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Brains Super Speciality Hospital
Facial Nerve Expressions

The facial nerve or the seventh cranial nerve is yet another crucial nerve that supplies all the muscles of the face hence the name. The muscles of the face are very special, unlike the other muscles in the body. Their origin and attachment are designed in such a way that when they contract they modify the appearance of the face. Depending on the thoughts, emotions and other circumstances these muscles can contract differently expressing different feelings on the face. These facial expressions can be very meaningful and at times can be supplementary or complimentary to the verbal language. That is why the aphorism face is the index of the mind came into existence.

This apart many special can be expressed exclusively by these muscles, particularly in dancers and actors. The Facial nerve is quite complex too and has predominant motor fibres, but also has visceral sensory and special sensory fibres. Hence it is connected to other nuclei as well in the brain stem. The motor component of the facial nerve takes its origin from the facial nucleus located in the pons. The motor fibres then go back and loop around the nucleus of the sixth nerve forming the facial colliculi on the floor of the fourth ventricle. Then turns forward and exits at the ponto-medullary junction lateral to the exit of the sixth nerve. The nerve then travels along the cerebellopontine angle cistern occupying the middle part to reach the bony foramen in the Petrous bone called Internal Acoustic Meatus. Here it is in association with the vestibulocochlear nerve and then enters the tympanic acuity of the middle ear. Here it travels through a special and tiny canal called the facial canal. In the facial canal, the corda tympani joins the Mandibular division of the Trigeminal nerve.

At the lower part, it gives a branch to the stapedidius muscle. This is called nerve to the stapedius. This muscle is attached to the tiny bone that is in the middle ear called Stapes, at the oval window. It controls the movement of this bone called auditory ossicles along with the Incus and the Maleus which regulate the entry of sound into the ear. Failure of this can make the sounds uncomfortably loud called hyperacusis. The main nerve goes further down and exits through a small hole located in between the styloid and mastoid bones so named stylomastoid foramen. Then the nerve reaches the face and divides into five branches to supply all the muscles of the face.

Temporal branch - supplies the frontal belly of the occipital frontalis in the forehead. In addition, it supplies the Corrugator cilia muscle and the Orbicularis oculi in the upper eyelid. They help in wrinkling and other movements of the forehead the eyebrows and closing the upper eyelid.

The Zygomatic branch supplies the lower eyelid muscle the orbicularis oculi, zygomaticus major and minor, Levetor labili superioris, and the Levetor alae Nasi. These are essentially the facial muscles of the cheek that help in smiling and movements of the upper lip and the nose.

Buccal branch - supplies the strong muscle of the cheek called the Buccinator, the Risorius, and orbicularis oris. This helps in the movements of the cheek, facial expressions and to hold food or liquid in the mouth while eating. The Marginal Mandibular branch supplies the triangularis or depressor oralis, depressor anguli inferioris, and the mentalis.

Cervical supplies the platysma.

In addition, facial supplies the posterior belly of the digastric and the stylohyoid muscles. They are the independent branches of the facial nerves. There is a special ganglion called the Geniculate ganglion which has special fibres of special visceral, general visceral, and special sensory fibres. The greater petrosal nerve forms in the facial canal goes up to the skull vase enters a hiatus and travels in the middle cranial fossa to enter the foramen lacerum. Once it comes out of the skull it enters the pterygoid canal into the pterygopalatine fossa.

This carries the parasympathetic fibres to the pterygoid palatine ganglion. In the same canal the deep petrosal nerve that carries sympathetic fibres from the carotid plexus. These are the postganglionic fibres from the superior cervical ganglion that travel along the carotid artery. These two nerves GSPN (parasympathetic) and the Deep petrosal nerve (Sympathetic) together in this pterygoid canal are called the Vidian nerve. The greater petrosal then moves forward to enter the inferior orbital fissure and supply the lacrimal gland that secretes tears. They also supply the nasal gland to produce nasal fluids, as well as palatine glands.

Facial nerves can be affected by many conditions and tumors. The common cause of paralysis is due to viral infection called Bell's palsy. It can be either a direct infection or a consequence due to immune mediated inflammation. It happens in the facial canal. It can cause loss of taste, hyperacusis, tympanic pain,loss of facial expressions, loss of salivation and tears,and complications as a result of difficulty in closing the eye, dryness of the eye, corneal ulcer, loss of smile, facial deformity, food getting stuck in the cheek, drooling of liquids, facial deviation, dryness of mouth, halitosis, gingival ulcers, injury from biting the cheek.

Each of these facial muscles is designed and aligned to produce a phenomenal depiction of facial expressions in our day-to-day lives. They can exhibit their mood, temper, feelings, and emotions so aptly. All the artists spend considerable time gaining control of these muscles to make those expressions more vivid and lively.