A study of chorda tympani nerve injury and related symptoms following middle-ear surgery

Push-Through Myringoplasty Versus External Auditory Canal Flap Tympanoplasty for Chronic Marginal Perforations

OBJECTIVE

We compared the operation times, graft success rates, and hearing gains between push-through (PT) myringoplasty and external auditory canal (EAC) flap tympanoplasty in patients with chronic marginal perforations.

MATERIALS AND METHODS

A total of 77 patients with chronic marginal perforations were randomly allocated to endoscopic perichondrium-cartilage myringoplasty with raising of the EAC flaps (n = 39) and PT technique (n = 38) groups. The graft outcomes, mean operation times, and postoperative complications were compared 6 months after operation.

RESULTS

The graft success rate was 97.4% (38/39) in the EAC group and 81.6% (31/38) in the PT group; the difference was significant (P = .056). The mean operation time was 40.7 ± 10.4 min in the EAC group and 42.4 ± 8.3 min in the PT group (P = .741). In the EAC group, the mean pre- and postoperative air-bone gap (ABG)s were 29.3 (range: 28.4 ± 8.6) and 12.1 (range: 11.8 ± 2.4) dB (P < .01), respectively; the respective values were 29.5 (range: 29.1 ± 5.4) and 12.6 (range: 12.0 ± 1.3) dB (P < .01) in the PT group. No significant group difference was observed in the pre- (P = .794) or postoperative (P = .689) ABG values or mean ABG gain (16.7 ± 5.3 vs 17.1 ± 7.7 dB; P = .526). In addition, graft medialization occurred in 7.9% patients in the PT group. However, graft lateralization, significant blunting, deteriorative sensorineural hearing loss, vertigo, or tinnitus were not encountered in either group. No taste change was reported and no inclusion cholesteatoma was seen in the EAC group.

CONCLUSION

Endoscopic perichondrium-cartilage myringoplasty with raising of an EAC flap is useful and minimally invasive to repair chronic marginal perforations; the technique is simple, has a high graft success rate in comparison to the PT technique.

Accurate Segmentation and Tracking of Chorda Tympani in Endoscopic Middle Ear Surgery with Artificial Intelligence

Objective: We introduce a novel endoscopic middle ear surgery dataset specifically designed for evaluating deep learning (DL)-based semantic segmentation of chorda tympani. Methods: We curated a dataset comprising 8240 images from 25 patients, divided into a training set (20%, 1648 images), validation set (5%, 412 images), and test set (75%, 6180 images). We employed data enhancement techniques to expand the picture size of the training and validation sets by 5 times (training set: 8240 images, verification set: 2060 images). Subsequently, we employed a multistage transfer learning training method to establish, train, and validate various convolutional neural networks. Results: On the validation set of 2060 labeled images, our proposed network achieved good results, with the U-net exhibiting the highest effectiveness (mIOU = 0.8737, mPA = 0.9263). Furthermore, when applied to the test dataset of 6180 raw images and contrasted with the prediction of otologists, the overall performance of the U-net was excellent (accuracy = 0.911, precision = 0.9823, sensitivity = 0.8777, specificity = 0.9714). Conclusions: Our findings demonstrate that DL can be successfully employed for automatic segmentation of chorda tympani in endoscopic middle ear surgery, yielding high-performance results. This study validates the potential feasibility of future intelligent navigation technologies to assist in endoscopic middle ear surgery.

Chorda tympani injury during endoscopic versus microscopic stapes surgery: a randomized controlled clinical trial

OBJECTIVES

The aim of this study was to compare the incidence of chorda tympani nerve (CTN) injury between endoscopic and microscopic stapes surgery.

METHODS

This randomized controlled clinical trial included 88 patients who were randomly divided into two groups: endoscopic stapedotomy group (n = 44) and microscopic stapedotomy group (n = 44). The incidence of chorda tympani nerve (CTN) injury after surgery was determined by both subjective taste testing and chemical taste tests, before and after surgery. The results were compared between the two groups.

RESULTS

The total number of patients who were identified as having CTN affection (based on the chemical testing) was 16 out of 88 (18.2%). The incidence was significantly lower in the endoscopic group (n = 2) than the microscopic group (n = 14) (p = 0.019).

CONCLUSION

Altered taste as a result of iatrogenic CTN injury can affect the patients' quality of life. Endoscopic ear surgery offers better visualization, less need for extensive manipulation of the chorda tympani, and consequently decreased incidence of CTN injury.

[Anatomical and clinical characteristics of the chorda tympani]

The article presents information about the applied and clinical anatomy of the chorda tympani. Brief information is given about the history of its discovery, embryonic and postnatal development, features of anatomy, topography and morphology. The clinical aspects of the lesion and methods of studying the function of the chorda tympani are described.

The impact of injury of the chorda tympani nerve during primary stapes surgery or cochlear implantation on taste function, quality of life and food preferences: A study protocol for a double-blind prospective prognostic association study

BACKGROUND

The chorda tympani nerve (CTN) is a mixed nerve, which carries sensory and parasympathetic fibres. The sensory component supplies the taste sensation of the anterior two-thirds of the ipsilateral side of the tongue. During middle ear surgery the CTN is exposed and frequently stretched or sacrificed, because it lacks a bony covering as it passes through the middle ear. Injury may cause hypogeusia, ageusia or altered taste sensation of the ipsilateral side of the tongue. To date, there is no consensus regarding which type of CTN injury (sacrificing or stretching), during middle ear surgery, leads to the least burden for the patient.

METHODS

A double-blind prospective prognostic association study was designed in a single medical centre in the Netherlands to determine the effect of CTN injury on postoperative taste disturbance and quality of life. 154 patients, who will undergo primary stapes surgery or cochlear implantation will be included. The taste sensation, food preferences and quality of life of these patients will be evaluated preoperatively and at one week, six weeks and six months postoperatively using the Taste Strip Test, Electrogustometry, supplementary questionnaire on taste disturbance, Macronutrient and Taste Preference Ranking Task, Appetite, Hunger and Sensory Perception questionnaire and Questionnaire of Olfactory Disorders to assess the association of these outcomes with CTN injury. Evaluation of olfactory function will only take place preoperatively and at one week postoperatively using the Sniffin' Sticks. The patient and outcome assessor are blinded to the presence or absence of CTN injury.

DISCUSSION

This study is the first to validate and quantify the effect of chorda tympani nerve injury on taste function. The findings of this study may lead to evidence-based proof of the effect of chorda tympani injury on taste function with consequences for surgical strategies.

TRIAL REGISTRATION

Netherlands Trial Register NL9791. Registered on 10 October 2021.

Chorda tympani nerve course and feasibility of its preservation during atresiaplasty for congenital aural atresia

Objectives

The association between the chorda tympani nerve (CTN) and atresiaplasty has not been investigated. This study aimed to describe the course of the CTN observed during atresiaplasty for congenital aural atresia (CAA) and explore the feasibility of CTN preservation.

Methods

In this retrospective study, six consecutive patients who underwent atresiaplasty in a tertiary academic center were included. The course of the tympanic segment of the CTN and its preservation feasibility were evaluated. Atresiaplasty was performed using an anterior approach. The average Jahrsdoerfer score was 8.7 points (range, 8-9 points).

Results

The CTN was located in the atretic plate in all patients. It emerged from an average of 5.6 mm (range, 5.2-6.1) inferior to the incus buttress and crossed the middle ear in an anterior-superior direction. The distance between the neck of the malleus and the CTN varied in the absence of the malleus handle. However, when the malleus handle developed, the CTN passed between the incus and the malleus handle. The CTN was preserved in two of the six patients. They had a Jahrsdoerfer score of 9 and grade I microtia.

Conclusion

The CTN was located in the atretic plate, emerging from an average distance of 5.6 mm inferior to the incus buttress. The incus buttress might serve as a good anatomical landmark to identify and preserve the CTN. CTN preservation is feasible in atresiaplasty candidates with a Jahrsdoerfer score of 9 and auricular deformity of grade I.

Level of Evidence

4.

Sacrifice of the chorda tympani nerve during middle-ear surgery can lead to resolution of dysgeusia

BACKGROUND

Cholesteatoma often presents with persistent otorrhoea, conductive hearing loss or vestibular dysfunction. Rarely, cholesteatoma can cause dysgeusia if the lesion invades into the chorda tympani nerve. This paper presents an individual with cholesteatoma whose dysgeusia resolved following a mastoidectomy in which the chorda tympani was sacrificed. The current literature was reviewed for explanations behind this phenomenon.

CASE REPORT

A previously fit 57-year-old man presented with a 3-month history of persistent otorrhoea and the complaint of a metallic taste in the mouth, and was diagnosed with cholesteatoma. The patient underwent radical mastoidectomy and the chorda tympani nerve was sacrificed. On post-operative review, he reported complete resolution of dysgeusia.

CONCLUSION

The sense of taste is mediated by a complex neural network. It is possible that once the diseased chorda tympani is transected, compensation arises from other parts of the network. Sectioning of the chorda tympani could lead to a beneficial outcome in selected patients.

Comparison of gustatory function between mucosal and squamous disease: a randomised controlled study

OBJECTIVE

The aim of this study was to evaluate and compare the gustatory function between patients with chronic mucosal and squamous diseases before and after the surgery.

METHOD

A total of 33 patients with mucosal diseases and 34 patients with squamous diseases were evaluated for gustatory function both in the pre-operative and post-operative periods. The taste scores were compared between the two groups.

RESULTS

The gustatory scores in the mucosal disease group were significantly better than the scores in the squamous disease group (p < 0.05). There was no significant correlation detected between the age of the patients or duration of the disease with the taste scores in any of the study groups.

CONCLUSION

The improvement in gustatory score was better in the chronic mucosal disease group than the squamous disease group. There was no significant correlation found between the age of the patients or duration of disease and the taste score in any of the study groups.

Blood supply to the chorda tympani: A review and clinical applications

The chorda tympani (CT) is important in gustatory sensation from the anterior two-thirds of the tongue and in secretomotor innervation to the submandibular and sublingual glands. Although the blood supply to the CT is not well delineated in the literature, some studies have shown that a posterior tympanic branch of the stylomastoid artery supplies CT at its origin from the mastoid segment of the facial nerve. We review the blood supply to the CT comprehensively. A better understanding of the vasculature involved is required to prevent iatrogenic injury during middle ear surgery and complications secondary to ischemia.

Taste Changes in Patients With Middle Ear Surgery by Intraoperative Manipulation of Chorda Tympani Nerve

OBJECTIVES

The aim of study was to evaluate the subjective changes of taste and salivation after middle ear surgery according to chorda tympani nerve (CTN) injury.

STUDY DESIGN

Prospective cohort study.

SETTING

Tertiary referral center.

PATIENTS

We enrolled 180 patients older than 13 years old who received middle ear surgery.

INTERVENTIONS

The patients were classified into cut, manipulated, and intact groups according to intraoperative assessments of the CTN. The patients responded taste and salivation surveys preoperatively, and 1, 3, and 6 months postoperatively.

MAIN OUTCOME MEASURES

We analyzed results of questionnaires including disturbance rates, severity and character to evaluate taste and salivation functions.

RESULTS

Taste disturbance rate was significantly improved in all groups during follow-up (p < 0.05). The incidence of taste disturbance did not differ significantly between the three groups at each follow-up (p > 0.05). The taste disturbance score improved gradually in the cut and intact groups (p < 0.001), but not in the manipulated group (p = 0.067). Among the patients with taste disturbance, hypoguesia was most common symptom. Incidence of salivation disturbance did not differ between the three groups (p = 0.298). However, this symptom improved significantly only in the intact group (p < 0.001). The taste and salivation disturbance rate was not different between patients with and without chronic otitis media at 3 and 6 months, and both groups showed significant improvement.

CONCLUSIONS

Prevalence of taste and salivation disturbance was similar between three groups until 6 months. However, taste disturbance did not improve in the manipulated group and salivation disturbance improved only in the intact group.

Feasibility of preservation of chorda tympani nerve during noninflammatory ear surgery: A systematic review

OBJECTIVE

The objective of our systematic review is to investigate the postoperative gustatory function of the chorda tympani nerve following noninflammatory ear surgery for which the chorda tympani is at risk for iatrogenic injury (stretching, handling, or sacrificing).

DATA SOURCES

PubMed and EMBASE.

REVIEW METHODS

A PubMed and EMBASE databases search was conducted on November 15, 2016. Study inclusion criteria included: 1) ear surgery performed for noninflammatory ear diseases, and 2) gustatory function of the chorda tympani reported as an outcome. The quality of eligible studies was assessed using the risk of bias assessment tool for nonrandomized studies. Study characteristics and outcome data of the included studies were extracted.

RESULTS

In total 1,094 articles were retrieved. Fourteen studies encompassing 1,062 operated ears were included after quality assessment. Stapedectomy was the most frequent surgical procedure performed in 398 ears. The follow-up time varied between 6 weeks and 99 months. Patients with a preserved chorda tympani were less symptomatic (24% was symptomatic) compared to patients with a stretched (53% was symptomatic) or sacrificed chorda tympani (47% was symptomatic). The recovery rate varied from 61% to 79%. The results of the electrogustometry and strip test showed a discrepancy with the subjective complaints of the patients.

CONCLUSION

Patients with a stretched chorda tympani were slightly more symptomatic compared to patients with a sacrificed chorda tympani. Therefore, in cases for which the chorda tympani greatly hinders a proper view of the surgical field, sacrificing the nerve could be considered to maximize surgical performance and have a satisfactory postoperative result. Laryngoscope, 1904-1913, 2018.

Taste disturbance after stapes surgery: an evaluation of frequency, severity, duration, and quality-of-life

CONCLUSION

The incidence of taste disturbance after stapes surgery is high (61.9%), whereas the majority (94.8%) recovers within 1 year. More severe surgical nerve trauma caused more disturbance, implying that the nerve should be handled carefully during surgery.

OBJECTIVES

Patients operated on for otosclerosis seem more often to complain about post-operative taste disturbance than those operated on for chronic otitis media, although the chorda tympani nerve more seldom becomes maltreated in stapedotomy. These observations seem paradoxical. It is unclear to what extent a post-operative taste disturbance affects the quality-of-life. This study aims to shed light on the occurrence of post-operative taste disturbances, on possible prognostic factors, and to what extent post-operative taste disturbance impairs the quality-of-life.

METHODS

One hundred and thirty-four adults undergoing primary stapedotomy were included. Questionnaires on taste disturbance and quality-of-life (SF-36) were answered before and after surgery, until 1 year post-operatively.

RESULTS

Eighty-three (61.9%) study persons reported post-operative taste disturbance. Seven (5.2%) reported persisting disturbance at 1 year. Surgically more traumatized chorda tympani nerves correlated with more severe taste disturbance post-operatively than less traumatized. Taste disturbance at 1 year post-operatively correlate with a decrease of the physical function domain in the SF-36.

Subannular tube insertion: anatomical considerations

Objectives:

To assess the distance between the bony groove created during subannular tubes placement and the chorda tympani, and examine the depth of the hypotympanum and retrotympanum.

Method:

Grooves drilled in cadaver temporal bones at two levels were imaged to measure: the distance between the chorda tympani nerve and the tympanic sulcus, and the depth of the hypotympanum and the retrotympanum relative to the annulus.

Results:

The chorda tympani was between 0 and 5 mm from the groove cut across the annulus. The hypotympanum average depth was 2 mm (0.44–6.40 mm) and the retrotympanum average depth was 1 mm (0–2.53 mm).

Conclusion:

Grooves drilled across the tympanic sulcus should be placed at a point 20 per cent of the height of the tympanic membrane or lower; this will ensure least risk of injury to the chorda tympani nerve. The depth of the hypotympanum and retrotympanum dictates that the posteroinferior part of a subannular tube flange should be approximately 2 × 1 mm.

Using Animal Models to Determine the Role of Gustatory Neural Input in the Control of Ingestive Behavior and the Maintenance of Body Weight

INTRODUCTION

Decades of research have suggested that nutritional intake contributes to the development of human disease, mainly by influencing the development of obesity and obesity-related conditions. A relatively large body of research indicates that functional variation in human taste perception can influence nutritional intake as well as body mass accumulation. However, there are a considerable number of studies that suggest that no link between these variables actually exists. These discrepancies in the literature likely result from the confounding influence of a variety of other, uncontrolled, factors that can influence ingestive behavior.

STRATEGY

In this review, the use of controlled animal experimentation to alleviate at least some of these issues related to the lack of control of experimental variables is discussed. Specific examples of the use of some of these techniques are examined.

DISCUSSION AND CONCLUSIONS

The review will close with some specific suggestions aimed at strengthening the link between gustatory neural input and its putative influence on ingestive behaviors and the maintenance of body weight.

The chorda tympani degenerates during chronic otitis media: an electron microscopy study

CONCLUSION

Chorda tympani nerve specimens from ears with chronic inflammatory middle ear disease exhibit structural signs of degeneration. These correlate well with taste disturbance. Simultaneously, they exhibit signs of regeneration, which may explain the ability for taste recovery.

OBJECTIVES

The chorda tympani, the major taste nerve, runs uncovered through the middle ear cavity. This situation exposes it to various forms of middle ear pathology. A difference has been noticed regarding taste symptoms pre- and postoperatively between inflammatory and non-inflammatory diseases. The present study aimed to investigate ultrastructural changes of chorda tympani in different forms of inflammatory middle ear disease, such as chronic suppurative otitis media and cholesteatoma, as compared with normal.

METHODS

Five chorda tympani specimens were collected from healthy middle ears of patients subjected to surgery for acoustic neuroma, to be used as normal controls, and five from middle ears with chronic otitis media or cholesteatoma, where the nerve could not be saved during the operation. Light and electron microscopy were performed.

RESULTS

For all five nerves from diseased ears, microscopy showed a higher percentage of axon and myelin sheath degeneration than in the normal controls. Furthermore, three of the five also exhibited sprouting.

Taste and olfaction in middle ear surgery

OBJECTIVE

The aim of this study was to assess pre- and postoperative taste ability in patients undergoing middle ear surgery for otosclerosis or chronic otitis media. Olfactory function was also evaluated to rule out taste deficits due to concomitant nasal pathology.

METHODS

All patients underwent ear, nose, and throat examination, otomicroscopy, nasal endoscopy, anterior rhinomanometry, taste testing, and olfactory testing. Patients were evaluated at 1 to 5 days preoperatively (T0), and at 1 (T1), 6 (T6), and 12 (T12) months postoperatively.

RESULTS

Both groups of patients experienced worsening of the mean taste threshold postoperatively. This phenomenon was more serious in poststapedotomy patients. Follow-up showed progressive improvement in both groups. All values of olfactory testing were within the normal range for otosclerosis patients. Patients with chronic otitis media showed variable postoperative findings.

CONCLUSION

Chorda tympani function can be negatively affected by middle ear surgery. Deficits may be more marked in stapedotomy patients than in those undergoing tympanoplasty. Postoperative recovery of taste is satisfactory, although with different timelines for the 2 types of pathology.

Surgery of the ear and the lateral skull base: pitfalls and complications

Surgery of the ear and the lateral skull base is a fascinating, yet challenging field in otorhinolaryngology. A thorough knowledge of the associated complications and pitfalls is indispensable for the surgeon, not only to provide the best possible care to his patients, but also to further improve his surgical skills. Following a summary about general aspects in pre-, intra-and postoperative care of patients with disorders of the ear/lateral skull base, this article covers the most common pitfalls and complications in stapes surgery, cochlear implantation and surgery of vestibular schwannomas and jugulotympanal paragangliomas. Based on these exemplary procedures, basic "dos and don'ts" of skull base surgery are explained, which the reader can easily transfer to other disorders. Special emphasis is laid on functional aspects, such as hearing, balance and facial nerve function. Furthermore, the topics of infection, bleeding, skull base defects, quality of life and indication for revision surgery are discussed. An open communication about complications and pitfalls in ear/lateral skull base surgery among surgeons is a prerequisite for the further advancement of this fascinating field in ENT surgery. This article is meant to be a contribution to this process.

Taste sensation following cochlear implantation surgery

OBJECTIVES

The chorda tympani nerve (CTN) is at risk of damage during cochlear implantation, especially during posterior tympanotomy. The aim of this study was, therefore, to elicit the risk of taste disorders following cochlear implantation surgery involving a mastoidectomy and a posterior tympanotomy approach.

METHOD

Twenty-six patients underwent a taste test before, 3 days after, and 6 weeks after cochlear implantation surgery. The taste sensations - sweet, sour, salt and bitter - were determined. Patients' self-ratings of taste function were also obtained. In addition, the surgeons provided information concerning the intraoperative status of the CTN.

RESULTS

In total, 19.2% (5 of 26) of the patients had postoperative taste dysfunction, as measured either subjectively or objectively or both. One of these five individuals had taste disturbance as assessed by both subjective and objective measures; in another, it was merely reported subjectively. Three patients were subjectively asymptomatic but the postoperative taste test revealed a dysfunction. Sixteen percent of the patients in whom the CTN was reported to be preserved intraoperatively had a postoperative taste dysfunction. Although the CTN was rerouted in five patients, only two of them (40%) had transient gustatory dysfunction. In two of those patients with postoperative taste dysfunction, the CTN was not intraoperatively exposed (being protected by bone) despite these individuals' experiencing postoperative taste problems. The recovery rate was 100% at 6 weeks after surgery.

CONCLUSION

Our study indicates that cochlear implantation entails only a minimal risk of taste dysfunction and that this is chiefly a transient problem.

A survey of oral cavity afferents to the rat nucleus tractus solitarii

Visualization of myelinated fiber arrangements, cytoarchitecture, and projection fields of afferent fibers in tandem revealed input target selectivity in identified subdivisions of the nucleus tractus solitarii (NTS). The central fibers of the chorda tympani (CT), greater superficial petrosal nerve (GSP), and glossopharyngeal nerve (IX), three nerves that innervate taste buds in the oral cavity, prominently occupy the gustatory-sensitive rostrocentral subdivision. In addition, CT and IX innervate and overlap in the rostrolateral subdivision, which is primarily targeted by the lingual branch of the trigeminal nerve (LV). In the rostrocentral subdivision, compared with the CT terminal field, GSP appeared more rostral and medial, and IX was more dorsal and caudal. Whereas IX and LV filled the rostrolateral subdivision diffusely, CT projected only to the dorsal and medial portions. The intermediate lateral subdivision received input from IX and LV but not CT or GSP. In the caudal NTS, the ventrolateral subdivision received notable innervation from CT, GSP, and LV, but not IX. No caudal subnuclei medial to the solitary tract contained labeled afferent fibers. The data indicate selectivity of fiber populations within each nerve for functionally distinct subdivisions of the NTS, highlighting the possibility of equally distinct functions for CT in the rostrolateral NTS, and CT and GSP in the caudal NTS. Further, this provides a useful anatomical template to study the role of oral cavity afferents in the taste-responsive subdivision of the NTS as well as in subdivisions that regulate ingestion and other oromotor behaviors.

Hyposalivation after undergoing stapedectomy

BACKGROUND

Treatment for otosclerosis involves patients' undergoing stapedectomy. Inadvertent damage to the chorda tympani nerve's (CTN's) secretory fibers during stapedectomy can result in inadequate secretory stimulation of the submandibular salivary glands (SMSGs) and sublingual salivary glands (SLSGs). Because most saliva originates from these glands, hyposalivation and subjective xerostomia manifest during resting periods when parotid gland secretions are minimal. Stimulation with food increases parotid gland salivation enough to overcome the subjective sense of dryness.

CASE DESCRIPTION

The author examined a 52-year-old man who had undergone bilateral stapedectomy because of hearing loss; his rheumatologist referred him to the Salivary Gland Center (New York City) because of a complaint of dry mouth. After the author examined the patient, he concluded that the patient had decreased SMSG and SLSG secretion and recommended that the patient use sugarless chewing gum or sour candy frequently to stimulate his parotid glands and use oral lubricants and sip water as needed.

CLINICAL IMPLICATIONS

Stimulation of parotid gland secretion is independent of SMSG and SLSG activation. Therefore, the dental practitioner must become aware of the innervation of the salivary glands and each gland's secretory production during periods of oral stimulation and of rest.

Gustatory changes in patients with chronic otitis media, before and after middle-ear surgery

Objective:

We investigated gustatory changes in patients with chronic otitis media, before and after middle-ear surgery.

Methods:

This prospective study included 38 patients with unilateral chronic otitis media. We used taste testing solutions to evaluate each patient's taste function. Intra-operative assessments of the chorda tympani nerve were also compared and analysed.

Results:

Patients with chronic otitis media had significantly worse ipsilateral perception of sour, bitter and salty tastes. In patients with good intra-operative preservation of the chorda tympani nerve, there was significant improvement in gustatory function one month post-operatively, compared with the pre-operative baseline. In patients who sustained intra-operative chorda tympani nerve injury, one month post-operative gustatory function was the same as the pre-operative baseline.

Conclusion:

Middle-ear surgery for chronic otitis media not only treats the ear but also improves gustatory function in the majority of patients. In patients with intra-operative injury to the chorda tympani nerve, post-operative taste decline is only temporary.

Taste disturbance after mastoid surgery: immediate and long-term effects of chorda tympani nerve sacrifice

Objective:

To determine the immediate and long-term taste effects of chorda tympani nerve sacrifice in patients undergoing open cavity mastoidectomy.

Design, setting and participants:

A retrospective, questionnaire survey of patients receiving follow up and aural toilet following open cavity mastoidectomy, over a four-month period. The questionnaire assessed taste disturbance, both immediately post-operative and current. Available surgical records were reviewed for chorda tympani references.

Results:

Of 57 patients, six had undergone surgery to both ears. Of those who could recall (37/57), 24.3 per cent were aware of taste disturbance immediately after surgery, while 8.7 per cent reported current disturbance (median post-operative interval, 28.5 years; range, one month to 67 years). No bilateral surgery patients were aware of taste disturbance.

Conclusion:

Mastoidectomy consent procedure emphasises the risk of hearing loss and facial nerve injury, yet in open cavity surgery chorda tympani division is almost inevitable. Reassuringly, most post-operative taste disturbance resolves, and most patients are not aware of long-term disturbance. However, a small percentage suffer ongoing taste disturbance; this could be significant for professional chefs and wine-tasters. The risk of taste disturbance should be addressed in the consent procedure.

Iatrogenic injury of the chorda tympani: a systematic review

Objective:

To review the currently available literature on iatrogenic injury of the adult chorda tympani.

Design:

Systematic literature review.

Method

Five electronic databases and one search engine were used to access available English language literature on the chorda tympani, focusing on iatrogenic injury.

Results:

The chorda tympani is most often injured during middle-ear surgery, after which at least 15–22 per cent of patients experience symptoms, mostly changes in taste and dryness of the mouth. Numerous factors influence whether injury to the chorda tympani causes symptoms, including the extent of injury, type of surgery, age of the patient, anatomical variables and subjective adaptation. Although most patients experience gradual symptomatic recovery, complaints can be persistent and troublesome.

Conclusion:

Care should be taken to preserve the chorda tympani during middle-ear surgery, and to warn patients pre-operatively about this potential complication. This is particularly important if surgery is bilateral.

Recovery from long-lasting post-tonsillectomy dysgeusia

Transient post-tonsillectomy taste dysgeusia (PTD) is a common complaint. Long-lasting PTD is less frequent but has significant consequences on patients' quality of life, with some cases leading to medicolegal issues. Treatment options and knowledge about mechanisms and factors favoring PTD are limited. PTD may result from direct surgical injury, tongue compression, inflammatory processes or side effects of local anesthetics. Some authors also claim that dietary zinc deficiency plays a role in the development of PTD. Although this latter cause had not yet received a lot of attention, we report a case of a female patient who reported a 4-year PTD and recovered within 2 months after oral intake of zinc sulfate. This clinical observation, together with recent findings on significant improvement of taste disorders after zinc treatments for other causes, opens again the question of what extent zinc deficiency plays a role in PTD.

Cutting the chorda tympani: not just a matter of taste

Introduction:

Chorda tympani injury as a complication of middle-ear surgery has been extensively studied with regard to its effects upon taste. However, the chorda tympani also carries parasympathetic fibres to the salivary glands of the oral cavity. To date, little has been reported about the effect of chorda tympani section upon salivary function.

Setting:

Tertiary care centre.

Material and methods:

We report a case series of three patients with bilateral chorda tympani lesions. Chorda tympani function was assessed using ‘taste strips’ and unstimulated sialometry. A careful history of oral symptoms was taken.

Results:

All patients showed transient or permanent bilateral ageusia of the anterior two-thirds of the tongue, and a decreased resting salivary flow rate. In addition, all patients suffered from transient or persistent, distressing xerostomia.

Conclusion:

Taste disorders may occur after middle-ear surgery but they are mostly transient, even when the chorda tympani nerves are sectioned bilaterally. In contrast, bilateral chorda tympani lesions may lead to severe, persistent and distressing xerostomia. Based on this neglected aspect of chorda tympani function, we emphasise the importance of preserving the chorda tympani whenever possible.

Taste change following cochlear implantation

Taste change is a well documented but under emphasised complication of middle ear surgery and is usually related to damage to the chorda tympani nerve (CTN). However, the taste outcomes following cochlear implantation have not been previously recorded. One hundred and forty one patients who had received cochlear implants between January 1997 and April 2006 were questioned using a postal survey regarding changes in the sense of taste following cochlear implantation. Sixty seven per cent of questionnaires were returned. Forty three patients (45%) experienced changes in taste following their surgery. Eighteen patients (19%) said that their symptoms had not resolved by the end of the follow up period (mean 51 months). CTN division produced taste change in 86%. Fifty per cent of patients who had CTN preservation developed taste change, presumably related to occult trauma to the nerve. The difference in the number of patients describing taste change in the two groups was statistically significant (p < 0.05). Resolution of symptoms took a mean of 20 weeks. For those patients in whom taste change was noted, resolution of symptoms was more likely if the CTN was divided rather than preserved although the difference was not statistically significant (p < 0.5). This may reflect neuronal injury during surgery which then fails to heal normally. These results are comparable to taste outcomes in patients undertaking middle ear surgery for non-inflammatory disease such as stapedectomy. The symptoms can be extremely troublesome and may not resolve with time. Careful consideration of the CTN intra-operatively is recommended and in the event of injury, the taste outcome may be better if the nerve is divided rather than left in situ but damaged. These findings have significant implications for patients as bilateral implantation becomes more commonplace.

Chorda tympani injury: operative findings and postoperative symptoms

OBJECTIVES

This study aims to assess whether operative findings of chorda tympani nerve (CTN) trauma correlate with postoperative symptoms.

STUDY DESIGN AND SETTING

A prospective study was conducted over 2 years on 140 middle ear operations analyzing taste disturbances. The operations were subdivided into myringoplasty/tympanoplasty (56 cases), mastoidectomy (64 cases), and tympanotomy (20 cases).

RESULTS

Twenty-one (15%) patients reported taste disturbance. Altered taste was most reported (n=15, 71%) with loss of taste reported by 29% (n=6). Symptoms were most observed in the tympanotomy group (45%). Stretching of the CTN was associated with more symptoms than nerve transection. Recovery was complete in 76% (n=16) of the symptomatic cases by 12 months.

CONCLUSION

Patients who undergo middle ear surgery should be thoroughly counseled with respect to CTN injury and symptoms regardless of the type of damage to the nerve.

SIGNIFICANCE

This study highlights the high incidence of postoperative alterations in taste after middle ear surgery, especially in non-diseased ears, and that CTN transection results in fewer symptoms than CTN stretching.

Chorda tympani nerve function after middle ear surgery

OBJECTIVE

To assess chorda tympani nerve function before and after different types of middle ear surgery. The hypothesis was that in cases with cholesteatoma, iatrogenic injury to the nerve results in less postoperative taste disturbance than those undergoing myringoplasty or stapedectomy.

STUDY DESIGN

Prospective questionnaire study.

SETTING

ENT Department of a district general hospital in England.

PATIENTS

Adult patients undergoing middle ear surgery in which there would be elevation of the anulus.

MAIN OUTCOME MEASURE

Patients' change in taste sensation after surgery with follow-up to demonstrate subsequent recovery.

RESULTS

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. The most common complaint after chorda tympani nerve injury is of a metallic taste sensation.

CONCLUSION

Despite the small patient cohort, the results support the hypothesis that iatrogenic chorda tympani nerve injury in surgery for cholesteatoma results in less postoperative taste disturbance than that for otosclerosis. This may be because the disease process of cholesteatoma renders the nerve hypofunctional. The situation after myringoplasty is less clear. A larger study may help validate these findings.