Phrenic Nerve

Question 1

What is the origin of the phrenic nerve?

Answer 1

Arises from anterior rami of C3, C4 & C5, but chiefly from C4

Question 2

What are the phrenic nerves relation to anterior scalene muscle ?

Answer 2

Passes inferomedially across the anterior surface

Question 3

What is the function of the phrenic nerves?

Answer 3

• sole motor innervation to the diaphragm (each nerve supplies ipsilateral half)
• sensory innervation to (a) central part diaphraam (including diaphragmatic pleura) (b) mediastinal pleura (c) pericardium

Question 4

What fibers are found within Phrenic nerves?

Answer 4

Efferent
Afferent
Sympathetic

Question 5

Where do the phrenic nerves begin?

Answer 5

At the superior part of the lateral border of the anterior scalene muscle
- at the level of superior border of the thyroid cartilage

Question 6

CLINICAL : what are the symptoms of phrenic nerve palsy?

Answer 6

paralysis of corresponding half of diaphragm, causing paradoxical movement : affected side moves upward during inspiration

Question 7

CLINICAL : What are the causes of phrenic nerve palsy?

Answer 7

(a) mechanical trauma
(b) compression - due to tumor within chest cavity
(c) Neuropathies

Question 8

What is the blood supply to the phrenic nerves?

Answer 8

pericardiophrenic A. - branch of internal thoracic A.

superior phrenic V. - drains into azygos V.

Question 9

IMAGING : What is a sign of phrenic nerve palsy on X-ray?

Answer 9

Diaphragm will appear elevated