Clinicopathological study of acute subdural haematoma in the chronic healing stage. Clinical, histological and ultrastructural comparisons with chronic subdural haematoma.

Seven cases of acute subdural haematoma in the chronic healing stage, were studied clinicopathologically. Operation was not performed until 17-30 days after major trauma, and revealed subdural granulation tissue of irregular thickness, but no visible inner membranes. Although this capsule contained blood pigment and numerous macrophages, new haemorrhagic foci or eosinophilic infiltrations were extremely rare. Capsular vessels generally had thick vascular walls, distinct basement membranes and tight endothelial junctions. Perivascular blood substance was presumably not secondary haemorrhage from these vessels, but residue from the acute subdural haematoma itself. The possibility of transition from this haematoma to chronic subdural haematoma is discussed.