Internal carotid artery dissection leading to occlusion in a patient with nonelongated styloid process: illustrative case.

backgroundEagle syndrome is characterized by an elongated styloid process causing mechanical stress on the internal carotid artery (ICA). The authors present the case of a patient who had cervical ICA dissection with a nonelongated styloid process. OBSERVATIONS: A 43-year-old man presented with left hemiparesis and hemispatial neglect. The patient underwent endovascular treatment for tandem occlusion of the M1 segment of the right middle cerebral artery and right cervical ICA. After M1 segment thrombectomy, stenting of the right cervical ICA dissection was performed. Notably, the tip of the styloid process matched the caudal end of the dissection cavity, which was located on the lateral side of the ICA, where the styloid process was located. Based on these findings, the authors concluded that mechanical stress from the styloid process caused ICA dissection. After reducing antiplatelet therapy, the styloid process was surgically removed. LESSONS: Mechanical stress from a nonelongated styloid process can lead to ICA dissection-induced occlusion. In patients with cervical ICA dissection, the anatomical relationship between the styloid process and dissection site, as well as the distance between the ICA and styloid process, should be evaluated. https://thejns.org/doi/10.3171/CASE24719.