Atypical intramuscular arterio-venous malformations and intramuscular capillary type hemangiomas (ICTH) of the head and neck: considerations on a case series of 13 patients.

Vascular anomalies can be harbored within a muscle. Slow-flow ones (venous malformations, fibro adipose vascular malformations, etc.) are frequent. However, high-flow intramuscular vascular anomalies (IFVA) are rare and poorly understood. A retrospective study was conducted on a case series of 13 patients suffering from IFVA of the head and neck area. For each case, the following were examined: clinical course, treatment, histological features and prognosis. Two distinct entities were revealed: intramuscular arteriovenous malformations (AVM) and intramuscular capillary-type hemangioma (ICTH). They were similar in many aspects. Both presented as slowly-growing, pulsating and warm tumefactions. They involved the masseter muscle in nine cases, the masseter and the temporalis in one, the sternocleidomastoid in one, the anterior and middle scalene in 1, and the frontalis in 1. On imaging, both showed the presence of a mass-like tissue with vessels within it. This appeared as T1 isointense and T2 hyperintense, and had vivid contrast enhancement. However, AVM had bigger and more prevalent vessels, while ICTH had smaller and fewer ones. On ultrasound imaging, AVM presented the typical features of shunting (low resistance index) whereas ICTH did not. AVM and ICTH were histologically different. Patients who were managed with accurate and complete resection did not relapse, whereas partial or subtotal removal resulted in disease recurrence. Intramuscular fast-flow vascular anomalies comprise AVM and ICTH. They share common features, but are different diseases. Complete surgical removal appears to be an effective method of treating both.