Intraoperative identification of regenerated chorda tympani nerve and its relationship to recovered taste function

This study demonstrated a simple method of repairing the severed chorda tympani nerve and a method of intraoperative identification of regenerated nerves, and evaluated taste function of regenerated nerves. Seven patients who underwent staged tympanoplasty and whose chorda tympani nerve was severed during primary surgery were evaluated. When the chorda tympani nerve was severed during primary surgery, proximal and distal stumps were anastomosed or approximated almost in the original position and fixed with fibrin glue on the temporal muscle fascia used to reconstruct the eardrum by the underlay method. During primary surgery, end-to-end anastomosis was possible in 3 patients but nerve gap defects remained in the other 4 patients. In all 7 patients, regenerated nerves were identified during secondary surgery not in the tympanic cavity but in the submucosal layer of the previously reconstructed eardrum. In all patients, complete or incomplete recovery of taste perception was observed by both the filter paper disk method and electrogustometry, suggesting that the regenerated nerves had actual taste function. From these results, it was concluded that the severed chorda tympani nerve could regenerate in the reconstructed eardrum even if nerve gap defects remained between the proximal and distal cut ends, when repair or approximation of the nerve was properly completed.