Morphologische Normwerte von Augenmuskeln (M. levator palpebrae superioris und M. rectus superior) im Vergleich zu Extremitätenmuskeln (M. deltoideus und M. quadriceps femoris)
by Ansgar Schmitz
Date of Examination:2025-02-05
Date of issue:2025-01-23
Advisor:Prof. Dr. Walter Joachim Schulz-Schaeffer
Referee:Prof. Dr. Walter Joachim Schulz-Schaeffer
Referee:Prof. Dr. Christoph Viebahn
Persistent Address:
http://dx.doi.org/10.53846/goediss-11035
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Abstract
English
The function of the eye muscles enables them to perform fast and precise movements while also exhibiting a pronounced resistance to fatigue. Although the structure and function of eye muscles differ from the limb musculature, there are no distinct established and standardized histomorphological analysis criteria. Therefore, this work is focused on a practical approach in routine diagnostics to improve the general understanding by describing the unique characteristics of eye muscles and to address the lack of standardized values. Particular attention was paid to histochemical stains commonly used in the primary diagnosis of muscle tissue: hematoxylin and eosin (HE), myoadenylate deaminase (MAD), Periodic acid–Schiff (PAS), Oil Red O (ORO), Elastica by van Gieson (EvG), nonspecific esterase (UE), nicotinamide adenine dinucleotide (NADH), menadione-linked alpha-glycerophosphatase (MAG), myofibrillar ATPase (ATPase), trichrome modified according to Gomori, acid phosphatase (AP), cytochrome c oxidase/succinate dehydrogenase (COX/SDH), supplemented by some more specific stains (LAMP-1, SERCA-1, Prohibitin). Compared to peripheral musculature, the eye muscles show a pronounced variation in muscle fiber caliber and abundant connective tissue. In addition, varying degrees of elastic fibers were particularly evident in the superior rectus muscle. The trichrome stain modified according to Gomori exhibited intensive fuchsinophilic stained fibers in up to 90% of all fibers per field of view. While in limb muscles, those fibers are defined as so called pathologic ragged red fibers, due to their common appearance in eye muscles a classification as pathologic would be a misinterpretation. There were frequently larger fractions of small fibers in the eye muscles, implying an overestimation of per definition pathologically atrophic fibers. Additionally, the assessment of the angularity of fibers as well as the identification of pyknotic core clusters was more challenging than in peripheral muscle tissue. Thus, the usual diagnostic criteria of muscle fiber atrophy and hypertrophy including the respective etiological classification are probably not equally applicable to the assessment of eye muscle tissue. Muscle fiber type assessment was also more challenging because of limited reciprocity of different stains (NADH, ATPase stain) and a partly wider staining spectrum. Other findings appearing to distinct eye from peripheral muscles were fibers with a stronger reaction in the PAS stain, a subtly increased fat content in some fibers, a slightly higher overall proportion of confluent vacuoles were noted in the ORO stain, more frequent COX deficiencies in the context of aging, a stronger reactivity in the UE stain in some fibers of the superior rectus muscle as well as an increased signal in the acid phosphatase reaction in the superior rectus muscle. All in all, due to the specific characteristics of the eye muscles classical assessment schemes and standard values obtained from the analysis of peripheral muscles are not uncritically applicable. Further studies on pathological eye muscle tissue are necessary to clearly differentiate normal from pathological findings.
Keywords: Ragged Red Fiber; Musculus rectus superior; Musculus levator palpebrae superioris
Schlagwörter: Ragged-Red-Fiber; Augenmuskeln; Musculus levator palpebrae superioris
