Overview
The phrenic nerve is a bilateral nerve that consists of the cervical nerves C3, C4 and C5. It carries sensitive fibers for the pericardium, pleura and peritoneum as well as motor parts that supply the diaphragm. Due to its function, the phrenic nerve is often associated with hiccups (singultus) and breathing difficulties that can occur when the diaphragm is paralyzed.
Nerve course
After the cervical nerves C3, C4 and C5 have joined together on the right and left sides to form the phrenic nerve, the latter runs downwards along the anterior scalene muscle, a lateral neck muscle. The course of the phrenic nerve is lateral to the vagus nerve. The phrenic nerve then runs between the vena cava and the subclavian artery into the thoracic cavity.
The further course is always along the sides of the mediastinum, a body cavity delimited by connective tissue plates, which lies between the two lung wings, down towards the diaphragm. It is important that the phrenic nerve is located towards the abdomen, towards the blood vessels and bronchial tubes leading to the lungs. When the diaphragm is reached, the left phrenic nerve passes through it together with the esophagus and the right nerve passes through the inferior vena cava. After the nerve has supplied the diaphragm with motor and sensitive fibers, it gives further sensitive branches, the so-called rami phrenicoabdominales, to innervate the peritoneum in the upper abdomen and then ends in its course. On its way, the phrenic nerve regularly releases further sensitive nerve branches for nerve supply of the pericardium and the lung skin.
Causes
One cause that can lead to irritation of the phrenic nerve is increased pressure in the abdomen, which nevertheless also affects the diaphragm. This can occur during a laparoscopy with keyhole technique or self-inflicted by a too fast and luxuriant food intake or similar. Behind damage to the phrenic nerve, which can be accompanied by paralysis of the diaphragm, there can be direct damage to the nerve, for example through surgical intervention in the thorax, in which the nerve is damaged or severed.
On the other hand, the phrenic nerve can lose its function through inflammation. In this context, the Guillain-Barré syndrome, multiple sclerosis and pathogens such as Borrelia bacteria should be mentioned. In case of inflammation, the symptoms can be reduced by treating the cause. However, a hundred percent restoration of the initial state cannot always be guaranteed.
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