Distal internal carotid artery dissection after carotid endarterectomy for a high cervical lesion suggesting an Eagle-like mechanism of shunt-related injury: illustrative case

BACKGROUND: Although intraluminal shunt insertion during carotid endarterectomy (CEA) is widely used to maintain cerebral perfusion, distal intimal injury of the internal carotid artery (ICA) can occur as a rare yet consequential complication. OBSERVATIONS: An 82-year-old man with an elongated styloid process who underwent CEA for left ICA stenosis at the C2 vertebral level developed a new progressive high-grade stenosis immediately distal to the endarterectomy site, likely associated with shunt manipulation. Preoperative images demonstrated that the distal ICA segment at the C1 vertebral level was positioned between the styloid process anterolaterally and the transverse process of C1 posteromedially, in closer proximity to these osseous structures than on the right side. The dissected segment corresponded to the region of closest proximity between the ICA and the transverse process of C1. The patient underwent carotid artery stent placement for the distal dissected stenosis without neurological sequelae. LESSONS: This case suggests that an Eagle syndrome-like osseous-vascular configuration may predispose the artery to shunt-related injury during CEA. Meticulous preoperative assessment of the relationship between the ICA and both the transverse process of C1 and the styloid process may help mitigate the risk of distal ICA dissection in high cervical lesions with an elongated styloid process. https://thejns.org/doi/10.3171/CASE26320.