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Hypoglossal Nerve: Function, Palsy & Damage

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  • 0:00 Function of the…
  • 1:32 Damage
  • 3:03 Diagnosis and Treatment
  • 4:06 Lesson Summary
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Lesson Transcript
Instructor
Laszlo Vass
Expert Contributor
Ana Benito Gonzalez

Ana has a PhD in Biology. She has taught college classes at leading U.S. universities, also works as a Biology tutor. She has published several scientific journals.

This lesson covers the function and structure of the hypoglossal nerve. We will also cover some of the effects of damage to this system, including paralysis.

Function of the Hypoglossal Nerve

Imagine the ramifications if you lost the ability to move your tongue. You'd have problems speaking, eating, and swallowing. Yikes! But, what could cause such a thing to happen? In this lesson, we discuss the hypoglossal nerve, the major nerve pathway in the mouth and throat.

The hypoglossal nerve is cranial nerve number 12. Here is a diagram that shows the pathway and location of the hypoglossal nerve:

Hypoglossal Nerve

It originates in the medulla oblongata, which is a part of the brain stem which controls involuntary muscles. It exits the skull through the hypoglossal canal. The nerve gets its name from its location, with hypo meaning 'under' and glossal meaning 'tongue.' This nerve is primarily responsible for the movement of the tongue. It's a mixed nerve, meaning it has both sensory and motor pathways; that is, it takes information both to the brain from the tongue and to the tongue from the brain. Its main function, however, is mostly motor in nature, controlling the muscle that makes up the tongue.

The hypoglossal nerve is used for daily functions most people take for granted, like eating and speech. It allows control of the tongue for such things as mixing food you have eaten into a ball, known as a bolus. It's also involved in tongue movements that allow you to swallow and form words for speech.

Damage

The hypoglossal nerve can be damaged in several ways. Strokes are a common cause of damage to this nerve. Often a stroke victim's inability to speak properly is due to hypoglossal damage. Other causes of damage are tumors on the brain stem and multiple sclerosis.

One word that is often used with regard to nerve damage is palsy, which refers to paralysis accompanied by muscular tremors and numbness. Palsy is a dated term, and the descriptions in the rest of this lesson will refer to paralysis rather than palsy. The terms are often used interchangeably except where a specific condition like Bell's palsy or cerebral palsy are discussed. The effect of damage can come in different forms. Most common is paralysis of one side of the tongue, known as unilateral paralysis. To test this, the patient is asked to stick his or her tongue straight out. If the nerve is damaged, the patient's tongue will point toward the side of the paralysis, like this:

Hypoglossal Nerve Damage

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Additional Activities

Physician Role Play

The hypoglossal nerve controls the movements of the tongue that help you to speak and swallow. In this physician role play exercise, you will pretend that you are a doctor that has a patient with potential unilateral paralysis. You will have to confirm the diagnosis and come up with an appropriate treatment plan. Answer the questions in the scenario shown below.

Scenario:

A 62 year old man comes to your office. He has suffered a stroke. The patient report says he is suffering from unilateral paralysis.

  1. What is unilateral paralysis?
  2. How can you test a patient for unilateral paralysis?
  3. What do you expect to see in this particular patient when you test for unilateral paralysis?
  4. Given that he has had a stroke, what other test would you recommend to confirm the damage to the hypoglossal nerve?
  5. The patient has trouble swallowing and pronouncing some words while speaking. What treatment would you recommend?

Answers:

  1. Unilateral paralysis is is paralysis of one side of the tongue. It is caused by damage to the the hypoglossal nerve from one side of the brain.
  2. You could quickly test for unilateral paralysis by asking the patient to stick out their tongue.
  3. You would expect the tongue to go toward one side, either left or right.
  4. Because the damage from the stroke is likely affecting tissues and nerves, you should recommend magnetic resonance imaging.
  5. To help the patient improve their tongue movement, you could recommend speech therapy and other tongue exercises to increase the strength of the tongue.

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