A case of post angiography subdural collection contrast enhancement: Time course of attenuation reduction.

The leakage of contrast material into the subdural space following intra-arterial or intravenous administration can present as hyperattenuating subdural collections on noncontrast head computed tomography (CT) scan, mimicking subdural hematomas. Such a finding can potentially initiate erroneous intervention or hinder thromboprophylaxis treatment. We report the time course of attenuation changes in enhancing subdural collections of a patient with suspected stroke following percutaneous coronary intervention. The patient had simple fluid attenuation subdural collections (hygromas) on preprocedure head CT scan, which showed gradually increasing attenuation on 2- and 10-hours post angiography CT scans. On delayed follow-up head CT scan, at 24 and 31 hours after the percutaneous coronary intervention, the subdural collection attenuation returned to preprocedural levels. In this patient, findings on an MRI obtained 9 hours after the procedure, were not in favor of a subdural hematoma. This case highlights the likelihood of contrast leakage into subdural space, mimicking extra-axial hemorrhage on head CT scans, and the time needed for normalization of subdural collection attenuation.