Imaging in sinonasal sarcoidosis: CT, MRI, 67Gallium scintigraphy and 18F-FDG PET/CT features.

OBJECTIVES: Attempt to describe and analyse the radiological and nuclear medicine patterns of sinonasal sarcoidosis (SNS) still poorly reported in the literature.

MATERIAL AND METHODS: Retrospective single institution study of 22 consecutive patients with symptomatic biopsy-proven SNS to evaluate the interest of CT, MRI, (67)Ga scintigraphy and (18)F-FDG PET/CT for diagnosis and therapeutic follow-up.

RESULTS: Nodules of the septum and turbinates are the most suggestive CT and MRI features. Other CT features such as sinusal filling, mucosal thickening, osteosclerosis or destructive sinonasal lesions are not specific and depend on clinical context and evolutive stage of SNS. (18)F-FDG PET/CT provides complete morphofunctional mapping of active inflammatory sites related to sarcoidosis with a better diagnostic sensitivity (100%) compared to (67)Gallium scintigraphy (75%). The changes in (18)F-FDG uptake intensity could reflect the efficacy of treatment.

CONCLUSION: SNS is an uncommon and probably underdiagnosed phenotype of sarcoidosis. Even if guided biopsy remains necessary for SNS confirmation, medical imaging plays an important role in diagnosis and therapeutic follow-up. CT features with nodules of the septum and/or turbinates are suggestive of SNS contrary to other nonspecific CT findings. CT imaging is directly related severity, reversibility and course of SNS and provide an original radiological staging system in order to predict patient clinical outcome. PET/CT may be used for diagnosis assessement but also to monitor treatment response in a given clinical context, in a patient with histopathologically-proven SNS. Prospective and long term studies are necessary to validate these preliminary results.