A standardized technique for the placement of electrodes in the two heads of the lateral pterygoid muscle.

The results of electromyographic research on the two heads of the lateral pterygoid muscle depend largely on correct placement of the electrodes. Measurements were carried out on 24 male and 27 female skulls of known age and sex to determine the direction and depth of penetration for the placement of wire electrodes in the two heads of the lateral pterygoid muscle separately. The method of placement was simulated on human dissecting room material. With the use of a modified dental facebow, endodontic needles were placed in the direction of the two heads of the lateral pterygoid muscle in 11 human cadavers. The point of penetration was the most cranial point of the lower border of the zygomatic arch, lateral to the sigmoid notch of the mandible; after dissection over 80% of the needles proved to be placed correctly. The technique has since been used over 60 times on both heads of the lateral pterygoid muscle in volunteering dental students, dentists, and patients with symptoms of craniomandibular dysfunction. The technique interferes with the maximal opening of the mouth, which was reduced by about 10 mm. Subjects suffered slight inconveniences after the removal of the electrodes at the end of the test procedures. These inconveniences consisted of stiffness in the jaws and muscle soreness. Hematomas or infections did not occur.