Advanced Phrenic Nerve Quiz

Q1. Why can an interscalene brachial plexus block cause temporary hemidiaphragmatic paresis?

• Local anesthetic can spread from the plexus region to the nearby phrenic nerve
• The brachial plexus directly innervates the diaphragm
• The vagus nerve is always intentionally blocked
• The subclavian artery carries anesthetic into the diaphragm

Q2. Why may diaphragmatic irritation produce pain near the shoulder rather than only at the diaphragm?

• The axillary nerve supplies the diaphragm
• The shoulder is innervated directly by the phrenic nerve
• Phrenic afferents and shoulder somatic afferents converge at C3-C5 spinal levels
• The diaphragm physically touches the shoulder

Q3. Why is the phrenic nerve vulnerable during surgery in the lower lateral neck?

• It descends on the exposed anterior surface of anterior scalene near the root of the neck
• It lies within the spinal cord
• It runs inside the thyroid follicles
• It passes through the external jugular vein

Q4. What anatomical relationship distinguishes the phrenic nerve from the vagus nerve at the lung root?

• Phrenic passes anterior and vagus passes posterior to the lung root
• Phrenic passes posterior and vagus passes anterior
• Both pass anterior to the lung root
• Both pass posterior to the lung root

Q5. Why can unilateral phrenic nerve injury cause paradoxical movement of one hemidiaphragm?

• The injured nerve causes permanent contraction of the diaphragm
• The intercostal nerves reverse their motor direction
• The opposite vagus nerve pulls the diaphragm upward
• The denervated hemidiaphragm cannot contract normally against respiratory pressure changes

Q6. Why can injury to cervical spinal cord segments C3-C5 threaten ventilation?

• They form the recurrent laryngeal nerves
• They contain the respiratory muscles themselves
• They contain the spinal motor contributions that reach the diaphragm through the phrenic nerves
• They are the only source of oxygen to the spinal cord

Q7. Why is an accessory phrenic nerve clinically relevant during nerve procedures?

• It supplies only the upper limb
• Variable additional fibers can alter the effect of injury or nerve blockade
• It is present only in the cranial cavity
• It always replaces both main phrenic nerves

Q8. What explains the close clinical relationship between the phrenic nerve and anterior scalene?

• Anterior scalene provides a consistent muscular surface along much of the cervical course
• The nerve originates within anterior scalene fibers
• Anterior scalene is innervated exclusively by the phrenic nerve
• The nerve inserts into the scalene tubercle

Q9. Why does irritation of the central diaphragmatic pleura tend to refer pain differently from irritation of peripheral diaphragmatic pleura?

• Both regions are supplied only by the vagus nerve
• Central regions use phrenic afferents, while peripheral regions mainly use intercostal afferents
• Peripheral pleura is supplied by the facial nerve
• Central pleura has no sensory innervation

Q10. Which statement best integrates phrenic nerve anatomy?

• It is a cervical nerve with a characteristic scalene course that provides essential diaphragmatic motor supply and important thoracic sensory innervation
• It is a cranial nerve supplying the larynx and tongue
• It is a terminal branch of the brachial plexus supplying the upper limb
• It is a sympathetic nerve supplying only thoracic blood vessels