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.