NERVE LIBRARY · Head, neck & respiratory

Phrenic nerve

Phrenic nerve

Unexplained respiratory weakness or weaning difficulty may prompt specialist assessment of nerve, muscle and NMJ causes.

Roots / nucleus
C3–C5, predominantly C4
Function
Diaphragm motor testing focus
3D protocols
Advanced localization guide

01Course and sensory territory

The diaphragm is the principal inspiratory muscle; the nerve also has related sensory functions.

02Motor supply

Diaphragm.

03Localization clues

Unexplained respiratory weakness or weaning difficulty may prompt specialist assessment of nerve, muscle and NMJ causes.

04Combine the studies

Combine phrenic conduction with diaphragm ultrasound and respiratory assessment; consider respiratory phase and volume conduction.

Related muscles

Diaphragm · C3–C5

Connect to a clinical question

Facial, blink and respiratory studies
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References and further reading

Educational synthesis; independent neuromuscular specialist review is pending. Publication dates and compilation dates are distinct. This is an original teaching synthesis; consult the source for complete methods and criteria.