the treatment of CSDH, serial CT brains were done
at 24 hours after removal of draining system, 1 week, 2 weeks, 4 weeks, 8 weeks postoperatively or whenever abnormal
neurological symptoms being suspicious for recurrence occurred.
Results: 102 CSDHs from 75 patients were included in the study. A total 450 serial CT brains were done and reviewed. Full
brain expansion after the surgery occurred 1% between the 1st and 2nd weeks, 5.9% between the 2nd and 4th weeks, 80.4%
between the 4th and 8th weeks and 12.7% after the 8th weeks. The incidence of recurrent CSDH was 9.8%. In patients with
recurrent CSDH, the recurrence was 10% before removal of draining system, 70% between the 1st and 2nd week, 10%
between the 2nd and 4th week and 10% after the 8th week.
Conclusion: Brain expansion after surgery of CSDH is a very slow process. There is a discrepancy between the timing of full
brain expansion and timing of recurrence. Recurrent CSDH mostly occurred between the 1st and 2nd week while full brain
expansion mostly occurred after the 4th week. The period between the 1st and 2nd week should be the crucial period of clinical follow-up. Persistence of subdural space on a random postoperative CT brain, without any symptoms, should be considered as a normal process of brain expansion.

Keywords: Chronic subdural hematoma, Brain expansion, Recurrence