Irradiated paragangliomas of the head and neck: CT and MR appearance.

PURPOSE To present the spectrum of CT and MR findings of glomus tumors of the head and neck successfully treated with radiation therapy. METHODS The patient charts and all CT and MR studies of 24 patients (25 tumors) who had been successfully treated with radiation therapy were retrospectively reviewed. Eighteen patients had pre- and posttreatment imaging studies. Tumor size, internal morphology, enhancement pattern, visualization of flow voids, and bone erosion were evaluated before and after radiation therapy. Statistical evaluation of the presence of flows voids and tumor size was performed using the Fischer Exact Test. RESULTS All patients had residual tumor after radiation therapy. Sixty-one percent of tumors demonstrated a reduction in size. Only one tumor with pretreatment bone destruction demonstrated healing of the bone. MR findings after radiation therapy included variable alteration in T2 signal, decreased heterogeneous enhancement, and a reduction in flow voids. There was a significant difference in the presence of flow voids based on tumor size. CONCLUSIONS Successfully irradiated paragangliomas demonstrate residual masses, the presence of which does not by itself indicate treatment failure. Stabilization or reduction in size, decreased enhancement, diminished flow voids, and reduced T2 signal after radiation therapy are a result of therapy and are indicative of local control. Persistent bone demineralization and erosion without progression is commonly seen in successfully controlled tumors. Paragangliomas are relatively homogeneous in internal morphology except for areas of flow void. Flow voids are not a reliable criterion for diagnosis in lesions less than 2.5 cm.