Recognition of Neuropathic Pain in Temporomandibular Joint Surgery
While the incidence of neuropathic pain has been well reported in the literature for other procedures in oral and maxillofacial surgery, few reports of persistent (lasting greater than 6 months) neuropathic pain after temporomandibular joint surgery exist
[23-25]. There is relatively good data on the incidence of neural injury during TMJ surgery, as well as the development of persistent neuropathic pain after direct neural insult. Thirty-five percent of patients who develop a peripheral trigeminal nerve injury will go on to develop a chronic nerve injury , and 23-45% of patients who seek care for a persistent peripheral trigeminal nerve injury will go on to develop painful dysesthesia [27, 28].
Shevel reported a single incidence of lower lip paresthesia and two cases of buccal nerve paresthesia lasting longer than 6 months in a series of 46 intraoral condyloto- mies for TMJ derangement . Multiple large, long-term studies of TMJ arthroscopy have been performed with a 0-3.6% incidence of temporary (less than 6 months) paresthesia to the trigeminal nerve reported [22, 30-35]. The majority of the injuries reported were in the distribution of the auriculotemporal branch [22, 33], although involvement of the lingual  and inferior alveolar [34, 35] branches was noted as well. In the largest series to date, 115 temporary and two persistent fifth nerve deficits were noted in 3146 patients . The distribution and characteristics of these injuries remain unclear. The majority of these injuries are thought to be related to neuropraxia secondary to the extravasation of irrigation fluid during the procedure. Direct damage to nerves is thought to be rare due to the surgical anatomy of the arthroscopic lateral approach ; however, direct injuries have been reported [22, 34], as well as trigem- inal-vagal-mediated bradycardia due to direct manipulation of the auriculotemporal branch [37, 38]. The position of the auriculotemporal nerve is intimate to the condyle, on average being found 10-13 mm inferior to the superior surface of the condyle and 1-2 mm posterior to the neck of the condyle . As a result, it is exceptionally susceptible to compressive neural damage during TMJ procedures and from pathology . Development of auriculotemporal (Frey) syndrome due to this damage is a unique case of neural insult and will be considered in a separate chapter. In open procedures utilizing the preauricular approach, rates of temporary auriculotemporal paresthesia have been reported ranging from 13% to 14% [20, 21].
Chronic dysesthesia secondary to temporomandibular joint surgery is rare with few evidence-based guidelines existing regarding the prognosis. It is the opinion of the authors that the prognosis is poor for complete resolution. Temporomandibular joint surgical patients presenting with a dysesthesia are likely to be multiply- operated patients with all the stigmata of chronic pain: central and peripheral sensitization, muscular hyperalgesia, phenotypic and cortical plasticity, as well as having genetic polymorphisms that predispose them to neuropathic pain. In the authors experience with managing this rare complication, successful management of their pain is very difficult.