The function of the chorda tympani in 76 patients treated by tympanoplasty at Tohoku Rosai Hospital was evaluated by electrogustometry (EGM) and salivary flowmetry of the submandibular gland.
1) Nineteen patients, in whom the chorda tympani was touched traumatically or sectioned during ear surgery, complained of dysgeusia postoperatively. EGM revealed a moderately elevated threshold (12.6±14.0dB) in the cases touched traumatically, but a very high threshold (29.2±9.6dB) when the chorda tympani had been sectioned. There was a greater variety of EGM elevations in the patients with trauma only than in those whose nerves were sectioned.
2) Recovery of EGM thresholds within one month after surgery was rare in the touched cases, and did not occur in the sectioned cases.
3) Salivary flow from the submandibular gland was measured in 13 patients pre- and postoperatively. One patient, whose chorda tympani was neither touched nor cut during surgery, showed no diminution of the salivary flow rate. Four of the nine patients whose chorda tympani was touched, showed slight diminution and the remaining five showed severe diminution of the salivary flow rate immediately after surgery. Of the three patients whose chorda tympani was cut, one showed moderate diminution and the other two severe diminution of the salivary flow rate.
4) We found a good correlation between the EGM threshold and the salivary flow rate in each patient.
5) Two of the 14 patients operated on bilaterally developed xerostomia.
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