Pseudoaneurysms of the superficial temporal artery can occur following blunt trauma to the head and various surgical procedures such as craniotomy or external drainage catheter placement. This diagnosis needs to be kept in mind while considering the differential for temporal fossa and forehead masses especially if there is a history of trauma. The clinical diagnosis is an easy one given the history and pulsatile nature of the mass. Occasional reports of these masses being non-pulsatile have been reported in which case they pose a clinical diagnostic dilemma. A bruit may also be heard.
The anterior branch of the superficial temporal artery is particularly vulnerable to being impinged against the calvarium. This is so because it courses over the frontal osseous ridge and its course prevents it from being displaced in the event of trauma and hence making it more susceptible to traumatic injuries. It may not produce any major symptoms but treatment may be indicated to reduce the risk of hemorrhage from subsequent trauma, relieve headaches if it causes any and for cosmetic purposes. Neurological symptoms are hardly ever present.
Ultrasound is diagnostic and shows a complex mass in the soft tissues in close proximity to the superficial temporal artery. The feeding artery can usually be identified. The differential diagnosis includes a hematoma, cyst, inflammatory lesion and vascular tumor. Color Doppler shows the characteristic findings of a pseudoaneurysm with a swirling flow and yin-yang pattern of color flow [bidirectional]. No flow would be visualized if it is thrombosed. A traumatic AV fistula may also coexist and can be diagnosed with ultrasound.
Ultrasound is also now assuming a therapeutic role in treating these pseudoaneurysms. Thrombin injection to cause thrombosis of the pseudoaneurysm is fast becoming an acceptable mode of treatment with success rates nearing 100% according to many studies. However, one study reported seizures and ischemia of the scalp as a complication of this procedure and hence caution should be exerted while injecting thrombin. The other alternatives include radiological embolization and surgical repair.