Topographic anatomy of the lingual nerve and variations in communication pattern of the mandibular nerve branches

Abstract

We made a thorough observation of the morphology and course of the lingual nerve (LN) and inferior alveolar nerve (IAN) to clarify their topographical relationships in the infratemporal fossa and in the paralingual area. Thirty-two Korean hemi-sectioned heads were dissected macroscopically and microscopically from a clinical viewpoint. On the 32 tracings on the radiograph, the average distance between the retromolar portion and the LN was 7.8 mm, and no case was found where the LN ran above the alveolar crest as passing along the mandibular lingual plate. The bifurcation of the LN and IAN was located around the mandibular notch, inferior to the otic ganglion in 66% of the cases, and a plexiform branching pattern of the mandibular nerve was observed in only two cases. The bifurcation spot of the LN and IAN was located 14.3 mm inferior to the foramen ovale and 16.5 mm superior to the tip of hamulus. Collateral nerve twigs from the LN to the retromolar area were observed in 26 cases (81.2%), with an average of one nerve twig. We observed four types of variations in terms of communication pattern. In four specimens, the mylohyoid nerve passed through the mylohyoid muscle and connected with the LN. In other four specimens, the IAN communicated with the auriculotemporal nerve. We also observed another type of variational communication between the IAN and the nerve to the lateral pterygoid (LPt); this was observed in only one specimen, and it could be predicted that motor innervation from the nerve to the LPt was transmitted via the mental nerve to the depressor anguli oris. Another type was observed where the IAN divided into two branches with the posterior branch being partially entrapped by the LPt muscle fibers.

The relationship of the lingual nerve to the third molar region using radiographic imaging

“…Due to analysing similar studies in the literature with this study, there are similarities between the mean values of vertical distance of the lingual nerve to the lingual crest of the mandible and the data of Pogrel et al 11 But some differ ences are found comparing Koreans 22 and our results. There are also some dif ferences in the mean values of horizon tal distance of the nerve to the lingual plate of the mandible with this study and the data of other studies.…”

“…9 However, it was 15.5 mm in Korean adult cadavers. 22 In the present study, this vertical distance was 9.56 mm ± 5.28 mm in adult cadav ers in Cologne. Our results are more similar to adult Caucasians than Kore ans' values.…”

“…1,4,[6][7][8][9]19,23 Some attempts to determine the anatomic relationships of the lingual nerve consisted of cadaveric dissections and clinical observations in the third molar region. 2,6,7,11,22 Moreover, the radiographs would have provided useful information for the localisation of the nerve in this area. The variability of the localisation emphasises the prob lem of safe surgery in this area.…”

“…1,3,8,14,19-21 some Previous studies have consisted of cadaveric dissections and clinical observations. 2,6,7,11,22 Fur thermore, in radiographic methods, the nerve could be seen in multiple planes. Additionally, it was confirmed that the distance between the lingual nerve and alveolar crest is variable.…”

Lower Third Molar Region

“…It is a thick nerve whose mean diameter is 2.56 mm (Karakas et al, 2007), and runs the infratemporal region and descends in search of the submandibular hiatus, through which it penetrates the paralingual space where it emits its terminal rami; at the height of the lower second molar, the lingual nerve makes a medial curve to surround the submandibular conduct and emit its terminal rami (Chan et al, 2010a). In its course, the lingual nerve can establish communications with the mylohyoid nerve, which completes its innervation and explains a percentage of aneasthetic failures (Behnia et al, 2000;Kim et al, 2004).…”