Internal carotid artery dissection caused by an elongated styloid process: usefulness of transoral ultrasonography.

We report a case of internal carotid artery (ICA) occlusion caused by arterial dissection triggered by an elongated styloid process. A 43-year-old man presented with a headache followed by speech disturbance. Magnetic resonance imaging and magnetic resonance angiography scans revealed acute infarction and right ICA occlusion. A T1-weighted magnetic resonance imaging scan revealed a hyperintensity in the occluded ICA, suggesting intramural hematoma. Computed tomographic angiography also revealed ICA occlusion and bilateral elongated styloid processes. We performed transoral carotid ultrasonography, which revealed the absence of flow signal in the double lumen of the dilated extracranial ICA. We diagnosed his condition as arterial dissection and treated him with antithrombotic drugs. Six months later, the occluded ICA recanalized spontaneously, and computed tomographic angiography at that time revealed a close relation between the tip of the styloid process and the recanalized ICA. This finding suggests that an elongated styloid process is involved in arterial dissection. In patients with ICA occlusion of unknown etiology, an evaluation for intramural hematoma and styloid process length are useful for the diagnosis of dissection and its etiology.