Trigeminal and taste sensations of the tongue after middle ear surgery.

Objective: To establish clinical tests for measurement of trigeminal sensitivity on the human tongue and objectively assess changes in oral trigeminal sensitivity and taste ability after chorda tympani nerve (CTN) injury.

Methods: Prospective study. Methods: University hospital. Methods: One-hundred and twenty-six patients with unilateral middle ear diseases who underwent primary middle ear surgery. Methods: Trigeminal sensation was measured each operated side as well as nonoperated side both before and 14 days after surgery using 3 kinds of tests: Semmes-Weinstein sensory test (SW test), 2-point discrimination test, and the electrostimulator test. Taste function was assessed with electrogustometry (EGM) similarly.

Results: The patients which the CTN was not touched (n = 6) showed no differences between preoperative and postoperative thresholds in any tests. In the patients with sectioned CTN (n=30), postoperative thresholds on the operated side were significantly higher than preoperative thresholds on the electrostimulator test, 2-point discrimination test, and EGM. In the patients with manipulated but not sectioned CTN (n = 90), postoperative thresholds were significantly higher than preoperative thresholds on the electrostimulator test and EGM. The patients with manipulated but not sectioned CTN and abnormal EGM postoperative thresholds (n = 48) showed that postoperative thresholds were significantly higher than preoperative thresholds in all tests.

Conclusions: These findings suggest that the electrostimulator test was most useful to objectively assess small changes of trigeminal sensation among the 3 tests. The finding that trigeminal sensitivity of the tongue deteriorated on the operated side after CTN injury suggests that CTN function affected both taste sensation and trigeminal sensation of the tongue.