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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 5  |  Issue : 1  |  Page : 24-28

Middle ear surgery and taste dysfunction: Prevalence and determinants


1 Department of ENT, INHS Asvini, Mumbai, India
2 Department of ENT, AFMC, Pune, Maharashtra, India

Date of Submission01-Jun-2020
Date of Acceptance05-Feb-2021
Date of Web Publication03-Jul-2021

Correspondence Address:
Dr. Renu Rajguru
Department of ENT, INHS Asvini, Mumbai - 400 005, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/aiao.aiao_9_20

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  Abstract 


Introduction: Middle ear surgery involves handling of chorda tympani nerve. Patients after middle ear surgery may complain of taste disturbance and lingual numbness. Clinical testing of taste is not a test which is routinely performed in ENT Clinics. Consequently, the prevalence of postoperative taste dysfunction remains largely unknown. Aim: The aim of this study is to determine taste function in patients before and after middle ear surgery with a clinically suitable test and to find out the factors which determine the extent of taste dysfunction. Setting: The study design involves tertiary care hospital. Materials and Methods: This was a prospective observational study conducted from October 2017 to October 2019 in the ENT department of a tertiary care hospital. Hundred patients undergoing middle ear surgery fulfilling the inclusion criteria were considered as the study population. All patients underwent assessment of taste thrice: the day before the operation, seventh postoperative day and at 3 weeks after surgery by administering three kinds of taste testing solutions for testing sour, sweet, and salty taste in varying concentrations. Scoring was done and tabulated followed by statistical analysis. Results: Nineteen (19.0%) participants had taste disturbance after undergoing middle ear surgery. The factors which influenced whether injury to the chorda tympani causes tastes dysfunction included the age of the patient, extent of the injury, type of middle ear disease, and the type of surgery done. Conclusions: Patients undergoing middle ear surgery may exhibit taste dysfunction. However, in the majority of the cases, this goes unnoticed by the patient and is transitory. The sense of taste has a great capacity to compensate after partial dysfunction. However, preoperative information to the patients regarding the existence of potential taste disturbance, and that it is transitory usually, but is untreatable if persistent, may prevent any medicolegal problems later.

Keywords: Chorda tympani nerve, middle ear surgery, taste assessment


How to cite this article:
Patil B, Rajguru R, Raghavan D, Singh I, Naga R. Middle ear surgery and taste dysfunction: Prevalence and determinants. Ann Indian Acad Otorhinolaryngol Head Neck Surg 2021;5:24-8

How to cite this URL:
Patil B, Rajguru R, Raghavan D, Singh I, Naga R. Middle ear surgery and taste dysfunction: Prevalence and determinants. Ann Indian Acad Otorhinolaryngol Head Neck Surg [serial online] 2021 [cited 2021 Dec 4];5:24-8. Available from: https://www.aiaohns.in/text.asp?2021/5/1/24/320579




  Introduction Top


Oral sensations (i.e., taste, oral somatosensation, retronasal olfaction) are integrated into a composite sense of flavor, which guides dietary choices with long-term health impact.[1] Gustation consists of the perception of sensations that are usually described as having one or more basic taste qualities: sweet, salty, sour, and bitter. The gustatory system's key function in guiding food intake makes it important to health and the prevention of chronic diseases and conditions.[2] Patients after middle ear surgery may complain of taste disturbance and lingual numbness.[3] One of the common reasons for alteration in taste sensation is injury to chorda tympani nerve (CTN). As most of the ENT surgeons consider hearing improvement and uptake of neotympanum as the most important postoperative outcome measure, postoperative taste disturbance does not draw much attention. Iatrogenic CTN injury, accidental or deliberate, is a well-recognized complication of middle ear surgery.[4] The overall reported prevalence of related symptoms after middle ear surgery is between 15% and 22%.[5] Various operative procedures that require the annulus to be elevated risk damaging the nerve by a variety of mechanisms including transection, stretching, ischemia, thermal injury, or excessive handling. Stretching is a common mechanism which can injure CTN, such as, when raising a tympanomeatal flap during myringoplasty or while manipulating CTN to place the piston during stapedotomy, or while removing disease in tympanoplasty and mastoidectomy. Various authors have reported thermal injury from bone drilling or diathermy and drying from the microscopic heat or from prolonged exposure without moistening.[6]

We conducted this study to determine taste function in patients before and after middle ear surgery with a clinically suitable test at the ENT department of a tertiary care hospital with an aim to identify the factors that determine the extent of taste dysfunction.


  Materials and Methods Top


It was a prospective observational study conducted over a period of 2 years from October 2017 to October 2019 in the ENT department of an academic tertiary care hospital. A sample size comprising of 100 patients undergoing middle ear surgery in the age group of 18–60 years of both sexes consenting to participate in the study were included. Patients with systemic diseases which might affect taste perception such as Endocrine disturbances (Thyroid gland dysfunction, Diabetes mellitus, Cushing's syndrome), systemic diseases (Chronic renal failure, liver cirrhosis), psychological disturbances such as depression, infectious diseases (Leprosy, Syphilis), neurological defects, previous surgery on the tongue, salivary gland or any other surgery that were likely to alter taste were excluded from the study. Patients with preexisting tongue lesions such as Glossitis, Xerostomia, malignancy, and post-radiotherapy status or patients who underwent middle ear surgery in past were also excluded from this study. Institutional ethical committee clearance was taken.

After taking informed written consent and a thorough general and otological examination, all patients underwent assessment of taste thrice: The day before the operation, seventh postoperative day, and at 3 weeks postsurgery. Three kinds of taste testing solutions were prepared, with varying degrees of concentration, as follows: sour (Citric Acid at 0.01, 0.05 and 0.25 g/ml)), sweet (Dextrose at 0.05, 0.10 and 0.25 g/ml), and salty (Sodium Chloride at 0.009, 0.015 and 0.03 g/ml). The lowest concentration solution for each taste type that could be identified correctly by more than half of the healthy participants was used, and the highest concentrations could be identified correctly by all of the participants.[3] The patient had to rinse his/her mouth after each test with plain water before the administration of the next taste solution. Scoring was done to indicate when each patient recognized a taste testing solution correctly. Scores for successful identification are as given in [Table 1].
Table 1: Scores for successful identification of taste solutions

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The patients were divided into three grades depending on the degree of intraoperative manipulation of the CTN as given in [Table 2].
Table 2: Grades of chorda tympani nerve injuries/degree of manipulation of chorda tympani nerve

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The result of the study was analyzed in terms of patients' taste results and intraoperative findings, focusing on the grade of CTN injury.

Statistical methods

The score for identification of taste was considered as the outcome variable. Age, the grade of nerve injury, disease, and type of surgery were considered as explanatory variables. The statistical analysis of taste disturbance after middle ear surgery was performed using Chi-square test. Thus, statistics can be evaluated by comparing the actual value against a critical value found in a Chi-Square distribution.

Descriptive analysis was carried out by mean and standard deviation for quantitative variables, frequency, and proportion for categorical variables. Non-normally distributed quantitative variables were summarized by the median and interquartile range (IQR). For non-normally distributed Quantitative parameters, Medians and IQR were compared between study groups using the Kruskal–Wallis test (>2 groups).

The change in the quantitative parameters, before and after the intervention was assessed by Kendall's W test (In case of comparison across more than 2 time periods).

To conclude the hypothesis with 95% confidence, P < 0.05 was considered statistically significant. IBM SPSS version 22 was used for statistical analysis.


  Results Top


Among the study population, 8 patients (8%) were aged up to 20 years, 45 (45%) between 21 and 40 years and 47 (47%) were aged between 41 and 60 years, the average age was 40.08 years. Forty-three (43%) participants were males and the remaining 57 (57%) participants were females. The disease distribution showed that 88 (88%) participants had chronic otitis media mucosal, 8 (8%) had chronic otitis media squamous, and the remaining 4 (4%) had Otosclerosis. Sixty-one (61%) participants had undergone cortical mastoidectomy with tympanoplasty, 24 (24%) had undergone tympanoplasty, 11 (11%) had undergone intact canal wall mastoidectomy with tympanoplasty, and the remaining 4 (4%) had undergone stapedotomy. Grade 1 nerve injury was found in 54 (54%) patients, 41 (41%) had grade 2 nerve injury and the remaining 5 (5%) had grade 3 nerve injury. Nineteen (19.0%) participants had taste disturbance after undergoing middle ear surgery.

The median score for taste identification before surgery was 3(IQR 3–3) in all age groups. The median score for postoperative 7th day and 3 weeks post surgery in all the age groups was 3(IQR 3–3) and was statistically significant (P = 0.003) [Table 3].
Table 3: Comparison of pre- and post-operative score for identification of taste across grade of nerve injury (n=100)

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In the age group up to 20 years one out of eight patients (12.50%) had taste disturbance, in the age group 21–40 years six out of 45 patients (13.33%), and in the age group 41–60 years, 12 out of 47 patients (25.53%) had taste disturbance. The prevalence of taste disturbance across various age groups was statistically significant (P < 0.001) [Table 4].
Table 4: Prevalence of taste disturbance in the study population (n=100) after undergoing middle ear surgery

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Taste disturbance was present in three out 54 patients (5.55%) with Grade 1 injury, in 11 out 41 patients (26.82%) with Grade 2 injury, and in all five patients (100%) who sustained Grade 3 injury. The incidence of taste dysfunction across various grades of nerve injuries was statistically significant (P < 0.001) [Table 5].
Table 5: Descriptive analysis of grade of nerve injury and frequency of taste disturbance in the study population (n=100) after undergoing middle ear surgery

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Using middle ear disease as a variable, we found postoperative taste disturbance in 11 out of 88 (12.50%) patients with COM mucosal disease, in five out of eight (62.50%) patients with COM squamous disease, and in three out of four (75.0%) patients with otosclerosis. The incidence of taste dysfunction with respect to various middle ear diseases was statistically significant (P < 0.001) [Table 6].
Table 6: Prevalence of taste disturbance with respect to middle ear diseases in the study population (n=100) after undergoing middle ear surgery

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Post-operative taste disturbance was experienced by six out of 61 (9.83%) patients who underwent cortical mastoidectomy with tympanoplasty, five out of 24 (20.83%) patients who underwent tympanoplasty, five out of 11 (45.45%) patients who underwent intact canal wall mastoidectomy with tympanoplasty, and three out of four (75.0%) patients who underwent stapedotomy. The incidence of taste dysfunction with respect to various middle ear surgeries was statistically significant (P < 0.028) [Table 7].
Table 7: Prevalence of taste disturbance with respect to the type of surgery done in the study population (n=100) after undergoing middle ear surgery

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  Discussion Top


In the present study, 19 (19.0%) participants had taste disturbance after undergoing middle ear surgery. McManus LJ et al. reported that at least 15%–22% of patients experience symptoms, mostly changes in taste and dryness of the mouth, following middle ear surgery.[5] Similar results were reported by Choi et al. who observed 15% taste disturbance in their study population which is slightly lesser than the present study.[7]

In our study, we found that taste disturbance in up to 20 years of age group was least (12.5%) and it was highest (25.53%) in patients in the age group 41–60 years. Age plays an important role in the recovery of taste function after middle ear surgery. In a study conducted by Terada et al. on patients with chronic otitis media, the postoperative threshold of the >60 years age group tended to be higher than that of the <60 years age group.[8] Nin et al. also reported that younger patients tend to have a higher ability to recover taste and CTN function as compared with middle-aged or older patients.[9] They also found that activity of growth factors is elevated in the geniculate ganglion after injury of CTN in an animal experiment. So younger age favors preservation of taste post middle ear surgery.

We also found that Grade 3 injury resulted in maximum (100%) taste disturbance as compared to Grade 1 (5.55%) and Grade 2 (26.82%) injury. According to a study by Mueller et al. taste dysfunction occurred in 47% of patients with minor manipulation of the CTN, and major manipulation resulted in taste disturbance in 56% of patients.[6] Choi et al. also classified CTN status into the cut, manipulated, and intact groups. The taste did not differ significantly between the three groups for 6 months postoperatively. The cut group consistently showed the highest rate of taste disturbance, but there was no statistical significance.[7]

In the current study, patients with otosclerosis were found to have maximum (75%) postoperative taste disturbance and patients with COM squamous (62.50%) had more postoperative taste disturbance as compared to COM mucosal (12.50%). In a similar study done by Sakagami et al., the rate of recovery of the electrogustometry (EGM) threshold to normal at two weeks after surgery was significantly lower in patients with non-inflammatory diseases (6/20 or 30.0%) than in COM patients (23/35 or 62.9%) or cholesteatoma patients (19/28 or 67.9%; P = 0.015 and 0.008, respectively).[10] Thus, the patients with non-inflammatory diseases had postoperative symptoms and elevation of the EGM threshold more frequently than the patients with inflammatory diseases. Another study report by Sakaguchi et al. showed that none of the patients with COM or cholesteatoma complained of subjective taste disturbance before surgery despite elevated EGM thresholds.[11] This may be because the disease process of cholesteatoma renders the nerve hypofunctional. Kiverniti and Watters in their study to determine the immediate and long-term taste effects of CTN sacrifice in patients undergoing open cavity mastoidectomy found that only 24.3% were aware of taste disturbance immediately after surgery, while 8.7% reported persistent taste disturbance.[12]

In our study, stapedotomy resulted in the highest incidence (75.0%) of postoperative taste disturbance. Intact canal wall mastoidectomy with tympanoplasty also resulted in a higher incidence (45.45%) of postoperative taste disturbance as compared to cortical mastoidectomy with tympanoplasty (11.47%), whereas in tympanoplasty incidence of taste disturbance was 20.83%. In this study, the incidence of taste dysfunction in tympanoplasty was higher as this surgery is usually done by junior residents as a part of their teaching curriculum, resulting in the handling of CTN while checking ossicular chain intactness and mobility. Clark and O'Malley in their study concluded that a significantly higher incidence of taste disturbance follows myringoplasty and stapedectomy than for procedures, in which the initial diagnosis was cholesteatoma, regardless of the extent of injury sustained by the nerve.[13] They concluded that iatrogenic CTN injury in surgery for cholesteatoma results in less postoperative taste disturbance than that for otosclerosis, maybe because of the disease process of cholesteatoma renders the nerve hypofunctional. Gopalan et al. in their study observed that patients with otosclerosis complain of taste disturbance after surgery more often than the patients with chronic middle ear diseases.[3] According to Gurung et al., amongst the different types of middle ear surgeries, the frequency of taste disturbances was 6/153 (3.9%) in the underlay myringoplasty group, 3/81 (3.7%) in the mastoidectomy group, 1/14 (7.1%) in the stapedectomy group, 0/7 (0%) in tympanoplasty group and 1/5 (20%) in tympanotomy group.[14] Hence, tympanotomy group had the highest rate of postoperative taste disturbance, followed by stapedectomy, myringoplasty, and mastoidectomy group. In a study conducted by Gopalan et al. in the myringoplasty group, only three patients (6.5%) developed symptoms. In the mastoidectomy group, six patients (15%) developed symptoms whereas in the tympanotomy group four patients (57%) did so.[3] The only symptom experienced by symptomatic patients in the myringoplasty group was absent taste sensation while in the mastoidectomy and tympanotomy groups, altered taste sensation was predominant (87% and 75%, respectively). Another study report by Sakaguchi et al. showed that that none of the patients with COM or cholesteatoma complained of subjective taste disturbance before surgery despite elevated threshold of EGM.[11]

Among our study population, 54 (54%) had grade 1 nerve injury, 41 (41%) had grade 2 nerve injury and the remaining 5 (5%) had grade 3 nerve injury. In a similar study conducted by Huang et al. 65.79% had minimal nerve injury, 23.68% had moderate (stretched) and 10.53% had severe (division) nerve injury.[4]


  Conclusions Top


Younger age group has the best chance of preservation and early recovery of taste function. The scale of CTN manipulation is important for the recovery of the taste function after middle ear surgery. Surgeons should make all efforts to preserve CTN intraoperatively, especially when an operation of the contralateral ear is also planned. More care needs to be exercised during stapes surgery as even after minor CTN manipulation, the rate of postoperative taste disorders or tongue symptoms, though transient, is high. Transient taste alteration should be mentioned before stapes surgery. Middle ear surgery consent procedure, especially mastoidectomy, emphasizes the risk of hearing loss and facial nerve injury, yet in open cavity surgery CTN division is almost inevitable. Reassuringly, most postoperative taste disturbance resolves, and most patients are not aware of the long-term disturbance. However, a small percentage, especially older patients, suffer ongoing taste disturbance. The risk of taste disturbance should be addressed in the consent procedure. The sense of taste has a great capacity to compensate after partial dysfunction. Thus most surgeons may never be confronted with this complication in their patients. However, preoperative information to the patients regarding the existence of potential taste disturbance, and that it is usually transitory, but if persistent, it is untreatable, may prevent any medicolegal problems later.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Snyder DJ, Bartoshuk LM. Oral sensory nerve damage: Causes and consequences. Rev Endocr Metab Disord 2016;17:149-58.  Back to cited text no. 1
    
2.
Coldwell SE, Mennella JA, Duffy VB, Pelchat ML, Griffith JW, Smutzer G, et al. Gustation assessment using the NIH Toolbox. Neurology 2013;80:S20-4.  Back to cited text no. 2
    
3.
Gopalan P, Kumar M, Gupta D, Phillipps JJ. A study of chorda tympani nerve injury and related symptoms following middle-ear surgery. J Laryngol Otol 2005;119:189-92.  Back to cited text no. 3
    
4.
Huang CC, Lin CD, Wang CY, Chen JH, Shiao YT, Tsai MH. Gustatory changes in patients with chronic otitis media, before and after middle-ear surgery. J Laryngol Otol 2012;126:470-4.  Back to cited text no. 4
    
5.
McManus LJ, Stringer MD, Dawes PJ. Iatrogenic injury of the chorda tympani: A systematic review. J Laryngol Otol 2012;126:8-14.  Back to cited text no. 5
    
6.
Mueller CA, Khatib S, Naka A, Temmel AF, Hummel T. Clinical assessment of gustatory function before and after middle ear surgery: A prospective study with a two-year follow-up period. Ann Otol Rhinol Laryngol 2008;117:769-73.  Back to cited text no. 6
    
7.
Choi N, Ahn J, Cho YS. Taste changes in patients with middle ear surgery by intraoperative manipulation of chorda tympani nerve. Otol Neurotol 2018;39:591-6.  Back to cited text no. 7
    
8.
Terada T, Sone M, Tsuji K, Mishiro Y, Sakagami M. Taste function in elderly patients with unilateral middle ear disease. Acta Otolaryngol Suppl 2004;553:113-6.  Back to cited text no. 8
    
9.
Nin T, Sakagami M, Sone-Okunaka M, Muto T, Mishiro Y, Fukazawa K. Taste function after section of chorda tympani nerve in middle ear surgery. Auris Nasus Larynx 2006;33:13-7.  Back to cited text no. 9
    
10.
Sakagami M. Taste disturbance and its recovery after middle ear surgery. Chem Senses 2005;30 Suppl 1:i220-1.  Back to cited text no. 10
    
11.
Sakaguchi A, Katsura H, Nin T, Adachi O, Mishiro Y, Daimon T, et al. Preoperative assessment of taste function in patients with middle ear disease. Otol Neurotol 2012;33:761-4.  Back to cited text no. 11
    
12.
Kiverniti E, Watters G. Taste disturbance after mastoid surgery: Immediate and long-term effects of chorda tympani nerve sacrifice. J Laryngol Otol 2012;126:34-7.  Back to cited text no. 12
    
13.
Clark MP, O'Malley S. Chorda tympani nerve function after middle ear surgery. Otol Neurotol 2007;28:335-40.  Back to cited text no. 13
    
14.
Gurung U, Bhattarai H, Shrivastav RP. Taste disturbances following middle ear surgery. J Inst Med 2010;32:318-23.  Back to cited text no. 14
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]



 

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