Deformation/displacement of posterior digastric and sternocleidomastoid muscles during posterior digastric muscle palpation using magnetic resonance imaging and image processing procedure

Abstract

Objective: As the process of palpation is basically subjective, the scientific evidence for masticatory muscle palpation, especially from an anatomical point of view, is scarce. Our previous study concerning the quantification of masseter muscle deformation during palpation using magnetic resonance imaging and image analysis procedure showed that masseter muscles are deformed and their fascia must be stretched during palpation (Ishikawa et al., Int J Prosthodont, in press). The aim of this study was to further evaluate the deformation/displacement of posterior digastric and sternocleidomastoid muscles during posterior digastric muscle palpation using almost the same procedure as in the previous study. Subjects and methods: Subjects were 10 male volunteers with an average age of 26·8 years. MR images were taken using a 1·5 T scanner (MAGNEX 150 SHIMAZU Co. Ltd, Kyoto, Japan). Images were obtained on the axial plane with a spin-echo, T1-weighted technique using a head coil. At first, non-compressed condition (control) was taken, then the continuously compressed condition of the bilateral posterior digastric muscle region using round plastic balls was taken. By superimposing a compressed image on a non-compressed image, deformation/displacement was subjectively evaluated and measured using free image analysing software (NIH-image). Results and conclusion: Deformation of the bilateral posterior digastric muscle was difficult to identify, however, the average amount of displacement in medial direction was 9·0 ± 5·3 mm. Although we tried to compress posterior digastric muscles, sternocleidomastoid muscles were additionally deformed and displaced. The amount of medial displacement was 9·3 ± 4·7 mm. The values contained in our results exhibited fairly substantial variance. These findings suggest that masticatory muscle palpation is subjective and inconsistent.