Objective evaluation of iatrogenic lingual nerve injuries using the jaw-opening reflex

Therapy of Neurophysiological Changes after Oral and Maxillofacial Surgery—A Systematic Review

Introduction: The purpose of this systematic review was to critically analyze the recent literature to present a guideline for management of neurophysiological changes after implant placement and oral and maxillofacial surgical procedures. Materials and methods: Three electronic databases and manual search approaches were used to identify relevant articles on neurophysiological changes. Only studies with a randomized controlled study design were included. Primary outcome was defined as the status of recovery and relief of pain states under various therapies. Two independent reviewers evaluated the data. Results: A total of eight studies from 2891 records identified met the inclusion criteria. Therapy options for patients with neurophysiological changes after implant placement and oral and maxillofacial surgery were low-level laser (LLL), stellate ganglion block (SGB), medication, and surgical removal of implants. Six studies dealt with LLL, providing a significant improvement in mechanical sensation. Only one study revealed the whole neurosensory profile including neuropathic pain states. All the included RCT studies presented at least one bias, and a considerable heterogeneity of the included studies was revealed. Conclusions: Reduced thermal sensation may be due to irritation of small fibers. LLL might help to improve nerve recovery.

Sensory Restoration of the Facial Region

Normal sensitivity of the face is very important for preserving its integrity and function as an efferent source of information for the brain. The trigeminal nerve, which is the largest cranial nerve, conducts most of facial sensory function through its 3 branches: the ophthalmic nerve (V1), the maxillary nerve (V2), and the mandibular nerve (V3). The trigeminal nerve may be damaged by a variety of etiologies including inflammatory disorders, brain tumor resection, trauma, iatrogenic injury, or congenital anomalies. Temporary or permanent damage can lead to numbness, lip-biting injury, corneal anesthesia, and, in the worst scenario, even blindness. Different age groups, mechanisms of the injury, and the time between injury and repair can affect the final result of the nerve repair. Unlike the well-understood facial nerve palsy, so far there is no universal approach to restore the facial sensory function. This article serves to thoroughly review the basic anatomy of trigeminal nerve, diagnosis of sensory nerve dysfunction, and attempts to establish a protocol for treatment and rehabilitation of affected patients.

Nerve regeneration techniques respecting the special characteristics of the inferior alveolar nerve

PURPOSE

The aim of this study was to examine the in situ regeneration of the inferior alveolar nerve (IAN) in its bony channel, using autologous tissue in combination with a recombinant human nerve growth factor (rhNGF).

MATERIALS AND METHODS

A total of 20 New Zealand rabbits were randomly divided into five groups. Following dissection of the IAN, the animals underwent reconstruction either with muscle tissue (groups 1 and 2) or with fat tissue (groups 3 and 4). In group 5 (control), the dissected nerve was resected and reconstructed by placement of the reversed autologous segment. After 2 and 4 weeks, 1 mL rhNGF was locally injected in groups 1 and 3. Nerve function was monitored by measuring the jaw-opening reflex using electromyography for a period of 24 weeks.

RESULTS

Regeneration of the nerve was achieved in all groups, but preoperative threshold values were not achieved. Comparing the experimental groups to the control, there was a significant difference in favor of the autologous nerve reconstruction. Differences between the experimental groups remained statistically not significant.

CONCLUSION

Regeneration of the IAN with autologous tissue is possible, but without achieving preoperative thresholds. Additional injection of a growth factor seems to improve the speed of regeneration for fat and muscle grafts.

Lingual nerve deficit following mandibular third molar removal: review of the literature and medicolegal considerations

The removal of mandibular third molars is probably the most frequently performed procedure in oral and maxillofacial surgery, and it is the most common surgical procedure associated with lingual nerve deficit. Lingual sensory impairment remains a clinical problem in oral and maxillofacial surgery and has serious medical and legal implications. In fact, damage to the lingual nerve is a common cause of litigation in dentistry. The purpose of this article was to review the literature about lingual nerve deficit following mandibular third molar removal and discuss the associated medicolegal aspects.

Testing of iatrogenic lingual nerve injury using a novel psychophysical method and oral reflexes

In a case of long-term sensory loss in the tongue following third molar extraction, a novel, efficient and effective psychophysical test was used. This initial test, which includes the presentation of pairs of a real and fake stimulus, and a forced-choice response, was applied to determine whether relatively thick or thin afferent fibres of the lingual nerve were affected. The results suggested that thick fibres on the right tongue side were mainly affected. Sensory loss was confirmed and its extent assessed by a standard test determining thresholds of light touch. Furthermore, sensory function was determined by an objective test based on inhibitory reflexes in masseteric electromyographic activity following electrical stimulation of oral tissue. Reflex features that are important for within-patient diagnosis are a difference between the injured and control sides in latency of the first reflex, and also in depth-contrast in signal amplitude between both sides at the post-stimulus time of the trough of an inhibition on the uninjured side. In agreement with the findings from the psychophysical tests, the finding of the absence of an early component of both inhibitions suggested sensory loss related to dysfunction of fast-conducting, relatively thick afferent fibres of the lingual nerve. Apart from being used for medicolegal reasons, the objective reflex test may have conclusive prognostic value or may influence surgical therapeutic decisions.