Cirsoid aneurysms, also known as scalp arteriovenous malformations (AVM), are 
rare congenital extracranial vascular anomalies that often present as an 
enlarging pulsatile scalp mass. A 14-yr-old male presented with a pulsatile 
scalp lesion that was first noticed 3 yr prior and had progressively enlarged. 
No history of trauma was reported. MRI demonstrated a 4 cm wide and 2 cm tall 
nidus and catheter angiography was performed to further define the vascular 
supply and drainage. The patient underwent transvenous endovascular embolization 
followed by surgical excision via a bicoronal incision, as shown in this 
operative video. Care was taken to identify, cauterize, and transect feeding 
vessels from the superficial temporal, supratrochlear, and supraorbital arteries 
circumferentially to completely devascularize and resect the galeal nidus from 
overlying scalp tissue and underlying pericranium. Previously unreported in the 
literature, transosseous emissary veins partially draining the lesion were noted 
on angiography and were waxed thoroughly during surgery. Six-month follow-up 
examination demonstrated a well-healed incision without evidence of AVM 
recurrence. The unique venous drainage of this cirsoid aneurysm highlights the 
value of diagnostic angiography to fully characterize these rare and complex 
vascular lesions prior to pursuing definitive treatment.  IRB approval was 
obtained from the Ann & Robert H. Lurie Children's Hospital of Chicago 
Institutional Review Board (IRB #2018-1799). The IRB waives the requirement of 
obtaining informed consent for this study in accordance with 45 CFR 46.116(d).