Transient ipsilateral mydriasis following carotid artery stenting.

Background and Importance: One of the most feared and devastating complications of carotid revascularization procedures is hyperperfusion hemorrhage. The acute onset of an ipsilateral mydriatic pupil following carotid endarterectomy (CEA) or carotid artery stenting (CAS) should prompt immediate neurosurgical evaluation to rule out hyperperfusion injury.
Clinical Presentation: We describe a case of benign, transient ipsilateral mydriasis following CAS. After undergoing right common and internal carotid artery (ICA) angioplasty and stenting with distal embolic protection, the patient developed anisocoria with a right-sided 5 mm minimally reactive pupil. Imaging demonstrated no acute pathology, and the mydriasis resolved spontaneously within 48 hours. We hypothesise that the pathophysiologic mechanism is secondary to transient ischemia of parasympathetic structures within the petrous/cavernous ICA from arterial ostium occlusion that occurred during device placement. Alternatively, sympathetic stimulation during angioplasty is also plausible.
Conclusions: Although an ipsilateral mydriatic pupil following carotid revascularization necessitates evaluation, it may represent a self-limiting process especially in the absence of other focal neurologic deficits.