A rare variation in the course of the inferior alveolar nerve

Abstract

Extra-canalicular variations of the inferior alveolar nerve are exceedingly rare and unreported. The authors report an unusual presentation of the inferior alveolar nerve perforating the ramus of the mandible with a very short intra-bony course and exiting laterally in a 20 year old indian female diagnosed with hemifacial microsomia. There was concomitant absence of the ipsilateral inferior alveolar canal and mental foramen. Variations in nerve architecture like these are of importance to clinicians who deal with surgery of the facial skeleton.

The mandibular nerve is the third division of the trigeminal nerve (V cranial nerve). It is predominantly a sensory nerve, but also has motor components. From the trigeminal ganglion, through the foramen ovale, the mandibular nerve descends down towards the mandibular foramen on the medial aspect of the mandiblar ramus. The position of this foramen and the course of the nerve are well established by many authors, for the purpose of local anesthetic techniques and various surgical procedures, including osteotomies.

The authors present an unusual case of an inferior alveolar nerve entering the mandible through the medial aspect at an unusually high position at the C1, C2 level then exiting through the lateral aspect of the ramus of the mandible without running through the corpus of the mandible. A literature search on this variation showed that this is the only reported case of such an unusual variation of inferior alveolar nerve.

Case report

A 20-year-old female patient presented with unilateral hemifacial microsomia (HFM) of the left side, including hypoplasia of the facial musculature with a mild degree of microtia with preauricular tags. No other associated abnormalities were present as a facio–auriculo–vertebral spectrum. Orthopantomographic (OPG) images were consistent with HFM, with absent mandibular canal and mental foramen on the hypoplastic side, there was also an abnormal finding of a more prominent radiolucent mandibular foramen area on the affected side ( Fig. 1 ). A series of three dimensional (3D) computed tomography (CT) images demonstrates the entry ( Fig. 2 ) and exit ( Fig. 3 ) of the inferior alveolar nerve through the width of the ramus.

Fig. 1
OPG showing absent mandibular canal and mental foramen on the hypoplastic side.

Fig. 2
3D CT demonstrating the entry of the nerve at an unusually high position.

Feb 8, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on A rare variation in the course of the inferior alveolar nerve
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