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A post-traumatic pulsatile nodule in the right pre-auricular region

A 48 year old window fitter was referred directly from his general practitioner to the maxillofacial department with an eight week history of a painless, slowly enlarging nodule in his right pre-auricular region. He had noticed the lump shortly after a minor bump on his head at work. He was otherwise fit and well.

Clinical examination confirmed a 10 mm firm and pulsatile nodule in the pre-auricular region. It was non-tender and non-fixed. Differential diagnoses included epidermal inclusion (sebaceous) cyst and lipoma. However, given his history of minor trauma, the maxillofacial team requested an ultrasound examination to confirm the nature of the lesion before further intervention.

Duplex ultrasound examination of the right pre-auricular region showed a pulsatile nodule adjacent to the superficial temporal artery and right parotid gland that contained turbulent arterialised blood flow. Tortuous afferent and efferent arterialised vessels were also seen adjacent to the parotid gland.



### 1. What are the differential diagnoses for a pulsatile mass in this location?

#### Answer

A pseudoaneurysm of the superficial temporal artery, true aneurysm, arteriovenous malformation, vascular tumour, and mass overlying the artery with transmitted pulsations.

#### Discussion

From clinical assessment and duplex ultrasound examination, the patient was diagnosed as having a pseudoaneurysm of the right superficial temporal artery. Duplex ultrasound examination of the right pre-auricular region (fig 1⇓) showed a nodule of pulsatility adjacent to the superficial temporal artery and right parotid gland.



Fig 1 Duplex ultrasound image of the right pre-auricular region showing a hypoechoic mass (arrowheads) containing central turbulent arterialised blood flow (C). Tortuous afferent (A) and efferent (B) arterial vessels are seen lying adjacent to the right parotid gland (P). The anatomical location of the vessels makes them consistent with the superficial temporal artery …