Roger A. Meyer

Microsurgical Repair of the Inferior Alveolar Nerve: Success Rate and Factors That Adversely Affect Outcome

PURPOSE The objectives of this study were to determine the likelihood of regaining functional sensory recovery (FSR) after microsurgical repair of the inferior alveolar nerve (IAN), and which variables significantly affected the outcome of that surgery in a large series of patients. MATERIALS AND METHODS This was a retrospective cohort study that evaluated all patients who had undergone microsurgical repair of the IAN by 1 of the senior surgeons (R.A.M.) from March 1986 through December 2005. The requirements for inclusion of a patient in the study included the availability of a complete chart record and a final follow-up visit at least 12 months after surgery. All other patients were excluded. The predictor variables were categorized as demographic, etiologic, and operative. The final outcome variable was the level of recovery of sensory function as determined by standardized neurosensory testing at the last postoperative visit of each patient and based on guidelines established by the Medical Research Council Scale. Risk factors for surgical failure to achieve useful sensory function were determined from analysis of descriptive statistics, including patient age, patient gender, etiology of nerve injury, chief sensory complaint (numbness, pain, or both), time from injury to surgical intervention (in months), intraoperative findings, and surgical procedure. Logistic regression methods and associated odds ratios were used to quantify the association between the risk factors and improvement. Receiver operator characteristic curve analysis was used to find the threshold of those variables that significantly affected patient outcome. RESULTS In total, 167 patients (41 male and 126 female patients; mean age, 38.7 years [range, 15-75 years]) underwent 186 IAN repairs (19 patients sustained bilateral IAN injuries). The mean time from injury until surgery was 10.7 months (range, 0-72 months). Successful recovery from neurosensory dysfunction (FSR, defined by the Medical Research Council Scale as ranging from useful sensory function to complete sensory recovery) was observed in 152 repaired IANs (81.7%). With increasing duration from date of injury to IAN repair, the likelihood of FSR decreased (odds ratio, 0.898; P < .001). The odds of achieving FSR exhibited a linear decline between the date of nerve injury and its repair, with a significant drop in rate of successful outcome (FSR) occurring beginning at 12 months after injury. There was also a significant negative relationship between increasing patient age and improvement (odds ratio, 0.97; P = .015), with a threshold drop of achieving FSR at 51 years of age. The cause of the injury, the operative findings, and the type of operation performed to repair the nerve had no significant effect on the likelihood of the patient regaining FSR. The presence of pain after nerve injury did not affect the likelihood of achieving FSR after repair in a statistically significant manner (P = .08). In those patients who did not have pain as a major complaint before nerve repair, pain did not develop after microneurosurgery. CONCLUSIONS Microsurgical repair of an IAN injury resulted in successful restoration of an acceptable level of neurosensory function (FSR) in most patients (152 of 186 repairs [81.7%]) in this study. The likelihood of regaining FSR was inversely related to both time between the injury and its repair and increasing patient age, with significant threshold drops at 12 months after nerve injury and at 51 years of age, respectively.

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.

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 patients 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 surgeons 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 Evaluation of Peripheral Trigeminal Nerve Injuries

This article presents a standardized method of clinical evaluation of the patient with a peripheral trigeminal nerve injury that provides both subjective and objective information. This evaluation scheme has been used by 1 author for more than 30 years (RAM) and by the other author (SCB) for 10 years. The information is easily obtained and recorded in the patients record, and it can be used by any clinician who performs subsequent evaluations on the same patient. The NST methods have been used successfully by specialists in other surgical disciplines for many years, and the various test results have been found to be closely correlated with the injuries found when the responsible nerve was surgically explored.Alternate testing methods or equipment are available that are used primarily in clinical and laboratory research rather than clinical practice. The reader who is interested in more information is encouraged to consult (Further Readings).

Etiology and Prevention of Nerve Injuries

Routine dental treatment procedures, surgical operations, and traumatic injuries to the oral and maxillofacial region often occur in close proximity to peripheral branches of the fifth (trigeminal) cranial nerve. Such clinical situations include local anesthetic injection, removal of teeth, placement of dental implants, ablative and reconstructive procedures, and fractures of facial bones, among many others, including endodontic therapy and orthognathic surgery. Such clinical situations include, among others, local anesthetic injections, removal of teeth, endodontic treatment, placement of dental implants, ablative, reconstructive and cosmetic operations, traumatic facial injuries, and orthognathic/craniomaxillofacial surgery. Despite the best of care, some nerve injuries are unavoidable; however, with careful planning, an excellent knowledge of regional anatomy and its possible variations, and modifications of surgical technique, the risk of injury to adjacent nerve structures may be reduced. In this chapter, the types of clinical scenarios that are associated with injuries to the peripheral branches of the trigeminal nerve will be presented, and measures that might be helpful in reducing these risks are discussed.

Microsurgical Reconstruction of the Trigeminal Nerve

Head and neck tumor surgery or traumatic injuries in the maxillofacial region often result in discontinuity defects of peripheral branches of the trigeminal (fifth cranial) nerve, causing loss of sensation to those areas of the face, mouth, or jaws supplied by this important nerve. Injuries to the peripheral branches of the trigeminal nerve can be repaired by microsurgical techniques, either at the time of the original injury or ablative operation if conditions are favorable, or at a later date. Repair of a peripheral nerve injury has a good chance of a satisfactory outcome if done in a timely fashion.

Clinical Evaluation of Nerve Injuries

The foundation of proper treatment of any medical condition is establishment of an accurate diagnosis, and the diagnosis is based upon a thorough evaluation of the patient’s condition. The patient with a peripheral trigeminal nerve injury may present with a myriad of symptoms, often not conforming to a stereotypical pattern. Likewise, the responses to a neurological examination are varied and require interpretation based upon the knowledge and experience of the clinician. However, in this chapter, the evaluation of the nerve-injured patient is presented in a manner easily understood and completed by any competent practitioner, whether a specialist in nerve injuries or not. The obtainment of a proper history and completion of an essential neurosensory examination will lead to the establishment of a diagnosis regarding the extent of the sensory neurological deficit and the classification of the nerve injury. Such an undertaking will allow the clinician to consider appropriate and timely treatment, and it should be a rewarding, rather than a confounding, experience, if the clinician follows the information presented in this chapter on clinical evaluation of nerve injuries.

When to refer a patient with a nerve injury to a specialist

BACKGROUND Nerve injury is a known and accepted risk of many oral surgical and dental procedures. Such injuries may occur despite the practitioners providing the best of care. Taking proactive measures during evaluation and surgery may reduce the incidence of nerve injury. RESULTS Injuries to the peripheral branches of the trigeminal nerve can cause unfavorable effects on orofacial sensation and related functions such as eating, drinking, washing, speaking, shaving and kissing. CONCLUSIONS When nerve injuries secondary to dental or oral surgery procedures fail to resolve promptly and the resulting dysesthesia is unacceptable to the patient, timely treatment gives the patient the best chance of a favorable outcome. Treatment may involve surgical exploration and repair of the injured nerve. PRACTICAL IMPLICATIONS Recognition of and prompt referral for nerve injuries give the patient the best chance of achieving improvement or recovery of sensory function in the distribution of the injured nerve.

Neuropathic Pain After Mandibular Ramus Sagittal Split Osteotomy

NEUROPATHIC PAIN AFTER MANDIBULAR RAMUS SAGITTAL SPLIT OSTEOTOMY To the Editor:—The report by Marchiori et al regarding neuropathic pain (NPP) after sagittal split ramus osteotomy of the mandible (SSRO) should serve as a cautionary tale for those surgeons who perform orthognathic surgery. Patients who undergo these elective operations are generally (but not always) ‘‘youthful, in good general health, and highly expectant of a result that renders them more facially attractive and functionally improved.’’ A complication such as NPP that arises after SSRO can be devastating to the uninformed or unprepared patient. Marchiori et al reported 7 cases of NPP among 1,671 patients in their study, for an incidence of 0.42%. However, their data might be inaccurate, because theirs was a retrospective study, and all necessary information might not have been recorded contemporaneously and be available for retrospective review in each patient’s record. Additionally, they failed to report how many, if any, other patients had sustained permanent nerve injuries, but had not developedNPP. Other studies, including our own, have found the incidence of NPPamong those patients who sustained peripheral trigeminal nerve injuries after SSRO to be about 5%, a much greater incidence than that reported by Marchiori et al. NPP in our patients was found to be associated with either inferior alveolar nerve (IAN) or lingual nerve (LN) injury. The patient most likely to develop NPP as a major chronic complaint after SSRO was the patient in whom the nerve injury repair was delayed for longer than 12 months, who was older than 45 years, and whose procedure involved compression or partial severance of the IANor complete discontinuityof the LNwith a proximal stump neuroma. Patients with chronic illnesses that compromise the healing process or place the patient at risk of developing peripheral neuropathy (eg, diabetes mellitus) or with pre-existing chronic pain from any cause (eg, low back pain, post-thoracotomy syndrome) are also known to be at greater risk of developing NPP after an operation. Gregg has previously reported on surgical intervention to address pain after peripheral trigeminal nerve injuries. He identified 4 distinct pain subtypes: anesthesia dolorosa (AD), sympatheticmediated pain (SMP), hyperalgesia (HA), and hyperpathia (HP). Surgical repair of the injured nerve producedpain reduction in 60.5% of the patients with HA and 58.3% of those with HP. Incontrast, only20.0%of the SMPpatients and14.6%of the AD patients gained any pain relief. The duration of pain before surgery had ranged from4weeks to12years (mean9months). Early surgical intervention is more likely to be successful for various reasons. In conclusion, we would emphasize that preoperative counseling of patients who are undergoing SSRO should include a discussion of the risk of nerve injury and sensory dysfunction (both loss of sensation and chronic pain). Spe-