phrenic nerve by ck 10-01-2011

Phrenic Nerve

By: Chaman Lal Karotia

Clinical Neurophysiology Trainee Batch2010-2012

The Aga Khan University Hospital Karachi.

Study Outlines

Introduction to the Cervical Plexus Anatomy of Phrenic NerveAnatomical Course of Phrenic NerveMotor & Sensory Supply of Phrenic NerveClinical Importance of the Muscles innervated

by Phrenic Nerve Injuries to Phrenic NervePhrenic Motor Nerve Conduction Study

TechniquesReferences

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Introduction to Cervical Plexus

• Cervical Plexus is formed by the contribution of anterior primary rami of first four cervical nerve roots (C1,C2,C3,C4)

• It is the looped plexus because four roots are joined to form three loops.


Branches of the Cervical Plexus

Ansa Cervicalis: Superior (C1) & Inferior (C2,3) roots

Lesser Occipital Nerve (C2)

Greater Auricular Nerve (C2,3)

Transverse Cervical Cut. Nerves\ (C2,3)

Supraclavicular Nerve (C3,4)

Deep branches

Phrenic Nerve (C3,4,5)


Origin of Phrenic Nerve

• Phrenic Nerve takes its origin from the Cervical Plexus roots.

• Phrenic nerve is derived from C3, C4 and C5 roots level1

, and there is larger contribution of the anterior primary of C4 .


Subclavian v.

Subclavian a.

Phrenic nerve


Vertebral a.

Phrenic nerve

SCM muscleAnterior scalene

m.

Middle scalene m.

Subclavian a.


Phrenic Nerve Course- It emerges at lateral and anterior border

of the scalenus anterior muscle undercover the sternocleidomastoid muscle (SCM)

- Deep to the prevertebral fascia

- Leaves the neck through the thoracic outlet b/w subclavian artery and vein.

- Crossing in front the origin of the internal thoracic artery, where it joins the pericardiacophrenic branch of this artery .


Subclavian a-v

Anterior and middle scalene

Apex of lung


Phrenic Nerve Course….Cont’d

• Both phrenic nerves runs from c3,c4 and c5 along the anterior scalene muscles.

• The right phrenic nerve passes over the brachiocephalic artery and then crosses the root of the right lung 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.


Phrenic Nerve Course


• The left phrenic nerve passes over the left ventricle and pierces the diaphragm separately.

Phrenic Nerve Course….Cont’d


Innervations of the Phrenic Nerve

Motor Supply:-Scaleni (elevation of upper thorax)Sole motor supply of the diaphragm

Sensory Supply:-PericardiumMediastinal PleuraPleural and peritonealAnd coverings of the central part of the

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1- Motor innervations of the diaphragm

2- Sensory

A-pericardium

B- mediastinal pleura

C- pleural and peritoneal

And coverings of the central part of the diaphragm


Accessory Phrenic Nerve.•Arises as a contribution of C5 to the phrenic nerve or a branch of the nerve to the subclavius C5•Descends lat. to the phrenic nerve•Post. to the subclavian vein•Joins the phrenic n below the first rib to supply the diaphragm.


• Each phrenic nerve contributes predominantly motor fibers to ipsilateral hemidiaphragm muscle which helps in breathing process by pushing up beneath the lungs to control the contraction and expansion during respiration, or breathing.

Clinical Importance Phrenic Innervations


18

Clinical Importance of Diaphragm

• With quite breathing, the diaphragm accounts about 75 to 80% of ventilation.

• The vertical movement of the diaphragm is 1 to 2 cm during quite breathing and 6 to 7 cm during deep breathing.

• Each cm of vertical movement contributes 300 to 400 ml of air during normal breathing.

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Diaphragm……cont’d

• The diaphragm comprise 2 parts: costal and crural portions.

• The costal portion is thinner and the crural portion is thicker.

• Both portions are innervated by the phrenic nerve.

• The costal portion flatten the diaphragm and lift the rib.

• The crural portion causes downward placement of the diaphragm( less effective in breathing.)

10-01-2011 Phrenic Nerve By: CK

• During inhalation, the diaphragm contracts to expand the lungs and allow air to fill the space. During expiration, the diaphragm relaxes and expands against the lungs, causing the lungs to contract and push out the used air.

• The diaphragm may also exert pressure on the abdominal cavity, helping out process such as the excretion of vomit, feces, or urine2.

Clinical Importance of Diaphragm


Phrenic Nerve


Injury To the Phrenic Nerve

• Injury to the phrenic nerve may lead to paralysis of involved hemidiaphragm. Isolated phrenic neuropathy can occur, possibly as variant of acute brachial plexopathy and it is unilateral.

• Bilateral phrenic neuropathy may be caused by GBS4 and amyotrophic lateralized sclerosis, which causes respiratory failure and is a major cause of death in ALS 8.


Injury To the Phrenic Nerve…..Cont’d

• Irritation of the phrenic sensory fibers tends to referred pain to the C4 dermatome territory and may present with hiccups.

• Phrenic nerve conduction techniques have been in use since number of years for evaluation of respiratory failure in neuromuscular disorder.


PHRENIC MOTOR NERVE CONDUCTION STUDY

• RECORDING SITE:-

Diaphragm muscleG1 placed two fingerbreadths above the xiphoid

processG2 placed over the anterior costal margin 16cm

from G1G3 in between recording and stimulating electrodes

• STIMULATION SITE:- Lateral neck: Posterior to the sternocleidomastoid muscle approximately 3cm above the clavicle.

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PHRENIC MOTOR NERVE CONDUCTION STUDY….cont’d


Placement number 1

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Placement number 2


Placement number 3

• Distal Distance:- Variable

• Key Points:-Firm pressure is needed when holding stimulatorIf stimulator is not in correct location , the spinal

accessory or brachial plexus can be stimulated.In thin individuals the diaphragm contraction is

often visualized with hiccups.Difficult study to perform in obese individuals.Avoid the co-stimulation




Contraindication:oDo not perform this study in the intensive care unit in patients who have external pacemaker (risk of current spread to heart)

Caution if an internal jugular catheter, implanted cardiac pacemaker, or cardioverter-defibrillator is nearby.


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Phrenic Nerve By: CK

References

• John Cunningham, Arthur Robinson. Cunningham’s text book of Anatomy. 5th Edition. William Wood and Company;1818:5: 699-701

• Shin J. OH. Clinical Electromyography: Nerve conduction studies second edition; Nerve conduction in focal neuropathies 508.

• Shin J. OH. Clinical Electromyography: Nerve conduction studies second edition; Uncommon nerve conduction studies: techniques and normal values; 165-166;


Thanks


phrenic nerve by ck 10-01-2011

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