Advanced Phrenic Nerve Quiz

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

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

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

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

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

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

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

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

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

• 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
• The injured nerve causes permanent contraction of the diaphragm

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

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

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

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

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

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

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

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

Q10. Which statement best integrates phrenic nerve anatomy?

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