These 12 nerves control facial and eye movements and sensation
There are 12 pairs of cranial nerves.
Each cranial nerve has a specific set of functions.
Several of the cranial nerves run through bones in the skull.
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This nerve detects odors and sends messages to the brain.
Location
Many tiny olfactory nerve fibers are embedded in your nose.
The fibers merge together in the olfactory bulb, which is located above your nose.
The nerve sends messages to the olfactory cortex, a region in the brain that distinguishes odors.
The sense of smell also plays a major role in mediating the perception of taste.
Due to its location and length, the olfactory nerve can become injured as a result of head trauma.
An injury of this nerve can result in a diminished sense of smell and decreased appreciation for taste.
A tumor in the area around your nose can also impair the function of your olfactory nerve.
Optic Nerve (Cranial Nerve Two)
Youroptic nervecontrols your sense of vision.
Within the brain, your optic nerves merge at theoptic chiasm, an area right below your pituitary gland.
Your optic nerve can become swollen due to a condition calledpapilledema.
This condition causes headaches and blurred vision.
It results from pressure in the back of the eye pushing on the optic nerve.
Your optic nerve can also be affected bydemyelination, which is loss of the protective myelin coating around nerves.
Demyelination occurs inmultiple sclerosis(MS) and causes vision loss.
A tumor or a traumatic injury to the optic nerve can affect your vision as well.
Oculomotor Nerve (Cranial Nerve Three)
Youroculomotor nervecontrols many of your eye movements.
This nerve provides stimulation to the muscles that control yourpupils.
Additionally, your oculomotor nerve stimulates the muscles that open your eyelids.
Each of your oculomotor nerves emerges from the midbrain, which is the upper region of the brainstem.
The oculomotor nerve divides into small branches, each of which sends messages to an individual muscle.
This nerve sends motor stimulation to the superior oblique muscle.
Your trochlear nerve emerges from your midbrain, below the level of your oculomotor nerve.
This nerve travels to your ipsilateral (on the same side) eye to power the superior oblique muscle.
Generally, trochlear nerve impairment affects only one eye, although in rare instances it can affect both eyes.
You may experience double vision, blurred vision, or nystagmus as a result of trochlear nerve impairment.
Yourtrigeminal nervehas three sensory nerve branchestheophthalmic nerve, the maxillary nerve, and themandibular nerve.
The trigeminal nerve emerges from the pons of the brainstem, which is below the midbrain.
Each of your abducens nerves stimulates the ipsilateral lateral rectus muscle.
This nerve emerges from the lower pons and travels to the eye toward the lateral rectus muscle.
Abducens nerve damage can cause diplopia or a lazy eye.
If you have damage to this nerve, it can cause your eye to deviate inward toward your nose.
A tumor or trauma can damage this nerve as well.
This is a large nerve with many branches.
It arises from two roots at the pontomedullary junction and divides into branches throughout the face.
Herpes simplex virus activation has become widely accepted as the likely cause of Bells palsy in most cases.
It can also be associated with herpes zoster, Lyme disease, diabetes-induced nerve disease, and pregnancy.
Toxins, infections, inflammation, a brain tumor, and trauma can damage this nerve.
The vestibulocochlear nerve can be impaired due to congenital (from birth) conditions as well.
It also detects sensation in the back of the throat and the ear.
This nerve travels down to the mouth and throat.
Damage or impairment of this nerve can occur due to a tumor or traumatic nerve damage.
A rare condition called glossopharyngeal neuralgia causes episodes of intermittent pain in the face or throat.
It is not known how or why this condition develops.
The vagus nerve emerges from the medulla.
This nerve travels outside the skull, alongside the carotid artery in the neck.
The vagus nerve divides into branches that reach the heart, lungs, and gastrointestinal system.
The vagus nerve or any of its branches can be damaged due to a tumor or trauma.
This can cause symptoms such as a hoarse voice, or parasympathetic deregulation such as breathing or heart issues.
The nerve stimulates thesternocleidomastoidandtrapeziusmuscles in your upper back and neck.
This nerve arises from the medulla and travels outside the skull down toward the sternocleidomastoid and trapezius muscles.
Your accessory nerve can be damaged due to trauma.
Damage to your accessory nerve would result in decreased ability to shrug your shoulders or turn your neck.
It may result in a physical sign described as winging, which is a protrusion of the shoulder blade.
The hypoglossal nerve emerges from the medulla and travels under the mouth to the muscles of the tongue.
Your hypoglossal nerve can become damaged due to direct trauma or nerve damage.
Hypoglossal nerve damage can result in diminished swallowing ability, which may result in choking.
Cranial Nerve Zero?
Some professionals recognize an extracranial nerve called the terminal nerve, or cranial nerve zero.
This nerve is a small, often microscopic, plexus of nerves near the olfactory nerve.
A Word From Verywell
The 12 pairs of cranial nerves are each involved in highly specialized functions.
Cranial nerve impairment can occur due to face, head, or neck trauma.
The results will guide your medical team in planning your treatment.
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