On images, a dermoid cyst is often described as resembling a "sack of marbles" or "marbles in a bag". Typically, it comprises an inhomogeneity filled with multiple nodules in a fluid matrix on both computed tomography and magnetic resonance imaging (MRI). How it appears, however, will vary depending on its histological contents, which may cause confusion in arriving at a diagnosis. This report describes a dermoid cyst in the floor of the mouth of a 55 year-old woman that showed an atypical internal appearance on MRI. Most of the lesion showed homogeneous high signal intensity on T1 - and T2-weighted images, suggesting that it was derived from fat. A small area within the mass, however, showed moderate signal intensity almost equal to that of muscle on T1-weighted images and high signal intensity on fat-suppressed T2-weighted images. Given the location of the lesion, a dermoid cyst was one possible diagnosis. A lipoma or lipoma variants were also considered, however, based on signal intensity. Histopathological section of the excised specimen revealed a dermoid cyst with sebaceous glands in its walls and keratin in its cavity. Dermoid cysts show variation in their internal structures and contents. Since MRI can reflect such histological variation, signal intensity requires careful interpretation.
FLAIR sequences provide a high signal in patients having painful TMJ, and it suggests that retrodiscal tissue in painful TMJ contains elements such as protein.
The hyoid bone is located in the middle of the cervical muscles involved in oral masticatory function. The position of the hyoid bone is commonly determined by lateral cephalometric analysis. Although cephalometric radiography is commonly used in orthodontic treatment, the modality remains rare ; routine dental care would bene t from precise identi cation of hyoid bone location using a more common modality, such as panoramic radiography. The purpose of this study was to investigate the usefulness of panoramic radiography compared to lateral cephalometric radiography for evaluating hyoid bone position as a potential screening method for oral hypofunction. The study included 347 patients referred for both a panoramic radiograph and a lateral cephalometric radiograph. The patients were divided into the following ve groups according to the appearance of the hyoid bone in the panoramic radiograph : Group 1 : hyoid bone could not be observed, or part of the greater horn was observed ; Group 2 : part of the hyoid body was observed, but not the most supero-anterior point of the hyoid bone ; Group 3 : the most supero-anterior point of the hyoid bone was observed ; Group 4 : all of the hyoid body was observed ; Group 5 : the hyoid body overlapped the mandible. The gold standard for measurement of hyoid bone position is the lateral cephalometric radiograph. Hyoid bone position as revealed by lateral cephalometric radiograph was compared among the groups. Hyoid bones that were observed in higher positions on lateral cephalometric radiograph were also observed in higher positions on panoramic radiograph. Hyoid bone position can be assessed by panoramic radiography, and this modality might be useful as a screening method for oral hypofunction.
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