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 histoche mical perspective. In this study, 30 muscle specimens were removed fro m 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 th e musculus uvulus in all specimens and examined by histochemical techn iques. The percentage of type 1 and type 2 fibers was different in iso lated cleft palate as compared with cleft lip and palate specimens, be ing, 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 reg arding normal palatal muscle. Isolated cleft palate muscle fibers also were minimally decreased in diameter as compared with normal facial m uscle. Fiber diameters of the combined cleft lip and palate muscles we re severely decreased in size compared with those muscles found in the deft lip. Abnormal mitochondrial accumulations also were found in cle ft lip and palate muscle specimens but not in isolated cleft palate mu scle specimens. We consider the decrease in muscle diameter found in i solated cleft palate to be secondary to functional atrophy, while that in the cleft lip and palate specimens is secondary to a primary hypop lasia together with a functional atrophy. This, together with the abno rmal mitochondria seen in cleft lip and palate, indicates a different pathogenesis for these two types of palatal clefts. This also helps ex plain the poor function and possible velopharyngeal dysfunction found in many patients following adequate palatal repair.