[Subdural hematoma from arterial rupture -mechanism of arterial rupture in minor head injury].

Five cases of subdural hematoma from arterial rupture (SDH-AR) are described and other 39 reported cases are reviewed. The average age of the patient is 59 and male to female ratio is 2:1. Fifty two percent of the patients have history of recent head injuries most of which are trivial. A very few patient have initial loss of consciousness. Approximately half of the patients with history of head trauma have long lucid interval (average of 7 days). Those patients without history of head trauma have spontaneous onset of the symptoms and some of the have acute onset of headache and loss of consciousness, simulating cerebrovascular accident. Natural history of the SDH-AR is progressing deterioration of the symptoms, resulting in coma and death. Skull fracture is seldom demonstrated in the patients with SDH-AR. Angiography shows and extracerebral avascular mass over the cerebral convexity with marked midline shift. In 3 cases including our 2 cases, extravasation of the contrast medium from the cortical artery is observed and this is a useful finding for making diagnosis of this disease. Computerized tomography reveals high density extracerebral mass with remarkable mass effect. Craniotomy discloses subdural clot and spurting arterial rupture from a branch of the cortical artery around the Sylvian fissure. In some cases, subarachnoid hemorrhage is observed but in none of the cases, cerebral contusion or laceration is present. It is presumed that the mechanism of the arterial rupture is gliding movement of the brain within the skull upon injury, tearing an arterial twig with dural attachment. Hypertension, arteriosclerosis and brain atrophy may be important contributing factors to this mechanism. Pseudoaneurysm of the cortical artery caused by closed head injury is also associated with this mechanism and may explain delayed sudden onset of the symptoms in some patients with SDH-AR.