Taste disturbance after stapes surgery – clinical and experimental study

Abstract

Conclusion: Most of the clinical cases experienced taste disturbance after stapes surgery, and in a few cases this disturbance persisted for a long time. The animal experiment suggested the role of geniculate ganglion (GG) cells in nerve generation. Objectives: To clinically examine taste disorder and its recovery after stapes surgery and experimentally demonstrate a role of GG. Patients and methods: Taste function after preservation of chorda tympani nerve (CTN) in stapes surgery was prospectively investigated with a questionnaire and electrogustometry (EGM). Further, expression of neurotrophic factors in GG after injury of CTN was examined by in situ hybridization histochemistry (ISSH) and RT-PCR. Results: Among the cases, 15/18 (83.3%) were associated with taste disturbance and 6/18 (33.3%) were associated with tongue numbness 2 weeks after surgery; however, the symptoms ceased in 14/18 cases (77.8%). Two weeks after surgery, the EGM threshold was found to be elevated in 15/18 cases (83.3%), while in 10/18 cases (55.6%), it did not decrease until 1 year after surgery. Expression of ISSH and amplified bands of BDNF and GFR increased at 7 and 14 days after nerve injury in ipsilateral GGs and also increased at 7 days on the contralateral side.

Iatrogenic injury of the chorda tympani: a systematic review

“…Patients with a permanent taste disturbance may to a variable extent adapt to this dysfunction over time, and either stop noticing the deficit or stop complaining 22 , 29 (although one patient still reported symptoms 21 years after chorda tympani transection) 7 . This is supported by observations that the recovery of electrogustometry taste threshold is slower than that of subjective taste, 3 , 19 , 22 , 23 and the fact that the chorda tympani supplies only 15 per cent of all taste buds 22 . Recovery is probably also influenced by the extent to which alternative taste pathways, such as the greater superficial petrosal nerve, are recruited 21 …”

“…Other preventive strategies have been discussed in relation to specific procedures or approaches, namely cochlear implantation, 49 , 50 stapes surgery 41 and tympanotomy 7 . In the case of bilateral surgery, several authors have recommended pre-operative taste testing, and waiting for the electrogustometry threshold to be restored to normal on the operated side prior to operating on the contralateral ear 23 , 25 …”

Minimally Invasive Transcanal Endoscopic Ear Surgery

“…Excessive removal of the bone for better visualization of the middle ear (ME) structures can rarely result in subluxation of the incus [49][50][51]. When the posterior part of the bony annulus is removed to visualize the stapes, the chorda tympani nerve (CTN) can be occasionally touched, stretched, manipulated or transected and result in 20-60% of postoperative taste disorders or tongue symptoms [52][53][54][55][56][57]. The existing data indicate that the CTN should be preserved whenever possible, especially if surgery is bilateral [53,54,57,58].…”

Study of 50 Cases of Otosclerosis by Stapedotomy: Our Experience

“…9 The reported rate of postoperative taste disorders or tongue symptoms after stapes surgery is 20-60% in patients whose CTN was manipulated or transected.…”