Spinal cord localization and characterization of the neurons which give rise to the accessory phrenic nerve in the adult rat.

This study describes the spinal cord location and morphology of the neurons which give rise to the accessory phrenic nerve in the rat. The results indicate that the cell bodies of the accessory phrenic nerve are a caudal extension of the phrenic nucleus. These cell bodies are located from cervical spinal cord levels C5 to upper C6 and comprise approximately 11% of the total phrenic motoneuron pool. The substantial phrenic contribution indicates the importance of the accessory phrenic nerve in both experimental and clinical manipulations of diaphragm innervation.