In this lesson, we will learn about the cranial nerves, focusing on the spinal accessory nerve. We will also discuss how injury occurs to the spinal accessory nerve, including symptoms and treatment options.

Nerve Injury

John had a routine medical procedure to remove his lymph nodes in his neck. After his surgery, he had weakness and pain in his shoulder and neck. John returned to the doctor and was told that he has a spinal accessory nerve injury. John wants to know what caused his injury and potential treatments.

Before we discuss the cause of John’s injury and treatment options, we will learn about nerves and the nervous system.

Nerves and the Nervous System

The nervous system is vital to our bodies and it can be thought of as a highway. A highway has many different roads to help cars get to and from different destinations. Nerves are parts of the body that transmit messages and act like a highway. Nerve impulses, or electrical signals sent from one part of the body to another, are the cars that travel on the nervous system highway. Nerve impulses are important because they are the messages that parts of the body send to one another and are vital for the body to communicate with other parts. For example, when your stomach is empty, a nerve impulse is sent to your brain to let you know that you’re hungry, and after you’ve eaten the stomach sends a signal to your brain to indicate that you’re full. If we didn’t have this highway system, we would never know when to eat!

Next, we’ll discuss the different parts of the nervous system.

The nervous system has three different parts: the central nervous system (or CNS), peripheral nervous system, and autonomic nervous system. Each part of the nervous system has a different function and includes different parts of the body. The CNS and the peripheral nervous system are responsible for sending and receiving signals to and from different parts of the body. The CNS includes the brain and spinal cord, and the peripheral nervous system includes nerves throughout your body that are not a part of the brain and spinal cord. Lastly, the autonomic nervous system includes involuntary muscles and glands that they control, like the heart.

Now that we have a general understanding of the nervous system, let’s focus on the peripheral nervous system. The peripheral nervous system creates a longer highway that extends from the skull to the limbs and extremities. The peripheral nervous system highway consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves. Since John injured one of his cranial nerves, next we will discuss the cranial nerves and their functions.

Cranial Nerves

Remember, there are 12 pairs of cranial nerves (CN) that are derived from the bottom of the brain. Each of the cranial nerves originate from the bottom of the brain and extend to parts of the head and neck regions to allow for communication between the brain and these parts of the body. These 12 pairs of cranial nerves are typically indicated with Roman numerals. Here’s a list of the pairs of nerves and their functions:

I. Olfactory nerve: Assists with sense of smell

II. Optic nerve: Assists with sight

III. Oculomotor nerve: Helps with eye movement

IV. Trochlear nerve: Helps with eye movement

V. Trigeminal nerve: Senses touch from face and mouth

VI. Abducens nerve: Helps with eye movement

VII. Facial nerve: Involved with taste, hearing, and muscles responsible for facial expressions

VIII. Vestibulocochlear nerve: Aids in hearing and balance

IX. Glossopharyngeal nerve: Aids in taste

X. Vagus Nerve: Involved in sensory and autonomic functions

XI. Spinal Accessory nerve: Helps with muscles in head movement and shoulder movement

XII. Hypoglossal nerve: Helps with muscles of the tongue

Inferior view of brain with accessory nerves

We will focus our discussion on the spinal accessory nerve (SAN) since that is the nerve that John has injured.

Causes, Symptoms, and Treatment of SAN injury

The spinal accessory nerve (SAN), also known as the cranial accessory nerve or accessory nerve, extends from the brain, down the side of the neck, and along the trapezius muscle. The SAN is highly prone to injury due to its long length and the fact that it’s not very deep underneath the skin.

Spinal accessory nerve along with trapezius muscle

SAN injuries often happen when patients like John have procedures or surgeries performed on areas in the neck near the SAN, but they can also be caused by trauma. Procedures and surgeries such as lymph node removal like John had, neck disc surgery, or when an IV is placed in a vein in the neck can cause SAN injuries. John’s symptoms include weakness and pain in his shoulder. Other symptoms of SAN injuries include a protruding shoulder blade, difficulty moving shoulders, and weakness in the trapezius muscle.

John’s treatment options include physical therapy and over-the-counter pain medication for a non-serious injury. More serious injuries may also be treated with nerve grafting, which is the process of replacing the parts of the damaged nerve with a healthy nerve from another part of the body. A successful nerve graft results in the nerve re-growing and the symptoms associated with the nerve damage hopefully disappearing. One downside of nerve grafting is that patients no longer have sensation in the area from which the healthy nerve is removed. Surgeons therefore opt to remove nerves from areas that are not deemed very important, like the side of the foot or back of the knee.

Since John’s injury is fairly new, he mostly likely will be advised to do physical therapy and be revisited at a later date to determine his progress.

Lesson Summary

Let’s recap.

The nervous system allows for the brain to communicate with the rest of the body. Nerves transport nerve impulses to and from different parts of the body. The nervous system has three different parts: the central nervous system , peripheral nervous system, and autonomic nervous system. The CNS and peripheral nervous system is responsible for sending and receiving signals to and from different parts of the body and the autonomic nervous system controls involuntary muscles and glands. The peripheral nervous system consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves that allow for nerve impulses to be sent to and from the brain to the limbs and extremities. There are 12 pairs of cranial nerves (CN) that are derived from the bottom of the brain and extend to the head and neck. Cranial nerves allow for the brain to communicate with parts of the head and neck regions.

The spinal accessory nerve (SAN) extends from the brain, down the side of the neck and along the trapezius muscle. The SAN is highly prone to injury due to its long length and being shallow underneath the skin. SAN injuries are mostly caused by medical procedures and surgeries. Symptoms of SAN injuries include weakness and pain in the shoulder, protruding shoulder blades, difficulty moving shoulders, and weakness in the trapezius muscle. Treatment options include physical therapy and over-the-counter pain medication for non-serious injuries. More serious injuries may be treated with nerve grafting, the process of replacing the parts of the damaged nerve with a healthy nerve from another part of the body.