The Important Phrenic Nerve

Posted by Nurse Linda in Life After Paralysis on February 09, 2022 # Health

Doctor holding a stethoscope The phrenic nerve is critical to the function of the diaphragm to ensure breathing. It is an interesting nerve as it is actually two separate nerves on each side of the body, even though it is typically referred to as one nerve. It exits each side of the spinal cord at three cervical nerve roots in the neck, C3, C4, and C5. Because it is outside of the central nervous system spinal cord nerves, it is a peripheral nerve in the body that allows treatment options. This is a huge benefit if it becomes ineffective through injury or disease.

Although several nerves and muscles support breathing, the diaphragm is the main muscle for breathing. Breathing is an interesting biological process as air is taken into the lungs when the diaphragm is activated or pulled down. The phrenic nerve stimulates the diaphragm to make this happen. Unlike other muscles in the body, which have a balance of muscles that push and muscles that pull, the diaphragm relaxes when the phrenic nerve is relaxed, which causes air to be expelled from the lungs. There is no nerve stimulation or opposite set of muscles to release the diaphragm from pulling down. The phrenic nerve is either ‘on’ pulling the diaphragm down or ‘off,’ allowing the diaphragm to relax to its natural resting state. Of course, these actions happen quite quickly as you breathe in and out.

There are other important functions that the diaphragm is required to perform for your health. Besides breathing in normal conditions as well as in challenging situations such as with exertion, the diaphragm is also needed for sneezing, gagging, and coughing. This keeps the airway clear. Use of the diaphragm is automatic for breathing but can also be voluntarily controlled for airway maintenance.

Much like the rest of the body, the phrenic nerve is actually two different nerves on both sides of the body. They begin at the three cervical nerves, C3, C4, C5, on each side of the spinal cord. Their path through the neck and chest is similar, with a bit of difference due to the positioning of the heart. They extend down the chest close between the lungs and heart to each side of the diaphragm below the lungs. The diaphragm is also actually two sections with one phrenic nerve controlling one section of the diaphragm, although the phrenic nerves and diaphragms work in unison which is why they are each thought of as one unit.

The phrenic nerve has both motor and sensory functions. Motor-wise, the phrenic nerve controls the diaphragm for breathing. Sensory functions include information about feelings or pain in the central part of the diaphragm, the pleura, which is the membrane or sac containing the lungs, the mediastinal pleura, which is the lining of the chest cavity, the peritoneum or lining or sac containing abdominal structures, and the pericardium or sac that surrounds your heart.

If the phrenic nerve loses some or all function, the diaphragm cannot be pulled down to let enough air into the lungs. The diagnosis of phrenic nerve palsy or paralysis is made. This affects your ability to breathe. Causes of phrenic nerve injury can be from mechanical trauma, as in severe injuries such as spinal cord injury, birth injury, surgical injury, or effects of the disease. Compression can pinch the phrenic nerve from surrounding injury, internal bleeding, and tumor. Other causes of injury to the phrenic nerve are radiation treatment and viruses. Neuropathies can occur from diseases or complications, such as diabetic neuropathy.

Because the phrenic nerve is actually two nerves on opposite sides of the body, injury can occur to one side or the other. Because the area in C3, C4, and C5 is such a small space, typically, injury close to the origin of the nerve results in bilateral injury especially due to internal inflammation. If an injury is on one side of the phrenic nerve or if the injury is slight or disease is mild, there may not be any symptoms. As the progression of disease increases or trauma is great, more symptoms may be noted. Early symptoms of phrenic nerve dysfunction can include fatigue on exertion, exercise intolerance, difficulty breathing when laying down but improved when sitting up, and fatigue. Severe injury can cause a lack of breathing, a medical emergency.

Testing for phrenic nerve damage has several components. A physical examination by listening to lung sounds with a stethoscope is a basic assessment. Physical symptoms of inadequate oxygenation include fatigue, insomnia, headaches, blue lips, finger and toenails, and strained breathing. A history of recent injuries and diseases can provide clues to possible phrenic nerve injury. Also, questions about the physical function such as the ability to perform activities of daily living or severe shortness of breath with exertion and ability to sleep while lying flat are typical questions. Hiccupping is another symptom as these are involuntary spasms of the diaphragm, which can indicate a miscommunication of the phrenic nerve. Lack of function by the phrenic nerve is inadequate or absence of breathing.

Testing can include imaging studies to see if both sides of the diaphragm are working in unison. Further testing includes a phrenic nerve stimulation test that includes an electrical or magnetic situation to the neck as the response of the phrenic nerve is measured. The phrenic nerve dysfunction can be diagnosed if the diaphragm does not respond. Lung function tests can indicate uniform movement of the diaphragm. Transdiaphragmatic pressure measurements is an invasive test that provides more information about diaphragm function.

Some cases of phrenic nerve dysfunction can be treated with noninvasive therapies such as physical therapy to strengthen the diaphragm and to increase engagement of the other muscles involved with breathing, such as the intercostal muscles (between the ribs), scalene muscles of the neck, and abdominal muscles to pull the diaphragm downward. CPAP may be an option for assistance in breathing. Mechanical ventilation is required if breathing is significantly impaired.

Since the phrenic nerve is a peripheral nerve (outside of the central nervous system consisting of the nerves in the brain or spinal cord), there are surgical options that will improve breathing. Removing scar tissue around and in the area of the nerve can release compression on the nerve allowing messages to flow through more efficiently. A nerve graft can be inserted into the phrenic nerve replacing damaged tissue. Rerouting a nerve from another muscle group such as the spinal accessory nerve or intercostal nerves to the phrenic nerve can improve breathing function. Phrenic nerve surgery takes about a year to realize full healing and the nerve regeneration process. Ongoing therapy is required during this recovery time.

Individuals with severe phrenic nerve injury will require mechanical ventilation. This treatment can be disruptive to quality of life, require round-the-clock assistance, and is expensive not only financial but to your overall health and wellbeing. Many individuals thrive on mechanical ventilation, but there is another option which is diaphragm pacing. In this process, electrical stimulation is supplied to the phrenic nerve. The nerve must be intact, but it is not functioning as it should. In the past, this procedure was controversial as it required open surgical techniques. However, improvements in the implantable devices, implant changes to laparoscopic (minimally invasive) surgery, and improved access to the procedure have greatly enhanced this option for everyone.

Diaphragmatic pacing reduces or eliminates mechanical ventilation use. Breathing may be accomplished without a tracheostomy. Speaking with a natural flow, not around your ventilator, is restored. Worrying about becoming detached from the ventilator is eliminated as the diaphragmatic pacer is implanted in your body which eases transfers and movement. External electrical sources are eliminated. Respiratory infections are decreased. Senses of taste and smell are returned. Studies have indicated life expectancy to be enhanced. Quality of life is increased.

Finding options for diaphragmatic pacing has been extended across the United States as well as in many countries. Surgeons who specialize in pulmonary or trauma are adept in the implant technique. The device is FDA-approved. You do not need to travel to a specialty clinic to obtain the device, although you may have to travel to a major medical center nearest to you. Many payors will approve the diaphragmatic pacing as it has so many positive effects.

The decision to opt for a diaphragmatic pacer can be a big one if you are accustomed to your current mechanical ventilator. Surgery and change can always be frightening when you are used to one way of doing things. However, weigh the risks and benefits for you. Educating yourself about the option or even being evaluated for it does not mean a commitment to change. Take each step as you are able and decide as you go. The more you know, the more you will understand which treatment choice is the right choice for you. Nurse Linda

Pediatric Consideration:

Parents are always looking for the best treatments for children. Not only for the present but also for the future. Making the decisions about the treatment of phrenic nerve injury can assist your child in a long and healthy life. Understanding options are critical. Some options will be better for your child’s situation. They might not be the most dramatic option. Work with your healthcare professional to make the best choice.

Children are still growing and developing, even as teens. Choices for your child and their circumstances will be different as each child is unique. Nurse Linda

Linda Schultz is a leader, teacher, and provider of rehabilitation nursing for over 30 years. In fact, Nurse Linda worked closely with Christopher Reeve on his recovery and has been advocating for the Reeve Foundation ever since.

In our community, Nurse Linda is a blogger where she focuses on contributing functional advice, providing the "how-to" on integrating various healthcare improvements into daily life, and answering your specific questions. Read her blogs here.

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The National Paralysis Resource Center website is supported by the Administration for Community Living (ACL), U.S. Department of Health and Human Services (HHS) as part of a financial assistance award totaling $8,700,000 with 100 percent funding by ACL/HHS. The contents are those of the author(s) and do not necessarily represent the official views of, nor an endorsement, by ACL/HHS, or the U.S. Government.