To test the hypothesis that soft palate muscles are abnormal in cleft
palate, we compared soft palate morphogenesis in fetuses with cleft pa
late (n=4) to age-matched (n=3) and nonmatched (n=1) control specimens
. The morphologic status of all soft palate and masticatory structures
were classified into one of six stages based on the level of histogen
esis. At 54 mm crown-rump length (CRL), the levator veli palatini (L),
palatopharyngeus (PP), and palatoglossus (PG) in cleft subjects demon
strated mesenchymal condensation into myoblastic fields, lagging behin
d the control specimens (97 mm CRL), which displayed definitive fields
of myoblasts and myotube formation. In the 175 mm and 225 mm cleft an
d the 170 mm and 192 mm control specimens, muscular morphology was sim
ilar and had reached its postnatal appearance for the tensor veil pala
tini (175 m only) and L, PP, PG (225 mm only). Muscle fiber directions
were, however, disoriented and disorganized, especially close to the
medial epithelial edge of the cleft. The levator veli palatini, could
not be distinguished as a discrete muscle in the cleft specimens, and
what we believed io be the PP and PG seemed ''normal'' at the level of
light microscopy, but malpositioned in a superior direction. This pre
liminary study demonstrates for the first time that early myogenesis i
n cleft palates differs from normal.