Neck Mass Caused by Spontaneous Arteriovenous Fistula of the Superior Thyroid Artery to its Homonymic Accompanying Vein by Duplex Ultrasonography

An arteriovenous (AV) fistula is an abnormal connection between an artery and vein. It is usually caused by congenital and acquired factors. A 65-year-old man presented to us with a neck mass of 4-year duration with no traumatic history. A Doppler study of the mass revealed a ‘whirlpool’ pattern in a cavity, and something resembling a thrombus adherent to the cavity wall. Based on the spectrum of blood flow, we strongly suspected a fistula. Digital subtraction angiography (DSA) was carried out to validate that the neck mass was caused by an AV fistula from the superior thyroid artery (STA) to the superior thyroid vein (STV).