The Auriculotemporal Nerve: A Comprehensive Review of Its Anatomical Variation and Clinical Manifestations

ABSTRACT

Objectives

Various studies have described anatomical variations of the auriculotemporal nerve (ATN), starting with its initial nerve roots and relationship to the middle meningeal artery (MMA). Despite its crucial role in innervating various regions, the precise anatomical course of ATN and its variants remains uncertain. This study aims to provide a comprehensive review of the ATN, including its anatomical course, variations, and clinical significance, particularly in relation to head and neck surgery.

Methods

A systematic literature review was conducted using Medline, Embase, and PubMed databases to identify all articles describing the clinical anatomy of ATN. This search strategy adhered to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta‐Analysis) guidelines. English‐language and human studies were selected. Additionally, dissections were performed on three human cadavers to obtain representative images.

Results

ATN exhibited 1–5 roots, most commonly two (52%), relevant to surgical planning and perineural tumor spread. An inferior alveolar root origination was present in 32.6% of specimens, potentially contributing to unexpected anesthesia or neuralgia. ATN enclosed the MMA in 72.2%, often forming a triangle/V‐shaped (61.4%) or “buttonhole” (1.7%) configuration. TMJ innervation was present in all specimens, with 5.8% of branches penetrating the lateral pterygoid, implicating TMJ pain. ATN branches crossed the superficial temporal artery in 73% of cases, relevant to migraine decompression. Parotid branches originated 2–16 mm from the tragus, impacting Frey's syndrome and tumor tracking. Facial nerve communication (> 90%) and greater auricular nerve connection (up to 30%) may underlie atypical facial pain and extended anesthesia fields.

Conclusions

Our review reveals considerable diversity in ATN origins, branching patterns, and relationships with adjacent vessels, challenging traditional anatomical depictions. Understanding these variations is crucial for managing compression and entrapment syndromes like temporomandibular disorder and surgical procedures such as parotidectomy, where iatrogenic damage can lead to complications such as Frey Syndrome.

Level of Evidence: 3.

1. Introduction

The auriculotemporal nerve (ATN) is a major sensory branch of the mandibular division of the trigeminal nerve (V₃) [1, 2, 3]. ATN arises from V₃ in the infratemporal fossa, and courses first through that space and then through the retromandibular fossa, before distributing to the temporal region on the head. Along its course, it gives rise to branches that innervate the temporomandibular joint, external auditory meatus (EAM), and anterior auricle, before distributing to the superficial temporal region of the head [2, 3, 4]. It also gives off branches that communicate with temporofacial branches of the facial nerve found in this region. Crucially, the ATN also carries autonomic fibers originating from the otic ganglion, which is found in the infratemporal fossa just below foramen ovale, and medial to V₃. These include parasympathetic secretomotor neurons that innervate the parotid gland, and postganglionic sympathetic fibers that originate from nearby blood vessels and pass through the ganglion to travel with the ATN [5, 6].

The complex path and functions of ATN warrant examination in terms of both clinical significance and surgical considerations. Within the infratemporal region, there are anatomical relationships between ATN and mastication muscles, the temporomandibular joint (TMJ), as well as surrounding vessels including the middle meningeal artery (MMA) [7]. These relationships provide an environment for compression and entrapment syndromes, potentiating the development of headaches, neuralgia, or paresthesia in any of its distal branches [8]. ATN disruption likely also results from temporomandibular disorder (TMD), an increasingly prevalent condition, with reportedly 40%–75% of adults having at least one sign of TMD and 33% among those with at least one symptom [9, 10]. TMD prevalence also may differ between subpopulations, with an increase noted in women during reproductive years [11]. With this disorder, entrapment may occur due to compression by normal anatomical structures or secondary to pathological changes such as masticatory muscle hypertrophy [10]. During surgical procedures, particularly TMJ surgery and parotidectomy, ATN is vulnerable to damage, leading to similar manifestations of terminal pain/paresthesia. Further, damage to parasympathetic fibers during parotidectomy can lead to inappropriate regeneration to sympathetic receptors, resulting in Auriculotemporal Syndrome (Frey's Syndrome) [7, 12, 13]. The variable course and branching pattern of ATN within the parotid region further complicate its preservation during glandular surgery, particularly in cases involving deep lobe tumors or extensive dissection [7, 13].

In addition to its roles in TMJ and parotid pathology, ATN has broader clinical implications across surgical, neurologic, and oncologic domains. It may act as a conduit for perineural tumor spread, particularly in parotid gland malignancies or cutaneous carcinomas of the face and ear. Its superficial branches, often coursing near the superficial temporal vessels, have been implicated in auriculotemporal neuralgia and migraine syndromes [8]. Anatomical variations along its course may influence the success of targeted nerve blocks used in the management of facial pain and headaches. Furthermore, in head and neck imaging, a detailed understanding of ATN anatomy, including its anastomoses with other cranial and cervical nerves, can aid in the detection of subtle signs of perineural invasion or nerve pathology. Thus, comprehensive anatomical knowledge of ATN anatomy is not only for surgical planning but also for accurate diagnosis, oncologic surveillance, and targeted therapeutics.

A number of clinical and anatomical studies have described anatomical variations of ATN, starting with its initial nerve roots and relationship to the MMA. Despite ATN's critical role in supplying innervation to various regions, as well as its clinical and surgical significance, there is still uncertainty surrounding its precise structure and course. To our knowledge, a summation of ATN's course and variants has not recently been described in detail. This comprehensive review aims to provide a thorough, current understanding of the anatomical course of ATN and its functions relevant to head and neck surgery.

2. Methods

2.1. Search Strategy

A systematic literature review of electronic databases Medline, Embase, and PubMed was performed in December 2023 by two independent reviewers (AK and PT). The goal was to identify all articles describing the clinical anatomy of the auriculotemporal nerve (ATN). The search was limited to English‐language studies and human subjects, but included foreign‐language articles with available English abstracts when relevant to the study objective. The search terms included “auriculotemporal nerve” and related subheadings. The search strategy used for the PubMed database is presented in Supporting Information 1. Secondary references were identified through citation chaining of included studies and evidence‐based findings from selected anatomy, physiology, and other reference texts. The search strategy and selection process adhered to the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) 2020 guidelines (Supporting Information 2) to ensure a transparent and reproducible review.

2.2. Inclusion and Exclusion Criteria

Inclusion criteria were clearly defined to include studies that provided specific and extractable anatomical descriptions of ATN, its branching pattern, relationship to the middle meningeal artery (MMA), or surrounding structures, and associated clinical implications. Studies were excluded if they were case reports without anatomical descriptions, letters to the editor, abstracts without available full text, or reviews without original data. A few animal‐based studies were included where needed to supplement the cadaver studies but were not involved in statistical analysis.

2.3. Cadaveric Images

Several dissections were conducted, and representative images of the ATN obtained by the authors using three human cadavers collected from the Department of Anatomy & Neurobiology at the University of Tennessee Health Science Center (UTHSC); these were fixed in a solution of 75.68% isopropanol, 18.92% dipropylene glycol, and 5% formalin. Data collection from the human cadavers qualified for exempt status by the UTHSC Institutional Review Board under Federal Regulations 45 CFR 46.102(f) definition of “Human Subjects.” The cadavers had been previously used in a Physical Therapy Anatomy course. All the cadavers were donors, and all donors sign a form that confirms that the donations may be used for scientific research on the donation form.

The cadaveric dissection protocol involved careful dissection of the ATN and documentation of possible anatomical variations, including its roots, branching patterns, and relationships with key anatomical landmarks such as the middle meningeal artery (MMA) and inferior alveolar nerve (IAN). Digital photographic documentation was obtained systematically to ensure reproducibility and accuracy.

2.4. Data Extraction and Statistical Analysis

Data extraction was performed by two reviewers (A.K. and P.T.) and disagreements were resolved through discussion and consensus or by consulting a third author (J.D.B.). Extracted data included study characteristics (author, year, country), specimen number, anatomical features of ATN (number of roots, branching patterns, relations to adjacent vessels), and relevant clinical implications. Due to heterogeneity across included studies regarding methodologies and outcomes reported, quantitative meta‐analysis was not feasible. Data were synthesized narratively, emphasizing consistent patterns, key variations, and significant clinical implications. Descriptive statistics (frequencies, percentages) were calculated to summarize anatomical variation prevalence. Chi‐square tests were used to compare proportions, with statistical significance set at p < 0.05.

3. Results

3.1. Study Selection

The initial database search yielded 850 records, with 150 duplicates removed. Following title and abstract screening, 200 full‐text articles were assessed; 180 retrieved; and 130 excluded due to not meeting criteria or insufficient data. Ultimately, 50 studies were included in the qualitative analysis Figure 1.

FIGURE 1.

PRISMA flowchart of included studies.

3.2. Anatomical Variation of the ATN

3.2.1. Nerve Origins

A short distance inferior to the foramen ovale, the trunk of the mandibular nerve divides into a smaller anterior division and a larger posterior division [3]. The posterior division quickly divides into several major branches, most prominently (from anterior to posterior) the lingual nerve, inferior alveolar nerve (IAN), and ATN. According to Baumel et al. [14], the ATN was classically depicted as originating from the posterior division via a single root which subsequently bifurcates, or via two separate roots. In either arrangement, the ATN tightly encircles the passing MMA before reconverging, referred to as a “button‐hole” configuration. In their seminal work, these authors challenged this morphology via examination of 85 cadaveric specimens, describing how 1–4 roots contribute to the formation of ATN, and with none of their dissections demonstrating the classic button‐hole relationship between ATN and MMA. The most common or typical configuration was in fact two more (relatively) widely separated roots: a larger superior root found lateral to the MMA, and a more slender inferior root medial to the MMA. However, in their examinations, these roots did not tightly envelope the MMA; instead, they formed a triangular or V‐shaped interval before joining together to form a main trunk prior to passing into the region of the TMJ (Figure 2A,B).

FIGURE 2.

Overall course of the auriculotemporal nerve (ATN), and branching patterns within the infratemporal fossa. (A) Overall schematic shows general course of ATN with major branches indicated. (B) Schematic illustrations of several ATN variants in relation to the middle meningeal artery (MMA) found in the infratemporal fossa, including those with 1–4 roots. The maxillary artery (MAX), which gives rise to the MMA, is also shown in relation to the one‐root variant. The most common arrangement involves 2 roots comprising a V‐shaped formation around the MMA (upper right). Note that there may also be variation in whether particular ATN roots are found medial or lateral to MMA; the superior root of ATN is most commonly found lateral to MMA, as illustrated in these examples. (C) Cadaveric dissection of V3 and ATN in the infratemporal fossa. This cadaver had 2 ATN roots conducting MMA, but also had a communicating branch from the superior root to the inferior alveolar nerve (IAN). Other abbreviations: EAM, external auditory meatus; LN, lingual nerve; TMJ, temporomandibular joint. Schematics in B were created based on data described in published sources [15, 16], and from our own dissections.

Subsequent reports have examined variation in the ATN's initial branching and morphology within the infratemporal fossa. We reviewed this morphology in 10 cadaveric anatomical studies (Table 1), including a total of 425 specimens. Overall, ATN root number across all studies ranged from 1 to 5, with a weighted mean of 2.33 roots (Table 2). The most common arrangement was 2 roots (52% of all specimens; p < 0.0005). One root was found in 21% of specimens, while the presence of 3–5 roots was less common (4%–16%) (Figure 2B). Another consideration noted in several studies involves one or more ATN roots originating at a slightly more inferior point in the fossa, from the inferior alveolar nerve (IAN) rather than the mandibular nerve [8, 14, 18, 19]. In the papers we reviewed, this possibility was examined in 258 specimens across six studies, with multi‐root variations possibly predisposing nerve roots to exit very low from the trunk [8]. Such contributions were noted in 32.6% of these specimens, with a range of 12.5%–48.7%. Variable contribution of IAN to ATN root formation could help explain atypical symptoms of anesthesia and ATN neuralgia following an IAN nerve block during dental procedures [8, 21]. In one of our own dissections, we noted a long branch originating from the upper root of ATN, looping over the maxillary artery, and joining IAN at an even more inferior point (Figure 2C). A similar variant was seen in a study of IANs by Anil et al. [22], and the presence of occasional communications from the root(s) of ATN to IAN was noted in other studies as well [14, 18]. Thotakura et al. [23] observed a communication between ATN and IAN in 5.5% of specimens, and Bhardwaj et al. [24] described a bilateral communication with IAN in one specimen (30 examined infratemporal regions). Anil et al. [22] described communication as a loop between ATN and IAN “reminiscent of the brachial plexus” in which the maxillary artery passed through, in two of 20 of their dissections. It is possible that this sort of connection can convey postganglionic fibers from the otic ganglion to IAN and through ATN to the lower labial glands.

TABLE 1.

Studies examining anatomical variation of the auriculotemporal nerve (ATN) in the infratemporal fossa.

Author(s)	Country	No. specimens or cadavers/specimens	Mean age or range	Female, male (%)
Baumel et al. [14]	USA	85 (includes one fetus)	n/a	n/a
Vrionas et al. [15]	USA	12	n/a	n/a
Fernandes et al. [17]	Brazil	40	n/a	n/a
Gulekon et al. [18]	Turkey	16/32	57.9	4, 12
Komarenitki et al. [8]	Poland	16	n/a	n/a
Dias et al. [19]	New Zealand	19/25	n/a	13, 6
Komarenitki et al. [5]	Poland	80/44 (22 adult, 22 fetal)	57–85	21, 23
Quadros et al. [16]	India	30	n/a	n/a
Chanasong et al. [20]	Thailand	73/39	44–89	14, 25
Moodley et al. [21]	South Africa	32/16	72.4	8, 8

TABLE 2.

Variation in auriculotemporal nerve (ATN) root number (%) by study.

Study	Number of roots (%)
	One	Two	Three	Four	Five
(15)	50	37.5	9	3	0
(16)	32	48	20	4	0
(17)	28	44	28	67	0
(14)	12	73	14	1	0
(23)	9.5	67.1	15	8	0
(52)	13.3	73	10	0	3
(51)	0	58	0	42	0
(8)	31	31	6	6	25
(29)	17.5	55	27.5	0	0
(5)	20	30	32.5	6	11.25
Average	21.3	51.7*	16.2	13.7	3.9

^*One‐way ANOVA, F[4, 45] = 14.22, p < 0.0001. Post hoc tests (Tukey) indicated “Two” significantly different from all other categories (p < 0.0005); no other comparisons were significant.*

The question of whether the roots of ATN enclose or conduct the MMA was examined in 274 specimens across eight studies. The vast majority of cases (72.2%) described an enclosing of MMA by ATN, and excluding the one‐root variants of ATN, 85.7% of multi‐root variants demonstrated this relationship (85.8%–87% for 2 or 3 roots respectively; 100% for 4–5 roots) (Table 3). In the one‐root variants, ATN passed medially to MMA in the majority of cases (67%) and laterally in the minority of cases (33%). In the majority of specimens, branches of the ATN formed a V‐shaped arrangement relative to the MMA [14, 19, 21]. Baumel et al. and Gulekon et al. did not note any “button hole” formation in any of their combined 117 dissections. Interestingly, Moodley et al. [21] noted that the MMA only passed through the identified V‐shaped formations 57% of the time in their study; two reports also noted the occasional presence of a button‐hole formation that did not enclose MMA or any other vasculature [19]. Finally, another less common enclosing variation noted in this region was the enclosing of the maxillary artery itself by ATN, seen in 16.6% (3/18) of specimens by Dias et al. and 8.2% (7/85) by Baumel et al.

TABLE 3.

Relationship of ATN with arteries, and presence of enclosure, in infratemporal fossa.

Study	Frequency of structure (%)
	“Buttonhole”	Triangle/V‐shape	ATN encloses MMA	ATN encloses maxillary
(16)	8 a	52	88.2	16.7
(17)	3 a	68.8	60.9
(14)	0		94.7	8.2
(23)			76.1
(52)			100
(51)			100
(8)			81.8
(15)	0
Average	1.7	61.4	85.7	9.7

Abbreviations: ATN, auriculotemporal nerve; Maxillary, maxillary artery; MMA, middle meningeal artery.

^a In these cases, MMA did not traverse buttonhole.

An important issue surrounding the root variation is whether different roots might consist of different functional components, i.e., the possibility that the minor root(s) might just consist of the autonomic fibers passing from the otic ganglion to the ATN. Although this is not addressed in most of the aforementioned studies, Baumel et al. [14] described variation in the sensory information present in each root, with fibers innervating the superficial temporal region and auricle predominating in the larger, upper root and innervation to the EAM in the lower root(s). Moreover, they state that both upper and lower roots receive communicating rami from the otic ganglion. This description fits well with more recent descriptions of the otic ganglion and its extensive connections within the infratemporal fossa [25, 26]. Postganglionic fibers from the ganglion often distribute to all major branches of V3, including ATN, via very small, short rami, and thus are not likely large enough to be seen as comprising separate ATN roots described in the studies in Table 2.

Root structure may also be asymmetric within individuals, with side‐to‐side differences commonly noted in several studies [18, 19]. The studies we reviewed were conducted on primarily (older) adult male and female cadavers, with the exception of two studies that included fetal cadavers (Table 1). Generally, however, the possible contribution of demographic variables such as age or sex was not considered or examined. Additionally, these studies were conducted in different countries, and in comparing their results to others, several authors noted possible variation between ethnic groups [20, 21]. Although incomplete, an adequate understanding of intra‐variation and variation between populations may be helpful for management of surgical procedures among different individuals.

3.2.2. TMJ Region

The roots of ATN course between the lateral pterygoid muscle and posterior portions of tensor veli palatini, and then are classically described to fuse (at a distance of ~1 to 2 cm posterior to V3), forming a trunk which extends posteriorly and inferiorly along the medial surface of the lateral pterygoid [8, 27]. ATN then emerges from the posteromedial aspect of the mandibular condyle at or below the level of the joint capsule, before ascending to the preauricular region (Figure 3A). At the posterior mandibular border, as ATN begins its superior course, terminal branches innervate the joint capsule, entering posteromedially and posterolaterally. With the ATN primarily providing innervation to the posterior and lateral aspects of the TMJ, other innervation to this structure includes the masseteric nerve anteriorly, the deep posterior temporal nerve anteromedially, and a small TMJ branch of the mandibular nerve medially [27, 28, 29].

FIGURE 3.

Temporomandibular joint (TMJ) innervation and superficial course of the auriculotemporal nerve (ATN). (A) Schematic from a posterior view depicts ATN's innervation of the TMJ capsule and terminal branching patterns. (B) Dissection of the lateral superficial head shows a single main nerve trunk just posterior to, and running alongside, the STA.

While the literature has described variations in TMJ innervation, ATN has proven to play a predominant role, as revealed in cadaveric studies. Davidson et al. [28] demonstrated ATN's contribution to the lateral TMJ capsule in 100% of its specimens (n = 24), with 75% of joints receiving additional, distinct masseteric branches to the anterior capsule, and 33% with a contribution to the medial aspect from a TMJ branch of the mandibular nerve. A more recent study showed, in 40 specimens, an average of 1.9 ATN, 1.0 masseteric, 0.2 posterior deep temporal nerve, and 0.65 TMJ branch of mandibular nerve branches innervating the TMJ [29]. Further, in 55% of these dissections (n = 20), the most commonly noted innervation pattern consisted of contributions from ATN, the masseteric nerve, and a TMJ branch of the mandibular nerve. In 25% of the dissections, ATN and the masseteric nerve were the sole source of innervation, while 10% showed posterior deep temporal nerve contributions in addition to ATN and masseteric.

Due to its course, ATN is at the greatest risk for entrapment or irritation relative to other sources of TMJ innervation [27]. Although relatively rare, previous studies have described an anatomical variation of ATN that penetrates the lateral pterygoid muscle, described by Komarnitki et al. [8] in 1 of their 16 studied specimens (a 5 root variant) [30]. Loughner et al. [31] described a similar rare variation in 5.8% of their dissections (n = 52), where ATN, along with the lingual and inferior alveolar nerves, all penetrated through the lower belly of the lateral pterygoid. Two of the three entrapments were found in the same specimen, and all three specimens also demonstrated entrapment of MMA. A second potential site for entrapment or impingement is in the proximity of the joint capsule or condyle; particularly, dislocations or displacements of TMJ structures may exert pressure on the ATN, producing symptoms [8, 27]. Schmidt et al. [27] highlighted that the ATN nerve trunk was in direct contact with the medial surface of the joint capsule or condyle in all studied specimens (n = 16) at the posterior border of the lateral pterygoid. However, the authors noted that despite the proximity of the nerve, there was no evidence of direct nerve impingement between the condyle and articular eminence. In a different study, the location of ATN with respect to the condyle was recorded in 40 specimens; the nerve was typically found to be slightly more inferior and posterior, suggesting that mechanical irritation would be less likely [17]. However, the authors acknowledged that if surrounding soft tissue became fibrotic or sclerotic, nerve entrapment would be a higher possibility. Johansson et al. [32] noted two joints in studied specimens with medial disc displacements, where ATN was nearly in contact with the medial aspect of the condyle, thus exposing the nerve to mechanical irritation during condyle movements in the anteromedial direction.

3.2.3. Supply to Parotid Gland

As it courses posterior to the condyle, the ATN divides into the rest of its subsequent or terminal branches, described as a “spray” of branches by Baumel et al. [14]. This includes a parotid branch(es), traveling through and terminating in the gland [17]. Parotid branches carry sensory fibers from the parotid fascia, as well as parasympathetic secretomotor and sympathetic vasomotor fibers innervating the glandular tissue itself [6, 14]. There appears to be considerable variation in the origin of these branches. In a study of 10 cadavers, Iwanaga et al. [33] found there to be two distinct branches in 30% of the nerves investigated. Additionally, the authors found that the parotid branches arose from a variety of different points along the length of the ATN, anterosuperiorly to the middle of the tragus and main trunk of ATN. The vertical and horizontal distances of the branch point relative to the tragus were 8.3 and 7.9 mm on average; however, the range of vertical distances was quite large, from ~2 to 16 mm. Identification of these branches during surgery may be important for the avoidance of post‐operative Frey's Syndrome and to assess for potential spread of malignant tumors along the course of the root outlets.

The autonomics traveling with ATN are typically associated with parotid gland innervation. These pathways are fairly well understood: Preganglionic, parasympathetic fibers originating from the inferior salivatory nucleus in the brainstem form part of the glossopharyngeal nerve and travel with its tympanic branch through the middle ear. These preganglionic fibers join the lesser petrosal nerve, exit from the skull through foramen ovale, and synapse within the otic ganglion in the infratemporal fossa [6, 26]. Although parasympathetic postganglionics are found traveling with all branches of V3 (but not always; see Senger [26]), a histological study (conducted with guinea pigs) indicated that most of these (50%–60%) are found in the ATN, with the majority presumably distributing to the parotid gland [25]. Parasympathetic fibers in other V3 branches may innervate other small salivary glands in buccal and oral mucosa [25]. ATN also has been shown to carry sympathetic fibers; these originate from a plexus around the MMA, communicate to the otic ganglion, pass through the ganglion, and distribute to V3 branches along with parasympathetics [26]. A recent cadaveric study found that anywhere from 3%–8% of the fibers within ATN (proximal to the parotid branches) are stained with tyrosine hydroxylase, a marker for sympathetic nerves [34]. The authors did not stain the parotid branches themselves, but postulated that the branches may donate some sympathetic fibers to the facial nerve deep within the gland.

3.2.4. Superficial Distribution and Anastomoses

The sensory innervation of the external auditory apparatus (including the pinna and EAM) is complex, with confirmed and potential contributions from the trigeminal, facial, glossopharyngeal, vagus, and cervical nerves [35, 36]. According to Baumel et al. [14], ATN contributes to this innervation via three terminal branches, all smaller than the terminal superficial temporal branch: an anterior auricular and two more deeply located branches to the EAM, including superior and inferior branches. These branches are described as leaving the main trunk of ATN as part of the terminal branch spray found just posterior to the mandibular condyle. However, Iwanaga et al. [4] describe a variant of the ATN where the anterior auricular branch arises more superiorly from the posterior of two main superficial temporal trunks. According to Peuker and Filler [35], the anterior auricular branch primarily innervates the anterior‐superior aspect of the pinna, including the tragus, spine, and crus of the helix. There is a relative lack of recent studies that systematically detail innervation patterns of the EAM or the tympanic membrane by its branches from ATN. Sources describe these (superior and inferior) nerve branches to the EAM as ramifying in its cutaneous lining and innervating the anterior and superior aspect, whereas the posterior/inferior aspect is innervated primarily by the auricular branch of the vagus nerve with possible contribution from the facial nerve [14, 36, 37]. Filaments of the ATN distribution also innervate the skin covering the lateral surface of the tympanic membrane [14, 38]. Most texts describe a complex innervation of this lateral surface, with contributions from CN V, VI, IX, and X. However, Saunders and Weider [39], in a study with patients with cranial nerve pathologies/nerve sections, demonstrated that sensation of the tympanic membrane was almost entirely dependent on an intact trigeminal nerve and not any of the other nerves thought to play a role in its sensory innervation.

Various studies have examined the ATN's distal course in the posterior temporal region, including the relationship between the nerve and superficial temporal vessels (Figure 3B). In this region, ATN has been historically depicted as a single main trunk, dividing into superficial temporal branches, with Baumel et al. [14] describing a variable 5–9 of these. Andersen et al. [40] later reported that ATN can have a single main branch (seen in 20% of specimens), divide into smaller branches (55%), or have a diffuse branching pattern (20%) (n = 20). More recently, Iwanaga et al. [4] noted that 79% of their specimens (n = 14) had one main trunk, while the remaining 21% had two main trunks, with terminal branches ranging from 2–7 in their specimens. Other findings included communications between terminal branches forming a loop (“ansa”), with one double ansa described in one specimen. In this study, the authors noted that ATN was always identified near the superficial temporal artery (STA), where ATN ascended superficial and posterior to the STA in cases with one main trunk. The relationship of the ATN to the STA was examined in a similar fashion in 138 specimens across five studies [40, 41, 42, 43, 44]. This relationship was present in 73% of examined specimens, with ATN crossing the STA superficially in 74% and crossing deeply in 18%. Additionally, a rare helical intertwining relationship was seen in 3.6% of specimens in two of the studies [43, 44]. Other variations of ATN have been described in case studies, such as an unusual case of a fenestrated superficial temporal vein by ATN as well as multiple loops of ATN encircling the STA, similar to the aforementioned helical intertwining [45, 46].

A variety of ATN anastomoses with other nerves have been described in the literature, some more common than others. This includes communicating auriculotemporal nerves (CATNs) that anastomose with branches of the facial nerve on the lateral head. CATNs are described to join the upper division of the facial nerve posteriorly, from ATN after it emerges deep in the upper parotid gland posteromedially to the TMJ on its route to supply the skin in the temporal region [14, 47]. Facial nerve branches innervate the upper facial expression muscles, and it has been suggested that CATNs that join facial branches may convey proprioceptive impulses from muscles to the trigeminal nuclei [47]. Kwak et al. [48] noted the presence of CATNs in 93.3% of their specimens (n = 30) while Namking et al. [47] and Tansatit et al. [49] both observed CATNs in 100% of cases (ns = 55 and 20, respectively). Baumel et al. [14] first described a range of 1–3 CATNs, with the majority of specimens having two, ~33% having three, and rare cases of single connections. Other studies have since noted a range of 1–4 CATNs, with variable findings in the predominant number of branches, most commonly 2 or 3 [47, 48, 49]. Anastomosis with the facial nerve has also been studied more distally in ATN's course, with one study identifying communications between the superficial temporal branches of ATN with the temporal branch of the facial nerve in 15% of dissections (n = 20) [40]. Namking et al. [47] found in the superficial region that 47% (n = 55) of CATNs crossed the STA anteriorly, 18% crossed posteriorly, and 35% crossed both anteriorly and posteriorly [48].

Other communications involving ATN include less commonly reported connections with the greater and lesser occipital nerves, as well as the greater auricular nerve. Andersen et al. [40] found connections with the greater occipital nerve in 20% and with the lesser occipital nerve in 10% of specimens (n = 20), demonstrating anastomosis of the cervical plexus and trigeminal nerve. Other studies similarly described communication between ATN and the great occipital nerve in 10% (2/20) of cases as well as the lesser occipital nerve in 10.5% (2/19) [50, 51]. One study found an interconnection between ATN and the greater auricular nerve in 30.4% of dissections (n = 46) within the intraparotid region, where the authors hypothesized that this connection would enable the greater auricular nerve to be considered a postganglionic nerve similarly to ATN [52].

4. Discussion

4.1. Clinical Implications and Manifestations of ATN

4.1.1. Within the Infratemporal Fossa and TMJ Pain Disorders

Understanding the precise location of ATN, its anatomical relationships with nearby structures, and its potential variation between and within individuals is of particular importance during surgery. Surgical examples in the infratemporal region include space‐occupying lesions such as ATN perineural tumors, MMA aneurysm, and intervention for TMJ pathologies [15, 19]. ATN perineural tumor spread may extend in the cranial direction through the foramen ovale, where V₃ passes into the cranial cavity [21]. This tumor progression can lead to trigeminal palsy/neuralgia, impinge on structures in the infratemporal fossa, and compromise vascular structure. These intricate relationships in this region, particularly the relationship between ATN and MMA, may lead to further complications. Iatrogenic injury or damage to ATN may result in clinical symptoms of migraine, neuralgia, and paresthesias in the overlying temporal region, external auditory canal, and TMJ [5, 16, 18, 20]. Additionally, damage may compromise glossopharyngeal nerve (CN IX) secretomotor fibers of the parotid gland [19, 27, 31, 44].

Based on previous studies, the two main determining factors for the presence of ATN entrapment and irritation within the infratemporal fossa include anatomical variation as well as dysfunction within the masticatory system, which can lead to regional morphological and pathological changes [8]. ATN entrapment may be attributed to compression by normal anatomical structures or pathological alterations, such as hypertrophic masticatory muscles, particularly the lateral pterygoid, or dislocations of the TMJ. Other pathology includes myositis or fibrositis, where ischemia and inflammation of the lateral pterygoid may impact ATN [27, 31]. Minimal displacement of disc and capsular tissues is required to irritate or possibly entrap ATN, due to the relationship of the nerve with the condyle near the articulating surface [27, 32]. Compression at the condyle could present with pain during jaw closing, with relief on decreased loading of the joint [27]. Another potential disruption of ATN would be during TMJ surgery or following arthroscopy, possibly as the result of compression from hematoma formation.

Pain syndromes of the face and masticatory system are a serious diagnostic and therapeutic concern. Symptoms of ATN entrapment include very intense pain, paresthesias or a “feeling of obstruction” of the external acoustic meatus and auricle, tinnitus, and pain that radiates to the mandible head and temporal region [8]. Symptoms may also present as facial tingling radiating to the upper jaw and occipital region. TMJ disorders are increasingly prevalent, with 10%–25% of the population presenting to clinics because of TMJ disorders, and at least one sign reported in 40%–75% of the population [9, 29, 53]. Knowledge of the pathophysiology of TMJ pain and innervation topography is essential for the success of TMJ and infratemporal interventions, such as nerve blockages and injections, minimally invasive procedures, arthroscopies, and surgeries [29]. TMJ pain is notably of recurrent nature, where follow‐up studies demonstrate a recurrence of symptoms in patients typically 3 to 18 months following procedural intervention [28].

4.1.2. Parotid Gland Involvement (Frey Syndrome, First Bite Syndrome)

ATN's intimate connection with the parotid gland and with other nerves in the region means that the nerve can play an important role in the spread of malignancies. ATN involvement in parotid malignancy is relatively uncommon and poorly described in the literature. However, a few studies have attempted to investigate this phenomenon, particularly as it relates to clinical presentation and findings. A 2019 study by Thompson et al. [54] conducted a retrospective analysis of 547 patients with a variety of parotid bed malignancies, some of which were primary tumors while others were cutaneous metastases to the gland. Twenty‐three of these tumors had radiological findings suggestive of ATN involvement, and 74% of these patients demonstrated facial weakness, and 83% had periauricular pain. Recognition of these symptoms in patients with parotid malignancy, along with an understanding of the different radiological patterns, could allow for earlier detection of ATN involvement and a more effective therapy. Another paper by Swendseid et al. [55] assessed rates of ATN participation with respect to recurrence of parotid bed tumors. ATN involvement appears underappreciated despite the fact that 44% of local recurrences demonstrate some degree of involvement. Recurrence along the ATN was associated with parameters such as intraoperative facial nerve sacrifice, failure to complete adjuvant therapy, and facial nerve weakness on physical exam [55]. Again, a recognition and understanding of ATN's potential role in parotid tumors could be vitally important in order to improve outcomes.

The autonomics of ATN are clinically relevant because of their role in Frey's Syndrome, an under‐reported condition characterized by pre‐auricular sweating, warmth, and redness following mastication or another salivary stimulus [56]. The consensus is that Frey's Syndrome is caused by aberrant regeneration of parasympathetic fibers along sympathetic pathways following an injury to the ATN and the sympathetic subcutaneous rootlets, most often during surgery [57]. The exact mechanism by which this regeneration occurs is disputed, but a recent paper by Hignett et al. [57] identified a neurotrophic factor called neurturin as a possible player in the pathogenesis of the disease. This factor is released from the parotid gland and surrounding sweat glands to facilitate autonomic innervation during early development, and the authors suggest that it may be again upregulated following injury to the ATN. This idea might explain the very high rate of Frey's Syndrome following parotidectomy, which by some reports is 96% [57]. It also may work to dispel other theories about the pathogenesis, particularly those that suggest that Frey's Syndrome is not mediated by regrowth of parasympathetics.

Another complication, associated with deep parotid lobe resection, is First Bite Syndrome, first described in 1998 as severe cramping or spasm pain in the parotid region associated with the first bite of each meal that improves with time [58]. This syndrome is thought to arise following damage to postganglionic sympathetic fibers, where subsequent parasympathetic hyperactivity occurs, leading to exaggerated myoepithelial cell contraction and associated pain [58, 59]. While ATN has been noted to be a major contributor to these symptoms, ATN resection was deemed to be an ineffective treatment option.

4.1.3. Distal Course Points of Compression and Communicative Anastomosis

The aforementioned neurovascular relationships are a suspected factor in migraine headaches and auriculotemporal neuralgia, caused by irritation and compression at various points along ATN's anatomical course, particularly in those with close positional relationships such as the helical intertwining of the STA. For example, in some patients, bulging veins in the temporal region, commonly associated with age, genetics, and exercise, can occur, and expansion can lead to a higher likelihood of ATN compression in variants closely associated with the STV [42]. Also, many migraine headaches are described as “pulsatile” in nature, which could be attributed to pulsatile irritation of ATN by the adjacent STA in this region [44]. In addition to migraines, chronic entrapment of ATN by vascular supply could result in chronic neuralgia, presenting with regional pain or referred pain to the external ear or tooth [33, 45]. ATN block is a treatment option for headache, and less common variants such as duplicated ATN may lead to treatment failure [17]. An understanding of variable potential relationships between ATN and superficial temporal vessels is warranted to both predict and treat factors associated with migraine headaches and neuralgia as well as conduct surgical procedures in the region, where a failure to recognize the anatomy of variants could result in iatrogenic injury [42, 45].

Anatomical evidence of anastomosis between ATN and various nerve branches may help explain clinical scenarios of unexpectedly extended anesthetic regions. Further, an improved understanding of these variable connections may help improve the management of neuralgias as well as aid in reconstructive and nerve transfer procedures [51]. Familiarity with these common variations in anatomy, such as connections with the facial nerve, may prove useful for facial nerve surgeries and removal of tumors in the parotid region [48]. Further studies are necessary to help provide better insight regarding the prevalence of these variations and communicative anastomosis.

4.1.4. Imaging Considerations and Perineural Tumor Invasion

Imaging of ATN plays a crucial role in evaluating perineural tumor spread, particularly in head and neck malignancies such as parotid gland tumors and cutaneous malignancies of the ear. While adenoid cystic carcinoma of the salivary gland is notorious for its propensity for early perineural invasion, a significant proportion of cases with perineural spread originate from primary squamous cell carcinoma of cutaneous origin [60]. Among the head and neck nerves, ATN is especially important due to its connections with the facial nerve, trigeminal nerve, and various anatomical variants, which facilitate the dissemination of tumors to distant areas.

On radiographic imaging, ATN is not usually visible, but pathological changes associated with perineural invasion may be detected. Computed tomography (CT) is effective for identifying bony alterations linked to perineural spread, but magnetic resonance imaging (MRI) is the preferred modality for assessing perineural invasion [61]. High‐resolution, fat‐suppressed axial and coronal T1‐weighted MRI with and without contrast is recommended for optimal detection [62, 63, 64]. Key imaging features indicative of perineural tumor spread include nerve thickening and abnormal enhancement, obliteration of perineural fat planes, widening and destruction of neural foramina [61, 62, 63]. Other notable findings include muscle denervation changes and potential skip lesions along the nerve's course [60]. However, radiological imaging may sometimes fail to detect these changes, underscoring the importance of correlating imaging results with clinical and pathological data.

The presence of perineural invasion is associated with poor prognosis, marked by high recurrence rates and reduced survival. This finding has significant implications for treatment planning, necessitating wider surgical resections or expanded radiation fields [62, 65]. Enhanced understanding of ATN anatomy and the patterns of perineural spread can greatly aid in devising effective treatment strategies.

4.2. Limitations and Strengths of This Review

This review has several limitations. It was limited to a primary focus on English‐language publications and those with accessible English abstracts, potentially introducing language bias. While efforts were made to minimize bias through assessments by two reviewers, subjective interpretation of anatomical descriptions remains a possible limitation. However, strengths include a comprehensive search strategy, rigorous methodology adhering to PRISMA guidelines, detailed anatomical synthesis, and inclusion of cadaveric validation.

4.3. Recommendations for Clinical Practice and Future Research

Clinicians should consider anatomical variations of ATN during surgical planning and diagnosis of pain syndromes. Further research should include prospective anatomical studies across diverse populations to clarify the clinical significance of specific ATN variations and to investigate the relationship between anatomical variations and clinical manifestations like Frey Syndrome or neuralgia.

5. Conclusions

In conclusion, ATN plays a crucial role in head and neck intervention, with significant clinical and surgical implications. This review highlights the variations of ATN through examination of its course within the infratemporal fossa, temporomandibular joint, parotid gland, and superficial temporal region. Understanding the anatomy in these regions helps shed light on potential entrapment syndromes, surgical considerations, and anatomical relationships with surrounding structures. Notably, our comprehensive review reveals considerable diversity in origins, branching patterns, and relationships with adjacent vessels, challenging traditional depictions found in anatomical atlases. The implications of ATN variations extend to surgical procedures, such as TMJ surgery and parotidectomy, where iatrogenic damage may lead to complications like temporomandibular disorder and Frey Syndrome. Furthermore, understanding the innervation patterns of ATN in these regions has significant relevance for addressing pain disorders and performing interventions. The distal course of ATN and its potential points of compression were explored, offering insights into the etiology of conditions such as migraines and neuralgia. The review emphasizes the importance of recognizing anatomical variations in ATN to enhance clinical outcomes, guide surgical interventions, and improve the management of associated neuralgias. Further studies are needed to explore the prevalence of these anatomical variations and their clinical implications, ultimately contributing to advancements in surgical techniques and patient care.

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

Data S1: PubMed Search Strategy.

Data S2: PRISMA 2020 Checklist.

Kadrie A., Toomey P., Callaway J., Gillespie M. B., and Boughter J. D. Jr., “The Auriculotemporal Nerve: A Comprehensive Review of Its Anatomical Variation and Clinical Manifestations,” Laryngoscope Investigative Otolaryngology 10, no. 4 (2025): e70238, 10.1002/lio2.70238.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.