Posterior Auricular Nerve Entrapment

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Great Auricular/Posterior Auricular Nerve Entrapment 2016 Springer International Publishing Switzerland Family Name Benton Particle Given Name

Leonard

Suffix Division Organization/University

Author

City

Ft. Myers

State

FL

Country

USA

Email Family Name

[email protected] Trescot

Particle Given Name

Andrea M.

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Abstract

Keywords (separated by “ - “)

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Pain and Headache Center

City

Wasilla

State

AK

Country

USA

Email [email protected] The great auricular nerve (GAN) and the posterior auricular nerve (PAN) provide sensation to the mastoid and ear regions. These nerves have a variable origin, and there is much confusion regarding their anatomy. Because of their location, the GAN and PAN are very easily injured during surgery and trauma, and since their anatomy is not well understood, they are often missed as an etiology of parietal pain and headaches. Great auricular nerve - Greater auricular nerve - Posterior auricular nerve Cryptogenic earache - Mastoid pain - Parietal pain - Parietal headache

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AUTHOR QUERIES

Q1 Please provide department and organisation name for “Leonard Benton” and also provide department name for “Andrea M. Trescot”.

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Great Auricular/Posterior Auricular Nerve Entrapment

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Leonard Benton and Andrea M. Trescot

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Introduction

Clinical Presentation (Table 16.1)

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The posterior auricular nerve (PAN) is the terminal branch of the great auricular nerve (GAN) (also known as the greater auricular nerve, which is technically incorrect, since there is no “lesser auricular nerve”) and provides innervation along the lower half of the ear and earlobe, the angle of the mandible, and the posterior auricular skin, as well as the side of the neck [1]. There is some confusion in names, since the posterior auricular nerve is sometimes described as arising from the facial nerve at the level of the stylomastoid foramen, running cephalad in front of the mastoid, and joining with the posterior branch of the GAN. It has several areas for entrapment and can also be a source of neuritis as a side effect from various types of surgeries including cranial, facial, and those requiring supporting of the neck and head along the base of the skull. It has been recognized that trauma to the PAN or GAN from various surgeries can cause chronic pain, dysesthesia, and/or anesthesia to the affected region. The surgical literature illuminates surgical attempts at recognizing the potential problem and tailoring positioning and surgical practices to reduce the risk. Each of these problems can cause a similar pattern of pain and dysesthesias.

Depending on the etiology, several clinical presentations of PAN entrapment can occur. Trescot described fullness in the ear, decreased hearing, tinnitus, and vertigo as possible symptoms (Fig. 16.1), described as “cryptogenic ear pain,” mimicking an ear infection [10]. Parietal pain, dysesthesia, and posterior occipital and parietal headaches have also been described as a result of trauma at the mastoid process, entrapment of the posterior auricular nerve by the ­ ­sternocleidomastoid muscle (SCM), or scar formation from mastoid infections or trauma [10]. This can occur during flexion/extension injuries, especially if the head was turned at impact [10], or with surgical positioning [6]. However, after resection during surgery, hypoesthesia and anesthesia are the symptoms most often mentioned [1–4, 6, 8, 9, 12–14]. Physical findings can include allodynia, hyperpathia, or hypoesthesia. Given that the PAN is sensory only, no muscle weakness should be noted, and electrodiagnostic studies would be expected to be normal. Interestingly, Brown et al. [1] described that a third of their patients developed gustatory sweating (which is usually associated with auriculotemporal nerve pathology – see Chap. 15) after parotidectomy surgery, with or without PAN-­ sparing techniques. Several authors have described the hyperesthesia noted with PAN resection during surgery, seen

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Table 16.1  Occupation/exercise/trauma history relevant to posterior/ great auricular nerve entrapment

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Electronic supplementary material The online version of this chapter (doi:10.1007/978-3-319-27482-9_16) contains supplementary material, which is available to authorized users. [AU1]

L. Benton, MD (*) Ft. Myers, FL, USA e-mail: [email protected] A.M. Trescot, MD Pain and Headache Center, Wasilla, AK, USA e-mail: [email protected]

Infection Trauma Surgery Surgical positioning Neurosurgical trauma Flexion/extension injuries Trigeminal neuralgia

Mastoid or parotid injections Blow to mastoid region Parotidectomy [1–4]; face-lift [5] Beach-chair position for shoulder surgery [6, 7] Craniotomy [8]; endolymphatic shunt [9] [10] Tic douloureux [11]

© Springer International Publishing Switzerland 2016 A.M. Trescot (ed.), Peripheral Nerve Entrapments: Clinical Diagnosis and Management, DOI 10.1007/978-3-319-27482-9_16

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L. Benton and A.M. Trescot Table 16.2  Anatomy of the posterior auricular nerve/great auricular nerve Origin General route

Sensory distribution

Motor innervation Anatomic variability Other relevant structures Fig. 16.1  Pattern of pain from posterior auricular neuralgia/great auricular neuralgia (Image courtesy of Andrea Trescot, MD) 52 53 54 55

in up to one-third of postoperative patients [1]. In those patients who were hypoesthetic after surgery, sensory loss at the angle of the mandible seems to be much better tolerated than sensory loss at the ear [1].

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Anatomy (Table 16.2)

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The posterior auricular region of the scalp has multiple contributing sensory nerves. The greatest contribution is from the GAN and PAN, which are the focus of this chapter. There is debate as to the use of landmarks to determine points of possible entrapment, given the variability of the various nerves that comprise all or part of the region’s innervation [13, 15–18]. The GAN is the largest ascending branch of the ­superficial cervical plexus (Figs. 16.2 and 16.3), providing sensation to the skin over the parotid gland, external ear, angle of the jaw, and posterior auricular region. It arises from ventral branches of spinal nerves C1, C2, C3, and C4 (but primarily C3), branches of which also make up the lesser occipital (Chap. 18) and suprascapular (Chap. 28) nerves and emerge from behind the posterior border of the sternocleidomastoid muscle (SCM) at Erb’s point (Figs. 16.2 and 16.3), puncturing the deep fascia just lateral to the lesser occipital nerve. It climbs the SCM (Fig. 16.4) either in the anterior or posterior surface of the muscle [15] and platysma to the parotid gland and supplies innervation of both sides of the ear (other than the tragus and the concha), the skin over the mastoid, and most of the skin over the parotid. A study by Tubbs et al. [19] postulated that the mastoid branch of the GAN could be injured by posterior cranial

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C1, C2, C3, and C4 form the superficial cervical plexus Cervical foramen at C2 and C3 to superficial cervical plexus to posterior border of the SCM Anterior branch to parotid region Posterior branch to mastoid region Anterior branch – the skin over parotid Posterior branch – the skin over mastoid, concha, ear lobe None Connections with facial, lesser occipital, and suprascapular nerves PAN may arise from the facial nerve at the stylomastoid foramen

fossa surgeries and is also potentially a cause of “trigeminal neuralgia.” Lefkowitz et al. [5] dissected 16 heads and identified a consistent relationship between the GAN and the SCM, finding the GAN at its most superficial location one-­ third the distance from either the mastoid process or the external auditory canal to the clavicle. The GAN can also be found by ultrasound approximately 1 cm superior and lateral to the external jugular vein [20]. At the inferior pole of the parotid, the GAN branches into an anterior and posterior branch. The anterior branch pierces the parotid and supplies the skin over the parotid gland and the angle of the jaw [21]. This branch is almost always ­sacrificed with a parotidectomy, and it is at risk during c­ ertain face-lift procedures [21]. The posterior branch, also known as the posterior auricular nerve (PAN), runs along the posterior border of the SCM, positioned superficially and immediately posterior to the mastoid. The posterior branch supplies the skin over the mastoid process and the angle of the jaw. It also supplies the lateral surface of the concha and ear lobe (Fig. 16.5) [1, 22]. Other innervations to this region include communication with the lesser occipital nerve (posteriorly) (Fig.  16.6) and the transverse cutaneous nerve of the neck (anteriorly), both of which also arise from C2 and C3 [1], as well as the auricular branch of the vagus nerve (nerve of Arnold) and the posterior auricular branch of the facial nerve [23]. Sand and Becser [16] dissected 17 GANs in 10 cadavers, and they were able to identify the PAN in 13 of the 17 dissections. The PAN has alternatively been described as arising from the facial nerve close to the stylomastoid foramen and running cephalad to the mastoid. Smith et al. [17] dissected 11 hemi-faces; they found that the PAN arose from the facial nerve trunk 1.6–11.1 mm from the stylomastoid foramen, either as a single branch (45.4 %) or from a common trunk that divided into two (36.4 %) or three branches (18.2 %),

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16  Great Auricular/Posterior Auricular Nerve Entrapment Fig. 16.2  Posterior auricular and great auricular nerve anatomy, ­lateral view (Image by Springer) Maxillary nerve Mandibular nerve Supraorbital nerve Supratrochlear nerve

Infraorbital nerve

Auriculotemporal nerve Posterior auricular nerve

Inferior alveolar nerve Mental nerve

Greater auricular nerve

Erb’s point

Superficial cervical plexus

Greater occipital nerve Occipital artery 3rd occipital nerve Lesser occipital nerve Greater/posterior auricular nerve Erb’s point Trapezius muscle

Fig. 16.3  Posterior auricular and great auricular nerve anatomy, posterior view (Image by Springer)

with the other branches passing into the parotid gland. The PAN continued deep (63 %), or lateral to the mastoid process (9.1 %), or through the tissue of the parotid gland (27.3 %). Becser et al. [15] dissected ten cadavers and found that the GAN can ascend either on the anterior or posterior surface of the SCM. Tubbs et al. [19] found that the GAN can have a mastoid branch that, on average, lies 9 cm lateral to the inion and 1 cm superior to the mastoid tip. Smith et al. [17] evaluated the PAN (they used the terminology PAN for the nerve from the facial nerve trunk) in 11 hemi-faces; the PAN arose as a single branch in 45.4 %, from a common trunk that divided into two branches in 36.4 % or three branches in 18.2 %, with the other branches passing into the parotid gland. Convinced that they have identified a “safe, reliable, and surgically relevant” technique of avoiding GAN injury, Murphy et al. [24] identified the external jugular vein (EJV), the platysma, and the GAN and found the distance between the EJV and GAN was consistently 1.17 cm. Liaqat and colleagues [25] reviewed 40 patients undergoing third molar extractions; 26 of the 40 patients required GAN injections in addition to the mandibular (inferior alveolar) nerve for analgesia at the angle of the jaw for the extraction.

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L. Benton and A.M. Trescot Fig. 16.4  MRI anatomy of the upper cervical region. DI digastric muscle, IO inferior oblique muscle, LC longus colli muscle, LE levator scapulae muscle, MAS masseter muscle, SC semispinalis cervicis muscle, SCM sternocleidomastoid muscle, SpC splenius capitis muscle, TRAP trapezius muscle, GA great auricular nerve, GON greater occipital nerve, GN glossopharyngeal nerve, LON lesser occipital nerve, TON third occipital nerve. Note the bifid spinous process (Image courtesy of Andrea Trescot, MD)

Fig 16.5  Sensory areas of the trigeminal and cervical nerve branches: A supraorbital nerve, B infraorbital nerve, C mental nerve, D buccal nerve, E lacrimal nerve, F auriculotemporal nerve, G superficial cervical plexus, H posterior auricular nerve/great auricular nerve, I occipital nerve (Image courtesy of Terri Dallas-Prunskis, MD)

Fig. 16.6  Anatomy of the lateral head, modified from an image from Bodies, The Exhibition, with permission. Note the connection between the posterior auricular nerve and the lesser occipital nerve, as well as the connection of the great and lesser occipital nerves (Image courtesy of Andrea Trescot, MD)

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Entrapment

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Entrapment of the PAN can occur along the posterior border of the SCM (Figs. 16.2 and 16.3), in the posterior and inferior extrinsic ligaments, extrinsic auricular musculature, or by scar tissue. More proximal entrapment can occur along the route of the GAN, including the C2–C3 anterior nerve roots, the fascia, the SCM, the superficial cervical plexus, or the platysma, and proximal entrapment would be part of the differential diagnosis if a diagnostic nerve block of the PAN is not effective at relieving symptoms. Ng and Page [6], as well as Park and Kim [7], noted GAN entrapment during shoulder surgery in the beach-chair position, which they attributed to the hard edge of the headrest used, though they also noted that traction, joint distention, and direct compression at other sites might be involved. Park and Kim suggested that the headrest and the ear should be carefully padded to avoid injury [7].

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Physical Exam The physical exam should begin with visualization to look for masses or surgical scars. A thorough neurological exam and full cervical spine exam including extension, flexion, rotation, distraction, etc., should be performed to rule out cervical disk or cervical spinal nerve etiology. Symptoms of entrapment often can be reproduced by application of digital pressure along the distribution of the posterior auricular nerve, as depicted in Fig. 16.7 (Video 16.1). The head should be supported at the forehead by the non-examining hand or by having the patient rest their forehead on their hands. The palm of the examining hand is placed across the occiput such that the fingers are along the contralateral mastoid and occiput; the thumb is then placed along the mastoid of the affected side. With the thumb, feel for the vertical groove between the mastoid process and the

Fig. 16.7  Posterior auricular/great auricular nerve examination (Image courtesy of Andrea Trescot, MD)

occiput. Application of pressure with the thumb should provoke the patient’s symptoms, indicating the general location of the entrapment.

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Differential Diagnosis (Table 16.3)

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The differential diagnosis should be determined from the history and physical exam. If a diagnostic nerve block in the region of the digital palpation of the exam did not provide relief, then one can consider examining and injecting more distally along the GAN. Other possibilities include entrapment along the distribution of the other posterior auricular innervations, including the lesser occipital nerve, the auricular branch of the facial nerve, and auricular branch of the vagus (nerve of Arnold) [26, 27]. For example, electrodiagnostic studies could suggest facial nerve etiology, given that the facial nerve innervates the stylohyoid and posterior digastric muscles before it enters the substance of the parotid gland [27]. Differential diagnosis also includes neuropraxia resulting from previous surgery [1, 3, 6, 8, 12, 28]. However, surgical resection usually causes hypoesthesia more often than hyperesthesia, which is usually not as distressing to a patient as pain [1]. Neuroma formation after surgery can cause painful symptoms and allodynia. High cervical nerve root compression (C1–C4) has been described as causing similar symptoms of chronic otalgia and headaches (Fig. 16.8) [29]. Other symptoms can include pain, hyporeflexia, hypoesthesia, and muscle weakness in the distribution of the nerves, which may be seen on exam. Otalgia from cranial nerves (e.g., the auricular branch of the vagus or nerve of Arnold) [26], glossopharyngeal neuralgia (see Chap. 27), or inner ear pathology should also be ruled out [30]. Table 16.4 lists some of the diagnostic tests for the GAN/ PAN. Electrodiagnostic and MRI may be beneficial in ­assessing the cause of the symptoms. Sand and Becser [16] evaluated 77 healthy volunteers and identified that the best site for diagnostic neurostimulation was on the SCM 6–7 cm from the external auditory meatus, noting that the amplitude of the sensory nerve action potential (SNAP) decreased ­significantly with age.

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Table 16.3  Differential diagnosis of ear and parietal pain

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Inner ear pathology C1 to C4 nerve root pathology Lesser occipital nerve entrapment Facial nerve entrapment Shingles/postherpetic neuralgia

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Potential distinguishing features ENT evaluation MRI, EMG evidence of radiculopathy Physical exam (see Chap. 18)

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EMG History of lesions

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L. Benton and A.M. Trescot

Fig. 16.8  Pattern of posterior cervical and occipital pain. A atlantoaxial joint, B atlantooccipital joint, C greater occipital nerve (GON), D posterior auricular nerve (PAN), E lesser occipital nerve (LON), F third occipital nerve (TON) (Image courtesy of Andrea Trescot, MD) t4.1

Table 16.4  Diagnostic tests for posterior auricular nerve pathology

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Potential distinguishing features Tenderness over the mastoid groove Diagnostic for the nerve The GAN can be identified on the SCM [33] Not usually visualized, but Ginsberg et al. [46] described visualization with both MRI and CT Not visualized Not visualized GAN conduction studies in normal volunteers showed the best stimulation at the posterior border of the SCM 6–7 cm from the external auditory meatus [16]

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Physical exam Injection Ultrasound

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MRI

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Arteriography X-rays Electrodiagnostic studies

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I dentification and Treatment of Contributing Factors Posterior auricular neuralgia is often seen weeks to years after blunt injury to the mastoid area. Trescot describes this neuralgia as being seen commonly in physically abused women; the left side is most often involved due to the ­preponderance of right-handed spouse abusers [10]. The clinical presentation consists of pain in the ear, along with a feeling of “fullness and tenderness.” This syndrome is often ­misdiagnosed as a chronic ear infection [31, 32]. Spasm of the SCM can entrap the GAN and PAN, so flexion/extension injuries, especially if the head was turned at impact, can be associated with GAN/ PAN entrapment. Trigger point ­ treatment of the SCM,

Fig. 16.9  Landmark-guided posterior auricular/great auricular nerve injection (Image courtesy of Andrea Trescot, MD)

i­ncluding myofascial release (see Chap. 5), trigger point injections, and botulinum toxin, can potentially relieve the GAN/PAN entrapment. Avoidance of the GAN/PAN at surgery can prevent subsequent pain and hypoesthesia.

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Injection Technique

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Landmark-Guided Technique

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After location of the entrapment via physical examination, the first course of action is to give a diagnostic or therapeutic injection into the region identified. Aseptic technique should be used, including the use of a povodine, alcohol, or chlorhexidine cleaning solution, and sterile gloves. As depicted in Fig. 16.9 and Video 16.2, straddle the groove of the intended injection site with the index and middle fingers of the gloved, non-injecting hand. Using a 27-g needle directed caudal to cephalad, inject a very small volume (