A Case of Internal Carotid Artery Dissection Caused by an Elongated Styloid Process: Successful Treatment with Carotid Artery Stenting and Partial Resection of the Styloid Process

We report a case of repeated cerebral infarction caused by internal carotid artery (ICA) dissection triggered by an elongated styloid process, a form of Eagle syndrome. A 41-year-old man presented with sudden, mild left hemidysesthesia. Magnetic resonance imaging (MRI) revealed a small acute cerebral infarction in the right parietal cortex and insular cortex. Magnetic resonance angiography and digital subtraction angiography (DSA) revealed a right-sided ICA dissection distal to the carotid bifurcation. Idiopathic carotid artery dissection was suspected, and the patient was prescribed aspirin and observed. However, 5 months after the initial cerebral infarction, he had a second episode of left hemiparesis and confusion accompanied by occlusion of the right ICA. Because the area of impaired perfusion in the right hemisphere was greater than that suggested by the diffusion-weighted images of head MRI and clinical status was worse than expected, we performed acute revascularization with aspiration of the thrombus and stenting to treat the carotid dissection. Recanalization with thrombolysis of cerebral infarction (TICI)-grade IIB was achieved. Computed tomographic (CT) angiography combined with analysis of bony structures revealed close proximity of the right ICA and an elongated styloid process with its tip directed toward the dissection. In an angiographic suite, a dynamic cone beam CT was performed with the head of the patient variedly rotated and tilted; the carotid artery dissection appeared to be triggered by the elongated styloid process. Resection of this process was performed to prevent recurrence of the cerebral infarction. Under the guidance of a navigation system, the elongated styloid process, which was located ventral to the anterior belly of the digastric muscle, was cut 3 cm from the tip. The patient was discharged on postoperative day 8 without medical problems, and no recurrence was observed for 12 months after the surgery.