CLASSIFICATION AND VARIATION OF PHRENIC NERVE AND ACCESSORY PHRENIC NERVE

The phrenic and accessory phrenic nerves of 180 cadavers of Chinese children were studied.It was found that the highest rate of the accessory phrenic nerve may be up to 73.8%.There is no significant difference between the two sides or the two sexes.The branches of the accessory phrenic nerve vary from 1—4,among which the single branch type is the most common one (76.1%).They have their origin from C_3 to C_(4—6).A few of them may arise from the ansa hypoglossi and supra- scapular nerve.Accessory nerve,therefore,is more related to the brachial plexus rather than the cervical plexus.It was found that there is a close relationship between the origin of the accessory phrenic nerve and its positional and connectional relation with its main trunk.The nerve originated from the brachial plexus and its branches is located at the lateral side of the main trunk and usually forms a lower connection with it.That comes from the cervical plexus and its branches is usually located at the medial side of the main trunk and forms a higher connection (above the subclavian vein,35.9%) with it.The accessory nerve comes from the lower part of the cervical plexus and upper part of the brachial plexux is at first located at the lateral side and,finally,after crossed over anteriorly or posteriorly,joins the medial side of the main trunk (posterior to the subclavian vein, 7.8%).Based upon the number of branches,the phrenic and accessory nerves can be grouped into 5 types.The tirst type that is with the phrenic nerve proper alone,(43.1%) and the second type that is 1 phrenic nerve and 1 accessory phrenic nerve (43.3%) are the standard types in the Chinese.