An adolescent male presented to Michigan State University’s Primary Care Sports Medicine Clinic after experiencing head trauma from a lacrosse ball while wearing a helmet. Since the event, he had developed a gradually enlarging mass where he was struck.

Two weeks following the trauma, the patient reported persistent swelling and pain in the right superolateral forehead, exacerbated by pressure. Physical examination revealed a soft, compressible, and pulsatile mass. Beyond this, there were no neurological deficits or other examination abnormalities. The point-of-care ultrasound (POCUS) showed Doppler flow in the mass. As a result, a formal US was ordered and showed a 1.1 × 0.6 × 0.8-cm pseudoaneurysm in the superiorlateral right scalp at the trauma site, located in the deep subcutaneous fat layer. Due to the severity and location, a follow-up computed tomography (CT) was performed, which confirmed the pseudoaneurysm, which originated from the frontal branch of the superficial temporal artery, and ruled out skull fractures or intracranial involvement. Neurosurgery was consulted at this time.

The superficial temporal artery is a terminal branch of the external carotid artery that supplies the anterior temporal and parietal regions of the scalp ^[1]. Most pseudoaneurysms involving this vessel result from direct blunt trauma and typically present as a painless, pulsatile mass that progressively enlarges over time ^[2]. Unlike true aneurysms, which often occur spontaneously, pseudoaneurysms arise from disruption of the arterial wall with formation of a contained hematoma ^[3]. Imaging plays a critical role in diagnosis, with ultrasound demonstrating characteristic turbulent flow and CT angiography confirming vascular origin and extent [4-6]. Several repots describe similar delayed presentation following blunt trauma, emphasizing progressive enlargement of a pulsatile mass [7-10]. In this case, the patient underwent surgical excision and coagulation of the affected 3-cm arterial segment under general anesthesia (Fig. 1). The post-operative course was uncomplicated, and the patient made a full recovery with return to athletic participation.

Figure 1: Resected superficial temporal artery pseudoaneurysm measuring approximately 3 cm in length.

Superficial temporal artery pseudoaneurysm is an uncommon but important diagnosis following blunt head trauma, particularly in young athletes. Delayed presentation and subtle initial symptoms may contribute to missed or late diagnosis. This case highlights the utility of POCUS as an initial diagnostic tool, followed by confirmatory imaging with CT. Prompt surgical management resulted in excellent clinical outcomes and a safe return to sport. Clinicians should maintain a high index of suspicion for vascular injury when evaluating post-traumatic scalp masses.

Persistent or enlarging pulsatile scalp masses after head trauma should be evaluated promptly with ultrasound and advanced imaging to rule out superficial temporal artery pseudoaneurysm and prevent delayed complications.