Recurring extracranial internal carotid artery vasospasm detected by intravascular ultrasound.

A 24-year-old woman presented with headache and left-sided focal signs following multiple episodes of right monocular visual impairment. Magnetic resonance angiography revealed a decreased vascular image intensity due to a suspicious stenosis in the right internal carotid artery (ICA). The stenosis was not demonstrated on duplex sonography as it was beyond the field of view of the investigation. Intravascular ultrasound (IVUS) revealed that the outer vessel diameter was significantly reduced during stenosis, supporting the presence of vasospasm. Idiopathic recurrent extracranial ICA vasospasm was diagnosed. Recurrent vasospasms of extracranial ICA may be a distinct entity that can cause ischemic stroke.