The posterior auricular nerve is a small sensory and motor nerve that arises from the facial nerve (cranial nerve VII). It’s generally involved in the sensation and movement of some parts of the ear.
Structure and Appearance
The posterior auricular nerve is a relatively small and slender branch of the facial nerve (cranial nerve VII). While the structure of the nerve may vary between individuals, it generally maintains the following structural elements:
Origin
The nerve usually originates just after the facial nerve exits the stylomastoid foramen. This foramen is a small opening at the base of the skull, just behind the ear.
Branching
After its origin, the posterior auricular nerve typically divides into two primary branches:
Auricular Branch: This is the part that supplies the intrinsic and extrinsic muscles of the auricle, the external part of the ear. These muscles are generally rudimentary in humans and have limited function.
Occipital Branch: This branch supplies the occipital belly of the occipitofrontalis muscle, a muscle involved in scalp movement and facial expression.
Fiber Type
The nerve consists of both motor and sensory fibers:
Motor Fibers: These are the predominant type and they innervate the muscles related to the auricle as well as the occipital belly of the occipitofrontalis muscle.
Sensory Fibers: These fibers are fewer in number and provide sensory innervation to a small region of the skin overlying the mastoid process and occasionally to parts of the auricle.
Course
The nerve courses in an upward and slightly posterior direction from its point of origin. It typically runs along the posterior aspect of the external auditory meatus and the mastoid process, which are both landmarks near the ear. It then branches out to perform its various functions in the vicinity of the ear and the adjacent scalp region.
Anastomoses
Though less common, the posterior auricular nerve may form anastomoses (connections) with other nearby nerves, such as branches of the greater auricular nerve or the lesser occipital nerve, which are derived from the cervical plexus.
Location
As the name suggests, the posterior auricular nerve is located near the ear, running posterior to it. After originating from the facial nerve, it courses upwards, supplying muscles and skin in the region of the auricle (the external part of the ear) and the adjacent portion of the scalp.
Function
- Motor Function: One of its main functions is to innervate the intrinsic and extrinsic muscles that attach to the auricle, allowing for minor movements of the ear. However, the capacity for humans to move their ears is generally limited compared to other animals.
- Sensory Function: Although its sensory role is limited, it does supply sensation to a small part of the skin of the ear and adjacent areas of the scalp.
- Accessory Role: Some anatomical variations might find it communicating with other nerves in the region, but this is generally minor.
Clinical significance
The clinical significance of the posterior auricular nerve primarily lies in its proximity to the facial nerve and its involvement in surgical procedures or pathological conditions affecting the ear, face, or surrounding regions. Understanding the anatomy and function of this nerve is important for avoiding complications and maximizing surgical outcomes. Here are some aspects of its clinical significance:
Surgical Procedures
- Parotidectomy: The posterior auricular nerve is in proximity to the parotid gland. Understanding its location is crucial to avoid damaging it during surgical removal of the parotid gland.
- Facelifts and Cosmetic Procedures: In aesthetic surgeries like facelifts, surgeons need to be aware of the posterior auricular nerve to prevent injury that can result in issues such as ear drooping or loss of sensation in the surrounding area.
- Ear Surgery: Procedures that involve the ear may risk damaging the posterior auricular nerve if the surgeon is not careful, which can lead to reduced motor function or sensation in the ear.
Trauma
Facial Injuries: Traumatic injuries involving the face or temporal region could potentially damage the posterior auricular nerve, leading to loss of function or sensation.
Pathological Conditions
- Facial Nerve Paralysis: In cases of facial nerve paralysis like Bell’s palsy, the function of the posterior auricular nerve can also be compromised since it is a branch of the facial nerve.
- Tumors or Lesions: Benign or malignant tumors around the parotid gland, facial nerve, or temporal bone could impinge on the posterior auricular nerve, affecting its function.
Diagnostic and Interventional Procedures
- Electromyography: Occasionally, the posterior auricular nerve may be studied using electromyography (EMG) to assess the integrity of the facial nerve, particularly in complex facial nerve paralysis cases.
- Nerve Blocks: For procedures or conditions that require local anesthesia around the ear or mastoid region, understanding the anatomy of the posterior auricular nerve is essential.
- Radiological Imaging: In some instances, advanced imaging techniques like MRI can visualize the nerve, particularly if pathology involving the nerve is suspected.
