Arteriovenous Malformation of the Trapezius Muscle: A Report of a Rare Case.

Arteriovenous malformations (AVMs) are rare congenital fast-flow vascular anomalies characterized by direct arteriovenous shunting through a nidus. Intramuscular AVMs are uncommon and are frequently mistaken for intramuscular hemangiomas or venous malformations, and involvement of the trapezius muscle is exceptionally rare. We report the case of a 31-year-old woman with a five-year history of chronic left-sided cervical pain that had been managed as a muscle spasm with no improvement. Examination revealed a fixed trapezius mass with localized tenderness. Ultrasonography and magnetic resonance imaging (MRI) demonstrated an intramuscular tangle of dilated vessels, and catheter angiography confirmed a high-flow AVM. Following multidisciplinary discussion, the patient underwent transarterial embolization and sclerotherapy with near-complete obliteration of the shunt and remained symptom-free without recurrence at two years. AVMs are suggested to be considered in persistent, atypical neck and shoulder masses, where minimally invasive endovascular treatment can yield excellent outcomes.