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.</p

Endoscopic vs. microscopic stapes surgery:An anatomical feasibility study

OBJECTIVES: To investigate the feasibility of the endoscopic approach vs. microscopic approach during stapes surgery, focusing on the visualization of the important anatomical structures of the middle ear, the volume of the resected scutum and chorda tympani (CT) injury. METHODS: Fresh frozen human cadaveric heads underwent two stapes surgeries using an operating microscope on one ear and an endoscope on the other ear. The surgeon documented the visualization of critical landmarks, as well as exposure and injury of the CT. The volume of resected scutum was evaluated using cone beam computed tomography scanning and three-dimensional imaging. RESULTS: We performed endoscopic stapes surgery in 10 ears and microscopic stapes surgery in 11 ears. A stapes prosthesis was placed in all ears. The volume of bony scutum resection was significantly lower in the endoscopic group (median = 2.20 mm 3, IQR = 4.17) than in the microscopic group (median 13.25 mm 3, IQR = 8.71). No scutum was removed in two endoscopic ears, while scutum was removed in all microscopic ears. The endoscopic and microscopic group had similar CT injury. CONCLUSIONS: This study showed that the endoscopic stapes surgery procedure is feasible and might be less invasive than microscopic stapes surgery. Future clinical prospective and functional studies will be needed to support our findings

Systematic review:Validity, reliability, and diagnostic accuracy of the electrogustometer

OBJECTIVE: What are the electrogustometer's (EGM) validity, reliability, and diagnostic accuracy in assessing taste sensation in adults compared to other taste tests?DATA SOURCES: PubMed Medline, Elseviers's Embase, and the six databases of Cochrane Library.METHODS: We conducted a systematic search on December 20, 2022, consisting of synonyms for EGM. We considered randomized controlled trials and observational studies with original data for inclusion if they included adults who underwent electrogustometry. Articles were excluded if no analysis regarding validity, reliability, or diagnostic accuracy had been performed or if these analyses could not be performed with the published data.RESULTS: Nineteen articles discussing 18 studies were included for data extraction. The included studies carry a high risk of bias. Overall, the association between a variety of reference taste tests and EGM was moderate or weak with correlation coefficients ranging from -0.51 to 0.40 with one outlier of -0.74 found in one study correlating EGM and taste solutions. Test-retest reliability was good with reported correlation coefficients between 0.78 and 1.0. The sensitivity, specificity, PPV, and NPV of EGM in identifying abnormal taste function varied widely between the four studies on diagnostic accuracy.CONCLUSION: The included studies in this review lack the required standards regarding study design to draw firm conclusions about the validity, reliability, and diagnostic accuracy of the EGM. Future research is needed to assess these measurement properties. Based on the reported results, we would not recommend using the EGM as a screening test for taste disturbance in clinical practice.LEVEL OF EVIDENCE: NA.</p

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

Systematic review:Validity, reliability, and diagnostic accuracy of the electrogustometer

OBJECTIVE: What are the electrogustometer's (EGM) validity, reliability, and diagnostic accuracy in assessing taste sensation in adults compared to other taste tests?DATA SOURCES: PubMed Medline, Elseviers's Embase, and the six databases of Cochrane Library.METHODS: We conducted a systematic search on December 20, 2022, consisting of synonyms for EGM. We considered randomized controlled trials and observational studies with original data for inclusion if they included adults who underwent electrogustometry. Articles were excluded if no analysis regarding validity, reliability, or diagnostic accuracy had been performed or if these analyses could not be performed with the published data.RESULTS: Nineteen articles discussing 18 studies were included for data extraction. The included studies carry a high risk of bias. Overall, the association between a variety of reference taste tests and EGM was moderate or weak with correlation coefficients ranging from -0.51 to 0.40 with one outlier of -0.74 found in one study correlating EGM and taste solutions. Test-retest reliability was good with reported correlation coefficients between 0.78 and 1.0. The sensitivity, specificity, PPV, and NPV of EGM in identifying abnormal taste function varied widely between the four studies on diagnostic accuracy.CONCLUSION: The included studies in this review lack the required standards regarding study design to draw firm conclusions about the validity, reliability, and diagnostic accuracy of the EGM. Future research is needed to assess these measurement properties. Based on the reported results, we would not recommend using the EGM as a screening test for taste disturbance in clinical practice.LEVEL OF EVIDENCE: NA.</p

The effect of piston diameter in primary stapes surgery on surgical success

PURPOSE: To evaluate the effect of piston diameter in patients undergoing primary stapes surgery on audiometric results and postoperative complications. METHODS: A retrospective single-center cohort study was performed. Adult patients who underwent primary stapes surgery between January 2013 and April 2022 and received a 0.4-mm-diameter piston or a 0.6-mm-diameter piston were included. The primary and secondary outcomes were pre- and postoperative pure-tone audiometry, pre- and postoperative speech audiometry, postoperative complications, intraoperative anatomical difficulties, and the need for revision stapes surgery. The pure-tone audiometry included air conduction, bone conduction, and air-bone gap averaged over 0.5, 1, 2 and 3 kHz. RESULTS: In total, 280 otosclerosis patients who underwent 321 primary stapes surgeries were included. The audiometric outcomes were significantly better in the 0.6 mm group compared to the 0.4 mm group in terms of gain in air conduction (median = 24 and 20 dB, respectively), postoperative air-bone gap (median = 7.5 and 9.4 dB, respectively), gain in air-bone gap (median = 20.0 and 18.1 dB, respectively), air-bone gap closure to 10 dB or less (75% and 59%, respectively) and 100% speech reception (median = 75 and 80 dB, respectively). We found no statistically significant difference in postoperative dizziness, postoperative complications and the need for revision stapes surgery between the 0.4 and 0.6 mm group. The incidence of anatomical difficulties was higher in the 0.4 mm group. CONCLUSION: The use of a 0.6-mm-diameter piston during stapes surgery seems to provide better audiometric results compared to a 0.4-mm-diameter piston, and should be the preferred piston size in otosclerosis surgery. We found no statistically significant difference in postoperative complications between the 0.4- and 0.6-mm-diameter piston. Based on the results, we recommend always using a 0.6-mm-diameter piston during primary stapes surgery unless anatomical difficulties do not allow it

Systematic review: Validity, reliability, and diagnostic accuracy of the electrogustometer

OBJECTIVE: What are the electrogustometer's (EGM) validity, reliability, and diagnostic accuracy in assessing taste sensation in adults compared to other taste tests? DATA SOURCES: PubMed Medline, Elseviers's Embase, and the six databases of Cochrane Library. METHODS: We conducted a systematic search on December 20, 2022, consisting of synonyms for EGM. We considered randomized controlled trials and observational studies with original data for inclusion if they included adults who underwent electrogustometry. Articles were excluded if no analysis regarding validity, reliability, or diagnostic accuracy had been performed or if these analyses could not be performed with the published data. RESULTS: Nineteen articles discussing 18 studies were included for data extraction. The included studies carry a high risk of bias. Overall, the association between a variety of reference taste tests and EGM was moderate or weak with correlation coefficients ranging from -0.51 to 0.40 with one outlier of -0.74 found in one study correlating EGM and taste solutions. Test-retest reliability was good with reported correlation coefficients between 0.78 and 1.0. The sensitivity, specificity, PPV, and NPV of EGM in identifying abnormal taste function varied widely between the four studies on diagnostic accuracy. CONCLUSION: The included studies in this review lack the required standards regarding study design to draw firm conclusions about the validity, reliability, and diagnostic accuracy of the EGM. Future research is needed to assess these measurement properties. Based on the reported results, we would not recommend using the EGM as a screening test for taste disturbance in clinical practice. LEVEL OF EVIDENCE: NA

Radiological and surgical aspects of round window visibility during cochlear implantation: a retrospective analysis

PURPOSE: The round window approach has become the most preferred option for cochlear implant (CI) insertion, however, sometimes it may not be possible due to the (in)visibility of the round window membrane (RWM). We addressed the prevalence, consequences and indicators of difficult detection of the RWM in cochlear implant surgery. METHODS: This study retrospectively analysed the operative reports and preoperative high resolution axial-computed tomography (CT) scans of a consecutive cohort of patients who underwent a CI insertion. The main outcomes were surgical outcomes of the RW approach, and assessment of radiological markers. RESULTS: The operative reports showed that RWM insertion was feasible in 151 out of 153 patients. In 18% of the patients the RWM was difficult to visualize. All these patients had at least one intraoperative event. The chorda tympani nerve (CTN) or posterior canal wall was affected in 8% of the 153 patients and the fallopian canal in 6%. These patients had a facial-chorda tympani nerve distance on the CT scan that was considerably smaller than normal patients (1.5 mm vs 2.3 mm). In addition, a prediction line towards the anterolateral side of the RWM was found to be more prevalent in these patients' CT scans (sensitivity 81%, specificity 63%). CONCLUSION: The RW approach is feasible in almost all patients undergoing CI surgery. Difficult visualisation of the RWM seems to lead to at least one intraoperative event. Radiological measures showed that these patients had a smaller facial recess and a more anteriorly placed facial nerve, which can be used to better plan a safe insertion approach