Background: Recent improvements in image quality have contributed to an increasing number of incidental findings (IF). Also called as "incidentalomas", this generic term refers to an entity discovered unexpectedly on an imaging examination performed for other reason. Commonly, normal variants, minor developmental anomalies and imaging artifacts are described as potential pathology. Some IF were reported in magnetic resonance imaging (MRI) exam of temporomandibular joint (TMJ), including IF in the brain, maxillary sinus, ethmoidal cells, mastoid cells, salivary glands, muscles. The aim of this study is to evaluate the prevalence of IF on MRI of TMJ from Japanese patients.
Methods: An image archive from 872 patients referred to MRI evaluation due to TMJ symptomatology was assessed. Three experienced radiologists evaluated all images, and the final diagnosis was achieved by consensus. The data regarding IF was recorded, considering only tumor and tumor-like lesions.
Results: A total of 12 (1.38%) of tumor and tumor-like lesions were observed from all 872 MRI exams evaluated. The most frequent lesion was arachnoid cyst (0.45%), followed by neoplastic lesions (0.22%).
Conclusions: The question "should every IF be reported?" is still difficult to answer. Relevant IF are rare, and radiologists are expected to be reasonable: think about the adverse effects of reporting an IF, and, based on their own judgment, choose for a positive or a negative answer.