MRI displays involvement of the temporalis muscle and the deep temporal artery in patients with giant cell arteritis

PURPOSE To assess deep temporal artery and temporalis muscle involvement in patients with giant cell arteritis (GCA). MATERIAL AND METHODS Ninety-nine patients who received magnetic resonance imaging (MRI) and superficial temporal artery biopsy (TAB) were included in this study. Patients with positive TAB (n = 61) were defined as GCA patients, those with negative TAB (n = 38) as the GCA-negative reference group. Contrast-enhanced T1w-images were acquired utilizing 1.5 T and 3 T MRI. Two radiologists assessed the images. Mural contrast-hyperenhancement and wall thickening of the deep temporal artery and hyperenhancement of the muscle were defined as inflammation. MRI results were correlated with jaw claudication in 70 patients. RESULTS The two observers found temporalis muscle involvement in 19.7 % (n = 12) and 21.3 % (n = 13) of GCA patients. It occurred bilaterally in 100 %. Specificities were 92/97 % and sensitivities were 20/21 %. Deep temporal artery involvement was found in 34.4 % (n = 21) and 49.2 % (n = 30) and occurred bilaterally in 80/90.5 %. Specificities were 84/95 % and sensitivities were 34/49 %. Both structures were affected simultaneously in 18/21.3 %. Jaw claudication correlated moderately with inflammation of the temporalis muscle (r = 0.31; p < 0.05) and the deep temporal artery (r = 0.38; p = 0.01). CONCLUSION MRI visualizes changes in the temporalis muscle and the deep temporal artery in GCA. Moderate correlation of clinical symptoms with MRI results was observed. KEY POINTS • Approximately 20 % of GCA patients presented with temporalis muscle inflammation. • A total of 34-49 % of GCA patients presented with vasculitis of the deep temporal artery. • In approximately 20 % of GCA patients, both structures were simultaneously involved. • Involvement of both structures correlated moderately with presence of jaw claudication. • MRI is a suitable tool for the assessment of vasculitis and muscle inflammation