Histological findings of levator muscle in unilateral congenital ptosis in different age groups

PURPOSE: To evaluate the different degree of muscle atrophy in specimens of levator muscle of patients operated on for unilateral congenital ptosis, as related to the age of the patient. METHODS: Histological analysis of the specimen of the levator muscle of 29 patients who underwent a unilateral levator muscle resection under the care of one surgeon was performed. The study population was divided into two different groups according to the timing of surgery: group 1 included 15 children operated on at 2 to 4 years, and group 2 included 14 children operated on at 4.1 to 11 years. RESULTS: Levator muscle of 12 patients of group 1 showed mild degree of muscle atrophy, with striated muscle fibres separated by thin fibrous septa incorporating groups of cells with peripheral nuclei and non-hyalinized cytoplasm (Masson's trichrome stain). In eight cases of group 2, levator muscle showed instead severe atrophy, with discontinuous striated muscle fibres separated by thick fibrous septa including cells with centralization of nuclei, hyalinization of cytoplasm (Masson's trichrome stain) and fatty infiltration. CONCLUSION: Myofibres found in specimens of levator muscle following levator resection for congenital ptosis show characteristics of a degenerative process. This study seems to demonstrate that atrophy in the levator muscle appears to be related to the age of the patient at surgery, as atrophy tends to be more evident in older children with congenital ptosis.