Longitudinal changes on cranial magnetic resonance imaging in relapsing giant cell arteritis.

There is a need for better tools to monitor disease activity in giant cell arteritis (GCA). Prior studies demonstrated that vascular enhancement on cranial vessel wall magnetic resonance imaging (vw-MRI) decreases with treatment of GCA, but whether enhancement increases during relapse is not well known. This study examined changes on vw-MRI during relapse of cranial GCA. Patients with active GCA acquired cranial vw-MRIs at enrollment and months 1, 6, and 12 and if suspected relapse occurred. Neuroradiologists graded vw-MRI enhancement for several structures. Changes in MRI scores were compared with clinically-determined disease activity and acute phase reactants (APR). Fourteen patients with GCA were included: 4 patients experienced a cranial or ocular relapse; 2 patients experienced a relapse with polymyalgia rheumatica (PMR) without cranial symptoms; and 8 patients were in sustained remission. All 4 patients who experienced cranial or ocular relapse had increased vw-MRI enhancement in at least one cranial structure. Two patients experiencing relapse of PMR had persistent but not increased enhancement, while 7 of 8 patients in sustained remission had decreased or normal enhancement on follow-up. Cranial structures that showed increased enhancement at relapse included the occipital artery, optic nerve sheath, and maxillary artery. APR levels remained normal in most relapses, likely impacted by use of tocilizumab. During relapse of cranial GCA, increased contrast enhancement of cranial structures is observed on vw-MRI even when APR levels remained normal. These data offer proof-of-concept that vw-MRI has potential for longitudinal disease monitoring of GCA.