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 Table of Contents  
CASE REPORT
Year : 2014  |  Volume : 2  |  Issue : 2  |  Page : 217-219

Bilateral communication between the mylohyoid and lingual nerves: Clinical implications


1 Department of Anatomy, Government Medical College, Patiala, Punjab, India
2 Department of Anaesthesiology and Intensive Care, Gian Sagar Medical College and Hospital, Ram Nagar, Banur, Punjab, India
3 Department of Orthopaedics, Gian Sagar Medical College and Hospital, Ram Nagar, Banur, Punjab, India

Date of Web Publication11-Nov-2014

Correspondence Address:
Sukhminder Jit Singh Bajwa
House No. 27-A, Ratan Nagar, Tripuri, Patiala - 147 001, Punjab
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2321-4848.144345

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  Abstract 

Although variations in the course of the mylohyoid nerve (MHN) in relation to the mandible are frequently found on dissection but these anatomical variations have not been conclusively described in the anatomical or surgical literature. However, it is a well-known fact that variations in the branching pattern of the mandibular nerve frequently account for the failure to obtain adequate anesthetic effect in routine oral and dental procedures and also for the unexpected injury to the branches of the nerves during surgery. Furthermore, anatomical variations might be responsible for unexpected and unexplained symptoms after a certain surgical procedures and in some cases of refractory neuralgias. We describe the presence of a rare bilateral communicating branch between the MHN and lingual nerves (LN) in an adult male cadaver, with a brief discussion of its anatomical, clinical and surgical implications as well as its possible role in the sensory innervations of the tongue. The present case reinforces the idea of a communicating branch between the MHN and LN, indicating that some of the sensory components of the MHN, instead of innervating the teeth or chin skin, might also innervate the tongue. This anatomical variation mandates to update the knowledge and awareness among surgeons and anesthesiologists who are frequently involved in oro-surgical procedures and nerve blocks of the face for various neuralgias so as to avoid any un-anticipated nerve injury.

Keywords: Inferior alveolar nerve, lingual nerve, mylohyoid nerve


How to cite this article:
Kaur HS, Upasana, Bajwa SS, Kalyan GS, Singh M. Bilateral communication between the mylohyoid and lingual nerves: Clinical implications . Arch Med Health Sci 2014;2:217-9

How to cite this URL:
Kaur HS, Upasana, Bajwa SS, Kalyan GS, Singh M. Bilateral communication between the mylohyoid and lingual nerves: Clinical implications . Arch Med Health Sci [serial online] 2014 [cited 2019 Oct 17];2:217-9. Available from: http://www.amhsjournal.org/text.asp?2014/2/2/217/144345


  Introduction Top


The mylohyoid nerve (MHN) is a branch of the inferior alveolar nerve (IAN), which arises above the mandibular foramen. The nerve then passes downward and anteriorly within the mylohyoid groove on the medial surface of the mandible. The nerve courses anteriorly and parallel to the mylohyoid muscle and giving branches that provide motor innervations to the mylohyoid and anterior belly of the digastric muscles. [1] The mylohyoid muscle plays a vital role in chewing, swallowing, respiration and phonation. [2] It has been analyzed that the MHN might have a role in the sensory innervations of the chin. [3] The role of the MHN in the mandibular posterior tooth sensation is still a controversial issue. However, the major clinical concerns pertain to the un-anticipated nerve injury during oro-facial surgeries or during administration of nerve blocks for various neuralgias. Furthermore, many patients are admitted with maxillo-facial trauma to the tertiary care centers that undergo the operative procedures for their related injuries. The possibilities of nerve injuries during operative procedures can be substantially high among this patient population. [4] Many patients also present to the dental outpatients department's for day care procedures and chances of nerve injuries are higher during administration of loc-regional anesthesia in such patients. [5] The incidence of such anatomical variations is not known exactly in various syndromes involving facial structure but risks of possible injuries to nerve during surgical procedures always remain substantially high due to malformed and abnormal facial-skeletal structures. [6]


  Case Report Top


During a routine dissection in the department of Anatomy, an abnormal bilateral communication between the MHN and lingual nerves (LN) of a middle aged male cadaver was found. In the present case, on the right side, the MHN gave a communicating branch to the LN beyond the level of mandibular foramen close to the intermediate tendon of digastric muscle [Figure 1], whereas on the left side the communicating branch was given at the level of mandibular foramen before the intermediate tendon of the digastric muscle [Figure 2]. Thereafter, the MHN followed its normal course and branching pattern. No other anatomical variations were found in the origin of inferior alveolar or the LN. Furthermore, no communicating branches between these two nerves were found. The LN, after receiving this communicating branch from the MHN, was observed taking its normal course and branching pattern.
Figure 1: Communicating branch between mylohyoid nerve and lingual nerve on right side beyond the mandibular foramen

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Figure 2: Communicating branch between mylohyoid nerve and lingual nerve on left side at the level of mandibular foramen

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  Discussion Top


The mylohyoid muscle plays a vital role in chewing, swallowing, respiration and phonation with a substantial role of the MHN in assisting these important functions. [2] It has also been put forth that the MHN might have a role in the sensory innervations of the chin and the lower incisor teeth while the role of the MHN in the mandibular posterior tooth sensation is still a controversial issue. The MHN is a branch of the IAN, which comes 14.7 mm above the mandibular foramen. The nerve then courses downward and anteriorly within the mylohyoid groove on the medial surface of the mandible. The nerve courses anteriorly to parallel the mylohyoid muscle, releasing branches that provide motor innervations to the mylohyoid and anterior belly of the digastric muscles. Although the MHN is generally considered to be a motor nerve, it has a sensory component that continues beyond the mylohyoid muscle and anterior belly of digastric muscle, by way of cutaneous branches.

Communicating branches between the IAN and the LN were well-described in the literature [7] and these communications have been identified as a possible explanation for the inefficiency of mandibular anesthesia. [8] The presence of communicating branches between the inferior alveolar and LN is very commonly mentioned in most of the anatomical text books. Nevertheless, a communicating branch between the MHN and LN is seldom described in literature and also not regularly mentioned in the anatomical or even surgical textbooks.

The communication between the MHN and LN in this case was found to occur after the LN passes in close relation to the third molar tooth. This close relationship of the LN and the third molar tooth makes it susceptible to injury during the third molar extraction. [9] The presence of a nerve communication like the one described in this case would help in the LN function recovery. [10] The communicating branch between the MHN and LN might also innervate the tongue and surgeons should be aware of this variation to avoid un-expected complications after oral surgeries. The role of the MHN in the mandibular posterior tooth sensation is still a controversial issue.

Although variations in the course of the MHN in relation to the mandible are frequently found on the dissecting room, they have not been conclusively described in the anatomical or surgical. It is considered that this information is not only of academic interest but can also be of huge clinical significance for oral and maxillofacial surgeons as well as anesthesiologists. Moreover, one of the major complications of a number of oral and maxillofacial surgery procedures is the injury of the LN. Due to its anatomical location, it may be damaged during third molar extraction, periodontal procedures, mandibular trauma management and excision of neoplastic lesions. [9] Another cause of LN injury may be the needle puncture during local anesthesia or during suturing. The major probable cause for this clinical mishap lies in the anatomic variations of the LN and the inability of the surgeons to know its precise location. [9] The purpose of reporting this case is to make surgical and clinical fraternity aware of this rare communication so as to keep in mind always while going for the surgical procedures in this particular area of the face [Figure 1] and [Figure 2]. Even during the post-operative period of maxillo-facial surgery, any complication related to chewing or phonation should always raise a suspicion for the possible injury due to this anatomical variation. Though not mentioned in literature, such nerve injuries can also become possible risk factors for aspiration. The purpose of this case report will be fulfilled if a message of this rare variation is aptly received by the clinical fraternity especially those dealing with maxillo-facial surgeries and neural blocks in this region.

 
  References Top

1.Clark S, Reader A, Beck M, Meyers WJ. Anesthetic efficacy of the mylohyoid nerve block and combination inferior alveolar nerve block/mylohyoid nerve block. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999;87:557-63.  Back to cited text no. 1
    
2.Ren M, Mu L. Intrinsic properties of the adult human mylohyoid muscle: Neural organization, fiber-type distribution, and myosin heavy chain expression. Dysphagia 2005;20:182-94.  Back to cited text no. 2
    
3.Guyot L, Layoun W, Richard O, Cheynet F, Gola R. Alteration of chin sensibility due to damage of the cutaneous branch of the mylohyoid nerve during genioplasty. J Oral Maxillofac Surg 2002;60:1371-3.  Back to cited text no. 3
    
4.Bajwa SJ, Kaur J, Singh A, Kapoor V, Bindra GS, Ghai GS. Clinical and critical care concerns of cranio-facial trauma: A retrospective study in a tertiary care institute. Natl J Maxillofac Surg 2012;3:133-8.  Back to cited text no. 4
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5.Bajwa SJ, Jindal R. Use of Articaine in loco-regional anesthesia for day care surgical procedures. J Anaesthesiol Clin Pharmacol 2012;28:444-50.  Back to cited text no. 5
[PUBMED]  Medknow Journal  
6.Bajwa SJ, Bajwa SK, Singh A, Khan B, Parmar SS, Singh G, et al. Anesthetic challenges and difficulties in the management of Treacher Collins syndrome. Anesth Essays Res 2011;5:111-3.  Back to cited text no. 6
  Medknow Journal  
7.Sakamoto Y, Akita K. Spatial relationships between masticatory muscles and their innervating nerves in man with special reference to the medial pterygoid muscle and its accessory muscle bundle. Surg Radiol Anat 2004;26:122-7.  Back to cited text no. 7
    
8.Rácz L, Maros T, Seres-Sturm L. Anatomical variations of the nervus alveolaris inferior and their importance for the practice (author's transl). Anat Anz 1981;149:329-32.  Back to cited text no. 8
    
9.Behnia H, Kheradvar A, Shahrokhi M. An anatomic study of the lingual nerve in the third molar region. J Oral Maxillofac Surg 2000;58:649-51.  Back to cited text no. 9
    
10.Fazan VP, Rodrigues Filho OA, Matamala F. Communication between the mylohyoid and lingual nerves: Clinical implications. Int J Morphol 2007;25:561-4.  Back to cited text no. 10
    


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