Focal Non-aneurysmal Subarachnoid Hemorrhage After Carotid Artery Stenting: A Case Report.

Minor non-aneurysmal subarachnoid hemorrhage (SAH) following carotid artery stenting (CAS) is exceedingly rare and less described, with its underlying mechanism elusive. Here, we present the case of a 75-year-old female who underwent CAS for progressive asymptomatic severe stenosis of the internal carotid artery. Her post-procedural course remained uneventful, with no intracranial hemorrhage detected on the following day's magnetic resonance imaging (MRI). However, a routine MRI on the seventh post-procedural day identified a small amount of SAH in the central sulcus on the operative side. In the absence of symptoms, the patient was discharged home after a computed tomography (CT) scan revealed no signs of hemorrhagic enlargement the following day. In this report, we document the rare occurrence of localized SAH post-CAS. There are limited reports of minor SAH following CAS, with the underlying mechanisms remaining unclear. In this report, the localization of SAH aligns with the most critical ischemic sites, indicating that the mechanism of focal SAH after CAS is associated with blood-brain barrier (BBB) disruption due to a rapid increase in blood flow to small vessels with impaired vascular autoregulation. Focal convexity SAH is an easily overlooked finding, and the medical team performing carotid artery revascularization procedures should be aware of the potential for such SAH postoperatively and exercise caution during postoperative imaging interpretation.