Introduction Superficial temporal artery (STA) arteriovenous fistulas (AVFs) and aneurysms are rare vascular anomalies, typically post‐traumatic or iatrogenic in origin. The concurrent presence of both lesions is exceedingly rare. Endovascular techniques offer a minimally invasive alternative to traditional surgical management, particularly in elderly patients with multiple comorbidities. We present a case of concurrent STA AVF and aneurysm discovered incidentally and successfully treated with Onyx embolization. Methods Case report and literature review. Results A 90‐year‐old male with multiple comorbidities was hospitalized for acute deep vein thrombosis and initiated on anticoagulation. On hospital day 4, he sustained an unwitnessed fall resulting in a left scalp laceration. He remained asymptomatic for vascular abnormalities. CT head revealed bilateral chronic subdural hematomas (SDHs), and anticoagulation was held. On day 9, during planned middle meningeal artery embolization, angiography incidentally revealed a direct high‐flow AVF between the left parietal branch of the STA and the superficial temporal vein, along with a distal STA aneurysm measuring 8.3 mm × 10 mm × 7.6 mm. Via transfemoral access using a 6F, 55 cm sheath, a 6F Envoy XB catheter was advanced into the left external carotid artery. A Headway Duo microcatheter over a Synchro 2 microwire was navigated into the aneurysm. A total of 2 cc of Onyx 34 was injected, achieving complete embolization of both the AVF and aneurysm. Post‐procedural angiography confirmed successful obliteration. The patient resumed antiplatelet therapy and returned to baseline without complications. One‐month follow‐up CT demonstrated persistent SDHs and a stable Onyx cast without evidence of scalp deformity, alopecia, or embolization‐related changes. Conclusion We report a rare case of concurrent STA AVF and aneurysm, incidentally diagnosed in an elderly trauma patient and successfully managed with Onyx endovascular embolization. This case highlights endovascular embolization as safe, minimally invasive, and effective treatment option, particularly for high surgical risk patients. Figure 1: Left External Carotid Artery Angiogram Anteroposterior (AP) views (Images A and C) and lateral views (Images B and D) of the left external carotid artery angiogram. Images A and B : Pre‐embolization angiography demonstrating a superficial temporal artery (STA) arteriovenous fistula (AVF) draining into the superficial temporal vein (STV) (blue arrow), along with a distal STA aneurysm measuring approximately 8.3 mm in height, 10 mm in width, and 7.6 mm in depth (red arrow). Images C and D : Post‐embolization angiography confirms the successful obliteration of the STA AVF and the distal STA aneurysm following Onyx embolization. Figure 2: Axial image from CT head/brain without contrast The blue arrow points to the Onyx cast in the left parietal scalp region adjacent to the mixed density left SDH (red arrow).
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