The innervation of the soft palate muscles involved in cleft palate: a review of the literature

Abstract

Objective: Surgical techniques to obtain adequate soft palate repair in cleft palate patients elaborate on the muscle repair; however, there is little available information regarding the innervation of muscles. Improved insights into the innervation of the musculature will likely allow improvements in the repair of the cleft palate and subsequently decrease the incidence of velopharyngeal insufficiency. We performed a literature review focusing on recent advances in the understanding of soft palate muscle innervation.

Material and methods: The Medline and Embase databases were searched for anatomical studies concerning the innervation of the soft palate.

Results: Our literature review highlights the lack of accurate information about the innervation of the levator veli palatini and palatopharyngeus muscles. It is probable that the lesser palatine nerve and the pharyngeal plexus dually innervate the levator veli palatini and palatopharyngeus muscles. Nerves of the superior-extravelar part of the levator veli palatini and palatopharyngeus muscles enter the muscle form the lateral side. Subsequently, the lesser palatine nerve enters from the lateral side of the inferior-velar part of the levator veli palatini muscle. This knowledge could aid surgeons during reconstruction of the cleft musculature. The innervation of the tensor veli palatini muscle by a small branch of the mandibular nerve was confirmed in all studies.

Conclusion: Both the levator veli palatini and palatopharyngeus muscles receive motor fibres from the accessory nerve (through the vagus nerve and the glossopharyngeal nerve) and also the lesser palatine nerve. A small branch of the mandibular nerve innervates the tensor veli palatini muscle.

Clinical relevance: Knowledge about these nerves could aid the cleft surgeon to perform a more careful dissection of the lateral side of the musculature.

Keywords: Glossopharyngeal nerve; Lesser palatine nerve; Levator veli palatini; Palatopharyngeus; Pharyngeal plexus; Tensor veli palatini; Vagus nerve.

Fig. 1

Adapted from Shimokawa et al. [13] by I. Janssen. Dorsal view. Distribution of the pharyngeal plexus in the superior-extravelar part of the LVP and nasal and oral parts of the PP. LVP levator veli palatini muscle, PP-N palatopharyngeus muscle nasal strand, PP-O palatopharyngeus muscle oral strand, PS palatopharyngeal sphincter, MU uvulae muscle, PPA palatopharyngeal arch, Cs constrictor superior muscle, H hamulus, NS nasal septum, U uvula, IX glossopharyngeal nerve, X vagus nerve

Fig. 2

Superior view on soft palate with the innervation by the lesser palatine nerve, adapted from Shimokawa et al. [13] by I. Janssen. A part of the LVP is removed for better view on the five nerve fibres of the lesser palatine nerve, which were found in the human cadaver study by Shimokawa et al. [13]. These nerves run underneath the palatine aponeurosis and the nasal part of the PP and penetrate the inferior-velar part of the LVP on its lateral surface close to the insertion of the LVP in the midline of the velum. LPN lesser palatine nerve, LVP levator veli palatini muscle, PA palatine aponeurosis, PP-N palatopharyngeus muscle nasal strand, PP-O palatopharyngeus muscle oral strand, TVP tensor veli palatini muscle, MU uvulae muscle

Fig. 3

The dual innervation of the soft palate by the LPN and the pharyngeal plexus (idea and design by RJH Logjes and CC Breugem after combining the two innervation patterns shown in Figs. 1 and 2, illustrated by I Janssen). View of the plastic surgeon on the soft palate; the pharyngeal plexus penetrates the superior-extravelar part of the LVP on the lower lateral border. The lesser palatine nerve runs through the lesser palatine foramen and runs over the palatine aponeurosis of the TVP and the nasal part of the PP to enter the inferior-velar part of the LVP on its lateral surface. Here, the LPN innervates the small inferior-velar part of the LVP and the anterior part of the oral part of the PP, together referred to as the anteromedial region of the soft palate muscles. LPF lesser palatine foramen, LPN lesser palatine nerve, IX glossopharyngeal nerve, X vagus nerve, TVP tensor veli palatine muscle, LVP levator veli palatini muscle, PP-N palatopharyngeus muscle nasal strand, PP-O palatopharyngeus muscle oral strand, U uvula