Prevalence of Xerostomia Among Cochlear Implant Recipients

The chorda tympani nerve provides parasympathetic innervation to the submandibular gland and is pivotal in basal salivary production.¹ Adequate salivation is critical to oral health, and gland hypofunction may lead to xerostomia, increasing the risk of dental disease.² In cochlear implant (CI) surgery, the chorda tympani nerve is at risk when opening the facial recess and may intentionally or unintentionally be sacrificed. Although dysgeusia is discussed,³ to our knowledge, there is a lack of literature regarding the association of middle ear surgery with salivation. Furthermore, the effect of either injury or sacrifice of the chorda tympani in the CI population is not well characterized. The purpose of this study was to calculate the prevalence of xerostomia among a population of adult CI recipients.

The study was a cross-sectional email survey sent to CI recipients from the Johns Hopkins Listening Center (Baltimore, Maryland). The study was approved by the Johns Hopkins institutional review board, and a waiver of informed consent was approved. Inclusion criteria included a history of a CI and age 18 years or older as of January 1, 2017. Exclusion criteria included age younger than 18 years, no email address, or being deceased. Demographic data, CI surgical history, comorbidities, medications, and dental health were self-reported. Xerostomia was calculated using the Xerostomia Inventory, a validated questionnaire.⁴ The survey was distributed via Qualtrics, and returned data were anonymous.

Percentages and means with standard deviations were calculated using Microsoft Excel, version 2016. A logistic regression was performed with Stata, version 14 (StataCorp), and statistical significance was set at P < .05. The primary outcome was the prevalence of xerostomia among CI recipients. In Thompsen et al,⁴ participants with a history of radiotherapy scored 30 or greater compared with controls who did not undergo irradiation (mean score, 20).⁴ Therefore, in this study, 30 or greater was defined as having xerostomia.

A total of 1278 surveys were sent, with a response rate of 21.8% (Figure). One participant was excluded from analysis, as less than 50% of the survey was completed. Characteristics of the study population are presented in the Table.

The prevalence of xerostomia was 20.5%. The mean (SD) Xerostomia Inventory score for all participants was 23.0 (8.1), 35.6 (5.3; range 30-50) for those with xerostomia, and 19.7 (4.9; range 10-29) for those without. After modeling, a history of revision CI surgery (odds ratio, 3.35; 95% CI, 1.36-8.24) and a disease associated with xerostomia (odds ratio, 3.02; 95% CI, 1.40-6.57) increased the risk. More participants with xerostomia reported poor dental health (Table).

In this study, one-fifth of participants self-reported symptoms consistent with xerostomia. Jeppsen et al⁵ found a decrease in salivary production in unilateral CI recipients; however, this was not associated with symptomatic reports of xerostomia. As they discussed, xerostomia may occur in those with bilateral implants. Our study included almost a third of bilateral recipients, which may explain the prevalence. However, the prevalence reported in our study may be overestimated, as this sample did consist of more participants with known xerostomia risk factors, including age and medications.⁶ Additionally, our low survey response rate may have affected this number.

As expected, having a history of a disease associated with xerostomia increased the odds of having xerostomia. It is interesting that a history of revision CI surgery remained an independent risk factor. Revision surgery may put chorda tympani at risk because of prior or needed exposure of the nerve, as well as possible sacrifice during revision. The true status of chorda tympani in these participants was unknown, as data were collected anonymously and could not be traced back to operative reports.

Additional research is needed to assess the attributable risk of CI surgery on the development of xerostomia and subsequent dental disease. Given the potential for morbidity and the unknown contribution of chorda tympani loss, it is wise to consider strategies that identify and preserve the chorda tympani during initial and revision CI surgeries.

Accepted for Publication: August 1, 2020

Corresponding Author: Heather M. Weinreich, MD, MPH, Department of Otolaryngology–Head and Neck Surgery, University of Illinois, Chicago, 1855 W Taylor St, MC 648, Chicago, IL 60612 (hweinre1@uic.edu).

Published Online: October 15, 2020. doi:10.1001/jamaoto.2020.3409

Author Contributions: Dr Weinreich had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Weinreich, Ostrander, Pross, Francis.

Acquisition, analysis, or interpretation of data: Weinreich, Ostrander, Pross, Dasgupta.

Drafting of the manuscript: Weinreich, Ostrander, Dasgupta.

Critical revision of the manuscript for important intellectual content: Weinreich, Ostrander, Pross, Francis.

Statistical analysis: Weinreich, Pross, Dasgupta.

Administrative, technical, or material support: Pross, Francis.

Supervision: Francis.

Conflict of Interest Disclosures: Dr Francis sits on the surgical advisory boards for Med-El, Advanced Bionics, and the Cochlear Corporation. No other disclosures were reported.

Meeting Presentations: This work was presented as a podium presentation at the 2019 American Ontological Society Combined Otolaryngology Spring Meeting; Mary 5, 2019; Austin, Texas.