Ultrastructural Characteristics of the Orbicularis Oris Muscle in the Microform Cleft Lip

ABSTRACT

RecentIy, increasing emphasis has been placed on the histochemical and ultrastructural characteristics of the muscle in the cleft lip. Schendelet al and Cho et al demonstrated a non-neurogenic muscle atrophy and mitochondrial myopathy, and Raposio examined an increased inflammatory reaction, but no mitochondrial abnormalities of the cleft lip muscle. However, no study has focused on the ultrastructure of the microform cleft lip muscle. Eleven muscle specimens were obtained from the microform cleft lip patients at the time of primary repair from Jun.1997 to Aug.1998 and they were submitted to histologic and histochemical examinations as well as electron microscopy. A non-neurogenic muscle atrophy was seen on HE stain. Modified Gomori trichrome stain revealed red granularity of the muscle fibers, suggesting an increase in mitochondrial activity, however, no ragged-red fibers, a typical sign of mitochondrial myopathy, was found. Electron microscopy revealed atrophy, disarray, and focal loss of myofibrils, dilated sarcoplasmic reticulum with glycogen deposit, and interstitial fibrosis. However, the mitochondrial morphology was well preserved with an increase of the number of the mitochondria which might be secondary change to muscle degeneration. In conclusion, ultrastructural characteristics of the orbicularis oris muscle in the microform cleft lip is non-neurogenic muscle atrophy without mitochondrial myopathy which is controversial in the complete cleft lip.