PRACTICE

IN BRIEF ● A rare case of mental nerve paraesthesia during orthodontic treatment is described. ● Mental nerve paraesthesia can present as the first sign of significant pathology elsewhere in the head and neck region ● The importance of thorough investigation of patients presenting with a history of facial numbness is highlighted. ● Guidelines for referral have been suggested where orthodontic treatment is suspected as the cause.

Temporary mental nerve paraesthesia secondary to orthodontic treatment — a case report and review

P. J. Willy,1 P. Brennan2 and J. Moore3

Patients complaining of facial paraesthesia may present to the dental practitioner. The differential diagnosis includes malignant neoplastic disease and therefore warrants prompt hospital referral. Mental nerve paraesthesia during orthodontic treatment is a very rare occurrence. A case of mental paraesthesia during fixed upper and lower orthodontic treatment is presented. This report highlights the importance of thorough investigation of patients presenting with a history of facial numbness, and provides a review of the aetiology and management of this problem for the dental practitioner. Guidelines for referral have been suggested where orthodontic treatment is suspected as the cause.

Neuropathies can affect a single nerve still potential lower sensation to be patient with decreased sensation on the (mononeuropathy) or several nerves (poly- altered. Reported dental causes of lower lip left side of his chin. The area of paraesthe- neuropathy) and result in sensory, motor paraesthesia include third molar extrac- sia had gradually spread superiorly to and/or autonomic deficits in the affected tions, surgical molar/premolar extractions, involve the left side of the lower lip as region. Causes of cranial neuropathies can implant placement, needle trauma following well as chin. The lower archwire was made be classified as intracranial or extracranial. IDN block, periapical inflammation, lower passive and the patient referred as a Intracranial causes include stroke, tran- denture compression of the mental nerve precaution for further investigation. sient ischaemic attack and tumours. and neural injury following endodontic Clinical examination revealed decreased Extracranial causes can include trauma, treatment. Mental nerve paraesthesia light touch and pin prick sensation con- malignancy (which can be primary,1 resulting from orthodontic treatment is fined to the left vermilion and upper region metastatic2 or haematological3 in origin) very rare and only four cases have been of the lower lip combined with paraesthesia and infection. Iatrogenic causes of altered previously described.4–6 This report of the left side of the chin. The teeth, gingi- function include radio- describes a further case of isolated mental vae and tongue were not affected. Sensa- therapy, chemotherapy and paraesthesia during orthodontic tion of the skin overlying the left side of the surgery. treatment. The investigation and manage- inferior mental symphysis was normal. In a general dental practice setting, a ment of this phenomenon — which can be Maxillary and ophthalmic divisions of the patient presenting with sudden onset of the first manifestation of significant trigeminal nerve as well as all other cranial facial paraesthesia is an unusual occur- underlying disease, is discussed. nerves were normal on both sides. General rence. Although the inferior dental nerve neurological examination revealed no fur- (IDN) is relatively protected by its tunnelled CASE REPORT ther deficits in either sensation or motor course through the bony there is A fit and well 17-year-old male undergo- function. ing orthodontic treatment was referred Intra-oral examination was uneventful. with gradual onset of left mental nerve Dental panoramic tomography (Fig. 1) 1Senior House Officer, Maxillofacial Department, Poole paraesthesia. The orthodontic treatment showed the lying immedi- Hospital, Dorset BH15 2JB; 2Consultant Oral and Maxillofacial Surgeon, Queen Alexandra Hospital, had been with pre-adjusted edgewise ately below the apex of the LL5 (35). The Portsmouth PO6 3LY; 3Specialist Orthodontist, fixed appliances in both arches over the apices of the molar teeth on the left side of 29 Alum Chine Road, Bournemouth BH4 8DT previous 15 months for a crowded Class II the mandible did not encroach on the inferi- Correspondence to: Peter Willy, Ground Floor Flat, 66 Pembroke Road, Clifton, Bristol BS8 3DX Division 2 malocclusion on a skeletal I or dental canal. The LL5 (35) was slightly Email: [email protected] base. The patient complained of a diffuse mesially angulated and had therefore been dull ache in the left side of the mandible subjected to some uprighting movement Refereed Paper for 2 weeks following the placement of a with levelling of the occlusal plane. doi:10.1038/sj.bdj.4810893 Received 13.10.02; Accepted 02.04.03 lower .020 steel aligning archwire. This The patient underwent magnetic reso- © British Dental Journal 2004; 196: 83–84 resolved gradually over 5 days but left the nance imaging (axial and coronal T1 and

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T2 weighted images) which excluded Isolated cranial nerve neuropathy can pathology in the upper neck, infratempo- present as the first symptom of intra- ral fossa, base of skull and intra-cranially. cranial or extra-cranial focal lesions. The There was evidence of inflammation in persistence of symptoms for warrants the right maxillary antrum consistent prompt referral for specialist investigation with sinusitis. Unfortunately, it was not and management, even if clinical exami- possible to visualise the IDN in the nation finds the neurological deficit con- mandibular canal as the images of both fined to one branch. Where orthodontic the mandible and maxilla were obscured treatment is a potential cause, symptoms by an artefact from the fixed appliance lasting more than 2 weeks following appli- metalwork. At review 3 weeks later (4 ance deactivation require further specialist weeks following previous archwire investigation. The presence of any metal- adjustment), the sensation in the chin and work (orthodontic or restorative) will cause lip had returned to normal. radiation scatter and image artefact with After the symptoms of numbness had Fig. 1 Close up of a dental panoramic tomogram both CT and MRI scanning. In this case the showing the proximity of the left second premolar resolved, treatment was resumed unevent- apex to the mental foramen. The inferior alveolar removal of the orthodontic brackets prior fully. One year later there had been no nerve has been highlighted to scanning would have enabled the prox- recurrence of paraesthesia. imity of the to the the molar region. A plexus innervated the lower second premolar apex to be assessed DISCUSSION premolar teeth with origins from the main in three dimensions. The mylohyoid and lingual nerves branch trunk, molar and incisive branches.10 from the main trunk of the mandibular Others have found that the anatomy of the CONCLUSION nerve before it pierces the mandible. Sen- IDN is variable, however in the majority of Although mental nerve paraesthesia during sation of the tongue, lingual mucosa and cases there is a plexus of nerves above the orthodontic treatment is rare, it may be skin overlying the lower mental symphysis main nerve trunk which supply sensation caused by many other processes. As the dif- was normal. The area of paraesthesia in to the teeth.8 ferential diagnosis of trigeminal nerve this case was limited to the lower lip and In the patient described in this report a paraesthesia includes malignant neo- chin only. Disruption of nerve function type 1 IDN was present according to Carter plasms, patients presenting in the dental appeared to originate close to the mental and Keen's classification.9 Visualisation of setting with previously undiagnosed cranial foramen as sensation in the labial gingiva the bucco-lingual position of the IDN from nerve neuropathies should be referred and vitality testing was normal. the MRI scan was not possible because of immediately. Where orthodontic treatment The mental foramen usually lies directly an artefact from the orthodontic metal- is a possible cause appliances should first be below the anatomical crown of the work. From the DPT, the mental foramen inactivated. If symptoms have not resolved mandibular second premolar and is situat- was positioned immediately below the long after 2 weeks specialist referral for further ed around 60% of the distance from the axis of the second premolar and the apex investigation should be instigated. second premolar buccal cusp tip to the was closely related to the mental foramen. inferior border of the mandible. The mental There was normal sensation in the teeth The authors would like to thank Mr A. F. Markus, Consultant Oral and Maxillofacial Surgeon, for foramen is intersected by the long axis of and gingivae suggesting that the cause of allowing us to report this case. We are also grateful the lower second premolar in only 11% of paraesthesia was compression of the men- to the medical photography department at Poole cases, in the remainder there is an approxi- tal nerve close to the mental foramen. Hospital for their help. mate 50:50 split where the foramen lies To the authors' knowledge, only four either anterior or posterior to this long cases of lower lip paraesthesia during 1. Raveh T, Neuman A R, Weinberg A, Alfeie M, Moor E V, 7 Caspi R, Lipton H A, Wexler M R. Treatment of axis. Bucco-lingually the IDN runs in con- orthodontic treatment have been previous- extensive malignant schwannoma of the mandibular tact with the lingual plate in the ramus and ly reported. Two of these cases were attrib- nerve. Ann Plast Surg 1995; 34: 637-641. usually stays close to the lingual plate uted to the mandibular second premolar 2. Laurencet F M, Anchisi S, Tullen E, Dietrich P Y. Mental throughout the mandible before turning and two to the mandibular second molar. neuropathy: report of five cases and review of the literature. Crit Rev Oncol Hematol 2000 ; 34: 71-79. sharply to traverse the body of the Stirrups presented two cases where the 3. Ojanguren J M, Garcia-Monco C, Capelastegui A, mandible in the premolar region and exit lower second premolar crown had been Matinez C, Atutxa K, Carrascosa T. Numb chin the mental foramen.8 moved in a buccal direction resulting in syndrome in four patients with haematological 4 malignancies. Haematolica 1999 ; 84: 952-953. Carter and Keen described three dis- mental paraesthesia. It was postulated that 4. Stirrups D R. Temporary mental paraesthesia: an tinct anatomical patterns of the intra- the ID canal ran lingual to the apices of unusual complication of orthodontic treatment. mandibular course of the IDN: type 1 — these teeth hence tooth movement caused Br J Orthod 1985 ; 12: 87-89. 5. Krogstad O, Omland G. Temporary paraesthesia of the the IDN courses straight towards the men- pressure on the neurovascular bundle. lower lip: a complication of orthodontic treatment. tal foramen lying close to the root apices; Krogstad et al. found that a lower second A case report. Br J Orthod 1997; 24: 13-15. type 2 — the nerve follows a lower path- molar tooth root was intimately related to a 6. Tang N C, Selwyn Barnett C L, Bligh SJ. Lip way in the mandible with dental branches lingually positioned ID canal with resultant paraesthesia associated with orthodontic treatment 5 — a case report. Br Dent J 1994 ; 176: 29-30. passing obliquely in an antero-superior mental paraesthesia. Tang et al. found that 7. Phillips J L, Weller R N, Kulild J C. The mental foramen: direction to the teeth; and type 3 where intrusion of the lower second molar tooth Part 1. Size, orientation and positional relationship to the IDN divides into two branches, one following placement of a heavy rectangu- the mandibular second premolar. J Endodont 1990; 6 16: 221-223. passing superiorly to supply the molar lar archwire was the probable cause. In all 8. Gowgiel J M. The position and course of the teeth and the other inferiorly to innervate cases the paraesthesia resolved within mandibular canal. J Oral Implantol 1992; 18: 383-85. the premolars, canines and incisors.9 2 days to 4 weeks of the archwire being 9. Carter R B, Keen E N. The intramandibular course In another study the main trunk of the removed or the relevant tooth being of the inferior alveolar nerve. J Anat 1971; 108: 433-440. IDN gave branches to the molar and pre- extruded. In three of these cases the onset 10. Wadu S G, Penhall B, Townsend G C. Morphological molar teeth immediately prior bifurcating of paraesthesia occurred following an variability of the human inferior alveolar nerve. Clin into the mental and incisive branches in archwire change. Anat 1997; 10: 82-87.

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