Asymmetric Petro-occipital Venous Plexus Thickening: A Valuable Diagnostic Sign of Reduced Flow in the ICA.

Thickening of the venous plexus surrounding the petrous ICA, known as Rektorzik venous plexus (RVP), is a marker of inward ICA remodeling from a substantial reduction in blood flow, but clinical application of its detection remains unexplored. We reviewed contrast-enhanced vessel wall MRI imaging (VWMRI) and CTA examinations of the head and neck acquired at our institutions to identify cases with asymmetric RVP thickening that influenced the diagnosis or medical management of neurovascular diseases. Five representative patients were included. Two patients with intracranial MRA or CTA interpreted as having normal findings had asymmetric RVP thickening, in one case leading to cervical imaging that identified high-grade carotid stenosis and in the other case drawing attention to a linear filling defect at the ipsilateral distal M1 branch of the MCA identified as a dissection on image reconstruction. The third patient had intracranial ICA stenosis not considered to be flow-limiting but the asymmetric RVP thickening suggested otherwise, which was supported by cervical ICA flow measurements by Doppler ultrasound. Two patients had resolution of asymmetric RVP thickening confirming flow restoration, one following treatment of intracranial vasospasm and the other after carotid revascularization. Asymmetric RVP thickening is a valuable biomarker that can identify flow-limiting stenosis, at times incidentally, and monitor changes in flow impairment, offering the potential for improved diagnostic accuracy and stroke-risk assessment.