Auriculotemporal Neuralgia Jose Geraldo Speciali, MD* and Daniela Aparecida Godoi Gonçalves, DDS Address School of Medicine, University of Sao Paulo at Ribeirao Preto, Department of Neurology, Psychiatry, and Medical Psychology, Av. Bandeirantes, 3900 Ribeirao Preto, Sao Paulo CEP 14049-900, Brazil. E-mail: speciali@netsite.com.br Current Pain and Headache Reports 2005, 9:277–280 Current Science Inc. ISSN 1531-3433 Copyright © 2005 by Current Science Inc. Introduction Stimulation of afferent nerves fibers or their correspondent central pathways may elicit stabbing or constant pain that is felt in the correspondingly innervated area. Although causal attribution sometimes may be demonstrated (eg, infection by herpes zoster or a structural abnormality demonstrated by neuroimaging), no apparent cause for neuralgic pain can be identified very often [1••]. The peripheral nervous system may be insulted in several ways, the entrapment of a nerve being one of them. The entrapment of a nerve occurs more often when the nerve passes through anatomic structures that have the potential of compressing it. Some of these anatomic sites are well known and usually are at predictable locations in the body [2]. One unusual compressing site that may cause nerve compression is the infratemporal fossa, a space behind the maxilla that contains several structures, includ- ing the lateral pterygoid muscle (LPM). Because the first and second divisions of the trigeminal nerve do not travel near the LPM at their proximal segments, only the third division is likely to be entrapped at this site, as it passes through the infratemporal fossa [3]. At the level of the roof of the infratemporal fossa, the mandibular nerve exits the cranium through the foramen ovale and then immediately divides, in close association with the LPM, into two divisions that originate terminal branches. The anterior division contains the anterior deep temporal, posterior deep temporal, and masseteric nerves and travels between the roof of the infratemporal fossa and the LPM. The posterior division contains the lingual, inferior alveolar, and auriculotemporal nerves and descends medial to the LPM [3] (Fig. 1). Of these, the auriculotemporal nerve (ATN), because of its course, is at greatest risk for irritation or entrapment [4]. Branches of the ATN are the main source of sensorial innervation to the temporomandibular joint (TMJ) [5]. The ATN is divided into the following five small branches: the nerve to the external auditory meatus, which innervates the skin of the meatus; the parotid branches; the communicating branch to the facial nerve, which connects to the temporal branches and zygomatic branches of the facial nerve; the ante- rior auricular nerve, which branches at the base of the auricle; and the superficial temporal nerve, a terminal branch. Each of the branches mentioned above origins several smaller branches to the TMJ [5]. Entrapment of the mandibular nerve is not uncommon. In a study conducted in cadavers by Loughner et al. [3] in 1990, the posterior trunk of the mandibular nerve was shown to be entrapped in 6% of the 52 studied cases. In sev- eral of these cases, the entrapment happened at the level of the LPM. In another postmortem study, Schmidt et al. [4], after dissecting eight cephalic segments, found that myositis or myofibrositis, local ischemia, and inflammation involv- ing the LPM were associated with previously reported senso- rial abnormalities in the distribution of the ATN, likely because of its proximity to the LPM. More recently, Anil et al. [6] conducted 20 dissections of the infratemporal fossa in 10 cadavers. They observed that the mandibular nerve was fixed between the foramen ovale and mandibular foramen and sometimes was compressed by the surrounding structures, particularly when passing between the medial and the lateral pterygoid muscles. They found that neurovascular anatomic variations in the infratemporal fossa are rare, but when present, may cause numbness, regional pain, or headache. Although several published studies have investigated the anatomic and neurophysiologic characteristics of the ATN, to the best of our knowledge, recent studies regarding specific pain syndromes secondary to lesions and dysfunc- tions of the ATN are unavailable. However, a syndrome involving this nerve is fairly well described. As a result of the close anatomic relation between the LPM and the ATN, it can be speculated that myospasm or other local changes in this muscle can cause nerve In this article, the anatomic and physiologic characteristics and clinical syndromes involving the auriculotemporal nerve (ATN) are reviewed. The ATN is a terminal branch of the mandibular nerve (third division of the trigeminal nerve). The syndrome of ATN neuralgia (ATNa), which is characterized by attacks of paroxysmal, moderate to severe pain on the preauricular area, often spreading to the ipsilateral temple, is discussed in this article. The classification of ATNa under the Second Edition of the International Classification of Headache Disorders, as well as our personal experience in diagnosing and treating this syndrome, also are reviewed.