Phrenic nerve

Phrenic nerve
Nerve: Phrenic nerve
The phrenic nerve and its relations with the vagus nerve. (Phrenic labeled at upper left.)
Plan of the cervical plexus. (Phrenic labeled at bottom right.)
Latin nervus phrenicus
Gray's subject #210 928
Innervates Diaphragm
From C3-C5 of cervical plexus

The phrenic nerve (Ancient Greek: φρήν phrēn "mind") originates mainly from the 4th cervical nerve, but also receives contributions from the 5th and 3rd cervical nerves (C3-C5) in humans.[1]

The phrenic nerves contain motor, sensory, and sympathetic nerve fibers. These nerves provide the only motor supply to the diaphragm as well as sensation to the central tendon. In the thorax, each phrenic nerve supplies the mediastinal pleura and pericardium.

The contribution of the C5 nerve to the phrenic nerve may be derived from an accessory phrenic nerve. Frequently, it is a branch of the nerve to the subclavius. If present, the accessory phrenic nerve lies lateral to the main nerve and descends posterior and sometimes anterior to the subclavian vein. The accessory phrenic nerve joins the phrenic nerve either in the root of the neck or in the thorax.

Contents

Path

The phrenic nerve descends obliquely with the IJV across the anterior scalene, deep to the prevertebral layer of deep cervical fascia and the transverse cervical and suprascapular arteries. On the left; the phrenic nerve crosses anterior to the first part of the subclavian artery. On the right; it lies on the anterior scalene muscle and crosses anterior to the 2nd part of the subclavian artery. On both sides, the phrenic nerve runs posterior to the subclavian vein and anterior to the internal thoracic artery as it enters the thorax.

Found in the middle mediastinum, both phrenic nerves run from C3, C4 and C5 along the anterior scalene muscle deep to the carotid sheath.

  • The right phrenic nerve passes over the brachiocephalic artery, posterior to the subclavian vein, and then crosses the root of the right lung anteriorly and then leaves the thorax by passing through the vena cava hiatus opening in the diaphragm at the level of T8. The right phrenic nerve passes over the right atrium.
  • The left phrenic nerve passes over the pericardium of the left ventricle and pierces the diaphragm separately.

On both sides the phrenic nerve runs posterior to the subclavian vein and posterior to the internal thoracic artery as it enters the thorax where it runs anterior to the root of the lung and into the pericardium between the fibrous and parietal layers.[1]

Both of these nerves supply motor fibres to the diaphragm and sensory fibres to the fibrous pericardium, mediastinal pleura, and diaphragmatic peritoneum.

The pericardiacophrenic arteries and veins travel with their respective phrenic nerves.

The contribution of the 5th cervical nerve may stem from an accessory phrenic nerve. Most often it is a branch of the nerve to the subclavius and may contain numerous phrenic nerve fibers. If the accessory phrenic nerve is present it lies lateral to the main nerve and descends posterior and occasionally inferior to the subclavian vein. The accessory phrenic nerve connects to the phrenic nerve in the thorax or the root of the neck.[1]

Clinical relevance

Pain arising from structures served by the phrenic nerve is often "referred" to other somatic regions served by spinal nerves C3-C5. For example, a subphrenic abscess beneath the right diaphragm might cause a patient to feel pain in the right shoulder (Kehr's sign). Irritation of the phrenic nerve (or the tissues supplied by it) leads to the hiccough reflex. A hiccough is a spasmodic contraction of the diaphragm, which pulls air against the closed folds of the larynx.

The phrenic nerve must be identified during thoracic surgery and preserved. It passes anterior to the hilum of the corresponding lung, and therefore can be identified easily. The right phrenic nerve may be crushed by the vena cava clamp during liver transplantation.[2] Severing the phrenic nerve, or a phrenectomy,[3] will paralyse that half of the diaphragm. Diaphragm paralysis is best demonstrated by sonography.[4] Breathing will be made more difficult but will continue provided the other nerve is intact.

Fortunately, the phrenic nerve arises from the neck (C3-C5) and innervates the diaphragm, which is much lower. Hence, patients who suffer spinal cord injuries below the neck are still able to breathe effectively, despite any paralysis of the lower limbs.

Additional images

References

  1. ^ a b c Moore, Keith L. (1999). Clinically oriented anatomy. Philadelphia: Lippincott Williams & Wilkins. ISBN 0-683-06141-0. 
  2. ^ Vivian C. McAlister, David R. Grant, Andre Roy, William F. Brown, Linda C. Hutton, David J. Leasa, Cameron N. Ghent, James E. Veitch, and William J. Wall. "Right Phrenic Nerve Injury in Orthotopic Liver Transplantation" Transplantation 55.4 (1993): 826-830.
  3. ^ Hine, Maynard Kiplinger (1975). Review of dentistry: questions and answers (6 ed.). Mosby. pp. 421. ISBN 0801621968. http://books.google.com/books?id=OPJpAAAAMAAJ&q=Phrenectomy+-wikipedia&dq=Phrenectomy+-wikipedia&client=firefox-a&pgis=1. Retrieved May 13, 2008. 
  4. ^ Vivian C. McAlister, David R. Grant, Andre Roy, William F. Brown, Linda C. Hutton, David J. Leasa, Cameron N. Ghent, James E. Veitch, and William J. Wall. "Right Phrenic Nerve Injury in Orthotopic Liver Transplantation" Transplantation 55.4 (1993): 826-830.

External links


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Look at other dictionaries:

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  • Phrenic Nerve Pacing — (PNP) or diaphragm pacing, is the rhythmic application of electrical impulses to the diaphragm, resulting in respiration for patients who would otherwise be dependent on a mechanical ventilator.This concept was originally referred to as… …   Wikipedia

  • phrenic nerve — noun one of a pair of nerves that arises from cervical spinal roots and passes down the thorax to innervate the diaphragm and control breathing • Syn: ↑nervus phrenicus • Hypernyms: ↑spinal nerve, ↑nervus spinalis * * * noun : a nerve of each… …   Useful english dictionary

  • phrenic nerve — the nerve that supplies the muscles of the diaphragm. On each side it arises in the neck from the third, fourth, and fifth cervical spinal roots and passes downwards between the lungs and the heart to reach the diaphragm. Impulses through the… …   The new mediacal dictionary

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  • Phrenic — Phren ic, a. [Gr. ?, ?, the midriff, or diaphragm, the heart, the mind: cf. F. phr[ e]nique.] (Anat.) Of or pertaining to the diaphragm; diaphragmatic; as, the phrenic nerve. [1913 Webster] …   The Collaborative International Dictionary of English

  • Phrenic plexus — Infobox Nerve Name = PAGENAME Latin = plexus phrenicus GraySubject = 220 GrayPage = 985 Caption = The celiac ganglia with the sympathetic plexuses of the abdominal viscera radiating from the ganglia. (Phrenic plexus labeled at upper left.)… …   Wikipedia

  • phrenic crush — 1) damage to the phrenic nerve as a result of trauma. 2) formerly, surgical crushing of a portion of the phrenic nerve. This paralyses the diaphragm on the side operated upon, which is then pushed upwards by the abdominal contents, thus pressing… …   The new mediacal dictionary

  • phrenic — 1. SYN: diaphragmatic. 2. Relating to the mind. * * * phren·ic fren ik adj of or relating to the diaphragm phrenic n PHRENIC NERVE * * * phren·ic (frenґik) 1. pertaining to the diaphragm of the body; called also diaphragmatic. 2 …   Medical dictionary

  • phrenic avulsion — formerly, the surgical removal of a section of the phrenic nerve, which paralyses the diaphragm. The procedure was used as a means of resting a lung infected with tuberculosis but is now obsolete …   Medical dictionary

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