[Research of the chorda tympani nerve in cholesteatoma]

To investigate the ultrastructure of the chorda tympani nerve and analyze the taste and facial nerve functions in patients with cholesteatoma.

1. The tympanic segments of chorda tympani nerves were collected for ultrastructural investigations in 19 cholesteatoma cases who underwent canal-wall-down tympanoplasty. 2. All these patients received a spatial (regional) taste test preoperatively and postoperatively, respectively. Multiple loci were tested in a given order (front of the tongue, foliate papillae, circumvallate papillae, and soft palate). The solutions used in this study were 1.0 mol/L sodium chloride (salty), 1.0 mol/L sucrose (sweet), 0.032 mol/L citric acid (sour) and 0.001 mol/L quinine hydrochloride (bitter). The analyses of variance was used. 3. House-Brackmann facial nerve grading system was conducted to evaluate the facial nerve function preoperatively and postoperatively.

1. There were obvious ultrastructural damages in all the chorda tympani nerves, such as swelling (100%), disarrangement (100%), vacuoles formation of myelin (89%), edema of Schwann cells (95%), intracytoplasmic vacuoles in Schwann cell (89%) and proliferation of the collagen tissue (89%). 2. Two patients complained of change of taste after operation. The analyses of variance showed that the taste function of the ipsilateral side of tympanoplasty were not statistically altered for each stimulus at each locus (P > 0.05). 3. No facial palsy occurred postoperatively.

This research suggested that the chorda tympani nerves underwent ultrastructural changes in patients with cholesteatoma. The dissection of chorda tympani nerve would not affect the taste and facial nerve functions.