Injuries of the Peripheral Mandibular Nerve, Evaluation of Interventions and Outcomes: A Systematic Review

Trigeminal nerve injuries are common and there is currently no consensus on both timing and type of intervention to achieve the best outcomes. A systematic review was performed to compare the outcomes of the many different types of therapeutic interventions for nerve injury. PubMed, EBSCO, and Cochrane Review databases were used to search for studies published from January 1, 2000 to December 31, 2019. Included studies detailed treatment of an injury to peripheral branches of the trigeminal nerve, either known transection or injury causing persistent alteration in sensation. The primary outcome was functional sensory recovery via the Medical Research Council scale. Twenty studies were included, detailing outcomes of 608 subjects undergoing intervention for 622 nerve injuries. Surgical interventions were able to achieve functional sensory recovery in approximately >80% or more of the subjects. There was heterogeneity among how procedures were performed, timing to intervention, and methods of measuring recovery. The data of this study supports the ability of surgical intervention to achieve functional sensory recovery in a significant number of subjects, and found evidence for better outcomes with intervention closer to the time of injury.

Trigeminal Nerve Injuries

The trigeminal nerve constitutes the largest sensory cortex representation in the brain compared to any other sensory nerve. This is likely due to the fact that the trigeminal nerve underpins our very existence, as it protects, sensorially, our senses including the organs that provide sight, smell, taste, hearing, speech and meninges protecting our brain.Neurophysiologically, our affective and limbic systems in our brains are alerted before we even set foot in the dental surgery and the patient’s brain is anticipating and aligned for pain experience. Thus, when trigeminal nerve injuries occur, which in the main are preventable, the majority of patients experience mixed symptoms including ongoing and elicited neuropathic pain, numbness and altered sensation. These neuropathic features cause significant impact on the patients’ ability to function, for example, cold allodynia prevents the patient enjoying cold foods and drinks and undertaking outdoor activities or elicited pain on touch frequently interferes with sleep. The resultant chronic symptoms and functional impedance often result in significant psychological morbidity.There is no magic bullet to resolve these sensory nerve injuries, and our specialty is beholden to prevent nerve injuries where possible. The patient must have the appropriate consent, and their expectation is managed with understanding the potential benefits and risks for their chosen interventions.Prevention and management of nerve injuries related to local anaesthesia, implants and third molar surgery are outlined in this chapter. There is insufficient capacity to go in-depth for each area, but the author has provided up to date evidence base where it exists and some strategies to minimize and manage optimally these unfortunate complications.