Subarachnoid contrast staining not attributable to endovascular therapy

Contrast staining within the brain refers to the leakage of iodinated contrast material through a disrupted blood-brain barrier, often in the setting of ischemia and endovascular intervention, which can mimic hemorrhage. While commonly seen within the parenchyma, it can be seen in the subarachnoid space especially after endovascular intervention. In the absence of endovascular intervention, subarachnoid hyperdensities on CT are typically presumed to be hemorrhage. However, in rare causes of trauma and stroke, subarachnoid contrast staining can be seen even in the absence of intervention. In this pictorial review, we present cases of patients with subarachnoid hyperdensities on CT which were subsequently confirmed to represent subarachnoid contrast staining. Awareness of this rare phenomenon is important for radiologists, particularly in the emergency setting, as it can have important clinical management and follow-up implications.