Phrenic Nerve

What is the phrenic nerve?

The phrenic nerve controls your diaphragm (the large dome-shaped muscle between your abdominal and chest cavities). It’s essential to breathing. Your nerve sends signals that cause your diaphragm to contract (become thicker and flatter). This movement gives your lungs room to expand and take in air (inhalation). After this, decreased firing of your phrenic nerve relaxes your diaphragm, and your lungs recoil, pushing out air (exhalation) and becoming smaller.

What is the purpose of the phrenic nerve?

Your phrenic nerve plays a critical role in your respiratory system to aid breathing. It’s the only nerve in your nervous system that provides motor (movement) function to your diaphragm. It sends signals that cause your diaphragm to expand and contract. These movements allow your lungs to inhale and exhale air.

Your phrenic nerve also provides touch and pain sensory information to your:

• Diaphragm and diaphragmatic pleura (thin tissue covering the upper part of your diaphragm).
• Mediastina pleura (thin tissue covering the chest cavity between your lungs).
• Pericardium (sac covering your heart).
• Peritoneum (thin tissue covering your abdominal organs).

Where is the phrenic nerve?

Your phrenic nerve connects to the C3 to C5 cervical (neck) nerve roots of your spinal cord. The nerve:

• Starts at the C3 vertebral level, the part that aligns with your jaw and helps you bend and rotate your neck.
• Connects to the C4 and C5 vertebral levels in your neck, below the C3 vertebra. A spinal cord injury between C3 and C5 can cause paralysis, making a person unable to breathe on their own.
• Travels through your neck and chest (thorax) and past your heart and lungs to reach your diaphragm.

What are the left and right phrenic nerves?

You have a left and right phrenic nerve. Each performs the same function. The left phrenic nerve sends signals to the left part of your diaphragm, while the right phrenic nerve controls your right side.

What conditions and disorders affect the phrenic nerve?

Damage to a phrenic nerve can lead to diaphragm weakness or paralysis. A paralyzed diaphragm affects your lungs’ ability to exchange air.

Depending on the location of phrenic nerve damage, paralysis may affect one side of your diaphragm (unilateral) or both sides (bilateral). People with severe bilateral diaphragm paralysis need mechanical ventilation to breathe.

What causes a paralyzed diaphragm?

Causes of diaphragm paralysis include:

• Autoimmune and inflammatory diseases like Guillain-Barré syndrome and neuralgic amyotrophy (Parsonage-Turner syndrome).
• Birth defects or trauma to an infant during labor and delivery.
• Cervical spondylosis (breakdown of bone and other spinal tissues in your neck).
• Complications from neck or chest surgeries, such as coronary artery bypass surgery.
• Other neurological disorders like amyotrophic lateral sclerosis (Lou Gehrig’s disease) and multiple sclerosis.
• Spinal cord injuries, including from trauma.
• Spine tumors, lung cancer and metastatic cancers.

What are the signs of a paralyzed diaphragm?

A person with unilateral diaphragm paralysis may not have significant symptoms (with some causes like neuralgic amyotrophy, there may be shoulder pain and arm weakness on their affected side). Signs of a bilateral paralyzed diaphragm include:

• Shortness of breath, especially when lying down flat, or when immersed (as in a swimming pool).
• Recurrent pneumonia.
• Sleep apnea, difficulty sleeping or excessive daytime fatigue.
• Weak cries (in an infant or child).

What role does the phrenic nerve have with hiccups?

Sometimes, an irritated phrenic nerve causes persistent hiccups that last for days or even a month or longer. Surgical procedures, tumors and other issues may irritate your phrenic nerve, bringing on persistent hiccups.

Persistent hiccups can be uncomfortable and annoying. They can affect your ability to talk, sleep and eat. Treatments for persistent hiccups include:

• Oral medications, including chlorpromazine.
• Nerve blocks to stop nerve signals that trigger diaphragm contractions.
• Surgery (phrenicotomy) to sever a phrenic nerve, permanently paralyzing one side of your diaphragm.

How can I protect my phrenic nerves?

These steps can keep your nervous system healthy:

• Exercise and eat a nutritious diet to achieve and maintain a healthy weight.
• Find healthy ways to manage stress, like meditation or listening to music.
• Get plenty of sleep.
• Manage conditions like diabetes and high blood pressure that can damage nerves.
• Seek help to quit smoking. Using tobacco restricts blood flow to nerves.

When should I talk to a doctor?

You should call your healthcare provider if you experience:

• Shortness of breath or difficulty breathing, especially if lying flat requires more pillows behind your head makes it easier to breathe.
• Unexplained shoulder pain, especially with arm weakness.
• Signs of sleep apnea, such as snoring and extreme fatigue.
• Hiccups that don’t go away easily.

A note from Cleveland Clinic

Your phrenic nerves are critical to breathing. They cause your diaphragm to become smaller or larger so your lungs can inhale and exhale air. Damage to a phrenic nerve can lead to a paralyzed diaphragm. You may experience shortness of breath and sleep problems. People who have severe damage to their phrenic nerve may need a mechanical ventilator to breathe.