What Factors Are Associated With Functional Sensory Recovery Following Lingual Nerve Repair?

Evaluating Lingual Nerve Repair Outcomes: A Systematic Review

PURPOSE

The lingual nerve (LN) is susceptible to injury during oral and maxillofacial procedures, leading to neurosensory deficits. Advances in microsurgical techniques necessitate a comprehensive review of overall effectiveness and influencing factors.

METHODS

A systematic review was performed via Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to identify studies. Inclusion criteria were full text availability, studies written in english, and studies published after 2000 reporting LN repair. The primary outcome was sensory improvement defined via functional sensory recovery (FSR) or neurosensory testing (NST). Sex, time from injury to repair, method of repair, and graft length were examined to see if each influenced outcomes.

RESULTS

A sample of 786 subjects across 17 studies was examined. Most patients were female (73.3%) and suffered injuries from third molar extractions (72.8%). Of the studies, 10 defined improvement by FSR with a total of 88.8% (500/563) of nerves achieving such. Of those achieving FSR, 91% did so within a year. The remaining 7 studies defined sensory improvement by individually setting various NST thresholds, with the combined improvement rate being 88.6% (203/229). Positive outcomes were achieved with graft lengths up to 70 mm. Results on time to repair were mixed. The methods of repairs were not different based on statistical analysis short of performing an equivalence trial.

CONCLUSION

Conclusions made from studies using FSR were similar to studies using NST, meaning the method of measuring outcomes does not seem to be a confounder. FSR is the superior scale due to being objective and standardized. LN repair produced high rates of sensory improvement, which is expected to occur within 1 year postoperative. Sex and graft length did not influence outcomes. More research is needed to determine the effect of time to repair on efficacy. Most methods of repair produced similar outcomes, suggesting multiple valid techniques exist.

Does the Low and Short Medial Cut Affect Lingual Nerve Recovery after Sagittal Split Osteotomy?

BACKGROUND

The purpose of this study was to evaluate the recovery of lingual nerve (LN) neurosensory function in patients undergoing sagittal split osteotomy (SSO) with a low and short medial horizontal cut.

METHODS

This was a prospective study of patients with mandibular deformities undergoing SSO with a low and short medial horizontal cut over a 4-year period. The outcomes of interest were neurosensory recovery of the LN, as assessed objectively using functional sensory recovery (FSR) and subjectively by patient report.

RESULTS

The sample included 123 SSOs in 62 subjects with a mean age of 19.3 ± 3.1 years. Thirty-seven subjects (61.7%) were female. Mandibular advancements were performed in 52 SSOs (42.3%); mandibular setbacks were performed in 71 SSOs (57.7%). One subject underwent revision BSSO. FSR was achieved at 122 LNs (99.1%) within 6 weeks postoperatively, with 120 sites (97.5%) having S4 sensation at 6 weeks. Decreased LN sensation was reported at 10 (8.3%) sites at 1 week postoperatively. At 6 weeks postoperatively, 118 sites (97.5%) had reported normal sensation. By 12 weeks postoperatively, all LN sites had S4 sensation and there were no subjective complaints. Revision sagittal split osteotomy was associated with prolonged (≥6 weeks) time to S4 sensation ( P = 0.02) and subjective complaint of decreased sensation ( P = 0.02).

CONCLUSIONS

LN sensory recovery occurs rapidly following the low and short SSO, with 99% of sites achieving FSR and subjectively normal sensation within 6 weeks of surgery and all patients achieving FSR with S4 sensation by 12 weeks postoperatively. LN sensory recovery may be prolonged in patients undergoing revision SSO.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Visualization of Inferior Alveolar and Lingual Nerve Pathology by 3D Double-Echo Steady-State MRI: Two Case Reports with Literature Review

Injury to the peripheral branches of the trigeminal nerve, particularly the lingual nerve (LN) and the inferior alveolar nerve (IAN), is a rare but serious complication that can occur during oral and maxillofacial surgery. Mandibular third molar surgery, one of the most common surgical procedures in dentistry, is most often associated with such a nerve injury. Proper preoperative radiologic assessment is hence key to avoiding neurosensory dysfunction. In addition to the well-established conventional X-ray-based imaging modalities, such as panoramic radiography and cone-beam computed tomography, radiation-free magnetic resonance imaging (MRI) with the recently introduced black-bone MRI sequences offers the possibility to simultaneously visualize osseous structures and neural tissue in the oral cavity with high spatial resolution and excellent soft-tissue contrast. Fortunately, most LN and IAN injuries recover spontaneously within six months. However, permanent damage may cause significant loss of quality of life for affected patients. Therefore, therapy should be initiated early in indicated cases, despite the inconsistency in the literature regarding the therapeutic time window. In this report, we present the visualization of two cases of nerve pathology using 3D double-echo steady-state MRI and evaluate evidence-based decision-making for iatrogenic nerve injury regarding a wait-and-see strategy, conservative drug treatment, or surgical re-intervention.

Factors Affecting Functional Sensory Recovery After Inferior Alveolar Nerve Repair Using the Nerve Sliding Technique

PURPOSE

The nerve sliding technique (NST) was introduced for repairing inferior alveolar nerve (IAN) defect and overcoming the disadvantages of conventional surgical treatment methods such as nerve graft. This study was conducted to identify factors associated with functional sensory recovery (FSR) following inferior alveolar nerve repair using the NST.

PATIENTS AND METHODS

This was a retrospective cohort study including all patients who underwent IAN repair using the NST at Seoul National University Dental Hospital, Department of Oral and Maxillofacial Surgery from February 2009 to March 2020. The damaged part of the IAN was excised, and the incisive branch was transected intentionally to perform direct anastomosis without tension. Cox proportional hazard analysis was utilized to determine the relationships between predictor variables (age, gender, chief complaints, preoperative sensory results, duration from injury to repair, length of nerve tissue resected during the procedure, and neuroma formation) and outcome variable (time to FSR).

RESULTS

The sample was composed of 16 patients with a mean age of 56.1 ± 10.1 years, 25% were males and 75% were females. The mean nerve gap deficit was 7.69 mm (3-15 mm). Ten patients (62.5%) achieved FSR with a median time from operative treatment to FSR of 84.5 days. Dental implant placement was found as the main cause for IAN injury (93.8%) and 56.2% of patients complained of hypoesthesia and dysesthesia. Factors associated with time to FSR at 1 year were age, chief complaint, and early repair. Younger patients (P = .041) and patients without dysesthesia (P = .019) were more likely to achieve FSR. Higher proportion of early repair group achieved FSR, although not statistically significant (P = .068).

CONCLUSIONS

The use of NST in repair of IAN defects up to 15 mm achieved 62.5% FSR. Younger age and absence of dysesthesia were associated with higher FSR.

Effect of Photobiomodulation (Diode 810 nm) on Long-Standing Neurosensory Alterations of the Inferior Alveolar Nerve: A Case Series Study

Objective: To evaluate and describe the results of photobiomodulation (PBM) therapy on the treatment of long-standing neurosensory inferior alveolar nerve (IAN) alterations after third molar extraction. Background: The use of PBM is an acceptable alternative method to improve the therapeutic outcomes of neural lesions. Materials and methods: Longitudinal case study research. Patients with >6 months of inferior alveolar neurosensory disturbance after third molar extraction were included. Fifteen laser sessions were done, irradiating intra- and extraoral points along the distribution of this nerve area. A semiconductor Ga,Al,As diode laser (Thor laser^®) was used. Before and after the treatment, variables such as Zuniga-Essick score, British Medical Research Council (BRC) scale, visual analog scale (VAS), and mapping of the affected area were described. Gender, age, and duration of the lesion were analyzed. Descriptive statistical study was carried out with SPSS 19.0. Results: Eleven patients with a mean age of 38.5 years [standard deviation (SD) ±15.22]. Average duration of the lesion was 13.2 (SD ±4) months. The results obtained with the Zuniga-Essick scale before treatment showed mild alteration in 36.3% (4), moderate in 18.2% (2), and severe in 45.4% (5). After treatment, the percentage score improved, obtaining normality in 54.5% (6) of the patients and mild degree in 27.2% (3). In the BRC score, before the treatment, 45.4% (5) of grade S2+ and 27% (3) of S3 and S3+ were obtained. The final percentage after treatment reached an improvement of S4 in a total of 36% (4) of cases and a recovery of S3+ in 54.5% (6). Reduction of the mapped altered area and an upturn of VAS were noted. Conclusions: The laser parameters and application protocol used result in subjective and objective improvement in mechanical sensory perception in long-standing neurosensory deficit in the IAN.

Outcomes of Direct Lingual Nerve Repair After an Injury: A Systematic Review

PURPOSE

The purpose of this study was to conduct a systematic review with meta-analysis to investigate the outcomes of direct lingual nerve repair after injury.

MATERIALS AND METHODS

The studies in this review were compiled by using PubMed/Medline and ScienceDirect, which were searched by a single reviewer (M.K.) from their inception until March 10, 2020. Two independent reviewers (M.K. and V.B.Z.) who were blinded to each other's assessments reviewed full-text articles to assess for study inclusion. Outcomes were dichotomized as either functional sensory recovery (FSR) or no FSR. Clinical testing must have been assessed at a minimum of 6 months postoperatively. FSR was defined as grade S3, S3⁺, or S4 on the British Medical Research Council scale of neurosensory function. Studies were only eligible if they provided the number of patients treated with conduits or time from injury to repair and the associated rates of FSR with each intervention.

RESULTS

The initial search using the key terms yielded 4,921 results, which was then eventually filtered down to 6 articles after multiple levels of appraisal. Five articles were retrospective cohort studies and 1 was a randomized controlled study. Four of the 6 studies reported an FSR of grade S3 or higher in 85% or more of the patients. Conduit use was not associated with a significantly greater likelihood of achieving FSR (pooled risk ratio = 1.10; 95% confidence interval, 0.96 to 1.27; P = .17). Repair within 6 months was associated with significantly improved likelihood of achieving FSR (pooled risk ratio = 0.84; 95% confidence interval, 0.71 to 0.99; P = .04).

CONCLUSIONS

The use of conduits during repair was not associated with clinically significant increased FSR. Early repair was associated with a beneficial effect on FSR; however, heterogeneity was an issue with the studies. There is a lack of strong evidence owing to the nature of studies analyzed and the need for further research is required.

Comparison of Subjective and Objective Assessments of Neurosensory Function after Lingual Nerve Repair

OBJECTIVE

Mandibular third molar extractions are important in oral maxillofacial surgery. Damage to the lingual nerves, although rare, is a possible complication. There are reports of postoperative recovery after lingual nerve repair, but few reports have compared subjective and objective assessments of neurosensory function. Therefore, this study aims to compare subjective and objective assessments of neurosensory function after lingual nerve repair.

SUBJECTS AND METHODS

This retrospective cohort study comprised 52 patients with lingual nerve anesthesia after third molar extraction at the Department of Oral and Maxillofacial Surgery, Wakayama Medical University Hospital, Wakayama, Japan, between December 2008 and December 2015. We recorded pre- and postoperative (6 months and 12 months) neurosensory examinations.

RESULTS

Patient's subjective assessments of neurosensory function suggested improvement between the preoperative period and 12 months postoperation, although this difference was not significant. Objective assessment based on examination and testing, on the other hand, showed a significant difference in improvement (p < 0.05).

CONCLUSIONS

There was no evidence that improvement of subjective preoperative and postoperative assessments was significantly associated with improvement of objective neurosensory assessments after lingual nerve repair. Overall physical condition and background were thought to affect subjective evaluation. Subjective assessment is important in conjunction with objective evaluation because it may reveal dysesthesia that would otherwise be missed. In the future, we will examine those cases in whom subjective assessments showed no improvement although objective assessments showed improvement.

Recovery of Impaired Somatosensory Evoked Fields After Improvement of Tongue Sensory Deficits With Neurosurgical Reconstruction

Somatosensory evoked fields (SEFs) induced by tongue stimulation can be useful as an objective parameter to assess sensory disturbances in the tongue. However, whether tongue SEFs can be useful as a clinical, objective follow-up assessment method of tongue sensation after oral surgery is unknown. We describe 2 cases in which tongue SEFs were successfully used in clinical assessment. Two patients with unilateral tongue sensory deficits caused by lingual nerve injury during lower third molar extraction were recruited. Both patients underwent surgery to repair the damaged nerve, and all tongue sensory evaluations were performed once before and once after surgery. SEFs were recorded by stimulating the affected and unaffected sides of the tongue separately, and cortical activity was evaluated over the contralateral hemisphere. The unilaterality of the deficit also was assessed. In both patients, stimulation of the unaffected side evoked reproducible cortical responses before and after surgery. Both patients also recovered some sensation after surgery, given that presurgery stimulation of the affected side failed to evoke cortical activity whereas postsurgery stimulation evoked cortical activity on both sides. Sensation was initially highly lateralized in both patients but was restored to approximately normal in the postsurgery evaluation. Finally, both patients rated their subjective tongue sensations on the affected side over 50% better after the surgical intervention. These cases indicate that tongue SEFs may have a clinical use as an objective parameter for assessing the course of tongue sensory recovery.

Evidence-based outcomes following inferior alveolar and lingual nerve injury and repair: a systematic review

The inferior alveolar nerve (IAN) and lingual (LN) are susceptible to iatrogenic surgical damage. Systematically review recent clinical evidence regarding IAN/LN repair methods and to develop updated guidelines for managing injury. Recent publications on IAN/LN microsurgical repair from Medline, Embase and Cochrane Library databases were screened by title/abstract. Main texts were appraised for exclusion criteria: no treatment performed or results provided, poor/lacking procedural description, cohort <3 patients. Of 366 retrieved papers, 27 were suitable for final analysis. Treatment type for injured IANs/LNs depended on injury type, injury timing, neurosensory disturbances and intra-operative findings. Best functional nerve recovery occurred after direct apposition and suturing if nerve ending gaps were <10 mm; larger gaps required nerve grafting (sural/greater auricular nerve). Timing of microneurosurgical repair after injury remains debated. Most authors recommend surgery when neurosensory deficit shows no improvement 90 days post-diagnosis. Nerve transection diagnosed intra-operatively should be repaired in situ; minor nerve injury repair can be delayed. No consensus exists regarding optimal methods and timing for IAN/LN repair. We suggest a schematic guideline for treating IAN/LN injury, based on the most current evidence. We acknowledge that additional RCTs are required to provide definitive confirmation of optimal treatment approaches.

Promotion of peripheral nerve regeneration and prevention of neuroma formation by PRGD/PDLLA/β-TCP conduit: report of two cases

In the field of nerve repair, one major challenge is the formation of neuroma. However, reports on both the promotion of nerve regeneration and prevention of traumatic neuroma in the clinical settings are rare in the field of nerve repair. One of the reasons could be the insufficiency in the follow-up system. We have conducted 33 cases of nerve repair using PRGD/PDLLA/β-TCP conduit without any sign of adverse reaction, especially no neuroma formation. Among them, we have selected two cases as representatives to report in this article. The first case was a patient with an upper limb nerve wound was bridged by PRGD/PDLLA/β-TCP conduit and a plate fixation was given. After nearly 3-years’ follow-up, the examination results demonstrated that nerve regeneration effect was very good. When the reoperation was performed to remove the steel plate we observed a uniform structure of the regenerated nerve without the formation of neuroma, and to our delight, the implanted conduit was completely degraded 23 months after the implantation. The second case had an obsolete nerve injury with neuroma formation. After removal of the neuroma, the nerve was bridged by PRGD/PDLLA/β-TCP conduit. Follow-up examinations showed that the structure and functional recovery were improved gradually in the 10-month follow-up; no end-enlargement and any other abnormal reaction associated with the characteristic of neuroma were found. Based on our 33-case studies, we have concluded that PRGD/PDLLA/β-TCP nerve conduit could both promote nerve regeneration and prevent neuroma formation; therefore, it is a good alternative for peripheral nerve repair.

Lingual Nerve Repair: To Graft or Not to Graft?

PURPOSE

Since no studies have compared direct and graft repair of the lingual nerve, we examined the subjective and objective outcomes of lingual nerve repair by direct epineurial repair and indirect graft repair, assessed the effect of other confounding variables, and compared the outcomes of autograft and allograft repairs.

PATIENTS AND METHODS

All patients who had undergone microneurosurgical repair of the lingual nerve from 2000 to 2012 by 1 surgeon (M.M.) were asked to complete an online questionnaire regarding their current neurosensory status at least 2 years after nerve repair. A direct comparison was made between patients who had undergone direct epineurial repair and those who had undergone interpositional nerve graft repair. Student's t test and χ(2) test were used to determine whether a significant difference existed in the success between the 2 techniques and whether age, gender, race, delay from injury to repair, or degree of initial nerve deficit influenced the success of nerve repair.

RESULTS

Of the 72 patients identified, 43, who had undergone 47 nerve repairs (18 direct, 29 indirect graft repairs [4 bilateral]; 28 female and 19 male patients; mean age 28.3 years), were interviewed. The objective results of functional sensory recovery, defined by a Medical Research Council Scale grade of S3, S3+, or S4, was 89% for the graft repairs and 85% for the direct repairs (P = .01). The subjective patient satisfaction score (0 to 10 scale) was 8.9 for the graft repairs and 8.1 for the direct repairs (P = .02). The autograft and allograft repairs performed comparably, and the other variables (ie, age, gender, race, delay from injury to nerve repair, gap length, and initial Sunderland grade injury) were not found to be significant (P > .05).

CONCLUSION

Graft repair of the lingual nerve provides superior long-term (>2 years) objective and subjective outcomes compared with direct repair. This might be because of the lack of tension at the repair site, more freedom with nerve stump preparation, and the addition of neurotropic and neurotrophic factors from the donor nerve graft at the site of injury to augment neurosensory recovery.