Three-dimensional imaging of palatal muscles in the human embryo and fetus: Development of levator veli palatini and clinical importance of the lesser palatine nerve.
BACKGROUND
After palatoplasty, incomplete velopharyngeal closure in speech articulation sometimes persists, despite restoration of deglutition function. The levator veli palatini (LVP) is believed to be significantly involved with velopharyngeal function in articulation; however, the development and innervation of LVP remain obscure. The development of LVP in human embryos and fetuses has not been systematically analyzed using the Carnegie stage (CS) to standardize documentation of development.


RESULTS
The anlage of LVP starts to develop at CS 21 beneath the aperture of the auditory tube (AT) to the pharynx. At CS 23, LVP runs along AT over its full length, as evidenced by three-dimensional image reconstruction. In the fetal stage, the lesser palatine nerve (LPN) is in contact with LVP.


CONCLUSIONS
The positional relationship between LVP and AT three-dimensionally, suggesting that LVP might be derived from the second branchial arch. Based on histological evidence, we hypothesize that motor components from the facial nerve may run along LPN, believed to be purely sensory. The multiple innervation of LVP by LPN and pharyngeal plexus may explain the postpalatoplasty discrepancy between the partial impairment in articulation vs. the functional restoration of deglutition. That is, the contribution of LPN is greater in articulation than in deglutition.
Department of Plastic and Reconstructive Surgery, Kyoto University Graduate School of Medicine, Kyoto, Japan.|Congenital Anomaly Research Center, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Hideaki
H
Kishimoto
Congenital Anomaly Research Center, Kyoto University Graduate School of Medicine, Kyoto, Japan.|Human Health Sciences, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Shigehito
S
Yamada
Human Health Sciences, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Toru
T
Kanahashi
Allied Health Sciences, Kitasato University, Kanagawa, Japan.
Akio
A
Yoneyama
Department of Systems Science, Graduate School of Informatics, Kyoto University, Kyoto, Japan.
Hirohiko
H
Imai
Department of Systems Science, Graduate School of Informatics, Kyoto University, Kyoto, Japan.
Tetsuya
T
Matsuda
Allied Health Sciences, Kitasato University, Kanagawa, Japan.
Tohoru
T
Takeda
Department of Plastic and Reconstructive Surgery, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Katsuya
K
Kawai
Department of Plastic and Reconstructive Surgery, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Shigehiko
S
Suzuki
D002972:Cleft Palate / Q000473:pathology*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D010156:Palatal Muscles / Q000196:embryology* / Q000294:innervation / Q000473:pathology; D010159:Palate / Q000196:embryology*
Kyoto collection; human embryo; human fetus; lesser palatine nerve; levator veli palatini muscle; palatoplasty; phase-contrast imaging