Dissection of the internal carotid artery is responsible for approximately 5% of ischemic strokes in adults. The pathophysiology of dissection can be either traumatic or spontaneous. The true incidence of spontaneous dissection is unknown. Once considered very rare, an increased awareness, combined with noninvasive evaluation by ultrasound and magnetic resonance angiography, has demonstrated a more frequent occurrence. Trivial trauma (ie, rather than external blunt or penetrating trauma) such as vomiting has rarely been documented as causing bilateral dissection. It is well recognized by neurologists but often not by other physicians. Prognosis is good, but delay in diagnosis may result in residual neurologic deficits. It should therefore be suspected early, especially in younger patients presenting with transient ischemic attacks or stroke.