[Traumatic posterior fossa epidural hematoma--especially the value of CT scan (author's transl)].

Epidural hematoma in the posterior fossa is a rare clinical entity which requires the early diagnosis and treatment, and the difficulty of the diagnosis has been pointed out. However, more recently CT scan began to use to make the valuable diagnostic method for traumatic posterior fossa hematomas. Epidural hematoma may be classified as acute, subacute and chronic, according to the time of free interval or lucid interval after injury. In this paper three acute cases and two subacute cases are reported. CT findings in acute cases show two different types. "Type I" shows crescent or lenticular high density area which is not enhanced after contrast infusion. "Type II" shows lenticular low density area with membranous high density region in its medial side after contrast infusion. In subacute cases plain CT scan shows lenticular iso or low density area with membranous high density region in its medial side. Forty five cases of posterior fossa epidural hematoma in the review of the literature of this country are discussed. Disturbances of the consciousness are the most predominant symptoms in acute cases, while in subacute cases cerebellar signs, vomiting, headache and choked disc are noted. Angiographical examinations may not always be valuable in collecting the direct information of the existence of the epidural hematoma. Liquor cavity in the posterior fossa which is thought to serve as a buffer action of hematoma is about 20 ml, so we discuss about the volume of hematoma, especially of 20 ml, associated with clinical course and prognosis. Volume of epidural hematoma is one of the most important factors affecting clinical course and prognosis. In summary of these our experiences, we again emphasize the value of CT scan as the rapid, noninvasive, accurate radiological examination in the diagnosis of traumatic posterior fossa epidural hematoma.