13) As has been shown in glycogen depletion studies, diffusion of botulinum toxin from an injected thyroarytenoid muscle into the adjacent lateral cricoarytenoid muscle
may also contribute to the arrest of adduction.
26] The third motor branch innervates the lateral cricoarytenoid muscle
(LCA), passing through it to terminate in the thyroarytenoid muscle (TA).
The posterior cricoarytenoid muscle can also be reached through the cricothyroid membrane, especially in females and some young men.
7] This is in contrast to other evidence that suggests that fast-twitch fibers in the thyroarytenoid and lateral cricoarytenoid muscles are reinnervated more rapidly and to a greater degree than slow-twitch fibers.
6,9,12,13) A typical finding is symmetric high uptake at the muscle origin and insertion of the arytenoid cartilage, posterior cricoarytenoid muscles
, and some less intense uptake along the course of thyroarytenoid and vocalis muscle (11) (Figure 1).