Patients frequently present to the emergency department with a variety of external ear complaints ranging from traumatic lacerations and hematomas to embedded earring backs and abscesses. Typically, oral and parenteral medications do not provide adequate pain relief, and procedural sedation has a sizeable risk burden. Injections directly into the external ear are painful and have a high risk of provider needlestick. On the other hand, a peripheral nerve block is typically a well-tolerated method to achieve analgesia for a procedure. Multiple nerves innervate the external ear and originate from both cranial nerves and the cervical plexus. Historically, the ring block was the most common method of peripheral external ear nerve block. With the increased availability and use of ultrasound in the emergency department, the literature shows that ultrasound-guided greater auricular nerve block to include the lesser occipital nerve and blocking of the auriculotemporal nerve is as, if not more effective, more direct, and provides equivalent analgesia using less anesthetic agent.
External ear anatomy ear includes the external auditory canal, auricle or pinna (comprised of the helix, antihelix, and lobule), the antitragus, the tragus, and the conchae. The sensory innervation arises from the greater auricular and lesser occipital nerves both branches of the second (C2) and third (C3) branches of the cervical plexus, the auriculotemporal nerve off the mandibular branch of the trigeminal nerve and the auricular branch of the vagus nerve known as Alderman's or Arnold's nerve. More specifically, the greater auricular nerve runs from the cervical plexus, winding around the posterior aspect of the sternocleidomastoid muscle most superficial approximately 6 to 7 cm below the external auditory meatus and runs anterosuperiorly coming in proximity to the lesser occipital nerve as it surfaces around the posterior edge of the sternocleidomastoid approximately 4 to 5 cm below the external auditory meatus. It then goes deeper dividing into its anterior and posterior branches.
The auricle comprised of the helix, concha, and lobule (collectively referred to as the lateral surface) receives its innervation from the greater auricular nerve. The antihelix, antitragus, tragus, and conchae (the medial surface) are innervated by mainly the greater auricular nerve and to a lesser degree the auricular branch of the vagus nerve. The superomedial helix (the crus and spine) is innervated primarily by the auriculotemporal nerve. The auricular branch of the vagus nerve solely innervates the external auditory canal in most cases.
Ring Block and Auricular Branch of the Vagus Nerve requires the following:
Medical professionals to include physicians, physician assistants and nurse practitioners who are trained and experienced in the performance of peripheral nerve blocks, as well as, skilled in ultrasound-guided procedures. One nonsterile person for assistance as needed.
Explain the risks and benefits of a peripheral nerve block to the patient and obtain written informed consent if the patient is able. Lay the patient in lateral decubitus position with the affected side up. Set the ultrasound machine on the opposite side of the stretcher from where you will be standing. Sterilize the linear ultrasound probe and place in a sterile probe cover. Clean the area of the external ear, the mastoid process, some of the face, and the neck along the sternocleidomastoid with 2% chlorhexidine. Drape the patient with sterile towels with prepped area exposed. Let the chlorhexidine dry completely before beginning the procedure. Apply sterile ultrasound gel to the area.
At completion, typically, the total amount of local anesthetic is approximately 10 to 12mL, and the trajectory of the injections will look like a V and an upside-down V encircling the ear.
Ultrasound-guided Greater Auricular and Lesser Occipital Nerve Block:
NOTE: To obtain complete anesthesia of the external ear particularly the superior-medial helix minus the external canal you will have to perform steps 7 and 8 of the ring block (to include the auriculotemporal nerve distribution) with the greater and lesser occipital nerve block.
Peripheral nerve block of the external ear is a valuable procedure utilized in a multitude of settings including the operating room, office, and emergency department. It is a well-tolerated, relatively quick procedure that can be used on its own or as an adjunct to other forms of analgesia.
Expeditious, humane and safe care of patients should always guide us in our practice. Peripheral nerve block of the external ear is a valuable procedure to become familiar with as it can expedite analgesia which will then accelerate completion of procedures and decrease patient discomfort whether suturing a laceration, draining an abscess, or removing a foreign body. By utilizing the peripheral nerve block, patient-centered care is at the forefront as it minimizes pain quickly and more safely than injecting directly into the external ear. The peripheral nerve improves safety with fewer needle-sticks to health professionals compared to direct local injection and shorter overall procedure duration utilizing fewer staff members when compared to moderate sedation or general anesthesia. The use of ultrasound improves locating the nerves, avoids vasculature and decreases the amount of anesthetic required.
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