Electrical stimulation to clinically identify position of the lingual nerve: results of 50 subjects with reliability and correlation with MRI.

PURPOSE: Recently we described mapping of the lingual nerve clinically in patients using electrical nerve stimulation. This paper reports results of a larger study with inter- and intra-observer reliability and comparison with positional measurements from magnetic resonance imaging (MRI). METHODS: In 50 healthy participants, measurements were taken when subjects felt a tingling sensation in the tongue induced by a stimulation probe over the lingual nerve. Three positions were measured in relation to the third molar. Measurement reliability was tested for both inter-observer and intra-observer agreement and positional data of the lingual nerve measured clinically was also compared with nerve position as measured from MRI scans. RESULTS: Out of 50 participants, 96 nerves (49 = left/47 = right) were included in the study. The lingual nerve was identified in 90% (87) of this sample. The mean of height of the nerve in points A, B and C were 9.64 mm, 10.77 mm and 12.34 respectively. Inter-and intra-observer agreement was considered to be good to excellent (ICC = 0.8-0.96). Agreement between nerve mapping measured values and MRI measured values was good (ICC < 0.6). CONCLUSION: This technique may prove useful for the clinical determination of lingual nerve position prior to procedures in the third molar region.

Schwannoma arising from the sublingual glandular branch of the lingual nerve radiologically masquerading as sublingual gland tumor.

We report a rare case of schwannoma arising from the sublingual glandular branch of the lingual nerve radiologically masquerading as sublingual gland tumor. A 42-year-old female was referred to our department with a painless swelling in the left submandibular region. Contrast-enhanced computed tomography showed a well-circumscribed, heterogeneous low-density tumor with cystic change in the left sublingual region. Magnetic resonance imaging showed a well-circumscribed, heterogeneous sublingual tumor with low-signal intensity on T1-weighted image and high-signal intensity in T2-weighted image. The lesion was diagnosed radiologically as benign sublingual gland tumor. The patient underwent resection of sublingual gland tumor under general anesthesia. There was no definitive continuity between the tumor and the sublingual gland, and the tumor originated from sublingual glandular branch of the lingual nerve. Pathological examination of the specimen showed schwannoma with highly cellular areas (Antoni A) and hypocellular areas (Antoni B). The postoperative course was uneventful without lingual nerve palsy, and there was no recurrence 4 years after surgery.

Appearance of normal MRI anatomy of the lingual nerve using steady-state free precession sequences at 3-T.

The aim of this study is to assess the value of SSFP MRI sequence in depicting the normal anatomy of the lingual nerve (LN), particularly in the molar region, in order to help the periodontists, dentists and oral surgeons in their daily practice. The study group included 24 patients who were to undergo MR study for a reason unrelated to our purpose. All imaging was performed by using a 3.0T system with a head and neck multiarray coil. The evaluation criteria included image quality factors such as the identification of the LN, its demarcation and its contrast to surrounding tissues on a five-point scale. The LN is clearly visible throughout its course from its origin from the mandibular nerve (MN) to the mylohyoid muscle. In edentulous patients, the LN could be damaged during surgical procedures especially it during the dissection and retraction of a lingual flap and, above all, during the suture due to a direct trauma caused by the needle or indirectly during tying the knot.

Solitary neurofibroma of the floor of the mouth: rare localization at lingual nerve with intraoral excision.

BACKGROUND: Neurofibromas (NF) are benign tumors of the peripheral nerves that are composed of Schwann cells, perineural-like cells and fibroblasts. The differential diagnosis for a solitary intraneural variant of neurofibroma arising in the floor of the mouth is broad and includes a submandibular gland neoplasm and adenopathy, among others. The intraoral approach is the best choice for a medium-sized lesion. CASE PRESENTATION: We report a rare case of a solitary neurofibroma of the floor of the mouth in a 31-year-old male. The patient consulted the dental emergency department for acute pain of the left mandible. Systematic clinical examination revealed the presence of a mass in the left mouth floor. The panoramic x-ray was not conclusive and the magnetic resonance imaging (MRI) revealed a well-defined soft tissue lesion with homogenous isosignal intensity on the T1-weighted image, high intensity signal on the T2-weighted image and heterogeneous enhancement following contrast-enhancement on the T1-weighted Fast Sat image. The surgical excision of the soft-tissue neoplasm was accomplished by an intraoral approach. The specimen was sent for histopathologic analysis and Immunohistochemical studies which confirmed the diagnosis of a myxoid predominant intraneural solitary neurofibroma. CONCLUSION: The diagnosis of neurofibroma was confirmed by histopathological evaluation and immunohistochemical studies which also excluded other entities in the histopathologic differential diagnosis including schwannoma and a malignant peripheral nerve sheath tumor among other. Localized (solitary) neurofibromas most often occur as sporadic lesions, however; diagnosis of a solitary neurofibroma prompts clinical evaluation to exclude the remote possibility of neurofibromatosis. The purpose of this case report is to raise awareness of the uncommon presentation of neurofibroma and to document the successful management of such a lesion using an intraoral approach.

Plunging ranula with lingual nerve tether: Case report and literature review.

Plunging ranulas are most often treated surgically; various surgical approaches may be necessary depending on the unique characteristics of each case. Here, we present the case of a plunging ranula noted on imaging to have a cordlike tether, which was revealed intraoperatively to be the lingual nerve. This case illustrates the importance of preoperative imaging for surgical planning, and when a transcervical approach may be the best choice for plunging ranulas.

Perineural Invasion and Perineural Tumor Spread in Head and Neck Cancer.

Perineural invasion (PNI), the neoplastic invasion of nerves, is a common pathologic finding in head and neck cancer that is associated with poor clinical outcomes. PNI is a histologic finding of tumor cell infiltration and is distinct from perineural tumor spread (PNTS), which is macroscopic tumor involvement along a nerve extending from the primary tumor that is by definition more advanced, being radiologically or clinically apparent. Despite widespread acknowledgment of the prognostic significance of PNI and PNTS, the mechanisms underlying its pathogenesis remain largely unknown, and specific therapies targeting nerve invasion are lacking. The use of radiation therapy for PNI and PNTS can improve local control and reduce devastating failures at the skull base. However, the optimal volumes to be delineated with respect to targeting cranial nerve pathways are not well defined, and radiation can carry risks of major toxicity secondary to the location of adjacent critical structures. Here we examine the pathogenesis of these phenomena, analyze the role of radiation in PNI and PNTS, and propose guidelines for radiation treatment design based on the best available evidence and the authors' collective experience to advance understanding and therapy of this ominous cancer phenotype.

The utility of three-dimensional optical projection tomography in nerve injection injury imaging.

The examination of nerve microarchitecture has hitherto been limited solely to two-dimensional imaging techniques. The objective of this study was to evaluate the ability of optical projection tomography to discern the nerve microarchitecture and injection injury in three dimensions. Five piglets were studied, whose median and lingual nerves were unilaterally injected post mortem with preset volumes of local anaesthetic, excised and subsequently made transparent with benzyl alcohol benzyl benzoate. Images were captured in three dimensions. The same contralateral nerves were used as controls. Using optical projection tomography, we observed differences between the internal organisation of the median and the lingual nerves, which potentially explain the variations in their susceptibility to injury. This was demonstrated in three dimensions as a disruption to the fascicles in the lingual nerve, and their displacement in the median nerve. This new technology offers potential for studying nerve microarchitecture topography and its tolerance to injection injury.

Clinical anatomy of the lingual nerve and identification with ultrasonography.

Our objective was to investigate the pathway of the lingual nerve and find out whether it can be identified using ultrasonography (US) intraorally. It is a dominant sensory nerve that branches from the posterior division of the mandibular aspect of the trigeminal nerve, and is one of the two most injured nerves during oral surgery. Its anatomy in the region of the third molar has been associated with lingual nerves of variable morphology. If surgeons can identify its precise location using US, morbidity should decrease. We searched published anatomical and specialty texts, journals, and websites for reference to its site and US. Cadavers (28 nerves) were dissected to analyse its orientation at the superior lingual alveolar crest (or lingual shelf). Volunteers (140 nerves) had US scans to identify the nerve intraorally. Our search of published books and journals found that descriptions of the nerve along the superior lingual alveolar crest were inadequate. We found no US studies of the nerve in humans. Dissections showed that the nerve was above (n=6, 21%) and below (n=22, 79%) the crest of the lingual plate. US scans showed 140 lingual nerves intraorally in 70 volunteers. The nerve lay either above or below the superior lingual alveolar crest, which led us to develop a high/low classification system. US can identify the lingual nerve and help to classify it preoperatively to avoid injury. Our results suggest that clinical anatomy of the lingual nerve includes the superior lingual alveolar crest at the third and second molars because of its surgical importance. US scans can successfully identify the nerve intraorally preoperatively.

CT-scan imaging of iron marked chorda tympani nerve: anatomical study and educational perspectives.

The chorda tympani nerve (CTN) is the last collateral branch of the facial nerve in its third intraosseous portion just over the stylomastoid foramen. After a curved course against the medial aspect of the tympanum where it is likely to be injured in middle ear surgery, CTN reaches the lingual nerve in the infratemporal fossa. Knowledge of CTN topographic anatomy is not easily achieved by the students because of the deep location of this thin structure. The aim of this study was to assess the spatial relationships of the CTN in the infratemporal fossa. Therefore, ten nerves were dissected in five fresh cadavers. All the nerves were catheterized with a 3/0 wire. After a meticulous repositioning of surrounding structures, standard X-ray and CT scan examinations were performed with multiplanar acquisitions and three-dimensional surface rendering reconstructions. Ventral projection of the CTN corresponded to the middle of the maxillary sinus. Lateral landmark was the mandibular condyle. The CTN was present and unique in all the dissections. The average length of the nerve, as measured on CT scans, was 31.8 mm (29-34, standard deviation of 1.62); the anastomosis of the CTN to the lingual nerve was located at a mean 24.9 mm below the skull base (24-27, standard deviation of 0.99), approximately in the same horizontal plane as the lower part of the mandibular notch. The acute angle opened dorsally and cranially between CTN and LN measured mean 63.2° (60-65, standard deviation of 1.67). Three-dimensional volumetric reconstructions using surface rendering technique provided realistic educational support at the students' disposal.

Inferior alveolar and lingual nerve imaging.

At present, there are no objective testing modalities available for evaluation of iatrogenic injury to the terminal branches of the trigeminal nerve, making such clinical diagnosis and management complicated for the oral and maxillofacial surgeon. Several imaging modalities can assist in the preoperative risk assessment of the trigeminal nerve as related to commonly performed procedures in the vicinity of the nerve, mostly third molar surgery. This article provides a review of all available imaging modalities and their clinical application relative to preoperative injury risk assessment of the inferior alveolar nerve and lingual nerve, and postinjury and postsurgical repair recovery status.

The significance of the lingual nerve during periodontal/implant surgery.

BACKGROUND: Understanding the position of the lingual nerve is important when performing third molar extractions and periodontal and implant surgeries in the mandible. The careless management of the lingual flap can potentially cause damage to the lingual nerve. The location of the lingual nerve in the third molar region was described in the literature; however, to our knowledge, its course mesial to the third molar region was not reported. The aim of this study is to identify and measure the location of lingual nerves in relation to mandibular teeth in fresh cadaver heads. METHODS: Thirty lingual nerves from 18 cadaver heads were dissected, and the vertical distance from the lingual nerve to the mid-lingual cemento-enamel junctions of mandibular molars and premolars and the position where the lingual nerve left the lingual plate and moved toward the tongue were determined. Two cadaver heads were randomly selected and exposed to cone-beam computed tomography (CBCT) scans after the insertion of a wrought wire into the nerve. The same vertical distance as the clinical measurement was determined and compared. RESULTS: Seventy-five percent of lingual nerves turned toward the tongue at the first and second molar region. The vertical distance was 9.6, 13, and 14.8 mm at the second molar, first molar, and second premolar, respectively. The difference between clinical and CBCT measurements was 0.57 +/- 2.62 mm. CONCLUSIONS: The course of the lingual nerve in relation to posterior teeth was described. This information can help surgeons gain more understanding of the location of the lingual nerve and perform safe surgeries in the mandible.

Spatial relationships between lingual nerve and mandibular ramus: original study method, clinical and educational applications.

Lingual nerve damage complicating oral surgery would sometimes require electrographic exploration. Nevertheless, direct recording of conduction in lingual nerve requires its puncture at the foramen ovale. This method is too dangerous to be practiced routinely in these diagnostic indications. The aim of our study was to assess spatial relationships between lingual nerve and mandibular ramus in the infratemporal fossa using an original technique. Therefore, ten lingual nerves were dissected on five fresh cadavers. All the nerves were catheterized with a 3/0 wire. After meticulous repositioning of the nerve and medial pterygoid muscle reinsertion, CT-scan examinations were performed with planar acquisitions and three-dimensional reconstructions. Localization of lingual nerve in the infratemporal fossa was assessed successively at the level of the sigmoid notch of the mandible, lingula and third molar. At the level of the lingula, lingual nerve was far from the maxillary vessels; mean distance between the nerve and the anterior border of the ramus was 19.6 mm. The posteriorly opened angle between the medial side of the ramus and the line joining the lingual nerve and the anterior border of the ramus measured 17 degrees . According to these findings, we suggest that the lingual nerve might be reached through the intra-oral puncture at the intermaxillary commissure; therefore, we modify the inferior alveolar nerve block technique to propose a safe and reproducible protocol likely to be performed routinely as electrographic exploration of the lingual nerve. What is more, this original study protocol provided interesting educational materials and could be developed for the conception of realistic 3D virtual anatomy supports.

Using ultrasound to visualize the lingual nerve.

PURPOSE: The purpose of this study was to assess the effectiveness of ultrasonography in visualizing the lingual nerve, calculating its distance from the lingual cortex at the area of the third molar, and in detecting injuries. MATERIALS AND METHODS: Using a standardized protocol, lingual nerve dissections were performed in Yorkshire pig cadaver heads. After nerve isolation was confirmed, the nerve was left intact, fully transected, or partially transected. The dissection flap was repositioned and the pig heads were given to 3 blinded evaluators. Using a handheld ultrasound device, the evaluators were asked to determine the status of the nerve and categorize their finding as intact, fully transected, or partially transected. The recorded ultrasound images from the 9 study specimens were then analyzed and the distances of the lingual nerves from the alveolus were measured. RESULTS: After becoming familiar with the ultrasonographic appearance of the lingual nerve, all of the evaluators were able to visualize and identify the nerve using the ultrasound machine. Lingual nerve injuries were accurately categorized in 17 out of the 27 total attempts (success rate, 63%). The average distance of the nerve from the alveolar cortex was measured to be an average distance of 1 mm. CONCLUSION: The results of this study indicate that ultrasonography can be effectively used to visualize the lingual nerve.

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

OBJECTIVE: Lingual nerve damage is a common complication during oral and maxillofacial surgery procedures to the third molar region. The anatomy of the lingual nerve is variable, therefore the precise knowledge of anatomy of this nerve is important for decreasing the damage risk. The purpose of this study was to determine the position and the shape of the lingual nerve in the third molar region using radiographic imaging. SETTING: The Anatomy Department of Cologne University in Germany. MATERIALS AND METHODS: Firstly, an anatomic dissection of the lingual nerve in the third molar region was done on 10 whole heads and one sagittal hemisection head specimen of adult cadavers. After marking the nerve, x-ray films were taken. Vertical and horizontal measurements were made from the radiographs with an electronic digital caliper. RESULTS: The mean vertical and horizontal distances of the nerve to the lingual crista and lingual plate of the mandible were found to be 9.5 +/- 5.2 mm and 4.1 +/- 1.9 mm respectively. Additionally, of the 21 lingual nerves examined, 17 (81%) were round and 4 (19%) were flat. CONCLUSIONS: The results reflect the relationship of the nerve to this area and may help the clinician to avoid the damage risk.

Morbidity of harvesting of retromolar bone grafts: a prospective study.

20 retromolar bone grafts were harvested in outpatients for augmentation of the implant site from January to June 2000 (10 female, 10 male, 40.9 +/- 12.8 years, minimum 17 years, maximum 66 years). The aim of the study was to assess typical complications of this procedure in a prospective manner. For the determination of the superficial sensory function of the inferior alveolar and the lingual nerve, an objective method was used. The bone grafts were harvested for single tooth reconstruction. In 14 cases a ridge augmentation and in 6 cases an endoscopically controlled crestal sinus floor elevation was performed. Preoperatively, the height of bone above the cranial aspect of the inferior alveolar nerve in the retromolar region was assessed radiologically with known markers. The maximum mouth opening was determined. The superficial sensory function of the inferior alveolar and the lingual nerve was assessed with the Pointed-Blunt Test, the Two-Point-Discrimination Test and the objective method of the 'Pain and Thermal Sensitivity' Test (PATH Test). Moreover, the pulp sensitivity of the teeth of the donor site was determined by cold vitality testing. All tests were repeated 1 week postoperatively. Intraoperatively, the width of the retromolar region was measured with a caliper. The patients rated the operative strain on a visual analogue scale. The height of bone above the inferior alveolar nerve in the retromolar region was 11.0 +/- 2.2 mm. The width of the retromolar area was 14.2 +/- 1.9 mm. Postoperatively, the maximal mouth opening changed significantly (40.8 +/- 3.5 mm preoperatively, 38.9 +/- 3.7 mm postoperatively, P = 0.006). However, the reduction was not relevant clinically. A direct injury of the inferior alveolar or lingual nerve did not occur. A sensitivity impairment could not be detected for either of the nerves by the different test methods 1 week postoperatively. The operative strain related to the donor site was significantly less than the strain generated by the implant placement (rating on a visual analogue scale 2.8 +/- 1.0 and 4.1 +/- 2.0, respectively, P = 0.027). Retromolar bone grafts are a viable method for augmentation of the implant site in conjunction with single tooth reconstruction with low strain on the patient and minimal risk of complications.

High resolution computed tomography of the inferior alveolar and lingual nerves.

Coronal and axial high resolution computed tomography of the mandible extends facilities in dentoalveolar surgery. Preoperatively the relationship between the mandibular canal and the roots of deeply displaced third molars can be determined precisely. After surgical removal of lower wisdom teeth iatrogenic defects of the lingual cortical bone can be detected. The additional information obtained when compared with conventional radiographs is demonstrated in case descriptions. Indications for this technique, radiation exposure and implications for surgery are discussed.