Experimental chronic subdural hematoma in mice. Gross morphology and light microscopic observations.

A new experimental model of chronic subdural hematoma in mice is described. A single intraperitoneal injection of 6-aminonicotinamide (25 mg/kg body weight) on the 5th postnatal day induced hydrocephalus in mice with almost 100% success. Approximately 60% of the mice spontaneously developed intracranial hemorrhage 20 days after the injection. About 1 week after the hemorrhage, a lens-shaped or spherical subdural hematoma was observed, accompanied by marked dilatation of the lateral ventricles and intraventricular hemorrhage. Histological examination revealed that the hematoma contained well-organized outer and inner membranes. Fresh hemorrhage surrounded by many hemosiderin-laden macrophages was seen at the margin of the hematoma adjacent to the organizing outer membrane, in which many fibroblasts and blood vessels were noted. The inner membrane of the hematoma was made up of several tiers of flattened cells with thin-walled blood vessels. The gross morphology and histology of these hematomas closely resembled those of human chronic subdural hematoma.