Histochemical analysis of cleft palate muscle.

Research has clarified the abnormal insertions and orientations of the involved musculature in cleft palate. However, little is known about the physiologic aspects of these muscles, specifically from a histochemical perspective. In this study, 30 muscle specimens were removed from the palatal cleft margin in patients undergoing primary palatoplasty. Nine patients had combined cleft lip and palate deformity, and seven had an isolated cleft palate. Biopsies were taken from the area of the musculus uvulus in all specimens and examined by histochemical techniques. The percentage of type 1 and type 2 fibers was different in isolated cleft palate as compared with cleft lip and palate specimens, being, respectively, 56.7 percent type 1 and 43.3 percent type 2 and 62.0 percent type 1 and 38.0 percent type 2 fibers. This is the opposite ratio from other facial muscles but is in line with the literature regarding normal palatal muscle. Isolated cleft palate muscle fibers also were minimally decreased in diameter as compared with normal facial muscle. Fiber diameters of the combined cleft lip and palate muscles were severely decreased in size compared with those muscles found in the cleft lip. Abnormal mitochondrial accumulations also were found in cleft lip and palate muscle specimens but not in isolated cleft palate muscle specimens. We consider the decrease in muscle diameter found in isolated cleft palate to be secondary to functional atrophy, while that in the cleft lip and palate specimens is secondary to a primary hypoplasia together with a functional atrophy.(ABSTRACT TRUNCATED AT 250 WORDS)