Oral Maxillofacial Surg Clin N Am 19 (2007) 105–115 Nerve Injuries After Third Molar Removal Vincent B. Ziccardi, DDS, MDa,*, John R. Zuniga, DMD, MS, PhDb a Department of Oral and Maxillofacial Surgery, University of Medicine and Dentistry of New Jersey, 110 Bergen Street, Room B-854, Newark, NJ 07103-2400, USA b Division of Oral and Maxillofacial Surgery, University of Texas Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9109, USA The peripheral branches of the trigeminal third molar removal are well documented. Mostnerve are susceptible to injury from the surgical patients report some degree of pain, bleeding,removal of third molars. These injuries can be swelling, trismus, bruising, and stretching of thedevastating for patients because of their eﬀects on lips, especially the area of the oral commissure.speech, mastication, swallowing, and social in- Temporary or permanent sensory nerve distur-teractions. Fortunately, most of these trigeminal bances are not uncommon; however, the incidencenerve injuries undergo spontaneous recovery. of lingual and IAN injuries reported ranges fromSome injuries may be permanent, however, with 0.4% to 22%. Sensory deﬁcits that last longervarying outcomes ranging from mild hypoesthesia than 1 year are likely to be permanent, andto complete paresthesia and neuropathic re- attempts for microsurgical repair are often un-sponses resulting in chronic pain syndromes . predictable after that time. Surgeons must be The face and perioral region have a high aware of this complication and provide detaileddensity of peripheral nerve receptors, which preoperative informed consent to their patientsmakes it unpleasant for patients to tolerate or [3,4].adapt to neurosensory disturbances. Pain, tem- The incidence of neurologic injuries from thirdperature, and proprioception are transmitted molar surgery may be related to multiple factors,centrally through the lingual, mental, inferior including surgeon experience and proximity of thealveolar, infraorbital, and supraorbital nerves. tooth relative to the IAN canal. HorizontallyEach of these sensory modalities must be evalu- impacted teeth are generally more diﬃcult toated in the neurosensory assessment of patients remove because of the increased need for boneand monitored for recovery postoperatively . removal and soft tissue manipulation when com-The goal of trigeminal microsurgery is to create pared with distoangular or mesioangular impac-an environment in which those nerves thought tions with a higher incidence of nerve injuries .not to be susceptible for spontaneous recovery Third molar surgery performed under general an-are given the best opportunity for regeneration. esthesia compared with surgery performed underThis article discusses patient assessment, micro- local anesthesia has been reported to have a highersurgical treatments, and outcome assessments for incidence of nerve injuries, presumably because ofpatients who sustain inferior alveolar nerve the supine position of the patient and extent of(IAN) and lingual nerve injuries from third molar soft tissue dissection, potential greater surgicalremoval. forces that may be applied under general anesthe- The complications and expected postoperative sia, and overall more diﬃcult surgical case selec-sequelae that result from the surgical removal of tion . Other studies have found no signiﬁcant relationship between nerve injury and the anes- thetic modality . IAN injury secondary to third molar removal * Corresponding author. also has been correlated with patient age over 35 E-mail address: email@example.com (V.B. Ziccardi). and the presence of completely developed roots.1042-3699/07/$ - see front matter Ó 2007 Elsevier Inc. All rights reserved.doi:10.1016/j.coms.2006.11.005 oralmaxsurgery.theclinics.com
106 ZICCARDI & ZUNIGAThe depth of impaction and the degree of impo- amount of nerve damage . Seddon proposedsition of the root structures over the inferior three categories of nerve injury, including neuro-alveolar canal space have been found to contrib- praxia, axonotmesis, and neurotmesis. Sunder-ute to an increased incidence of postoperative land expanded the Seddon classiﬁcation tonerve injuries. The use of rotary instrumentation include ﬁve degrees of nerve injury.and surgical sectioning of teeth with exposure of Neuropraxia (Sunderland ﬁrst-degree injury)the mandibular canal also can be associated with results from minor compression or traction of thesensory nerve disturbances. Teeth with one large nerve trunk, which results in a conduction block-root requiring buccal bone removal with rotary ade. Axonal continuity is maintained, whichinstrumentation, however, have been associated results in a temporary conduction blockade.with a higher incidence of lingual nerve injuries Signiﬁcant traction injuries may result in vascular. Consideration may be given for the use of in- stasis with focal neural demyelination. Patientstentional partial odontectomy in patients thought clinically report sensory disturbances lasting fromto be at high risk for potential nerve injuries hours to months, depending on the severity ofprovided no pathologic condition is present. injury with complete recovery. Trigeminal micro- Lingual nerve injuries that result from third surgery is not indicated unless a foreign body ismolar surgery have been reported to occur in present, which would be an indication for0.5% to 22% of all patients. Patients with lingual microsurgery.nerve injury report drooling, tongue biting, ther- Axonotmesis (Sunderland second-degree in-mal burns, changes in speech, and swallowing and jury) is produced by crush or signiﬁcant tractiontaste perception alterations. Because of the poten- injuries. These injuries are similar to ﬁrst-degreetially varied anatomic position of the lingual injuries with some degree of Wallerian degenera-nerve, the surgeon is not always able to identify tion distal to the zone of injury. There is noits location. Studies have described the position of degeneration of the endoneurium, perineurium, orthe lingual nerve using cadaveric dissections and epineurium, which allows for the axons to re-MRI to lie above the lingual crest in 10% of generate. Sensory recovery is usually complete inpatients and even in direct contact with the lingual 2 to 4 months but may take up to 1 year forplate in up to 25% of patients [9,10]. Any surgical complete recovery. Trigeminal nerve microsurgeryincisions placed too far lingually or breaching the is not indicated unless a foreign body is impedinglingual cortex with a surgical bur may jeopardize nerve regeneration.the lingual nerve. Other anatomic factors, such Third- and fourth-degree Sunderland injuriesas lingual angulation of the third molar, need do not have a corresponding Seddon category.for vertical sectioning, prolonged operating time, Third-degree injuries result from moderate toand surgeon inexperience, have been found to in- severe crushing or traction of the nerve. Walleriancrease the risk for lingual nerve injury . The degeneration is present, with some neuron deathuse of lingual ﬂap retraction during third molar occurring. Disruption of the endoneurium doessurgery has been associated with an increased in- not allow complete regeneration of the axon,cidence of transient sensory disturbances; how- which results in mild to moderate permanentever, it is neither protective nor detrimental in sensory nerve disturbances. Trigeminal nerveregards to permanent lingual nerve injury . microsurgery may be indicated if there is no sensory nerve recovery after 3 months. No abso- lute optimal time for repair of trigeminal nerve injuries has been established.Classiﬁcation of trigeminal nerve injuries Fourth-degree Sunderland injuries occur with Seddon  and Sunderland  developed endoneural and perineural disruption and resultclassiﬁcation systems for nerve injuries based on in permanent alteration of the blood-nerve bar-the degree of nerve disruption that are still useful rier. Neuronal loss occurs with the possibility ofcurrently (Table 1). These systems were based on neuroma formation. Intraneural scars and ﬁbrosisthe degree of injury aﬀecting the endoneurium, also may develop, which can further impede theperineurium, epineurium, and supporting tissues. process of regeneration. An increase in the intra-Seddon’s classiﬁcation is based on the time from neural pressure contributes to degeneration andinjury and degree of observed sensory recovery, adversely aﬀects the prognosis for recovery. Mi-whereas the Sunderland classiﬁcation emphasizes crosurgical intervention is indicated if there is nothe fascicular structure of the nerve and the signiﬁcant sensory recovery by 3 or more months.
NERVE INJURIES AFTER THIRD MOLAR REMOVAL 107Table 1Seddon and Sunderland classiﬁcation of nerve injuriesInjury classiﬁcation Cause Healing MicrosurgeryNeuropraxia (Seddon) Minor nerve Spontaneous recovery in Not indicated unlessFirst-degree injury compression or less than 2 months foreign body (Sunderland) traction injury impeding nerve regenerationAxonotmesis (Seddon) Crush or traction injury Spontaneous recovery in Not indicated unlessSecond-degree injury 2–4 months foreign body present (Sunderland) Up to 1 year for complete recoveryThird-degree injury Traction, compression, Some spontaneous Microsurgery indicated (Sunderland) or crush injury recovery, but not if no improvement by complete 3 monthsFourth-degree injury Traction, compression, Poor prognosis for Microsurgery indicated (Sunderland) injection, or chemical spontaneous recovery if no signiﬁcant injury High probability for improvement after neuroma formation 3 months or intraneural ﬁbrosisNeurotmesis (Seddon) Transection, avulsion, Poor prognosis Microsurgery indicatedFifth-degree injury or laceration of nerve Extensive ﬁbrosis, if no improvement (Sunderland) trunk neuroma formation, after 3 months or or neuropathic development of changes neuropathic response Neurotmesis (Sunderland ﬁfth-degree injury) is with the patient seated comfortably in a semi-characterized by complete transection of the nerve reclined and comfortable position. The aﬀectedtrunk aﬀecting all layers of the nerve. This injury area is ﬁrst mapped using the directional brushresults in complete disruption of the nerve with stroke to discern normal from abnormal areas.possible neuroma formation and poor prognosis This procedure may be accomplished by markingfor spontaneous recovery. These lesions clinically directly on the patient’s skin and photographingdemonstrate complete anesthesia of the aﬀected the area for documentation or recording ontarget area with the potential for the development a standardized testing form. Mapping is used toof neuropathic responses. Trigeminal microsur- delineate the area where testing should begery is deﬁnitely indicated for this group of performed.injuries. Static light touch is assessed using the Von Frey monoﬁlaments, which are calibrated with the log base ten of the magnitude of force in milli- grams required to bend the ﬁlament, whichClinical neurosensory testing evaluates the A-beta ﬁbers and pressure percep- Neurosensory testing should be performed to tion. The monoﬁlament is applied perpendiculardetermine the degree of sensory impairment, to the skin and pressure is applied just until themonitor recovery, and determine whether trigem- ﬁlament begins to bend in sequential order untilinal nerve microsurgery is indicated. Clinical the patient can perceive the sensation. For theneurosensory testing can be divided into mecha- trigeminal nerve, detection of the 1.65 to 2.36noceptive and nociceptive testing based on the monoﬁlament is considered normal for static lightspeciﬁc receptor stimulated. Mechanoceptive test- touch. If the Von Frey monoﬁlaments are noting includes two-point discrimination, static light available, a crude approximation of static lighttouch, brush stroke, and vibrational sense. Noci- touch is achieved by using a wisp of cotton toceptive testing includes pain stimuli and thermal stroke the skin gently to determine sensorydiscrimination. Mechanoceptive testing should be perception.completed before nociceptive testing. Testing Two-point discrimination can be tested usingshould be performed in a reproducible manner an ECG caliper, boley gauge, or two-point
108 ZICCARDI & ZUNIGAanesthesiometer. The test is performed and re- collateral macrosprouting has developed frompeated in 2-mm increments until the patient can adjacent nerves. If diagnostic nerve blocks areno longer perceive two distinct points. The boley eﬀective in relieving pain, microsurgery may begauge is useful for this purpose because it is indicated. Patients who experience no relief fromreadily available and accurate to within 1 mm. diagnostic nerve blocks may have a centrallyNormal values for the inferior alveolar and mediated pain syndrome, which would be a con-lingual nerve distributions are approximately traindication for trigeminal microsurgery and4 mm and 3 mm, respectively. Values more than consideration for pharmacologic management.20 mm are not recorded because it would measure Zuniga and colleagues  demonstrated thatsensation from the contralateral zone of clinical neurosensory testing is a reliable diagnos-innervation. tic tool in evaluating lingual nerve injuries based Brush directional discrimination is assessed on preoperative testing compared with actual in-using a ﬁne hairbrush or the baseline Von Frey traoperative ﬁndings from trigeminal microsur-monoﬁlament used for the static light touch. This gery. For inferior alveolar injuries, they reportedtest assesses the integrity of the large myelinated that clinical neurosensory testing was useful forA-alpha and A-beta ﬁbers. The brush is stroked ruling in IAN injuries but less reliable for rulingacross the skin in a 1-cm area and the patient is out inferior alveolar injuries. Based on these ﬁnd-asked whether he or she perceives the sensation ings, they concluded that clinician also must con-and the direction of the stroke. The patient should sider other factors, such as patient age,be able to perceive the stroke sensation and travel mechanism of injury, time since injury, and thedirection in at least 90% of the application for presence of neuropathic pain regarding indica-a normal result. tions for trigeminal nerve microsurgery. Pin pressure nociception assesses the free nerveendings innervated by the lightly myelinated A-delta and unmyelinated C-ﬁbers. This test is Indications for trigeminal nerve microsurgerysimply performed by using a sterile dental needle,which is applied in a quick prick fashion in If symptoms of nerve injury persist for moresuﬃcient intensity to be perceived by the patient. than 3 months with no improvement, microsurgi-Appropriate response would be the perception of cal intervention may be considered. Indicationssharp and not just pressure. Alternatively, a pres- for trigeminal nerve microsurgery include (1)sure algesiometer may be used to consistently observed nerve transection, (2) no improvementprovide a standardized amount of pressure, usu- in hypoesthesia for 3 months, (3) development ofally 25 g. pain caused by nerve entrapment or neuroma Thermal discrimination can be performed formation, (4) presence of a foreign body, (5)using a cotton applicator sprayed with ethyl progressively worsening hypoesthesia or dysesthe-chloride for the perception of cold, which is sia, and (6) hypoesthesia that is intolerable to themediated by the unmyelinated C-ﬁbers. Heat patient. Contraindications for trigeminal micro-perception is transmitted by the A-delta ﬁber, surgery include (1) central neuropathic pain, (2)which may be tested using heated gutta percha. evidence of improving sensory function, (3) hypo-Minnesota thermal discs also may be used to test esthesia that is acceptable to the patient, (4)for thermal discrimination. metabolic neuropathy, (5) severely medically Diagnostic nerve blocks can be a useful ad- compromised patient, (6) extremes of age, andjunct in the assessment of patients who have pain (7) excessive time since injury.as a presenting symptom. The purpose of di- Nerve repairs are categorized as primary,agnostic nerve blocks is to isolate the aﬀected delayed primary, and secondary depending onregion of the nerve and determine what level of their timing relative to the initial injury. Primaryﬁber is aﬀected. Dilute local anesthetic agents can nerve repairs are performed immediately at theblock the small nerve ﬁbers, whereas higher time of an observed injury. If a surgeon is notconcentrations are required to block the larger proﬁcient in trigeminal microsurgery, these pa-myelinated ﬁbers. These blocks are usually initi- tients may be sent to a microsurgeon who couldated at the periphery and then administered perform the repair within a few weeks for a de-centrally along trigeminal nerve pathways. In- layed primary repair. Unobserved injuries, whicheﬀective nerve blocks may indicate either that are the most common, are injuries that present tothe nerve was not appropriately blocked or that the surgeon after surgery has been completed.
NERVE INJURIES AFTER THIRD MOLAR REMOVAL 109These patients should undergo serial neurosensory proliferation and lead to further extrinsic scarringexaminations and be considered as microsurgical and compression-induced ischemia, creating pos-candidates based on the previously mentioned sible demyelination and reduced sensory recovery.criteria. Hemostasis can be enhanced with the use of reverse Trendelenberg position, hypotensive anes- thetic techniques, and local anesthesia with vaso- constrictor. Bone bleeding may be controlledTrigeminal nerve microsurgery through use of bone wax or other hemostatic Trigeminal microsurgery generally should be agents. Electocoagulation is facilitated using bi-performed before 1 year if reinnervation of distal polar cautery to minimize collateral injury to theend organs is to be expected. Signiﬁcant distal nerve.nerve scarring and atrophy occur by 1 year, which A transoral approach is most commonly usedmakes microsurgery less predictable. Microsur- for trigeminal microneurosurgery. Exposure ofgery is best performed in the operating room the IAN can be accomplished after decorticatingunder general anesthesia with complete muscle the lateral cortex through a vestibular incision.relaxation. The operating room table is turned 90 Alternatively, a cutaneous incision placed inrelative to the anesthesiologist to allow for place- a resting skin line may be indicated for cases inment of the surgical microscope. Repair may be which the area of injury is not readily accessibleperformed using surgical loupes; however, an by an intraoral approach. The lingual nerve isoperating microscope with multiple heads allows approached through either a paralingual or lin-the surgeon and assistant simultaneous views of gual gingival sulcus incision. The paralingualthe surgical ﬁeld (Fig. 1). Instrumentation for tri- mucosal incision is completed with blunt andgeminal nerve microsurgery minimally consists of sharp dissection to expose the nerve. Advantagesmicroforceps, scissors, needle holders, and nerve of the paralingual approach include use ofhooks. A beaver blade is useful for internal dissec- a smaller incision with direct visualization; how-tion and preparation of the nerve for neurorrha- ever, transected nerve ends may retract from thephy or excision of scar tissue. surgical ﬁeld on blunt dissection. The lingual Basic surgical principles for trigeminal nerve gingival sulcus incision requires a lateral releasemicrosurgery include exposure, hemostasis, visu- along the external oblique ridge for complete ﬂapalization, removal of scar tissue, nerve prepara- mobilization. The nerve is visualized from belowtion, and nerve anastomosis without tension. the periosteum once the ﬂap is elevated, whichClotted blood in proximity to a nerve repair allows the nerve to be dissected bluntly from themay increase the amount of connective tissue ﬂap. This technique requires a larger incision than Fig. 1. Use of multiple head operating microscope for trigeminal nerve microsurgery.
110 ZICCARDI ZUNIGAthe paralingual mucosal incision design; however, epineural ﬁbrosis, the nerve may expand, whichthe proximal and distal nerve ends do not retract indicates a successful internal neurolysis proce-from the ﬁeld during dissection (Figs. 2 and 3) dure. A circumferential portion of the epineurium. may be removed in a procedure called epifascic- External neurolysis is the surgical procedure to ular epineurectomy. If no expansion is noted andfree the nerve from its tissue bed and remove any complete ﬁbrosis is observed, the aﬀected segmentrestrictive scar tissue or bone in the case of IAN should be excised and the nerve prepared forinjuries. Damage to soft tissues surrounding primary neurorrhaphy.a nerve may result in scar tissue formation and Excision of neuromas is performed to allow forcreate a compressive entrapment-type injury. reanastomosis of complete nerve injuries in anExternal neurolysis is generally performed under eﬀort to re-establish continuity and allow forsome magniﬁcation to grossly assess the nerve and nerve regeneration. After excision of the neuromaisolate any physical abnormalities . For some or nonviable nerve tissue, the resulting segmentspatients, external neurolysis may be the only sur- are examined under magniﬁcation to ascertaingical procedure indicated. Once the external neu- whether normal tissue is present, which is de-rolysis is completed, the nerve is examined under termined by the presence of herniated intrafascic-magniﬁcation and intraoperative ﬁndings dictate ular tissues. The goal is to allow the suturingany additional procedures. Foreign bodies, such of the two nerve ends together without tension inas endodontic ﬁlling material, tooth fragments, a process called primary neurorrhaphy. The twoor implant materials, should be removed at this nerve segments are approximated using 7-0point. or smaller nonreactive epineural sutures. This Internal neurolysis is indicated when there is portion of the procedure is completed usingevidence of nerve ﬁbrosis or gross changes in the microinstrumentation under magniﬁcation. Mo-external appearance of the nerve. This procedure bilization of the IAN may be augmented by distalrequires the opening of the epineurium to examine and proximal nerve dissection or sacriﬁce of thethe internal fascicular structure of the nerve. incisive branch of the IAN, which requires de-Because the trigeminal nerve has a sparse amount cortication of the IAN from the site of injury toof epineurium, any manipulation potentially can the mental foramina (Figs. 4–6). This manipula-lead to further scar tissue formation. Therefore, tion may allow up to an additional 10 mm of mo-some surgeons question the use of this procedure. bilization to facilitate tension-free nerve repairsThe procedure begins with the elevation of the . Regardless of the suture technique selected,epineurium facilitated through the injection of tension across the nerve repair must be minimized.saline within the aﬀected nerve segment. A longi- Tension more than 25 g has been demonstrated totudinal incision is made through the epineurium have a deleterious eﬀect on nerve regeneration be-using a beaver blade to expose the internal cause of gapping and formation of scar tissue,structures in a procedure referred to as an which may inhibit axon proliferation throughepifascicular epineurotomy. With release of the the site of repair .Fig. 2. (A) Intraoperative view depicts proximal and distal lingual nerve before preparation for neurorrhaphy. (B) Lin-gual nerve after primary neurorrhaphy.
NERVE INJURIES AFTER THIRD MOLAR REMOVAL 111 (eg, sensory or motor), ease of graft procurement, and potential donor site morbidity. For trigeminal nerve repairs, the sural and greater auricular nerves meet most of these requirements, including ease of procurement and relatively tolerable resultant donor site anesthesia . Diameter of the donor nerve graft should correlate with the diameter of the host nerve. The IAN averages approximately 2.4 mm diam- eter and the lingual nerve 3.2 mm diameter. The sural nerve is approximately 2.1 mm in diameter and the greater auricular nerve averages 1.5 mm diameter; thus, there is no exact match available for trigeminal nerve grafting. Cross-sectional shape of the IAN and lingual nerves is generally round, whereas the sural nerve is ﬂat and the greater auricular nerve is oval. The fascicular number and size of fascicles should correspond between the donor and re- cipient sites. The IAN has between 18 and 21 fascicles in the third molar region, which decreases to approximately 12 fascicles at the mental nerve, whereas the lingual nerve commonly has between 15 and 18 fascicles in the third molar region andFig. 3. Intraoperative photograph of a complete lingual more at the distal termination. The sural nervenerve injury before preparation for repair. generally provides 11 to 12 fascicles, and the greater auricular nerve usually has 8 or 9 fasciclesNerve grafts as a single graft. Pogrel and colleagues  re- The primary indication for trigeminal nerve ported that the lingual nerve had a mean of 3 fas-grafting involves cases that result in a continuity cicles (range 1–8) at the level of the lingula anddefect that cannot be repaired primarily or a mean of 20 fascicles (range 7–39) at the thirdwithout excessive tension. The selection of a donor molar region. Four specimens were monofascicu-site for interpositional nerve grafting is predicated lar at the level of the lingula. The IAN hadon several factors, such as nerve diameter and a mean of 7.2 fascicles (range 3–14) at the levelfascicular pattern, correlation of neural function of the lingula. In all cases, the lingual nerve had the same number or fewer fascicles than the IAN at the level of the lingula. Because of the smaller fascicular size and overall nerve diameter, the sural nerve graft precludes direct fascicular alignment, but chance apposition of the fascicular cross-section at the suture line allows passage of regenerative axonal sprouts. This eﬀect is en- hanced by the sparse epineurium present within the trigeminal nerve . The ﬁnal consideration in nerve graft procurement is donor site morbid- ity. The sural nerve graft results in numbness over the heel and lateral aspect of the foot, whereas the greater auricular nerve harvest results in numbness to the lateral neck, skin overlying the posterior mandible, and the ear .Fig. 4. Panoramic radiograph of patient who sustained Several other materials have been proposed forIAN injury after third molar removal. Note the superim- nerve grafting, including alloplastic tubules, skel-position of the third molar roots over the IAN canal etal muscle, and vein grafts. The technique ofshadow. entubilization using alloplastic materials is an
112 ZICCARDI ZUNIGAFig. 5. (A) Panoramic radiograph of patient who sustained IAN injury after removal of third molar in an edentulousmandible. (B) Clinical photograph demonstrates microrepair of the IAN injury depicted in (A).attractive alternative to grafting because there is performed intraorally and the fact that the veinno donor site morbidity and the alloplast theo- graft may collapse or kink with movements ofretically could guide the regenerating axons and the tongue . Another alternative to autoge-prevent displacement or rotation of the proximal nous nerve grafting is the use of skeletal muscleand distal nerve stumps. Clinical results have not interpositional grafts .been consistent, however, and alloplastic mate-rials are not generally recommended for periph-eral trigeminal nerve reconstruction . Vein Outcomes of trigeminal nerve microsurgerygrafting also has been described as an alternativeto autogenous grafting. Clinical results demon- The clinical literature on the microsurgicalstrated that continuity defects repaired with vein repair of trigeminal nerve injuries and their post-grafts for the IAN demonstrated outcomes com- operative outcomes is limited, with most dataparable to autogenous nerve grafts when com- derived from case reports and case series. Dodsonpleted through an extraoral approach. Lingual and Kaban  completed an evidence-basednerve defects repaired with vein grafts demon- medicine study to develop treatment guidelinesstrated acceptable sensory recovery with defects based on the results described from clinical stud-smaller than 5 mm. This success may be related ies. Their summary recommendations for the op-to the lingual nerve surgical procedure being erative management of trigeminal nerve injuriesFig. 6. (A) Radiograph of patient who underwent intentional partial odontectomy to avoid potential IAN injury andwho continued to have persistent hypoesthesia after surgery. (B) Surgical view after external and internal decompressionof the IAN and removal of root fragment.
NERVE INJURIES AFTER THIRD MOLAR REMOVAL 113include (1) tension-free primary repair whenever methylene blue staining and videophotography ofpossible, (2) use of autogenous nerve grafts the fungiform papillae of the tongue. The reduc-when direct primary repair is not possible, and tion in the number of fungiform papillae, pores,(3) use autogenous nerve grafts or hollow conduits and ratio of pores per papilla demonstrated thatused for entubilization of nerve gaps 3 cm or severe lingual nerve injuries resulted in a sensori-smaller when direct repair is not possible. neural taste disorder. The progressive increase in Pogrel  reviewed his patients evaluated in the number of fungiform papillae, pores, and ratioa 5-year period with a diagnosis of lingual and of pores per papillae along with increased re-IAN injuries. The patients who met his criteria sponse to citric acid stimuli after microsurgical re-for trigeminal nerve microsurgery were compared pair of the lingual nerve in 50% of cases providewith patients who did not meet the criteria, and evidence that taste may regenerate after the lin-results for patients who underwent microsurgery gual nerve repair. Transected lingual nerves thatwere evaluated. In this study of 880 consecutive undergo microsurgical repair can result in thepatients, 96 patients met the criteria for microsur- recovery of taste, regeneration of fungiform tastegery and 51 patients had a microsurgical proce- receptors, and recovery of some neurosensorydure. No diﬀerences were noted in the results function. Early repair of complete lingual nervebased on gender, with slightly better success in injuries is recommended to provide the optimalthe IAN group compared with the lingual nerve chance for some gustatory return .group. Repairs completed before 10 weeks afterinjury appeared to do better than late repairs, al-though results of neurosensory testing and pa- Sensory re-educationtients’ subjective evaluations did not alwayscorrelate. No patients developed dysesthesia post- Sensory re-education may help patients maxi-operatively when it did not exist preoperatively. mize their quality of sensory recovery. PatientsThe author concluded that in select cases, trigem- must be educated preoperatively as to what can beinal microsurgery can provide a reasonable result expected realistically after trigeminal nerve micro-in improved sensation for inferior alveolar and surgery. All patients initially are anesthetic in thelingual nerve injuries, with more than 50% of pa- region of the nerve repair postoperatively. Dyses-tients experiencing some sensory improvement. thesias are usually diminished or eliminated in this Patients with chronic pain after trigeminal immediate period; however, usually some sensi-nerve injuries may have varied outcomes based tivity is noted in the aﬀected area. The innervatedon their speciﬁc presenting pain complaints. zone should be stimulated with diﬀerent texturesGregg [30,31] reviewed outcomes for microsurgery to create the varied perceived sensations. Patientsin this population and found an overall reduction could stroke the area with a cotton swab whilein pain severity of approximately 50%. The great- looking in the mirror and focus on ﬁne touch andest reduction in pain was observed in patients di- directional sense. Alternatively, they may stimu-agnosed with hyperalgesia (61%) and hyperpathia late the area with toothbrush bristles to facilitate(58%) compared with patients with anesthesia do- ﬁne touch, pressure, and directional movements.lorosa and sympathetic mediated pain, who had The goal of sensory re-education is to stimulatepain reduction of approximately 15% and 21%, the peripheral receptors so that the central ner-respectively. Patients who have central deaﬀeren- vous system can begin processing this informationtation pain pose the greatest challenge to the clini- again.cian because of lack of diagnostic or predictive Patients must understand clearly that mosttests. Treatments for central deaﬀerentation pain likely they will never experience complete sensorygenerally involve use of anticonvulsant agents in recovery and probably will always have somecombination with tricyclic antidepressants or psy- subjective feeling of altered sensation. The goalchotropic agents. Patients who have dysesthesia is for this sensory deﬁcit not to interfere withmay have more psychiatric issues than patients activities of daily living. Some unpleasant sensa-who present with no pain . It is incumbent tions and the feelings of tingling, electrical shocks,upon the microsurgeon to rule out centrally medi- and crawling within the aﬀected region can occurated pain, which has a poor prognosis with early in the healing process. These feelings are tomicrosurgery. be expected. More complex sensory functions, End-organ receptor regeneration has been such as vibration, ﬁne touch, and directionaldemonstrated by Zuniga and colleagues  using sense, can be delayed for up to 1 year, which
114 ZICCARDI ZUNIGAindicates the importance of serial examinations to  Gulicher D, Gerlach KL. Sensory impairment of thedemonstrate areas of improvement. The perceived lingual and inferior alveolar nerves following re-changes occur so slowly that the patient has moval of impacted mandibular third molars. Int Jdiﬃculty interpreting any signiﬁcant improve- Oral Maxillofac Surg 2001;30:306–12.  Behnia H, Kheradvar A, Shabrohbi M. An ana-ment. After examination, it is important to discuss tomic study of the lingual nerve in the third molartheir improvement and review how certain abnor- region. J Oral Maxillofac Surg 2000;58:649–51.mal behaviors, such as tongue biting, drooling,  Miloro M, Halkias LE, Slone HW, et al. Assessmentand food incompetence, have dissipated and pro- of the lingual nerve in the third molar region usingtective reﬂexes have returned. The sensory levels magnetic resonance imaging. J Oral Maxillofacachieved by 1 year are basically the ﬁnal level Surg 1997;55:134–7.obtained by patients.  Valmaseda-Castellon E, Berini-Aytes L, Gay-Escoda C. Lingual nerve damage after third lower molarSummary surgical extraction. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2000;90:567–73. Injury to peripheral branches of the trigeminal  Pichler JW, Beirne OR. Lingual ﬂap retraction andnerve, namely the lingual and inferior alveolar prevention of lingual nerve damage associated withbranches, is a known complication of third molar third molar surgery: a systematic review of the liter-surgery. Surgeons should inform patients pre- ature. Oral Surg Oral Med Oral Pathol Oral Radioloperatively of this risk as part of the informed Endod 2001;91:395–401.  Seddon HJ. Three types of nerve injury. Brain 1943;consent process and closely monitor any patients 66:237–88.postoperatively who present with hypoesthesia or  Sunderland S. A classiﬁcation of peripheral nervedysesthesia. It is imperative that surgeons docu- injury producing loss of function. Brain 1951;74:ment the extent of injury and perform some basic 491–516.neurosensory function testing in the postoperative  Dao TTT, Mellor A. Sensory disturbances associ-period. Any patient who does not resolve sponta- ated with implant surgery. Int J Prosthodont 1998;neously should be referred to a surgeon skilled in 11:462–9.trigeminal nerve microsurgery for assessment and  Zuniga JR, Meyer RA, Gregg JM, et al. The accu-possible treatment. Trigeminal nerve microsur- racy of clinical neurosensory testing for nerve injurygery has been demonstrated to improve sensory diagnosis. J Oral Maxillofac Surg 1998;56:2–8.  Zuniga JR, LaBanc JP. Advances in microsurgicalfunction in these patients. nerve repair. J Oral Maxillofac Surg 1993;51(SupplReferences 1):62–8.  Joshi A, Rood JP. External neurolysis of the lingual  Eliav E, Gracely RH. Sensory changes in the terri- nerve. Int J Oral Maxillofac Surg 2002;31:40–3. tory of the lingual and inferior alveolar nerves fol-  Meyer RA. Applications of microneurosurgery to lowing lower third molar extraction. Pain 1998;77: the repair of trigeminal nerve injuries. Oral Maxillo- 191–9. fac Surg Clin North Am 1992;4:405–16.  Akal UK, Sayan NB, Aydogan S, et al. Evaluation  Terzis J, Faibisoﬀ B, Williams HB. The nerve gap: of the neurosensory deﬁciencies of oral and maxillo- suture under tension versus graft. Plast Reconstr facial region following surgery. Int J Oral Maxillofac Surg 1975;56:166. Surg 2000;29:331–6.  Eppley BL, Snyders RV. Microanatomic analysis of  Venta I, Lindqvist C, Ylipaavalniemi P. Malpractice the trigeminal nerve and potential nerve graft donor claims for permanent nerve injuries related to third sites. J Oral Maxillofac Surg 1991;49:612–8. molar removals. Acta Odontol Scand 1998;56:193–5.  Pogrel AM, Renaut A, Schmidt B, et al. The rela-  Ziccardi VB, Assael LA. Mechanisms of trigeminal tionship of the lingual nerve to the mandibular third nerve injuries. Atlas Oral Maxillofac Surg Clin molar region: an anatomic study. J Oral Maxillofac North Am 2001;9:1–11. Surg 1995;53:1176–81.  Hill CM, Mostafa P, Thomas DW, et al. Nerve mor-  Brammer JP, Epker BN. Anatomic-histologic survey bidity following wisdom tooth removal under local of the sural nerve: implications for inferior alveolar and general anaesthesia. Br J Oral Maxillofac Surg nerve grafting. J Oral Maxillofac Surg 1988;46:111–7. 2001;39:423–8.  Wolford LM. Autogenous nerve graft repairs of the  Brann CR, Brickley MR, Shepherd JP. Factors trigeminal nerve. Oral Maxillofac Surg Clin North inﬂuencing nerve damage during lower third molar Am 1992;4:447–57. surgery. Br Dent J 1999;186:514–6.  Pitta MC, Wolford LM, Mebra P, et al. Use of Gore-  Rehman K, Webster K, Dover MS. Links between Tex tubing as a conduit for inferior alveolar and lin- anaesthetic modality and nerve damage during gual nerve repair: experience with 6 cases. J Oral lower third molar surgery. Br Dent J 2002;193:43–5. Maxillofac Surg 2001;59:493–6.
NERVE INJURIES AFTER THIRD MOLAR REMOVAL 115 Pogrel MA, Magben A. The use of autogenous vein  Gregg JM. Studies of traumatic neuralgias in the grafts for inferior alveolar and lingual nerve recon- maxillofacial region: surgical pathology and neural struction. J Oral Maxillofac Surg 2001;59:985–8. mechanisms. J Oral Maxillofac Surg 1990;48: Rath EM. Skeletal muscle autograft for repair of the 228–37. human inferior alveolar nerve: a case report. J Oral  Sandstedt P, Sorensen S. Neurosensory disturbances Maxillofac Surg 2002;60:330–4. of the trigeminal nerve: a long-term follow-up of Dodson TB, Kaban LB. Recommendations for traumatic injuries. J Oral Maxillofac Surg 1995;53: management of trigeminal nerve defects based on 498–505. a critical appraisal of the literature. J Oral Maxillo-  Zuniga JR, Chen N, Phillips CL. Chemosensory and fac Surg 1997;55:1380–6. somatosensory regeneration after lingual nerve re- Pogrel MA. The results of microneurosurgery of the pairs in humans. J Oral Maxillofac Surg 1997;55: inferior alveolar and lingual nerve. J Oral Maxillofac 2–13. Surg 2002;60:485–9.  Hillerup S, Hjorting-Hansen E, Reumert T. Repair Gregg JM. Studies of traumatic neuralgia in the max- of the lingual nerve after iatrogenic injury: a fol- illofacial region: symptom complexes and response to low-up study of return of sensation and taste. microsurgery. J Oral Maxillofac Surg 1990;48:135–40. J Oral Maxillofac Surg 1994;52:1028–31.