Applications of Microneurosurgery to the Repair of Trigeminal Nerve Injuries

Diagnosis and Management of Lingual Nerve Injuries

Injury to the lingual nerve is a well-recognized risk associated with certain routine dental and oral surgical procedures. The assessment and management of a patient with a traumatic lingual nerve neuropathy requires a logical and stepwise approach. The proper application and interpretation of the various neurosensory tests and maneuvers is critical to establishing an accurate diagnosis. The implementation of a surgical or nonsurgical treatment strategy is based not only on the established diagnosis, but also a multitude of variables including patient age, timing and nature of the injury, and the emotional or psychological impact.

Management of mandibular nerve injuries from dental implants

Treatment of the patient who has sustained a nerve injury from dental implant procedures involves prompt recognition of this complication, evaluation of sensory dysfunction, the position of the nerve vis-à-vis the implant, and timely management of the injured nerve. In some patients, removal or repositioning of the implant and surgical exploration and repair of the injured nerve will maximize the implant patient's potential for a successful recovery from nerve injury.

Nerve injuries from mandibular third molar removal

Injuries to peripheral branches (IAN, LN, LBN) of the trigeminal nerve during the removal of M3s are known and accepted risks in oral and maxillofacial surgery practice. These risks might be reduced by modifications of evaluation or surgical techniques, depending on the surgeon's judgment in individual patients. If a nerve injury does occur, prompt recognition, subjective and objective evaluation,and development of a treatment plan, if the sensory deficit fails to resolve in a reasonable period and is unacceptable to the patient, give the patient the best chance of achieving improvement or recovery of sensory function in the distribution of the injured nerve. Microneurosurgery may produce return of useful sensory function or complete sensory recovery, if done in a timely fashion by an experienced microsurgeon, in greater than 80% of patients who sustain nerve injuries during the removal of M3s.

Clinical characteristics of trigeminal nerve injury referrals to a university centre

The aim of this retrospective study was to determine the aetiology and characteristics of trigeminal nerve injuries referred to a university centre with nerve injury care. Fifty-nine patients with 73 injured trigeminal nerves were referred in 10 months. The most common aetiologies were odontectomy (third molar surgery) (52.1% of nerves), local anaesthetic (LA) injections (12.3%), orthognathic surgery (12.3%) and implant surgery (11.0%). The inferior alveolar nerve (IAN) was most commonly injured nerve (64.4%), followed by the lingual nerve (LN) (28.8%). About a quarter of IAN injuries (27.3%) and half of LN injuries (57.1%) from odontectomy had severe sensory impairment. There were twice as many LN than IAN injuries from local anaesthetic injections, but all had mild or no sensory impairment. Nerve injuries from implant surgery occurred only in IAN injuries; none had severe sensory impairment. Neuropathic pain occurred in 14.9% of IAN injuries and only in those with mild or no sensory impairment. Nerve surgery was offered to 45.8% of patients; a third underwent surgery.

Does Early Repair of Lingual Nerve Injuries Improve Functional Sensory Recovery?

PURPOSE

This study evaluated the relationship between timing of lingual nerve repair and functional sensory recovery.

MATERIALS AND METHODS

Using a retrospective cohort study design, the investigators enrolled a sample of subjects who had lingual nerve repair. The predictor variable was time between injury and repair, categorized as early (<90 days after injury) or late (>90 days after injury). The outcome variable was the time to functional sensory recovery (FSR), measured in days. Other variables were categorized as demographic, anatomic, and operative. Uni- and multivariate Cox proportional hazards models were used to evaluate the association between the timing of the repair and time to FSR.

RESULTS

The study sample was composed of 64 subjects who had lingual nerve repair between January 1998 and January 2005. The mean time between injury and repair was 153.2 (31-1606) days; 21.9% of subjects had early repair. The mean age was 28.4 +/- 8.0 years, 62.5% of subjects were female; 77% of the injured nerves were repaired by direct suture, and 23% had surgical exploration with decompression/neurolysis. In bivariate analyses, early repair, method of repair, and neuroma were statistically or near-statistically associated with time to FSR (P <or= .12). In a multiple Cox proportional hazards model, early repair was associated with time to FSR (P = .02). Ninety-three percent of subjects in the early repair group achieved FSR within 1 year, compared with 62.9% in the late group (P = .05).

CONCLUSIONS

Early repair of lingual nerve injuries results in FSR more frequently and earlier than late repair.

Functional Sensory Recovery After Trigeminal Nerve Repair

PURPOSE

The aim of this study was to estimate the proportion of subjects who achieved functional sensory recovery (FSR) 1 year after inferior alveolar or lingual nerve repair and to identify risk factors associated with failure to achieve FSR.

METHODS

Using a retrospective cohort study design, we developed a sample composed of subjects who underwent lingual or inferior alveolar nerve repair. Eligible subjects had at least 1 postoperative visit. For subjects having bilateral nerve repair, 1 side was selected randomly for analysis. Predictor variables were categorized as demographic, anatomic, and operative. The outcome variable was the time to FSR, measured in days. Kaplan-Meier survival methods were used to estimate the proportion of subjects with FSR at 1 year. Uni- and multivariate Cox proportional hazard models were used to identify risk factors for the failure to reach FSR at 1 year.

RESULTS

The study sample was composed of 60 subjects with a mean age of 28.7 +/- 8.3 years; 68.3% were female. The majority (86.7%) of subjects presented with a preoperative chief complaint of altered sensation and had lingual nerve damage (93.3%) that was repaired by direct suturing (75%). The mean interval between injury and repair was 145.9 +/- 200.0 days. At 1 year postoperatively, 75% of the subjects had achieved FSR (95% confidence interval [CI]: 64% to 86%).

CONCLUSIONS

The majority of subjects undergoing trigeminal (V(3)) nerve repair achieved functional sensory recovery within 1 year of surgical repair. Patients with evidence of neuroma formation were less likely to achieve FSR at 1 year in a multivariate model.

Efficacy of low level laser therapy on neurosensory recovery after injury to the inferior alveolar nerve

BACKGROUND

The most severe complication after the removal of mandibular third molars is injury to the inferior alveolar nerve or the lingual nerve. These complications are rather uncommon (0.4% to 8.4%) and most of them are transient. However, some of them persist for longer than 6 months, which can leave various degrees of long-term permanent disability. While several methods such as pharmacologic therapy, microneurosurgery, autogenous and alloplastic grafting can be used for the treatment of long-standing sensory aberrations in the inferior alveolar nerve, there are few reports regarding low level laser treatment. This paper reports the effects of low level laser therapy in 4 patients with longstanding sensory nerve impairment following mandibular third molar surgery.

METHODS

Four female patients had complaints of paresthesia and dysesthesia of the lip, chin and gingiva, and buccal regions. Each patient had undergone mandibular third molar surgery at least 1 year before. All patients were treated with low level laser therapy. Clinical neurosensory tests (the brush stroke directional discrimination test, 2-point discrimination test, and a subjective assessment of neurosensory function using a visual analog scale) were used before and after treatment, and the responses were plotted over time.

RESULTS

When the neurosensory assessment scores after treatment with LLL therapy were compared with the baseline values prior to treatment, there was a significant acceleration in the time course, as well as in the magnitude, of neurosensory return. The VAS analysis revealed progressive improvement over time.

CONCLUSION

Low level laser therapy seemed to be conducive to the reduction of long-standing sensory nerve impairment following third molar surgery. Further studies are worthwhile regarding the clinical application of this treatment modality.

Long-Term Outcome Assessment for Lingual Nerve Microsurgery

OBJECTIVE

A retrospective study was undertaken to investigate the clinical outcomes resulting from the microsurgical repair of lingual nerve injuries. The study was based on patient chart review.

PATIENTS AND METHODS

A total of 20 patients referred to the principal investigator (V.B.Z.), with a diagnosis of lingual nerve injury who underwent trigeminal nerve microsurgery during a 3-year period (1999 to 2002), were entered in this study. All patients received a complete history and physical examination, and thorough preoperative and postoperative neurosensory testing to evaluate clinical response to hot, cold, cotton wisp, vibration, 2-point discrimination, directional stroke, and fine touch as determined by Von-Frey filaments.

RESULTS

All patients underwent an external neurolysis procedure in combination with an internal neurolysis, neuroma excision, or primary neurorrhaphy under microscopic guidance depending on the intraoperative findings. The average time from injury to surgery was 8 months. The patients were followed for an average of 9 months after surgery, and assessment was based on the patients subjective experience as well as standardized neurosensory testing. Eighteen patients (90%) had some improvement in neurosensory function and 2 patients (10%) reported no improvement. One of the patients exhibiting no clinical improvement had a prolonged delay in seeking treatment, and the distal nerve could not be localized intraoperatively. Most patients were operated on between 2.5 and 7 months after injury, and there was no statistical difference in outcome as a function of the time from injury to repair in this group of patients. This subgroup of responding patients averaged at least 50% improvement in neurosensory function.

CONCLUSION

Microsurgical repair of lingual nerves provides moderate to significant improvements in clinical sensory function and is a useful option in treating affected individuals, especially when implemented soon after injury.

Current management of damage to the inferior alveolar and lingual nerves as a result of removal of third molars

In this review we present algorithms to guide the clinical management of patients who sustain damage to the inferior alveolar or lingual nerves during the removal of lower third molars. Monitoring recovery using simple sensory testing allows those patients who may benefit from some form of intervention to be identified. There is good evidence that some surgical procedures produce worthwhile improvements in sensation but management of nerve injury-induced dysaesthesia remains problematic.

The results of microneurosurgery of the inferior alveolar and lingual nerve

PURPOSE

The goal was to evaluate the experience of one surgical unit during a 5-year period in the evaluation and management of patients with injuries of the inferior alveolar and lingual nerve with particular reference to indications for and results of microneurosurgery.

PATIENTS AND METHODS

This study includes all patients referred with a diagnosis of injury to the inferior alveolar or lingual nerve during 5-year period from January 1, 1994, to January 1, 1999. All patients were evaluated with Frey's hairs for touch and direction sense, 2-point discrimination, and hot and cold water and Minnesota thermal discs for temperature sensation. Patients who fulfilled certain specified criteria were offered microneurosurgery, and the results were evaluated for those who underwent microneurosurgery.

RESULTS

The study consisted of 880 consecutive patients; 96 were thought to fulfill the criteria for microneurosurgery. Of these, 51 underwent microneurosurgical exploration and repair. In 5 patients, no injury could be detected at surgery, and no corrective surgery was performed other than decompression. In 26 patients, excision and direct anastomosis were performed, and in an additional 20 patients, nerve gap reconstruction was performed. In 16 of these 20 patients, reconstruction was performed with an autogenous vein graft, and in 2 patients, a Gore-Tex tube graft (W.L. Gore & Associates, Inc, Flagstaff, AZ) was used to bridge the nerve gap. In 2 patients, an autogenous nerve was used. Thirty-four of the repairs were made on the lingual nerve, and 17 were made on the inferior alveolar nerve. With the use of established criteria, 10 patients were considered to have had a good improvement in sensation, 18 patients were considered to have had some improvement in sensation, and 22 patients were considered to have had no improvement in sensation; 1 patient reported an increase in dysesthesia after surgery. The semiobjective assessment of patients did not always correspond with the patients' subjective evaluation.

CONCLUSION

In a relatively small study in selected cases, microneurosurgery can provide a reasonable result in improving sensation in the inferior alveolar and lingual nerve. More than 50% of patients experienced some improvement in sensation, and dysesthesia did not develop after surgery in any patient who did not have it before surgery.

The use of autogenous vein grafts for inferior alveolar and lingual nerve reconstruction

PURPOSE

This study evaluated whether an autogenous vein graft forms a satisfactory conduit for nerve regeneration.

PATIENTS AND METHODS

Fifteen patients received a total of 16 autogenous vein grafts to repair continuity defects of the inferior alveolar (6) and lingual nerves (10) nerves. All were treated between 4 and 10 months after injury. At surgery, the postresection defects ranged from 2 to 14 mm. All lingual nerves were repaired with saphenous vein grafts from an intraoral approach and all inferior alveolar nerves were repaired with facial vein grafts inserted from an extraoral approach.

RESULTS

Lingual nerve repair in 3 cases where the gap between the nerve ends was 5 mm or less resulted in some return of sensation. In 7 cases where the gap was between 5 and 14 mm, there was no return of sensation. In the 6 inferior alveolar nerve repairs there was some return of sensation in all cases and there was good return of sensation in 3 cases. One patient redeveloped dysesthesia in the inferior alveolar nerve and subsequently had a neurectomy. Histologic material was available from this case.

CONCLUSIONS

It appears that a vein graft can form a physiologic conduit for nerve regeneration. The results are more successful with shorter gaps, which indicates that, in some respects, the vein acts like a barrier membrane. The increased success rate in the inferior alveolar nerve repair may be because the vein remains straight and patent in the inferior alveolar canal. The lack of success with a long lingual nerve gap repair may be because the vein is collapsed or kinked by movement of the tongue, which may inhibit neural regeneration. Therefore, vein grafts should not be used for long lingual nerve continuity defects.

Gore-Tex tubing as a conduit for repair of lingual and inferior alveolar nerve continuity defects: a preliminary report

PURPOSE

This report describes the results of using a Gore-Tex (Gore Company, Flagstaff, AZ) tube as a conduit for repair of continuity defects in the inferior alveolar or lingual nerves.

PATIENTS AND METHODS

Seven nerve repairs were performed in five patients (M:F = 1:4) with an age range of 16 to 56 years. The duration from injury to repair ranged from 4 to 30 months. Two inferior alveolar and five lingual nerves were repaired.

RESULTS

All seven patients had anesthesia by objective testing preoperatively and had a continuity defect at the time of operation. The size of the defects ranged from 2 to 15 mm. Two of the seven patients had some return of sensation, occurring in defects of 3 mm or smaller.

CONCLUSION

The results of this pilot study indicate that Gore-Tex tubing may not be effective in the repair of continuity defects except in those defects 3 mm or smaller, in which it may act as a protective barrier membrane rather than as a conduit.

Lingual nerve paresthesia following third molar surgery: a retrospective clinical study

Lingual nerve anesthesia, paresthesia, and dysesthesia are possible side effects of third molar extraction. These unwanted complications are frequently disturbing to both the patient and practitioner. The incidence of lingual nerve damage following third molar surgery is more frequent than once thought. Six hundred questionnaires were sent to randomly selected Fellows of the American Association of Oral and Maxillofacial Surgeons in 50 states to determine the parameters surrounding this phenomenon. Of the 452 respondents, 76.05% reported having had patients with lingual anesthesia, dysesthesia, or paresthesia. Of all the reported cases, 18.64% of the cases failed to resolve. Of the reported cases, only three underwent surgical intervention. Because many cases of lingual nerve dysfunction do not resolve, it is important to inform patients that microsurgical nerve repair techniques are available as a modality of treatment following diagnosis. It has also been recommended that if the paresthesia does not resolve within 10 to 12 weeks, then management options including microsurgical nerve reconstruction within a short period of time should be discussed as a plan with the patient.

[Microneural reconstruction after iatrogenic lesions of the lingual nerve and the inferior alveolar nerve. Critical evaluation]

As microneural repair techniques of the sensory mandibular branches enter the third decade of their clinical use, there are but a few long-term investigations into the value of these procedures in the treatment of iatrogenic injury to the lingual (LN), inferior alveolar (IAN) or mental (MN) nerve. To establish the efficacy of microneural repair in lesions of the LN, IAN or MN with loss of continuity, the outcome of sensory recovery was evaluated in a series of 92 patients (LN: direct coaptation n = 39, coaptation + sural nerve grafting n = 23; IAN: direct coaptation n = 11 coaptation + sural nerve grafting n = 10; MN: direct coaptation n = 11). The minimum duration of follow-up was 14 months postoperatively. The persistent sensory deficit was assessed using standardized neurosensory testing and gustometric stimuli. In addition the patients answered a multiple-choice questionnaire containing a list of complaints. To obtain a numeric estimate for interindividual and intergroup comparison the information from clinical measurements and patient reports was condensed into a 'neurological score' and a 'complaint score', respectively. Furthermore, adequate items from both scores were combined to affirm or deny the return of sensory function in terms of protective and discriminative sensation. The overall results show a broad range of variation in the scores, sometimes reflecting severe degrees of persistent sensory impairment. The lowest scores, corresponding to the best regeneration, were found after direct coaptation of the LN, IAN and NM, but even the best results did not provide sensory recovery to a preinjury level. After direct coaptation of LN 69% of the patients exhibited protective sensation and 41% regained discriminative function. In contrast, LN grafting was ensued from restoration of protective function in 39% and discriminative function in 17% of the patients. More striking differences were found between coaptation and grafting of the IAN (IAN coaptation: 91% protective function; 18% discriminative function; IAN grafting: 60% protective function, 0% discriminative function). In the LN coaptation group low scores and improved taste perception were convincingly associated with short periods since injury (i.e. timing of repair). In conclusion, we feel there is sufficient justification to optimize the potential results of microneural repair by immediate (LN/MN) or early (IAN) reexposure of the injured site in order to clarify the precise nature of the underlying nerve damage and prevent delay, if patients present with complete loss of sensory function subsequent to dentoalveolar or oral surgery. However, clinical and electrophysiologic findings suggesting impairment or partial loss of sensory function are considered a contraindication to microneural intervention, in view of the limited prospects of sensory recovery after surgical repair.

Restoring sensation after trigeminal nerve injury: a review of current management

After a year, even the most expert peripheral nerve repair carries a poor prognosis. Early referral and intervention offer the best management of trigeminal nerve injuries.

Donor site morbidity of greater auricular nerve graft harvesting

To better understand the risks of obtaining greater auricular nerve (GAN) grafts, a retrospective analysis of 29 patients who underwent GAN graft procurement between 1985 and 1990 was conducted. No short-term morbidity was noted. Thirteen patients developed symptomatic nerve injuries, of which 6 reported spontaneous resolution in an average of 4.6 months. Three patients developed neuromas and 1 formed a hypertrophic scar. Persistent nerve injury symptoms were well tolerated in all but one patient, who developed sympathetic-mediated pain.