[Magnetic resonance imaging of supratentorial and parafalcial empyema]

The authors report the MR imaging of two patients with multiple subdural empyemas, including one in the interhemispheric fissure. MRI demonstrated convexity and interhemispheric collections which were mild hyperintense relative to CSF, hypointense relative to gray and white matter on T1W1, and marked hyperintense relative to CSF, and brain on T2W1. On the basis of signal intensity differences, MRI can distinguish subdural empyemas from most sterile effusions and chronic subdural hematomas with similar CT appearances. MRI was found to be clearly more sensitive to subdural empyemas than CT, though such lesions missed on CT were considered to be relevant. MR was superior to CT in demonstrating the nature, presence, and extent of these lesions. In both cases, the capsule of the lesions demonstrated enhancement, and connection between each lesion was obvious on contrast-enhanced MRI. It seems that contrast-enhanced MR image may detect encapsulation of an abscess which can not be detected from contrast-enhanced CT. We emphasized that the most significant factor in the successful surgical management of multiple subdural empyema, particularly including interhemispheric collections is the accurate location of pus. This can be reliably achieved with MR imaging.