Management of lingual nerve injury: a case report

Abstract

and sublingual salivary glands, the latter follow the fibers of the lingual nerve to the taste buds. Once separated from the mandibular nerve, it runs between the internal pterygoid muscle and the medial wall of the mandibular ramus. At the retromolar trigone and molar (particularly the third) level, the nerve runs on the upper medial margin of the alveolar ridge and can be very superficial. The LN then runs into the oral floor and terminates in the lingual pelvis (1). Anatomical studies of the LN mainly focus on its course at the oral cavity floor and the retromolar trigone level, as it is most susceptible to injury during surgical procedures (2-6). In a cadaver dissection study, 669 LNs were analyzed. 14.05% were located above the lingual crest, 0.15% in the retro molar trigone and 85.80% in the typical position, i.e. at a vertical distance from the lingual crest of 3.01±0.42 mm and at a horizontal distance from the lingual plate of 2.06 ± 1.10 mm (7). In its typical position, the LN, in 23.27% of the cases, is directly in contact with the lingual plate of the alveolar process. However, when the LN is located in the retromolar area, it runs between the mandibular ramus and the medial pterygoid muscle, instead of proceeding in its normal course along the medial surface of the mandible and lying near the roots of the third molars. It heads towards the retromolar trigone, then it runs posterior to the third molar and, finally, it descends at an acute angle in the direction of the medial surface of the mandible, resuming its normal course (8). Aetiology of lingual nerve injuryThe most frequent cause of LN lesion is to be sought in the extraction surgery of the lower third molars: LN is, in fact, damaged during 0.6-2% of extractions of these tooth elements (9, 10). However, implant surgery, removal of calculi from the Warton's duct, treatment of ranula located in the postero-lateral portion of the mouth floor, removal of mandibular cysts, of impacted or supernumerary teeth, of benign lesions or demolition for malignant neoformations, orthognathic surgery, osteoradionecrosis, osteomyelitis and maxillofacial trauma may also be among the causes of LN injury (11,12). Performing truncular anaesthesia can also cause neurological injury. The incidence of temporary injuries of the LN following the performance of truncular anaesthesia ranges between 0.15% and 0.54%, while permanent ones range 0.01% approximately (13,14). The etiopathogenetic mechanism may be related to a needle injury, to the potential neurotoxicity of the anaesthetic agent and its ischaemic effect with possible subsequent degeneration of axons (15).