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Cranial Nerves: What to Know

Medically Reviewed by Jabeen Begum, MD on September 01, 2022

Your brain is directly connected to various parts of your head, neck, and trunk by twelve pairs of nerves – these are your cranial nerves. They play an important role in sensing, controlling muscles, regulating glands, and more.

What Are Cranial Nerves?

What are cranial nerves? They’re a dozen pairs of nerves on the backside of your brain that transmit electrical signals to and from your torso, neck, face, and brain. Thanks to your cranial nerves, you can experience the five senses, make different facial expressions, blink, move your tongue around, and more. Your cranial nerves are an important aspect of your nervous system.

The following list names all twelve cranial nerves:

  • Olfactory: Associated with smelling. Smell molecules in your nasal cavity trigger nerve impulses that come through the olfactory nerve.
  • Optic: Associated with seeing. Your retinas take in visual information and convey it to the optic nerves. The optic nerve from each eye passes signals to opposite ends of the brain.
  • Oculomotor: Associated with seeing. It allows for motor function in many of the muscles surrounding your eyes as they move and focus. The oculomotor nerve also controls the dilation and constriction of your pupils as they respond to light.
  • Trochlear: Associated with muscle movement. The trochlear nerve operates the superior oblique muscles, which perform many eye movements (inward, outward, and downward).
  • Trigeminal: Associated with collecting information. The trigeminal nerve is composed of three divisions (ophthalmic, maxillary, and mandibular) that share information from various parts of your head with your brain.
  • Abducens: Associated with muscle movement. The abducens nerve controls another eye muscle (lateral rectus muscle) that allows for outward eye movements such as looking to either side.
  • Facial: Associated with muscle movement and collecting information. The facial nerve takes information from your taste buds, helps you make facial expressions, and supplies the glands that make saliva and produce tears.
  • Vestibulocochlear: Associated with hearing. The vestibulocochlear nerve is composed of two divisions (cochlear and vestibular) that collect information about balance and head orientation, detect vibrations from sounds, and receive hearing signals.
  • Glossopharyngeal: Associated with muscle movement and collecting information. The glossopharyngeal nerve shares information from your external and middle ear, the back area of your tongue, and your sinuses at the back of your throat.
  • Vagus: Associated with muscle movement and collecting information. The vagus nerve has a lot of functions, including transmitting information about parts of your throat, organs in your chest and trunk, and tastes on your tongue.
  • Accessory: Associated with muscle movement. Also known as the spinal accessory nerve, it allows you to move your shoulders, neck, and head, in addition to muscles that help you swallow.
  • Hypoglossal: Associated with muscle movement. The hypoglossal nerve makes it possible for you to move your tongue around.

Are you wondering how to remember cranial nerves? You can try mnemonic devices like:

  • Ooh, ooh, ooh to touch and feel very good velvet. Such heaven!
  • On old Olympus’s towering top, a Finn and German viewed some hops.

What Do Cranial Nerves Do?

Cranial nerve function varies depending on the type of nerve. Generally speaking, these nerves control your motor skills in your face and trigger sensations (tasting, smelling, hearing, feeling, seeing). Some nerves only serve one of these functions, but some do both.

Where Are Cranial Nerves Located?

Where are the cranial nerves located? 

Two pairs of cranial nerves start in your cerebrum, the biggest part of your brain, which is found directly on top of your brainstem. These are the olfactory and optic nerves, which help you smell and see, respectively. The other ten cranial nerves originate in your brainstem, the piece that connects your spinal cord and brain. 

Keep in mind that these are just the places of origin for the twelve nerves. Depending on the size and purpose of each nerve, they can reach other parts of your body. For example, the vagus nerve is the longest cranial nerve. It serves both sensory and motor purposes and runs through your digestive system, heart, throat, tongue, and more.

Signs Something Could Be Wrong with Your Cranial Nerves

Your cranial nerves are imperative to how your neck, head, and face function. Any damage to these 12 nerves could have a great impact on your day-to-day life. The majority of these nerves can be found at the surface level of your skull, which means they’re very susceptible to injury because they’re only covered by your facial tissue and muscles. 

Depending on which nerves are damaged, you’ll have different symptoms. Olfactory nerve damage would affect your sense of smell, facial nerve damage would affect your ability to make facial expressions, and so on. General signs of nerve damage include:

  • Inability to feel part of your face
  • Feeling weak
  • General pain
  • Tingling feelings
  • Abnormal vision
  • Paralyzed or weak muscles
  • Difficulty balancing
  • Difficulty swallowing

What Conditions Affect Cranial Nerves?

A number of conditions might affect your cranial nerves, including:

  • Trigeminal neuralgia
  • Hemifacial spasm
  • Glossopharyngeal neuralgia
  • Tumors
  • Amyotrophic lateral sclerosis (ALS)
  • Bell’s palsy
  • Internuclear ophthalmoplegia
  • Oculomotor palsy
  • Stroke
  • Traumatic brain injury

How Can You Keep Cranial Nerves Healthy?

You can take preventative measures to keep your cranial nerves healthy, including:

  • Keeping a generally healthy lifestyle
  • Eating a balanced diet
  • Maintaining a healthy weight
  • Avoiding smoking
  • Lowering your blood pressure
  • Avoiding situations that could lead to head injuries
  • Taking measures to prevent diabetes
  • Lowering alcohol intake
  • Exercising on a regular basis

When to See A Healthcare Provider for Cranial Nerve Concerns

If you’re concerned that you might have a condition that is affecting your cranial nerves, you should see your healthcare provider. You’ll likely be referred to a neurologist initially and maybe a neurosurgeon later on. Neurologists specialize in managing cranial nerve conditions with medicine, and neurosurgeons take over if medical intervention has failed for some reason.

If you experience any of the following symptoms, seek medical attention immediately:

  • Drooling involuntarily
  • Drooping on one side of your face
  • Experiencing muscle paralysis or weakness
  • Slurring speech
  • Losing your sense of vision

Show Sources

SOURCES:

Cleveland Clinic: “Cranial Nerves.”

Penn Medicine: “Cranial Nerve Disorders.”

Simply Psychology: “The 12 Cranial Nerves.”

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