Absence of Muscle Spindles in Human Facial Muscles

Background: It has not previously been clarified if human facial muscles possess either typical muscle spindles, spindle-like structures or no spindles at all. Methods: Six patients from the Institute of Anatomy were used to investigate the Mm. orbiculares oculi and orbiculares oris. The age ranged from 53 to 91 years; three were males, three females. The specimens were imbedded in paraffin and examined in serial sections. Muscles were prepared for histological (H&E and Elastica van Gieson) and immunohistochemical (protein S-100, neurofilaments, and PGP 9.5) stainings. Results: All biopsies showed skeletal muscl…