An 84-year-old male patient presented with a swelling on his forehead which had developed gradually over a period of three weeks after a fall. Ultrasound examination revealed a complex fluid collection with a yin-yang flow pattern (revealed by colour Doppler imaging), which was suggestive of a pseudoaneurysm of the frontal branch of the superficial temporal artery. This was successfully treated with an injection of thrombin.
Diagnosis: traumatic pseudoaneurysm of the superficial temporal artery.