SELECTIVE RESECTION OF THE PHRENIC-NERVE ROOTS IN RABBITS .1. CARTOGRAPHY OF THE RESIDUAL INNERVATION

Partial unilateral diaphragmatic paralysis remains poorly understood. This study evaluates the residual innervation of the diaphragm after s elective resection of one or several roots of the right phrenic nerve in rabbits. Forty-seven animals were operated on according to five roo t resection modalities. Seven animals served as control. Eight weeks a fter surgery, the different regions of each hemidiaphragm were analyze d. Electromyographic activity was measured during quiet inspiration an d the following histomorphometric parameters were studied: mean fiber area, fiber area dispersion, and ratio large diameter over small diame ter. The results obtained from the two measurements were similar. When the accessory phrenic nerve was spared, the crural diaphragmatic regi on was preserved; denervation was encountered in anterior and lateral parts of the hemidiaphragm. When the highest root of the right phrenic nerve was resected, denervation was limited to the sternal region. Wh en resection of the two highest roots was performed, partial denervati on was observed in each region, with residual innervation in the poste rior hemidiaphragm. When resection of both the lowest roots was perfor med, denervation was maximal in the costal region; sternal region rema ined intact. No contralateral innervation was observed. We conclude th at in rabbits: 1) resection of a single root of the phrenic nerve pres erves consistent residual innervation. 2) somatotopy of the diaphragm innervation follows an anteroposterior distribution. (C) 1997 Elsevier Science B.V.