The nerve is important for breathing because it provides exclusive motor control of the diaphragm, the primary muscle of respiration.

From its origin in the neck, the nerve travels downward into the chest to pass between the heart and lungs towards the diaphragm.

[4] In the cat, horse, ox, and small ruminant the phrenic nerve arises variably from C4-C7.

To confirm the identity of the phrenic nerve, a doctor may gently manipulate it to elicit a dartle (diaphragmatic startle) response.

Bilateral diaphragmatic paralysis or BDP can also be caused by spinal cord injury, motor neuron disease, infection, pneumonia, sarcoidosis, multiple sclerosis, polyneuropathy, myopathy and amyotrophy, cardiac surgery, lung transplantation, or mediastinal tumors.

Hence, patients suffering spinal cord injuries below the neck are still able to breathe effectively, despite any paralysis of the lower limbs.

Brachial plexus injuries can cause paralysis in various regions in the arm, forearm, and hand depending on the severed nerves.