Accessory Phrenic Nerve

nervus phrenicus accessorius

The accessory phrenic nerve is an inconstant nerve arising from C5 (occasionally also C4) that joins the main phrenic nerve (C3-C5) below the level of the clavicle or in the thorax. It is present in approximately 30-75% of individuals. When present, it must be identified and divided during thoracoscopic or open phrenic nerve section to achieve complete ipsilateral diaphragm paralysis for lung volume reduction or phrenic nerve crush procedures.

Region: Neck

Clinical Relevance

Clinical Notes

The accessory phrenic nerve is clinically relevant in procedures involving the phrenic nerve. Phrenic nerve palsy from brachial plexus birth injury may spare diaphragm function if a large accessory phrenic nerve is present, complicating the interpretation of diaphragm dysfunction in these patients. During thoracoscopic phrenic nerve pacing implantation, the accessory phrenic nerve must be identified and included in the electrode placement. In cervical approaches to the phrenic nerve, the accessory branch passing posterior to the subclavian vein may be missed if not specifically sought.

Pathology

Common Injuries & Conditions

Accessory Phrenic Nerve Preservation in Phrenic Nerve Surgery

Phrenic nerve procedures including diaphragm pacing, phrenoplasty, and nerve crush for hiccups must identify and include any accessory phrenic nerve arising from C5; failure to address the accessory branch leaves residual diaphragm function that may defeat the surgical aim.