Eagle syndrome causing cerebral infarction attributed to the synergistic effect of mild compression of the styloid process and carotid artery arteriosclerosis: a case report

BACKGROUND: Cerebral infarction in Eagle syndrome is caused by blood flow disruption attributed to direct compression of the internal carotid artery by the styloid process. Herein, we report a rare case of Eagle syndrome in which mild compression of the styloid process and stylohyoid ligament caused tortuosity of the proximal internal carotid artery, leading to severe stenosis and cerebral infarction. CASE PRESENTATION: An 80-year-old Japanese female patient was urgently transferred from another hospital after experiencing sudden-onset aphasia. Upon arrival at the Emergency Room, magnetic resonance imaging (MRI) was performed, and the patient's neurological symptoms had resolved, and the initial MRI did not show new ischemic lesions. However, after 8 days, a new infarction was observed in the left parietal lobe on diffusion-weighted imaging/magnetic resonance imaging. Carotid ultrasonography revealed mild stenosis at the left carotid bifurcation with an elevated peak systolic velocity (190 cm/s). As shown on digital subtraction cerebral angiography (DSA), the styloid process and calcified stylohyoid ligament compressed a portion of the left internal carotid artery, causing mild stenosis. Severe stenosis caused by vascular tortuosity was observed in the proximal internal carotid artery. Surgical resection of the styloid process and calcified stylohyoid ligament was performed using the cervical approach. Postoperative DSA confirmed the resolution of mild stenosis. Further, the vascular tortuosity improved, which then led to the normalization of the stenosis. The postoperative course was uneventful. CONCLUSION: This case emphasizes the synergistic effect of mild compression and arteriosclerosis in causing cerebral infarction in Eagle syndrome.