If one branch of the phrenic nerve is paralyzed, what is the likely result?

If one branch of the phrenic nerve is paralyzed, what is the likely result?

• A. Complete diaphragmatic paralysis
• B. Loss of function on the affected side
• C. Bilateral diaphragmatic overactivity
• D. No effect

Answer: (B)

Unilateral diaphragmatic control by the phrenic nerves means that injury to the nerve supply on one side leaves the opposite side functioning normally. If one branch is paralyzed, the diaphragm on that side cannot contract, so that half loses its movement and function. The other hemidiaphragm remains active, so breathing is reduced but not abolished. This is why the likely result is loss of function on the affected side.

Unilateral diaphragmatic control by the phrenic nerves means that injury to the nerve supply on one side leaves the opposite side functioning normally. If one branch is paralyzed, the diaphragm on that side cannot contract, so that half loses its movement and function. The other hemidiaphragm remains active, so breathing is reduced but not abolished. This is why the likely result is loss of function on the affected side.