J Med Cases
Journal of Medical Cases, ISSN 1923-4155 print, 1923-4163 online, Open Access
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Case Report

Volume 9, Number 12, December 2018, pages 403-405


Extramandibular Presentation in the Course of the Inferior Alveolar Nerve: A Case Report and Review of the Literature

Ilson Sepulvedaa, b, c, d, h, J. Patricio Ulload, e, Francisco Rivas-Rodriguezf, Rodrigo Barrosg

aSchool of Dentistry, Finis Terrae University, Concepcion, Chile
bRadiology Department, ENT-Head and Neck Surgery, Concepcion, Chile
cDental-Maxillofacial and Nuclear Medicine Services, General Hospital of Concepcion, Concepcion, Chile
dENT-Head and Neck Surgery Service, General Hospital of Concepcion, Concepcion, Chile
eUniversity of Concepcion School of Medicine, Concepcion, Chile
fDivision of Neuroradiology, Radiology Department, University of Michigan Health System, Ann Arbor, MI 48109, USA
gEmergency and Internal Medicine Services, General Hospital of Concepcion, Concepcion, Chile
hCorresponding Author: Ilson Sepulveda, ENT-Head and Neck Surgery Service, General Hospital of Concepcion, San Martin Av. 1436, Concepcion, Chile

Manuscript submitted November 13, 2018, accepted November 21, 2018
Short title: Extramandibular Submucosal Course of IAN
doi: https://doi.org/10.14740/jmc3215

Abstract▴Top 

The inferior alveolar nerve (IAN) is a branch of the mandibular nerve, the third division of the trigeminal nerve (V cranial nerve). Its location and course into the mandible is very important because of its susceptibility to the injury during any surgical or prosthetic approaches. Cone beam computed tomography (CBCT) is a three-dimensional imaging modality, with less exposure than multi slice computed tomography (MSCT), being considered an ideal imaging tool for maxillofacial diagnosis. We present an unusual extramandibular submucosal course of IAN in relationship with a mandibular exostosis, and with no association with the sensory disorder.

Keywords: Atrophic; Mandible; Exostosis; Incidental finding; Cone beam computed tomography

Introduction▴Top 

The inferior alveolar nerve (IAN) enters to the mandible by the mandibular foramen, located on medial aspect of the ramus, and runs in anterior and lateral direction inside the mandibular body, until exits by the mental foramen at the premolar region. In this course, it gives sensory nerves from incisive (through incisive nerve) to molar region, including to the mentolabial area. The knowledge of its considerable variation in the course, shape, curve, and directions is essential at moment to any surgical procedure plan in this area. Cone beam computed tomography (CBCT) provides an accurate location, and to determine any anatomical variation in the course of the mandibular canal and its relation with neighbor anatomical structures [1, 2].

Case Report▴Top 

A 75-years-old female without a significant medical history, presented for imaging study of swelling on the medial aspect of the right mandibular body. The clinical exam revealed total edentulous jaw and hard swelling in the area mentioned above, without ulceration, pain or paresthesia. No other injuries or cervical lymphadenopathy were identified. Also, the patient presented no other symptoms.

CBCT was performed showing a hyperdense exostosis of the cortical bone without compromise of the bone marrow. As incidental finding demonstrated the entry and exit of the IAN canal in relationship with the exostosis (Fig. 1a, b), the volume rendering with virtual representation of the IAN confirmed this finding (Fig. 1c, d).

Figure 1.
Click for large image
Figure 1. CBCT of the mandible shows a cortical bone exostosis in medial aspect of the right mandibular body (red arrow), exit and entry holes of the mandibular canal (yellow arrows). As shown the three- dimensional IAN course representation (red). (a) Coronal. (b) Oblique sagittal. (c, d) Osseous volume rendering.
Discussion▴Top 

IAN located outside of the mandible is a rare condition; it’s the most common presentation which is associated to severe atrophy in edentulous mandibles or hypoplastic condition in dentulous mandible [1]. Various imaging modalities including the conventional and computerized tomography have been used to evaluate mandibular morphology before a surgical procedure. In CBCT the appearance of the mandibular canal usually is a well-defined hypodense zone, lined by hyperdense borders [2].

From its origin, IAN runs obliquely down and forward, enters the medial mandibular ramus through the mandibular foramen; runs more or less horizontal, and ends between the apices of the first and second premolar, exiting the mental foramen giving terminal mental and incisive nerves [3].

Worthington described that there are three different configurations of the inferior alveolar canal (IAC) as follows: 1) A progressive curve rising from anterior to posterior; 2) A steep ascent from anterior to posterior; and 3) A catenary-like canal [4].

Sanam M. et al evaluated the IAN course in three age groups and demonstrated that straight and progressive descending pattern were the most prevalent pattern in the 20 - 29 years age group. In the 30 - 44 and 45 - 59 years age group the most prevalent category was recorded as straight and catenary, respectively, without any statistically significant difference between the three age groups [5].

Therefore, information on the buccolingual, superior and inferior position of the canal could assist surgeons in avoiding injury to the IAN [6]. Atieh Safaee et al established that the greatest distance, from IAC to the buccal cortex existed at the second molar region, where the lingual distances in some cases reached zero [7]. In the vertical dimension, A. Ozturk et al demonstrated that on average, the IAC rans almost 1 cm (range 6.10 - 15.30 mm) above the inferior border of the body of the mandible in the molar region [8].

Extracanalicular variations of the IAN are exceedingly rare and unreported. R. Manikandhan et al reported absent mandibular canal and mental foramen associated to unilateral hemifacial microsomia, including hypoplasia of the facial musculature with a mild degree of microtia [9]. C. Herlin et al reported a very short course in the left IAC, opening onto the lateral surface of the mandibular angle. There was no other foramen on the lateral wall of the left mandibular body. No morphological abnormality of the face was noted on clinical examination [10].

Conclusions

Better understanding of the anatomic variation of the nerve may alter the planning of surgical procedures. Based on anatomical features and imaging findings, potential damage of the IAN during oral and dental operative treatment procedures in this region can be alleviated.

Financial Support

None.


References▴Top 
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