Degeneration process of fungiform taste buds after severing the human chorda tympani nerve--observation by confocal laser scanning microscopy.
OBJECTIVE
To elucidate the degeneration process of fungiform taste buds after severing the chorda tympani nerve (CTN) by confocal laser scanning microscopy in vivo.


METHODS
Prospective study.


METHODS
University hospital.


METHODS
Seven consecutive patients whose CTN was severed during tympanoplasty for middle ear cholesteatoma.


METHODS
Diagnostic.


METHODS
Preoperative and postoperative gustatory functions were assessed by electrogustometry (EGM). An average of 10 fungiform papillae (FP) in the midlateral region of the tongue were periodically observed, and the number of taste buds was counted using a confocal laser microscope. Among them, 2 to 3 reference FPs were selected based on the typical form of the FP or characteristic arrangements of taste pores. Observation was performed before surgery, 1 or 2 days after surgery, 2 or 3 times a week until 2 weeks after surgery, once a week between 2 and 4 weeks, and every 2 to 4 weeks thereafter until all taste buds had disappeared.


RESULTS
EGM thresholds showed no response within 1 month after surgery in all patients. The initial change in the degeneration process was the disappearance of taste pores. The surface of taste buds became covered with epithelium. Finally, taste buds themselves atrofied and disappeared. The time course of degeneration differed depending upon individuals, each FP, and each taste bud. By employing the generalized linear mixed model under the Poisson distribution, it was calculated that all taste buds would disappear at around 50 days after surgery.


CONCLUSIONS
Confocal laser scanning microscopy was useful for clarifying the degeneration process of fungiform taste buds.
*Department of Otolaryngology, Head and Neck Surgery, Faculty of Medicine, †Research and Education Program for Life Science, and ‡Department of Anatomy, Faculty of Medicine, University of Fukui, Japan.
Takehisa
T
Saito
Tetsufumi
T
Ito
Yumi
Y
Ito
Yuji
Y
Kato
Yasuhiro
Y
Manabe
Norihiko
N
Narita
D000328:Adult; D000368:Aged; D018424:Cholesteatoma, Middle Ear / Q000601:surgery*; D002814:Chorda Tympani Nerve / Q000293:injuries*; D005260:Female; D006801:Humans; D007431:Intraoperative Complications / Q000473:pathology*; D018613:Microscopy, Confocal; D008875:Middle Aged; D009410:Nerve Degeneration / Q000209:etiology / Q000473:pathology*; D011184:Postoperative Period; D011446:Prospective Studies; D013649:Taste / Q000502:physiology; D013650:Taste Buds / Q000473:pathology*; D014059:Tongue / Q000294:innervation; D014433:Tympanoplasty / Q000009:adverse effects*