The Course and Distribution of the Facial Nerve Quiz

Answer: VII

The facial nerve is the seventh of twelve cranial nerves, all of which arise from the brainstem. It is actually the motor branch that emerges from the pontomedullary junction. The nerve of Wrisberg, also called nervus intermedius, arises at this same point between the facial and vestibulocochlear (VIII) nerves and gives rise to the sensory branch of the facial nerve.

Answer: Petrous temporal bone

The temporal bone is a bilateral structure, i.e. there is one located on each side of the face by the temple. The bone consists of four parts, one of which is the petrous part, also called the pyramid. The internal auditory meatus is a canal within this part of the bone, through which the facial nerve (and also the vestibulocochlear [VIII] nerve) travels toward the inner ear.

Answer: Facial

The facial canal is also called the Fallopian canal after Italian anatomist Gabriele Fallopio. It travels through the temporal bone and is approximately 3-4cm in length - this makes it the longest osseous canal in the body that a nerve travels through. Within the canal, the facial nerve first forms the labyrinthine segment and then changes direction at the first genu.

Then comes the tympanic segment and the second genu, and finally the mastoidal segment. The segments are named according to their proximity to the inner ear (labyrinthine), tympanic membrane, and mastoid part of the temporal bone.

Answer: Stylomastoid foramen

The stylomastoid foramen is effectively the end of the facial canal and is situated between the styloid and mastoid processes of the temporal bone, the latter of which can be felt as the large lump behind each ear. Along with the facial nerve, the stylomastoid artery runs through the foramen.

The five branches the nerve divides into are as follows: temporal, zygomatic, buccal, marginal mandibular and cervical.

Answer: No

Although it travels through it, the nerve does not actually supply the parotid gland, which is instead supplied by parasympathetic fibers from the otic ganglion (from the glossopharyngeal [IX] nerve). Because of the nerve's position within the gland, it can be damaged during parotid operations.

It can be reanimated either statically or dynamically: static reanimation usually involves connective tissue from the fascia lata in the thigh, but unfortunately doesn't restore movement. Dynamic reanimation involves joining fibers from the hypoglossal (XII) nerve to the damaged facial nerve. If it has been more than 12 months since the damage, the muscles of the face will likely be atrophied, so muscle grafts can also be performed.

This method does restore movement.

Answer: Glossal ganglion

The glossal ganglion does not exist, although the facial nerve does give rise to the chorda tympani, which supplies the taste buds of the anterior tongue and brings taste information to the brain.

The submandibular ganglion is a continuation of the chorda tympani and is parasympathetic in function, supplying the submandibular and sublingual salivary glands. It also contains fibers from the trigeminal (V) nerve.

The geniculate ganglion forms in the facial canal and receives motor, sensory and parasympathetic fibers. It supplies many structures including the muscles of facial expression, the lacrimal glands, and the tongue.

The pterygopalatine ganglion receives its parasympathetic root from the facial nerve and supplies the nasal glands and mucous membranes of the face.

Answer: Masseter

Masseter is one of four muscles in the face that are termed muscles of mastication, rather than of facial expression; the other three are temporalis, and the lateral and medial pterygoid muscles. They are supplied by the mandibular branch of the trigeminal nerve (cranial nerve V).

With the exception of frontalis, the muscles of facial expression tend to be short, rather like thin rectangular strips, and most are bilateral structures. They have their own specialized functions, for example orbicularis oculi surrounds the eye and closes the eyelid; risorius sits by the corner of the mouth and pulls it out, but this expression tends not to look like a sincere smile without the action of other muscles, such as zygomaticus major, which raises the mouth and pulls it back.

Answer: Marginal mandibular branch

The platysma muscle is a large sheet that extends from the chin down the side of the neck. Although it is in the neck, some consider it a muscle of facial expression and it is indeed innervated by the facial nerve. The muscle's actions include depressing the lower lip and contorting the face in a grimace.

As suggested by its name, the marginal mandibular branch travels along the mandible. The nerve can be damaged during removal of the submandibular salivary gland or during facelifts. This results in paralysis of the lip depressors.

Answer: Anterior inferior cerebellar artery

The anterior inferior cerebellar artery is a branch of the basilar artery and emerges at the junction between the pons and medulla oblongata in the brainstem, where the facial nerve also emerges. The artery enters the internal auditory meatus with the nerve.

The middle cerebral artery gives off a Rolandic branch, which supplies the cortical motor area of the face. Also, the posterior auricular artery supplies the facial nerve at and distal to the stylomastoid foramen.

Answer: Bell's palsy

The facial paralysis seen in Bell's palsy can have determinable causes such as a stroke, but when no cause can be found, the condition is said to be "idiopathic" and diagnosed as Bell's palsy. It was named after Scottish anatomist Charles Bell. The paralysis is usually unilateral, and resolves itself in most patients.

It is thought that the nerve becomes inflamed and swells in the facial canal, becoming compressed, thus it is usually treated with corticosteroids. Various viruses, including herpes simplex type 1 and herpes zoster, have been implicated in the condition, but research is still ongoing.