Peripheral branching of levator superioris muscle and Müller muscle origin

Abstract

<h4>Purpose</h4>To examine the structure of the distal levator superioris muscle and the origin of the Müller muscle.<h4>Design</h4>Experimental dissectional study.<h4>Methods</h4>Specimens from 10 postmortem upper eyelids and orbits of 7 white cadavers (6 right eyes and 4 left eyes; age range, 78 to 101 years of age at death; age average, 87.7 years) were used for microscopic observations. The upper eyelids and orbits with sagittal full-thickness sections of the central part were examined microscopically using Masson trichrome staining.<h4>Results</h4>Sections from 9 of the specimens were suitable for analysis. The levator superioris muscle divided into a superior and an inferior branch by connective tissue in the peripheral region in all 9 samples. Although the thickness of each branch varied, that of the superior branch tended to be thicker than that of the inferior branch. In 8 specimens of 7 cadavers, the Müller muscle originated from the distal end of the inferior branch of the levator superioris muscle. In one specimen, the Müller muscle originated from the distal end as well as the posterior aspect of the levator superioris muscle. The levator aponeurosis originated from the superior branch.<h4>Conclusions</h4>The distal levator superioris muscle consisted of a branched structure, and the Müller muscle originated from the inferior branch of the levator superioris muscle.