Neuroradiologic diagnosis of subdural empyema and CT limitations.

Five cases of subdural empyema are described. Two of the cases eluded a definitive computed tomography (CT) diagnosis despite classical clinical background. Extracerebral collection with definitive border enhancement was seen in the other three cases. Mass effect, present in all five cases, was related to the extracerebral collection in three cases and diffuse cerebral edema and/or infarction in two. Angiography in four cases initially demonstrated an extracerebral collection in three and inflammatory angiospasm in two. Repeat angiography demonstrated an extracerebral collection in the fourth case. In the proper clinical setting subdural empyema should be considered even in the absence of an extracerebral collection when mass effect or an infarction pattern is seen on CT. Angiography may be diagnostic in such cases. Hopefully, newer techniques will further the diagnostic efficacy of CT in this disease.