PREVIOUS studies have shown that the stapedius muscle of several vertebrates including man is uniquely endowed with a rich neuromuscular substrate. This substrate is presumably required for the finely coordinated contractions exhibited by the muscle in effectively dampening the transmission of potentially damaging frequencies of sound across the middle ear. It is characterized by an exceedingly rich motor nerve supply, small motor unit sizes, and limited sensory innervation compared to other skeletal muscles.1-6 These features of nerve-muscle relationships are now well established for middle ear muscles, but there are no observations concerning the effect of age, acoustic trauma, or pathological conditions on the number of nerve and muscle fibers or the ratio of nerve fibers to muscle fibers (ie, the size of the motor unit).
Constant bombardment by sound, susceptibility to infection or degenerative change, and normal aging processes are forces which continuously influence the efficiency of the middle
Blevins CE. Motor Units in the Stapedius Muscle. Arch Otolaryngol. 1968;87(3):249–254. doi:10.1001/archotol.1968.00760060251007