Continuing Education Activity

Patients frequently present to the emergency department with various external ear complaints. These complaints may include embedded foreign bodies, traumatic injuries, such as lacerations and avulsions, or auricular collections that require drainage, such as hematomas and abscesses. Oral and parenteral medications rarely provide adequate pain relief during the procedures required to remedy these clinical scenarios. Procedural sedation has a sizeable risk burden, particularly for pediatric patients. Injections directly into the external ear are painful and have a high risk of provider needlestick.

Alternatively, a peripheral nerve block is typically a well-tolerated method to achieve analgesia for a procedure on the external ear. The innervation of the external ear is complex and involves multiple nerves originating from cranial nerves and the cervical plexus. A comprehensive understanding of the innervation of each section of the external ear facilitates selecting the appropriate nerve block method and is critical to the success of this procedure. This activity for healthcare professionals reviews the indications and contraindications of an external ear peripheral nerve block, the procedural steps to perform with and without ultrasonographic guidance, and the common complications following the procedure. The activity also highlights the role of the interprofessional team in improving outcomes for patients undergoing this peripheral nerve block.

Objectives:

• Identify patients who may benefit from a peripheral nerve block of the external ear based on their clinical history.

• Differentiate the anatomical course of each sensory nerve of the external ear.

• Apply best practices when performing peripheral nerve blocks of the external ear.

• Collaborate with interprofessional team members to provide efficient, comprehensive, and coordinated care when managing patients with external ear conditions who may benefit from an ear nerve block for analgesia.

Introduction

Patients frequently present to the emergency department with various external ear complaints, including traumatic injuries, auricular collections that require drainage, or embedded foreign bodies. Oral and parenteral medications typically do not provide adequate pain relief for the localized procedures required to treat these complaints, and procedural sedation has a sizeable risk burden, particularly in pediatric patients. Injections directly into the external ear are painful and have a high risk of provider needlestick.[1][2]

However, if a larger area of analgesia for the ear is needed, a peripheral nerve block is typically a well-tolerated anesthetic method. Multiple nerves innervate the external ear; these nerves originate from cranial nerves and the cervical plexus. Historically, the ring block was the most common method of peripheral nerve block used to anesthetize the external ear. With the increased availability and utility of ultrasound in the emergency department, the literature demonstrates that ultrasound can help localize the great auricular nerve and the lesser occipital nerve for anesthetic blockade.[3][4] Additional nerve block of the auriculotemporal nerve is as, if not more effective, more direct and provides equivalent analgesia using less anesthetic agent than the traditional ring block.

Anatomy and Physiology

The anatomy of the external ear includes the external auditory canal, auricle (or pinna, consisting of the helix, antihelix, and lobule), the antitragus, the tragus, and the concha. The sensory innervation of the external ear originates from the great auricular and lesser occipital nerves, both branches of the second (C2) and third (C3) branches of the cervical plexus, the auriculotemporal nerve from the mandibular branch of the trigeminal nerve, and the Alderman or Arnold nerve, the auricular branch of the vagus nerve. The great auricular nerve courses around the posterior aspect of the sternocleidomastoid muscle, becoming most superficial approximately 6 to 7 cm caudad to the external auditory meatus. The great auricular nerve arborizes into an anterior and posterior branch toward the front and underside of the ear, respectively. The lesser occipital nerve courses around the posterior edge of the sternocleidomastoid approximately 4 to 5 cm, caudad to the external auditory meatus, and deviates toward the backside of the ear. The auriculotemporal nerve originates from the 3rd branch of the trigeminal nerve, the mandibular nerve. The nerve ascends in front of the ear anterior to the tragus. The auricular branch of the vagus nerve exits the temporal bone at the tympanomastoid suture, deep to the concha.

Sensory innervation to the auricle is regional.[5] The helix, concha, and lobule receive their innervation from the great auricular nerve. The antihelix, antitragus, tragus, and concha are innervated mainly by the great auricular nerve and, to a lesser degree, by the auricular branch of the vagus nerve. The auriculotemporal nerve innervates the superomedial helix (the crus and spine). Three nerves innervate the back side of the auricle: the great auricular nerve, the lesser occipital nerve, and the auricular branch of the vagus nerve. Variable sensory distributions and patterns between and among these nerves have been described. These regional distributions overlap to a greater degree in the more medial aspects of the external auditory canal, and achieving necessary anesthesia in this area is challenging with directed nerve blocks alone. If anesthesia in the medial external auditory canal is required, topical application of concentrated lidocaine or a formal 4-quadrant subcutaneous injection may be necessary.

Indications

In the emergency department, a nerve block of the external ear is most suitable for several clinical situations. These situations include but are not limited to:

• Analgesia to allow for a more thorough exam 
• Patients with contraindications to general anesthesia and procedural sedation
• Incision and drainage, followed by packing of an auricular hematoma
• Incision and drainage of abscesses and cysts
• Laceration repair
• Foreign body removal [2]
• Red ear syndrome [6][7]
• Great auricular neuralgia [8][9][10]

Contraindications

Contraindications to external ear anesthetic blockade include:

• Known anesthetic agent allergy        
• Uncooperative patient
• Coagulopathy
• Cellulitis or erythema overlying the injection site is a relative contraindication due to the theoretical risk of spreading the infection.

Equipment

The equipment required to complete an external ear nerve block typically includes:

Ring Block Requirements

• Sterile gloves
• Surgical mask with eye protection/goggles
• Anesthetic agent: 0.5% bupivacaine or 1% lidocaine with or without epinephrine*
• 25 or 27 gauge 1.5-inch needle
• 10 mL syringe
• Antiseptic solution (povidone-iodine 7.5% or chlorhexidine 2%)**
• Sterile 4 x 4 gauze

Ultrasound-Guided Greater Auricular Nerve Block Requirements

• Sterile gloves
• Surgical mask with eye protection/goggles
• Anesthetic agent: 0.5% bupivacaine or 1% lidocaine with or without epinephrine*
• 25- or 27-gauge 1.5-inch needle
• 10-mL syringe
• Antiseptic solution (povidone-iodine 7.5% or chlorhexidine 2%)**
• Sterile 4 x 4 gauze
• Ultrasound machine with a high-frequency linear probe
• Sterile ultrasound gel [11][12]

*Historically, the addition of epinephrine to the local anesthetic injected into the auricle was contraindicated, but recent literature demonstrates its safety without the risk of ischemic necrosis.[13][14]

**Concern for potential keratitis and ototoxicity has limited the use of chlorhexidine antiseptic solution in head and neck procedures. However, chlorhexidine may provide a lower risk of postprocedural infection if there is no concern for tympanic membrane perforation and the cleansed area is limited to the periauricular area.[15][16][17][18][19][20]

Personnel

The procedure requires medical professionals, including physicians or advanced practitioners, who are trained and experienced in performing peripheral nerve blocks and skilled in ultrasound-guided procedures. One nonsterile person can provide assistance as needed.  

Preparation

Explain the risks and benefits of a peripheral nerve block to the patient and obtain written informed consent if the patient can do so. Lay the patient in a lateral decubitus position with the affected side up. This peripheral nerve block can also be performed with the patient supine and their head rotated away from the practitioner with the affected ear up. Cleanse the anterior and posterior surfaces of the auricle, the postauricular area, the mastoid process, the front of the ear, and the lateral neck along the sternocleidomastoid muscle with the antiseptic solution; if using chlorhexidine 2%, let it dry completely before beginning the procedure. Drape the patient with sterile towels exposing the prepared area.

If performing an ultrasound-guided procedure, set the ultrasound machine opposite the stretcher from where the practitioner will stand. Sterilize the linear ultrasound probe and place it in a sterile probe cover. Apply sterile ultrasound gel to the affected area after preparing and draping the affected area.

Technique or Treatment

Ring Block

1.  Insert the 1.5-inch needle subcutaneously below the earlobe in line with the external auditory meatus.
2.  Aspirate before injecting to ensure that vascular injection does not occur.
3.  Inject 1 mL of the anesthetic agent into the spot of needle entry.
4.  Direct the needle behind the ear towards and over the mastoid process 2 to 4 mm deep, and advance it parallel to the skin nearly the entire length of the needle, and inject approximately 2 mL of anesthetic as the needle is withdrawn.
5.  Stop just shy of withdrawing the needle completely from the skin once back to the first position.
6.  Direct the needle anterior to the external ear towards the area just in front of the tragus, aspirate, then inject another 2 mL as the needle is withdrawn completely.
7.  Insert the needle subcutaneously directly above the ear again in line with the external auditory canal.
8.  Repeat steps 2 through 6 but with the needle facing caudally towards and over the mastoid process and immediately anterior to the tragus.

The typical amount of local anesthetic required to complete a ring block is approximately 10 mL to 12 mL. The trajectory of the injections will resemble an upright V for the inferior ear block and an upside-down or inverted V for the superior ear block; the needle tracts should encircle the ear. This technique frequently only incompletely anesthetizes the concha and external auditory meatus.[2]

Ultrasound-Guided Great Auricular and Lesser Occipital Nerve Block

1. Place the linear ultrasound probe, in the transverse orientation, at the middle of the sternocleidomastoid and track slowly upward toward the earlobe along the posterior edge of the sternocleidomastoid until 2 hypoechoic nerve structures are visible approximately 4 to 5 cm inferior to the ear lobule.
2. Insert the needle in-plane so the tip of the needle is visualized on the screen.
3. Advance the needle slowly until it is almost at the nerve—do not inject anesthetic into the nerve.
4. Aspirate and then inject 1 mL to 2 mL into the space between the needle tip and the nerve.

Auriculotemporal Nerve Block

1. Insert the 1.5-inch needle into the subcutaneous tissue anteriorly to the tragus to a depth of 4 to 6 mm.
2. Aspirate and then inject 1 mL to 2 mL into the space.

Useful Tips

• To quickly access the great auricular nerve as it courses across the sternocleidomastoid muscle using external topographic landmarks, the great auricular nerve is located at the junction of the upper one-third and lower two-thirds of the muscle between the mastoid process and clavicle.[21]
• To obtain complete anesthesia of the external ear, particularly the superiomedial helix excluding the external canal, the clinician will have to perform steps 7 and 8 of the ring block with all steps of the great and lesser occipital nerve block. Steps 7 and 8 of the ring block will anesthetize the auriculotemporal nerve distribution.
• The ring block provides analgesia for the external ear, except for the concha and external auditory canal.

Complications

Complications of ear nerve block include:

• Pain or inadequate anesthesia
• Bleeding
• Infection
• Allergic reaction to the anesthetic agent
• Hematoma formation
• Injury to surrounding vasculature
• Systemic anesthetic toxicity 
• Diffusion of anesthetic to the facial nerve leading to temporary facial paralysis.

Clinical Significance

Peripheral nerve block of the external ear is a valuable procedure utilized in many settings, including the operating room, office, and emergency department. This nerve block is a well-tolerated, relatively quick procedure that can be used independently or as an adjunct to other forms of analgesia. 

Enhancing Healthcare Team Outcomes

Expeditious, humane, and safe care of patients should always guide medical practice. Peripheral nerve block of the external ear is a valuable procedure. This nerve block can expedite analgesia, thereby accelerating the completion of procedures and decreasing patient discomfort when suturing a laceration, draining an abscess, or removing a foreign body. This procedure can also be used to manage various painful conditions, such as occipital neuralgia and red ear syndrome. By utilizing the peripheral nerve block, patient-centered care is at the forefront as it minimizes pain quickly and more safely than injecting local anesthetic directly into the external ear. 

The ear nerve block improves safety with fewer needle sticks to health professionals compared to direct local injection and shorter overall procedure duration utilizing fewer staff members compared to moderate sedation or general anesthesia. Using ultrasound improves locating the nerves, avoids vasculature, and decreases the amount of anesthetic required. Interprofessional teamwork between the clinician and nursing staff during and following the procedure improves patient outcomes.