The LN is one of the sensory branches of the mandibular division of the trigeminal nerve. After the mandibular division enters the infratemporal fossa through foramen ovale, it gives off the auriculotemporal, inferior alveolar, and lingual nerves in the infratemporal fossa. The LN receives the chorda tympani approximately 1 cm below the bifurcation of the lingual and inferior alveolar nerves, while carrying taste sensation to the anterior two-thirds of the tongue and parasympathetic innervation to the submandibular and sublingual salivary glands [19]. Although the LN pathway is well-known, its injury during oral surgical procedures and head and neck surgeries are not uncommon, especially in the lingual side of the mandibule [20, 21]. Described as a potential complication during palatal surgery when using the PR as a fixation point [12], in this work, we have sought to explain the anatomy of the LN concerning the oropharyngeal walls and the PR.

In this study, the presence of a tendinous band compatible with the PR was only present in 25% of specimens. The concept of the PR as a tendinous band is not supported by cadaveric studies [22]. Shimada et al. in an anatomical study including 110 sides, concluded that the PR was only partially present in the 28% of specimens. In the rest of the specimens, the PR was absent (36%), or both muscles (BM and SCM) were only separated by fascia (36%). The authors concluded that the mucosa fold on those specimens was redundant mucosa that was accentuated into a vertical fold when opening the mouth [15]. Regarding radiological studies, Brown et al [23] where able to identify a tendinous structure in an axial nasopharyngeal plane compatible with the PR in 63% of the subjects included in their study. They also concluded that MAD treatment response and the amount of maximum advancement improved in subjects without PR. It is essential to bear in mind when performing intra pharyngeal surgery that the PR is an anatomical structure that is only present in approximately one-third of patients, especially if it is to be considered as an anchor point. Nowadays, the best option to study the presence of the PR is through MRI. However, the techniques described are limited to locating its position by identifying the junction of the SCM and the BM, and its prevalence through the imaging studies described differs from anatomical studies [22,23,24]. For this reason it is necessary to rely on certain bony grips such as the pterygoid hamulus and not refer to the PR.

As described in previous anatomical studies [19,20,21] and also from a surgical perspective (transoral approach), in all the specimens, the LN passed downward, superiorly–inferiorly and laterally–medially, between the ramus of the mandible and the MPM. All the specimen evaluated showed a well-developed MPM with a typical penniform structure made up of alternating muscular/ aponeurotic layers and tendinous intramuscular sheets as described in an anatomical study performed by El Haddioui et al. [17]. After having crossed through the muscle, the LN takes an antero-medial direction at the anterior border of the MPM and the posterior attachment of the mylohyoid muscle, and most of the time medial, below and behind the third molar, it re-emerges into the mouth lateral to the styloglossus muscle and towards the lateral surface of the tongue, by passing beneath the lower border of the SCM.

Because the PR was not present in all the specimens, and that in those cases in which it was identified, its anatomical position was modified due to a disruption of the buccopharyngeal fascia plane and its loss of tension during dissection, this structure could not be used as a reference measure in the study. The antero-medial border of the MPM was present in all the specimens and its position remained the same after the dissection. Previous anatomic and radiological studies described that the antero-medial border of the MPM is in contact with the antero-lateral border of the SCM [22, 25, 26]. In the specimens included in the study, it was also possible to appreciate the proximity of the antero-medial border of the MPM to the point of intersection between the SCM and the BM.

The relationship of the LN with other structures such as the submandibular duct, the hypoglossal nerve, the inferior alveolar nerve, or the region of mandibular third molar have been described [21, 27, 28]. However, we have not been able to find in the literature studies with similar measurements. Although it had been previously described that there is a potential risk of damaging the LN during palate surgeries, due to its proximity to the lower edge of the PR, the results obtained describe from an objective point of view the anatomic relationship between both structures. The main limitations of this study are the small sample of specimens, the disturbance of the native anatomic location of the structures during dissection, and that all cadaveric specimens were at least 50 years of age, therefore, younger specimens might offer slightly different quantitative results. Although the exact distance between the PR and the LN was not assessed, based on the anatomical findings and previous studies we consider that the distance between the anterior border of the MPM and LN approximates the distance between the PR and the LN.