A subdural hematoma is a collection of blood that forms between the brain surface and the dura mater, the tough outer membrane covering the brain. It is typically caused by tearing of bridging veins from trauma, and it can occur in the acute, subacute, or chronic setting. While CT is the primary imaging tool for subdural hematomas in adults, ultrasound can play a role in infants whose open fontanelles provide an acoustic window to the brain. On cranial ultrasound, a subdural hematoma may appear as an echogenic or complex collection in the subdural space, between the brain surface and the calvarium. Ultrasound is also used for bedside monitoring of known collections in neonatal intensive care units where transporting critically ill infants to CT is risky.
Sonography Term