Assessment of the stylohoid chain by 3D-CT

To assess the variations of stylohyoid chain (SHC) using 3D-CT.

We evaluated a total of 200 SHC on the head/neck CT scans of 100 patients (44 females, 56 males, age range 18-73 years). All of the patients had been scanned for neck lesions other than those concerning the region of the SHC. The morphology of both SHCs was examined in the 3D-CT images and the following aspects were evaluated; 1. length, 2. thickness, 3. mediolateral angling (MLA), 4. anteroposterior angling (APA), and 5. bending of the SHC.

Absence of the styloid process (n: 5), double proximal origin (n: 2), segmentation (n: 49), and complete ossification (n: 2) were found. The length of the SHC was 27.9 +/- 11.3 mm, and 26.2 +/- 11.1 mm on the right and left, respectively. The mean thickness of the SHC was 5 mm, and it showed positive correlation with length (P < 0.05). MLA was 73.2 +/- 6.7 and 70.7 degrees +/- 8.0 degrees for the right and left, respectively. APA was 64.6 degrees +/- 10.1 degrees and 62.7 degrees +/- 10.2 degrees for the right and left, respectively. There was a negative correlation between the right and left MLA (P = 0.001), and a positive correlation between the right and left APA (P = 0.001). Nine SHCs had bending of the lower end.

Three-dimensional CT gives detailed and reliable information about the SHC. We propose that the bending and thickness, which are new parameters, should be taken into consideration in the CT evaluation and classification of SHC variations.