Head CT scan may be helpful in the diagnosis of subdural empyema. CT scan is secondary to MRI for subdural empyema imaging. Findings on CT scan suggestive of subdural empyema include a crescentic shape, although collection pockets may appear bi-convex. A surrounding membrane that enhances intensely and uniformly following contrast administration is typically identified.^[1]

Head CT scan may be helpful in the diagnosis of subdural empyema. A contrast-enhanced head CT with axial and coronal places is an accessible and cost-effective imaging study, however the number of false-negative results (approximately 50%) make it a less reliable test than MRI. However, CT scan is the modality of choice in comatose or critically ill patients, where the MRI is not possible or contraindicated.^[2] On CT scan, findings suggesting of subdural empyema include a hypodense, crescentic shape over the cerebral convexity, extending over one or both hemispheres or in the inter hemispheric fissure, with a surrounding rim, enhanced by the use of contrast.^[3] CT scan may also demonstrate cranial bone involvement and the presence of sinusitis, otitis, or mastoiditis. A mass effect may also be noted.