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Surgical and Radiologic Anatomy ISSN 0930-1038 Surg Radiol AnatDOI 10.1007/s00276-014-1329-z

Variations in the branching pattern ofposterior division of mandibular nerve: acase report

Aparna Muraleedharan, RaveendranathVeeramani & Parkash Chand

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Surg Radiol AnatDOI 10.1007/s00276-014-1329-z

AnAtOmIc VARIAtIOnS

Variations in the branching pattern of posterior division of mandibular nerve: a case report

Aparna Muraleedharan · Raveendranath Veeramani · Parkash Chand

Received: 11 April 2014 / Accepted: 12 June 2014 © Springer-Verlag France 2014

teeth and gums of lower jaw, the lower lip, the skin in the temporal region, part of the auricle, the external acoustic meatus and tympanic membrane, the lower part of face and the mucosa of the anterior two-thirds of the tongue and the floor of oral cavity. the motor branches innervate the mus-cles of mastication [1].

It has a large sensory root and a small motor root which passes through the foramen ovale and unites to form the trunk of the mandibular nerve. the nerve then passes between tensor veli palatini medially, and lateral pterygoid muscle (LP) laterally, where it gives off a meningeal branch (nervus spinosus) and the nerve to medial pterygoid. the nerve then divides into a small anterior and a large poste-rior division. the anterior division gives off three motor branches to the muscles of mastication namely lateral pterygoid, masseter, and temporalis and the only sensory branch, the buccal branch which is sensory to the cheek. the posterior division gives off two sensory branches, the auriculotemporal (Atn) and lingual (Ln) nerves and a mixed nerve the inferior alveolar nerve (IAn) which con-tains motor fibres that supply the mylohyoid muscle and the anterior belly of digastric [1].

Several studies have described anatomical variations in the branching pattern of the mandibular nerve. Knowledge of the variations of the mandibular nerve, its branches and communications are clinically important especially for den-tal surgeons to understand the effectiveness of the nerve block and complications following regional anesthesia. Possible communications between the Atn and IAn have been described earlier in literature. However, such con-nections are found to be infrequent [12]. the only named branch of IAn before it enters the mandibular foramen is the nerve to mylohyoid (mHn). Some additional variant branches of IAn have also been reported in the literature [3].

Abstract Purpose Abnormal communications among the branches of mandibular nerve especially the posterior division are significant due to various procedures undertaken in this region. these variations are worth reporting as they pose serious implications in several interventions in this region, and may even lead to false diagnosis.Methods During routine dissection, the mandibular nerve and its branches were dissected in the infratemporal fossa. the branches from the posterior division of the mandibu-lar nerve namely the inferior alveolar and auriculotemporal nerves were carefully dissected, and their abnormal branch-ing pattern was noted.Results there was a communicating branch between left inferior alveolar and auriculotemporal nerve. there was also a variant recurrent branch from the left inferior alveo-lar nerve that supplied the lateral pterygoid muscle.Conclusions Such variant branches and communications between the branches of mandibular nerve as seen in this case have an embryological basis and are clinically important in this region especially for dental surgeries and anesthesia.

Keywords Inferior alveolar · Auriculotemporal · Lateral pterygoid · mandibular

Purpose

the mandibular nerve is the largest division of trigeminal nerve and is a mixed nerve. Its sensory branches supply the

A. muraleedharan (*) · R. Veeramani · P. chand Department of Anatomy, Jawaharlal Institute of Postgraduate medical Education and Research (JIPmER), Dhanvantri nagar, Puducherry, 605006, Indiae-mail: aparnamuraleedharan18@gmail.com

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All these variations probably account for the failure to obtain adequate anesthesia in oral and dental procedures and also for the unexpected injury to the branches of the mandibular nerve during surgical interventions [5]. Anasto-mosis between the fibres of the Atn and IAn could com-promise the efficacy of the IAn block and even result in serious post-operative morbidity. Here we describe a case of variations in the sensory and motor branches of the pos-terior division of mandibular nerve. there was a communi-cating branch between the IAn and Atn as well as a vari-ant recurrent branch from the IAn supplying lower head of lateral pterygoid muscle (LP).

Materials and methods

Routine dissection of a 60-year-old male cadaver preserved in 10 % formalin was performed in the gross anatomy dis-section hall of Department of Anatomy at Jawaharlal Insti-tute of Post graduate medical Education and Research, Pondicherry, India. the mandibular nerve and its branches were dissected in the infratemporal fossa. the masseter muscle was reflected inferiorly with the zygomatic arch. the temporalis muscle with the coronoid process was cut from the ramus of the mandible, and reflected upwards. the ramus of mandible was cut for better exposure of the infratemporal fossa. the termination of external carotid artery and its terminal branches namely maxillary artery and superficial temporal artery were identified. the lateral and medial pterygoid muscles were identified. the lateral pterygoid muscle was carefully removed from the infratem-poral fossa. the condylar process of mandible was cut at the neck of the mandible, and removed carefully with the insertion of the lateral pterygoid muscle. the branches of maxillary artery and mandibular nerve were dissected and preserved as far as possible. Later, the maxillary artery was divided at its origin from external carotid artery and reflected medially to demonstrate both the roots of Atn and the communication between the IAn and Atn.

Results

the variations in the branches of posterior division of man-dibular nerve were found in the left infratemporal fossa. Ln, IAn and Atn were given off normally. the nerve to lateral pterygoid (LP) was given off from the left IAn 25 mm distal to its origin and 3 mm proximal to the origin of the mHn (Fig. 1). In addition, there was a communicat-ing branch between the IAn 15 mm distal to its origin and Atn 18 mm distal to its origin. the communicating branch was 7 mm long (Fig. 2). the other branches from the man-dibular nerve and the branches of the maxillary artery

(mA) and their relationship with the LP and mandibular canal on the left side displayed a normal pattern. Also the right mandibular nerve displayed a normal branching pat-tern. there were no communications between Ln and IAn.

Discussion

Several communicating branches between the IAn and Ln have been described in the literature and these have been postulated to explain the inefficient mandibular anesthesia during dental procedures [7]. though in this case, there was no communication between IAn and Ln an incidence as high as 25 % has been reported in literature. the commu-nications between IAn and Atn have also been reported though not very common [12].

Before entering the mandible, IAn can give multiple branches which are usually associated with accessory man-dibular foramina and mandibular canals [11]. It has also been reported that in most cases where there are no associ-ated accessory foramina, such branches innervate the LP. In some cases this additional branch from IAn penetrates the LP after supplying it to join the main trunk of mandibu-lar nerve, its divisions or any of its branches. In the pre-sent case, a single recurrent variant branch of the IAn was

Fig. 1 Left infratemporal fossa showing variant recurrent branch from inferior alveolar nerve to lateral pterygoid muscle. DTA deep temporal artery, LN lingual nerve, IAN inferior alveolar nerve, RM ramus of mandible, CM condyle of mandible, ST squamous part of temporal bone, LTP lateral pterygoid plate, LP lateral pterygoid mus-cle, NLP nerve to lateral pterygoid, PSA posterior superior alveolar artery, MA maxillary artery, MM middle meningeal artery, MHN nerve to mylohyoid, a origin of IAn from posterior division of man-dibular nerve, b origin of recurrent variant branch from IAn, c origin of mHn from IAn. Distance a–b = 25 mm, b–c = 3 mm

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given off just proximal to the origin of the mHn in the left infratemporal fossa. the variant branch was found to termi-nate within the lower head of LP by supplying it. In such cases, the IAn can even be compressed during contraction of LP thus resulting in neuropathic pain [9].

the mandibular nerve and its branches develop from the neural crest cells in the head region, which migrate ven-trally through the mesoderm of the first pharyngeal arch which is thought to be influenced by F-spondin [2] and T-cadherin [10] liberated from the caudal somites. Vari-able levels in these molecules might lead to the variations in these nerves. Based on the above knowledge of embryo-genesis, abnormal or reverse migration of the neural crest cells could be postulated as a possible reason for the recur-rent variant branch as seen in this case. As IAn is a mixed nerve, the motor and sensory fibres may develop via dif-ferent pathways which may lead to the formation of addi-tional roots which may unite to form a single trunk. these additional roots may arise from Ln, Atn or posterior divi-sion of mandibular nerve itself which might appear as com-municating branches. Studies have proven the pivotal role of mandibular nerve in the development of the mandible.

Hence detailed study of the nerve, its branches and varia-tions could further our understanding of embryogenesis of the bone too thus aiding orthopedic procedures [4].

complications in the auricular sensation following IAn block have been reported clinically. One of the reasons for profound numbness of the auricle on the side of the block even in a meticulous procedure was attributed to a low ori-gin of Atn close to IAn [8]. this could also occur if there is a communicating branch between IAn and Atn [8] as was seen in the present case. Abnormal communication between IAn and Atn may also be a source of neuropathic and referred pain. Auriculotemporal neuralgia is considered as pain referred to the tooth from the ear and is a common possible cause of non-odontogenic toothache [6]. the exact pathophysiology of this is not known. clinically, odonto-genic toothache is also commonly referred to the ear. Just as the symptomatic relief with Atn blockade was achieved in the first case [6], we suggest that relief of symptoms fol-lowing IAn blockade could probably confirm the presence of communication between the two nerves in the case of toothache referred to the ear. this can relieve the pain and can even be therapeutic in such situations.

mandibular nerve block anesthesia has been reported to have only a poor success rate. Incomplete anesthesia can be explained by considering the several anatomic variations, such as communications between the mandibular nerve branches and presence of collateral branches [5].

though geniohyoid and digastric are the main muscles that open the jaw, LP is the only masticatory muscle that depresses mandible [1]. Injury to IAn in a patient where LP is solely supplied by a branch from IAn can affect opening of mouth. the additional branch from the IAn to LP suggests the probability that IAn might have additional motor fibres which is clinically important, because the motor components may extend to its terminal branch, the mental nerve [5], thus giving additional motor innervation to the depressor anguli oris muscle [5] which is clinically significant.

Conclusions

A communicating branch was identified between the left inferior alveolar nerve and the auriculotemporal nerve. there was also a recurrent variant branch from the infe-rior alveolar nerve to the lateral pterygoid muscle on the same side. Such variations suggest variable migration of neuroblasts and myoblasts in this area during embryogen-esis. the above variations have to be kept in mind espe-cially when the clinician approaches a patient with jaw pain or prior to giving regional anesthesia as well as to know the complications that might ensue following a surgery or anesthesia to this region. For effective local anesthesia

Fig. 2 Left infratemporal fossa showing abnormal communica-tion between inferior alveolar nerve and auriculotemporal nerve tri-ple asterisk after removing the lateral pterygoid muscle. Inset shows the abnormal communication after maxillary artery has been cut and reflected medially. DTA deep temporal artery, LN lingual nerve, IAN inferior alveolar nerve, IAA inferior alveolar artery, RM ramus of mandible, PSA posterior superior alveolar artery, MA maxillary artery, MM middle meningeal artery, PMF pterygomaxillary fissure, ATN auriculotemporal nerve, CT chorda tympani nerve, ECA exter-nal carotid artery, STA superficial temporal artery, MHN nerve to mylohyoid, MNP posterior division of mandibular nerve, a origin of IAn from posterior division of mandibular nerve, x–z abnormal com-munication between IAn and Atn, y origin of Atn from posterior division of mandibular nerve. Distance a–x = 15 mm, y–z = 18 mm, x–z = 7 mm

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precise knowledge of normal anatomy and possible varia-tions of mandibular nerve should be kept in mind in order to prevent complications.

Conflict of interest the authors declare that they have no conflict of interest.

References

1. Berkovitz BK (2005) Infratemporal region and temporomandib-ular joint. In: Standring S (ed) Gray’s anatomy: the anatomical basis of clinical practice, 40th edn. Elsevier churchill Living-stone, Edinburgh, pp 541–543

2. Bronner-Fraser m (1993) Environmental influences on neural crest cell migration. J neurobiol 24(2):233–247. doi:10.1002/neu.480240209

3. Buch HA, Agnihotri RG (2012) A recurrent variant branch of the inferior alveolar nerve: is it unique? clin Anat 25(4):437–443. doi:10.1002/ca.22040

4. curien R, Braun m, Perez m, Bravetti P, coqueugniot H (2011) Discriminant study of the development of the mandibular units in a neural reference system. Surg Radiol Anat 33:191–196. doi:10.1007/s00276-010-0744-z

5. Kim SY, Hu KS, chung IH, Lee EW, Kim HJ (2004) topographic anatomy of the lingual nerve and variations in communication

pattern of the mandibular nerve branches. Surg Radiol Anat 26:128–135. doi:10.1007/s00276-003-0179-x

6. murayama RA, Stuginski-Barbosa J, moraes nP, Speciali JG (2009) toothache referred from auriculotemporal neural-gia: case report. Int Endod J 42(9):845–851. doi:10.1111/j. 1365-2591.2009.01599.x

7. nayak SR, Rai RL, Krishnamurthy A, Prabhu LV, Ranade AV, mansur DI, Kumar S (2008) An unusual course and entrapment of the lingual nerve in the infratemporal fossa. Bratisl Lek Listy 109(11):525–527

8. ngeow Wc, chai WL (2009) numbness of the ear following inferior alveolar nerve block: the forgotten complication. Br Dent J 207(1):19–21. doi:10.1038/sj.bdj.2009.559

9. Piagkou mn, Demesticha t, Piagkos G, Androutsos G, Skandalakis P (2011) mandibular nerve entrapment in the infratemporal fossa. Surg Radiol Anat 33:291–299. doi:10.1007/s00276-010-0706-5

10. Ranscht B, Bronner- Fraser m (1991) t-cadherin expression alternates with migrating neural crest cells in the trunk of the avian embryo. Development 111:15–22

11. Rodella LF, Buffoli B, Labanca m, Rezzani R (2012) A review of the mandibular and maxillary nerve supplies and their clini-cal relevance. Arch Oral Biol 57:323–334. doi:10.1016/j.archoralbio.2011.09.007

12. thotakura B, Rajendran SS, Gnanasundaram V, Subramaniam A (2013) Variations in the posterior division branches of the man-dibular nerve in human cadavers. Singapore med J 54(3):149–151. doi:10.11622/smedj.2013051

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