Objectives To investigate whether CT images reflect the anatomical condition of mylohyoid muscle defects by confirmation with subsequent dissection of cadavers, and to evaluate whether CT images are useful for detecting such defects. Methods CT scans of the head and upper neck were performed in six cadavers. Multiplanar reconstruction was carried out to obtain 2-mm-thick axial and coronal images of the mylohyoid muscle. The number of defects was determined. All the cadavers were subsequently dissected for comparison with the CT findings. The contents of the defects were also identified. Results CT demonstrated the presence of one or more mylohyoid defects in four of the six cadavers. Defects were seen bilaterally in three of the four cadavers. Five of eight defects were observed on both axial and coronal images, whereas two were not observed on coronal images and one was not observed on axial images. The defects contained part of the sublingual gland bilaterally in one cadaver and unilaterally in another. In one cadaver, the submental artery passed through the defect bilaterally. In the other cadaver, there were bilateral defects without any substantial contents. Conclusions Our results indicate that mylohyoid defects are commonly seen anatomically, and that some of them show herniation of the sublingual gland. CT images can demonstrate mylohyoid defects on multiplanar reconstructed images.

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