Diagnostic pitfall of computed tomography in patients with superficial siderosis of the central nervous system.

Superficial siderosis of the central nervous system (SSCN) is a well-described entity with distinct clinical presentation as well as computed tomography (CT) and magnetic resonance imaging (MRI) findings. However, it is critical that when a patient previously diagnosed with SSCN undergoes CT on the brain at a later date, that this scan not be misinterpreted as a new subarachnoid hemorrhage (SAH) so unecessary repeated angiograms are not performed. This report describes such a situation and discusses unique CT findings in SSCN that have been under-recognized and under-emphasized. While conditions such as SAH should not be ruled out, they would be considered atypical. Combined with an adequate prior diagnostic testing history, physicians should proceed to MRI without subjecting the patient to repeat angiography.