Arteriovenous Malformations of the Temporalis Muscle: A Comprehensive Review

Arteriovenous malformations of the temporalis muscle (TM-AVMs) are rare lesions commonly considered as a variant of scalp AVMs. A study was designed in order to analyze TM-AVMs features and to confirm them as a certain entity different from scalp AVMs. Seven TM-AVMs cases (5 from literature plus 2 from our database) were studied. Clinical, epidemiological, radiological, and therapeutic data were analyzed and compared to common scalp AVMs features. All TM-AVMs presented as large soft tumor-like masses on the temporal region (mean diameter: 6 cm). Pain was referred in half of cases, while overlying cutaneous stigmas were described only once. No masticatory malfunction was reported. TM-AVMs tend to appear in young patients (mean: 29 yr), commonly as longstanding and slow-evolving lesions (mean evolution time before diagnosis: 5 yr). All cases displayed a diffuse slow-flow blush on angiogram. All TM-AVMs were completely located within the TM, with no involvement of scalp or bone. The pathological analysis of all cases demonstrated the presence of striate muscular bundles intermingled with fairly mature arterial and venous vessels. No clearly distorted vessel was found within the TM-AVMs. Surgery was performed for all cases with complete removal. Preoperative embolization was done in 4 cases to reduce blood loss during surgery. No clinical/radiological recurrence was reported. Opposite to TM-AVMs, scalp AVMs commonly present as high-flow lesions with no evident tumor mass, mainly located in the subcutaneous tissue. TM-AVMs present clearly distinct features compared to scalp AVMs, for which they should be considered as a certain pathological entity and not as a variant of scalp AVMs.