Phrenic Nerve
Description
Name
- Phrenic Nerve
- Diaphragmatic nerve
- Cervical diaphragm nerve
- Nerve to the diaphragm
- Respiratory nerve
- Nerve of the diaphragm
Introduction
- Bilateral, mixed nerve that originates from cranial nerves in the neck
- Descends through the thorax to innervate the diaphragm
- Nerve roots: Anterior rami of C3, C4, C5
- Motor: diaphragm
- Sensory: central part of diaphragm, pericardium, mediastinal part of parietal pleura
Anatomic Course
- Originates from cervical spinal roots C3, C4 and C5 bilaterally
- Arises at the lateral border of the anterior scalene muscle
- Then passes inferiorly over the anterior surface of anterior scalene
- Deep to the prevertebral layer of cervical fascia
- Nerve runs posterior to the subclavian vein
- From here, the course of the phrenic nerve differs between the left and right
Right Phrenic Nerve
- Passes anteriorly over the lateral part of the right subclavian artery
- Enters the thorax via the superior thoracic aperture
- Descends anteriorly along the right lung root
- Courses along the pericardium of the right atrium of the heart
- Pierces the diaphragm at the inferior vena cava opening
- Innervates the inferior surface of the diaphragm.
Left Phrenic Nerve
- Passes anteriorly over the medial part of the left subclavian artery
- Enters the thorax via the superior thoracic aperture
- Descends anterior to the left lung root
- Crosses the aortic arch and bypasses the vagus nerve
- Courses along the pericardium of the left ventricle
- Pierces and innervates the inferior surface of the diaphragm
Motor Functions
- Innervation to the Diaphragm
Sensory Functions
- Central part of the diaphragm, including the surrounding pleura and peritoneum
- Mediastinal pleura
- Pericardium
Clinical Significance
Pathology
- Phrenic nerve injury or paralysis
- Phrenic Neuropathy
- Thoracic or cervical malignancy
- Iatrogenic Injury