A study of changes in levator muscle in congenital ptosis.

Purpose: To study microscopic and ultrastructural changes of levator palpebrae superioris (LPS) muscle in congenital ptosis.

Methods: In this prospective observational study, LPS muscle was studied in 77 eyelids with congenital ptosis; 35-simple congenital ptosis (SCP), 12-Marcus Gunn jaw winking phenomenon (MGJWP), and 30-blepharophimosis epicanthus inversus syndrome (BPES). Light microscopy, enzyme histochemistry, immunohistochemistry and electron microscopy were performed, and results were analyzed.

Results: Muscle fibers were detected in 83.33% of MGJWP, 22.86% of SCP and 16.67% of BPES eyelids. Fibers were detected significantly more in individuals with moderate ptosis, LPS action > 4 mm, present eyelid crease and eyelid fold. Severe endomysial and perimysial fibrosis was seen significantly more in individuals with MGJWP. Fat infiltration and nuclei internalization were seen in all three groups. The absence of degenerating or regenerating fibers and inflammatory cells, normal staining pattern on immunohistochemistry and absence of accumulation of any abnormal substance were found in all three groups. Abnormal mitochondrial staining pattern was seen occasionally in three groups. On electron microscopy, muscle was detected in 1 SCP eyelid and 8 MGJWP eyelids out of which 4 had myofibrillary disruption. All other eyelids where muscle fibers were not detected had only fibrocollagenous tissue.

Conclusion: Fibrocollagenous tissue predominated in all the cases, and muscle fibers detected correlated inversely with the severity of ptosis. The absence of degenerating, regenerating fibers and inflammatory cells supported the theory of dysgenesis of muscle. However, internalization of nucleus seen in all the subtypes is a feature favoring dystrophy.