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Article

Comparison of Perioperative Electrophysiological Measurements and Postoperative Results in Cochlear Implantation with a Slim Straight Electrode

by
Tina Gabrovec
1,
Jana Dragar
1,
Domen Guzelj
1,
Petra Povalej Bržan
1,2 and
Janez Rebol
1,3,*
1
Faculty of Medicine, University of Maribor, 2000 Maribor, Slovenia
2
Faculty of Electrical Engineering and Computer Science, University of Maribor, 2000 Maribor, Slovenia
3
Department of Otorhinolaryngology, University Medical Centre Maribor, 2000 Maribor, Slovenia
*
Author to whom correspondence should be addressed.
Appl. Sci. 2023, 13(5), 3292; https://doi.org/10.3390/app13053292
Submission received: 13 December 2022 / Revised: 1 March 2023 / Accepted: 2 March 2023 / Published: 4 March 2023
(This article belongs to the Section Applied Biosciences and Bioengineering)
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Abstract

:
This research aims to determine whether a neural response telemetry (NRT) threshold determines the success of surgery. Furthermore, we examined whether the patient’s age, the etiology of their hearing loss, the depth of the electrode insertion, and a slow electrode insertion affect the result of postoperative speech audiometry (PSA). A total of 23 patients that had operations in a tertiary medical centre were included in the research. All of them received a slim straight electrode that was inserted through the round window into the lateral part of scala tympani The duration of the insertion was consistently 2 min in 52.2% and less than 2 min in 47.8% of cases. Statistical analyses were performed in the IBM SPSSTM program. Patients that were diagnosed with sensorineural hearing loss (SNHL) had statistically lower average NRT threshold values in comparison to patients diagnosed with otosclerosis (t = 3.069; p = 0.034). The depth of electrode insertion is inversely proportional to the average of all NRT thresholds (r = −0.464; p = 0.026). No correlation was found between slow electrode insertion and postoperative average values of tone audiometry (U = 44.000; p = 0.300). No statistically significant correlation could be drawn between the average of all NRT thresholds and postoperative speech audiometry (rho = −0.070; p = 0.751).

1. Introduction

A cochlear implant (CI) is a surgically implanted device for the treatment of severe to profound sensorineural hearing loss (SNHL). It works by transducing acoustic energy into an electrical signal, which is used to stimulate surviving spiral ganglion cells of the auditory nerve. Despite the difficulties in inserting the electrode array due to potential ossification of the cochlea and facial nerve stimulation, cochlear implantation is also extensively beneficial for patients with otosclerosis [1,2].
Although speech perception capabilities of patients with CI have improved significantly over the years, the degree of postsurgical speech recognition has been unpredictable and variable [3]. The reason behind this variability is not completely understood, and so far there is no accurate way of precisely predicting the outcome of the implantation. Understanding and explaining the reasons for diverse outcomes following implantation is a very challenging research problem that has, due to its clinical significance, been the subject of great interest [4]. Pisoni et al. [4] emphasized the issue of patients’ individual differences, the lack of preimplant predictors of outcomes, and the question of what to do with a CI-user who has a poor outcome. The importance of recognizing factors that influence CI outcomes lies in favorable effects on counseling, improved surgical approaches, and better device fitting, and can ultimately lead to maximized performance and satisfaction for each recipient [5].
An important factor that affects speech outcomes of patients with CIs is the condition of the auditory nerve [3]. Neurons rapidly propagate signals over large distances. There is a threshold value for each neuron to be depolarized. By reaching the threshold value, electrical pulses called action potentials are generated in the neuron [6]. Neural response telemetry (NRT) is an objective method, performed intraoperatively, which captures the action potential of the distal part of the auditory nerve in CIs and thus represents a direct method of assessing the in vivo functional characteristics of ganglion cells and other auditory neural structures. The action potential that is reflected by NRT represents the synchronized firing of many auditory nerve fibers and consequently illustrates the sum of the electrical activity of hundreds of neurons [7].
The electrode in the cochlear implant is a major factor in hearing performance as it represents the interface between the cochlear implant and the recipient’s auditory neural pathways. The long-term advantages of the slim straight electrode are low-frequency preservation of residual hearing, significant improvement of speech understanding in quiet and noisy environments, avoidance of intracochlear trauma, and greater adaptability in anatomical and pathological variations where the cochlea is not suitable for the perimodiolar electrode insertion [8]. Furthermore, the findings of Woodson et al. suggest that the choice of electrode does not significantly affect the outcome of the procedure [9]. At the top, the diameter is only 0.3 mm, and the depth of insertion could vary in cases of hearing preservation. It has 22 medial-facing, half-banded platinum electrode contacts positioned over 20 mm [10].
Our research aims to determine whether a low intraoperative NRT threshold determines the surgery’s success. Furthermore, we aimed to explore whether the patient’s age, the etiology of their hearing loss, the depth of the electrode insertion, and the slow insertion of the electrode affect the results of postoperative speech audiometry (PSA).
Our research advantage lies in a unified surgical approach. All our patients received a slim straight electrode, inserted through a round window into the lateral part of the scala tympani. The duration of the insertion was consistently 2 min in 52.2% and less than 2 min in 47.8% of cases. The insertions were performed by the same surgeon. These controlled circumstances enabled us to effectively compare the influence of perioperative electrophysiological measurements on postoperative cochlear implantation results. Furthermore, we were able to examine the impact those variables have on one another. If we can predict the exact correlation and importance of the variables individually as well as combined, we will get closer to predicting the cochlear implantation’s success rate.
The main contributions of our research are:
  • Examining the effect of the NRT threshold on the surgery’s succes under controlled circumstances, i.e., a unified surgical approach through a round window into the lateral part of scala tympani with comparable duration of insertion, done by the same surgeon who used a slim straight electrode in all patients.
  • Effectively comparing the influence of different perioperative electrophysiological measurements on postoperative cochlear implantation results.
  • Effectively comparing the impact that perioperative electrophysiological measurements have on one another.
  • If we can predict the exact correlation and importance of the variables individually as well as combined, we will get closer to predicting the cochlear implantation’s success rate which will have a significant clinical importance in choosing suitable patients for this type of surgery.

2. Materials and Methods

The study was conducted following the Declaration of Helsinki and with the approval of the Ethics Committee of a tertiary medical centre. We included 23 patients with CIs. All patients had a slim straight electrode inserted through the round window into the scala tympani by the same surgeon, allowing the greatest possibility for mutual comparison. The depth of the electrode insertion was measured radiographically as degrees of angular rotation within the cochlea. The duration of the electrode insertion was consistently 2 min in 52.2% and less than 2 min in 47.8% of patients. In all cases, the lumen of the cochlea was checked on CT and MRI preoperatively, and the choice of inserting a slim straight electrode in patients with otosclerosis was made when the lumen of the cochlea was not affected by otosclerosis.
Questionnaires that were given to the patients at home were used to collect demographic data. We acquired the intraoperative NRT measurements, preoperative and postoperative tone audiometry thresholds measured without additional hearing aids, together with tone and speech audiometry measurements with an implanted CI. Postoperative measurements were performed approximately 6 months after the cochlear implantation.
All data were collected and organized in Microsoft Office ExcelTM version 2103 (16.0.13901.20400). It was then exported to IBM SPSSTM version 28.0.0.0. For the NRT data set, we calculated and used the average value of all 22 electrode thresholds in microvolts. Some studies measured NRT on specific electrodes, which varied from case to case. Consequently, we decided to take the average of all NRT electrode thresholds for better comparison. We also compared preoperative and postoperative tone audiometry thresholds to assess the level of postoperative residual hearing preservation.
Nominal variables are presented with frequencies (percentages) and numerical variables with mean ± standard deviation or median (95% CI) when the normality assumption was violated. Normality was tested using the Shapiro–Wilk normality test. The Pearson correlation coefficient was calculated for normally distributed variables and the Spearman correlation coefficient for non-normal distributions. The Fisher exact test, Student t-test, and Mann–Whitney U test were used in the comparison of otosclerosis and SNHL groups.

3. Results

3.1. Demographics

A total of 23 patients participated in the study; the median age was 66 years (59, 71). The youngest patient was 22 years old, and the oldest patient was 89 years old. Out of all the patients, 14 (60.9%) were female and 9 (39.1%) were male. The external processor wear time in 10 (43.5%) of the patients was more than 16 h per day, in 11 (47.8%) patients between 11 and 15 h per day, and in 2 (8.7%) patients less than 8 h per day. Otosclerosis was diagnosed in 4 (17.4%) patients and sensorineural hearing loss (SNHL) in 18 (78.3%) patients. One (4.3%) patient was diagnosed with Usher syndrome (Table 1). The SNHL and otosclerosis groups are not significantly different in age (p = 0.457) and gender distribution (p = 0.602).

3.2. Preoperative Measurements

The average duration of hearing loss in the operated ear was 20 ± 12 years with a minimum value of 2 years and a maximum value of 45 years. The average duration of hearing loss in the non-operated ear was 21 ± 12 years, with a minimum value of 2 years and a maximum value of 45 years (Table 1). The average tone audiometry before surgery was 89.0 ± 15.8 dB (56.3 dB, 115.0 dB) (Table 2).

3.3. Intraoperative Measurements

The electrode was inserted slowly; the duration of the insertion was more than 2 min-in 12 (52.2%) patients. In the remaining 11 (47.8%) patients, the electrode was inserted faster. The average depth of the electrode was 415 ± 54 degrees, with a minimum of 300 degrees and a maximum of 495 degrees. The insertion depth was not significantly different in the SNHL and otosclerosis groups (p = 0.099). The average of NRT threshold values across all electrodes was 190.8 ± 17.9 microvolts, with a minimum value of 158.4 and a maximum value of 231.2 microvolts (Table 2). The average of NRT threshold values of patients that were diagnosed with otosclerosis was 213.1 ± 16.0 (195.4, 231.2) microvolts and the average of all NRT threshold values of patients that were diagnosed with SNHL was 186.3 ± 15.0 (158, 210) microvolts (Table 3). Figure 1 shows intraoperative electrode insertion process.

3.4. Postoperative Measurements

The median time between surgery and speech audiometry was 316 (224, 533) days. The median value of all recognised words on speech audiometry at 65 dB was 85% (70%, 90%). Residual hearing improved in one (4.3%) patient, remained unchanged in 6 (26.1%) patients (±10 dB), worsened by 10 to 20 dB in 9 (39.1%) patients, and worsened by more than 20 dB in 7 (30.4%) patients. Other data can be observed in Table 2 and Table 3.

3.5. Correlations Found

The average of all NRT threshold values was lower in patients that were diagnosed with SNHL than with otosclerosis (t = 3.069; p = 0.034) (Figure 2). The electrode insertion depth was negatively correlated with the average of all NRT threshold values (r = −0.464; p = 0.026).
There was no statistically significant correlation between the average of all NRT threshold values and the patient’s age (r = 0.262; p = 0.227); the average of all NRT threshold values and duration of hearing loss before surgery in years (rho = 0.056; p = 0.788); the average of all NRT threshold values and hearing preservation (r = 0.080; p = 0.751); slow electrode insertion and postoperative average values of tone audiometry (U = 44.000; p = 0.300); the average of all NRT threshold values and speech audiometry at 65 dB (rho = −0.070; p = 0.751); and the percentage of words recognized on speech audiometry with electrode insertion depth (rho = 0.386; p = 0.069).

4. Discussion

The purpose of this study was to explore in detail the effects of specific pre- and intraoperative factors on postoperative results in cochlear implantation. We discovered to what extent these factors co-influence one another. We were able to compare measurements by inserting the same type of electrode array, using the same electrode position within the cochlea, and measuring the duration of the insertion in the cochlea, which resulted in a consistent distance from the nerve in all patients.

4.1. The Influence of Etiology on NRT and PSA

4.1.1. Etiology and NRT

We found a correlation between the etiology and the average of all NRT threshold values. Patients that were diagnosed with SNHL had significantly lower average NRT thresholds compared to otosclerosis patients. In otosclerosis, there is pathological bone growth, caused by increased activity of osteoblasts, which peaks with an increase in the otic capsule. Excessive bone growth in the cochlea could increase the energy that is required for stimulation, which would increase NRT measurements [11]. Guedes et al. [11] also detected a slight increase in NRT thresholds in subjects with deafness due to otosclerosis and meningitis in comparison to other etiologies. Pathological bone growth can also be found in meningitis [11].
Other studies indicated a prevalence in the absence of response in all electrodes in progressive and ossifying conditions [11,12]. Venail et al. [13] compared NRT thresholds within different hearing loss etiologies, including progressive sensorineural deafness in 11 cases and otosclerosis in 3 cases. They found no impact of hearing loss etiology on NRT thresholds, however, they found a nearly significant effect of patient’s ototoxic exposure, e.g., to drugs [13].

4.1.2. Etiology and PSA

There have been many different conclusions about whether the etiology of deafness has a significant effect on postoperative speech perception in patients with CIs. It is known that meningitis leads to cochlear ossification and sensorineural hearing loss. A systematic review demonstrated that the audiological post-implantation outcomes achieved in patients with meningitis were comparable to those in a wider group of implanted patients that were deafened by other causes [14]. On the other hand, Ménière’s disease patients’ hearing outcomes seemed to be worse than the general CI population [15]. In one of the studies, it was found that the preservation of residual neurons affects the results of PSA more than the etiology of the hearing loss itself [13]. In our study, etiology did not influence the PSA result.

4.2. The Influence of Slim Straight Electrode Insertion Depth on NRT and PSA

4.2.1. Electrode Insertion Depth and NRT

NRT thresholds depend on the proximity of the electrode array and the spiral ganglion cells. In the apex, the diameter of the cochlea is smaller, and the electrode array converges to the spiral ganglion cells, hence NRT thresholds are lower in the apex than in the base and that is why an electrode with a greater insertion angle can be assumed to correlate with a smaller NRT ratio [10,16,17]. In our research, we found that the slim straight electrode insertion depth is inversely proportional to the average of all NRT thresholds. This means that the deeper the electrode insertion depth the lower the NRT, although the spiral ganglion cells are in the cochlea only up to a depth of 17 mm [18]. Certainly, the length of the cochlea varies individually. Another study confirmed the importance of electrode positioning in relation to the modiolus in the stimulation of the auditory nerve fibers [19]. Venail et al. [13] demonstrated that NRT thresholds depend on the depth of the insertion of the electrode into the cochlea, the size of the cochlea, the number of residually functional neurons, and the duration of hearing loss. Contrarily, Mittman et al. [10] did not prove the correlation between a greater insertion angle and a smaller NRT ratio.

4.2.2. Electrode Insertion Depth and PSA

No correlation was found between the depth of electrode insertion and PSA at 65 dB word discrimination. Similar conclusions were found by Lee et al. [20], who made sure to control other variants that might influence speech performance such as the duration of deafness, sound-processing strategy, potential for central impairment, and age at implantation.
The study by Skinner et al. [21] found monosyllabic word comprehension scores significantly correlated with electrode insertion depth one year after implantation. Other potentially disturbing factors that can affect the functioning of the CI were not controlled in their study. Lee et al. [20] argued that there is a possibility that a reduction in variability in subjects who all used the same implant system (Nucleus 22) and speech-processing strategy (SPEAK) increased the relative saliency of the insertion-metric’s effect. Other studies have found that the site of cochlear stimulation can affect speech perception [22,23,24].

4.3. The Influence of Age on NRT and PSA

4.3.1. Age and NRT

Age is not significantly associated with the average of all NRT thresholds, which is also supported by Wu et al. [25] and Venail et al. [13].

4.3.2. Age and PSA

Age as a predictor of cochlear implantation success varies between studies. Blamey et al. [26] found poorer speech perception in people over 60 years of age. Friedland et al. [27] reported significantly higher speech recognition scores 1 year after implantation for those younger than 65 years. The age of 65 years represents an appropriate age distribution for assessing the onset of cognitive influences on PSA performance [5]. In our research, the median patient age was 66 years and had no significant influence on PSA. On average, PSA was performed 6 months after the implantation. Similarly, Budenz et al. [28] observed no difference in speech recognition 2 years post-implantation between patients that were younger and older than 70 years. Moreover, Carlson et al. [29] found no differences in monosyllabic words or sentences measured in a noisy environment between cochlear implant users aged 80 years or older and those between 18 and 79 years of age.

4.4. Influences on Hearing Preservation

4.4.1. Slow Electrode Insertion and Hearing Preservation

According to previous research, slow insertion of the electrodes should reduce the insertion force [30] which should reduce the trauma from the insertion itself and reduce intracochlear fluid pressure, which also has a traumatic potential [31,32]. Kesler et al. [33] demonstrated that the standard continuous forward velocity surgeons achieve is 52.3 mm/min with a standard deviation of 19 mm/min. Studies definitively show that slower insertion speeds are associated with improved audiological outcomes [33]. We inserted the electrode in 2 min. As the active length of the slim straight electrode is 20 mm, we divided the active length into quarters and inserted one quarter of the electrode per half a minute.
The slow insertion of the electrodes is said to be particularly important for preserving residual hearing, which is supposed to improve PSA [34]. In our research, we compared the results of tone audiometry, i.e., the preservation of residual hearing, in patients operated with and without the slow insertion of a slim straight electrode. We found that there was no significant change due to slow insertion. There is a possibility that atraumatic insertion was carried out even prior to using the slow insertion technique.
In a study by de Carvalho et al. [35] an even lower degree of hearing preservation was achieved when using slow electrode insertion. The authors suggest that auditory insertion speed might be directly related to the consistency of insertion [34].
On the other hand, the research by Gotamco et al. [36] found that the speed of electrode insertion indeed influenced either complete or partial preservation of residual hearing. With complete preservation, the speed was 33.03 ± 16.66 mm/min, and with partial preservation, it was 43.68 ± 18.27 mm/min. However, it should be emphasized that in their group, in addition to the slow insertion of electrodes, other evidence-based practices were applied to preserve residual hearing, such as electrode selection (slim straight electrode), surgical technique (complete opening of the round window), etc. [36].

4.4.2. The Electrode Depth Insertion and Hearing Preservation

There was no statistically significant association between electrode insertion depth and hearing preservation rate in our research. Some studies support this discovery, and some have shown the opposite results, therefore, the dilemma exists of whether to implant a shorter electrode and increase the likelihood of hearing preservation or to choose a longer electrode and maximize cochlear coverage [24]. Nordfalk et al. [37] discovered no relationship between the angular insertion depth and loss of low-frequency pure-tone average, however, frequency-specific analysis revealed a weak but significant relationship between the angular insertion depth and loss of residual hearing at 250 Hz. Lee et al. [38] and Erixon et al. [39] also discovered no significant correlation between the depth of implantation and hearing preservation, which is consistent with our findings. In contrast, O’Connell et al. [24] found that deeper insertions were associated with greater loss in low-frequency hearing.

4.5. Correlation between NRT and PSA

No significant association was found between the average of all NRT thresholds and PSA at 65 dB in our study. A systematic review of compound action potentials as predictors of cochlear implant performance by van Eijl et al. [40] overviewed 25 articles, out of which seven made a statement about the NRT threshold. Cosetti et al. [41] found no significant association between the NRT threshold and speech perception in adults and children, el Shennawy et al. [42] concluded the same for the adult population and four other studies [43,44,45,46] also found no significant correlation between the NRT threshold and speech perception [40]. All of the above-mentioned studies support our findings. They measured the NRT threshold from different numbers of electrodes and different electrodes were picked. Cosetti et al. [41] used electrodes E5, E10, E15, and E20; el Shennawy et al. [42] measured E2, E4, E6, E8, E10, and E12; Brown et al. [43] captured E4 and E8; and Kiefer et al. [45] used electrodes E3, E5, E10, E15, and E20.
In a Chinese study, lower intraoperative NRT thresholds were associated with a lower NRT threshold in postoperative mapping and the latter significantly affected speech and tone perception [25]. On the other hand, Wu et al. [25] also concluded that intraoperative NRT thresholds are not significantly associated with postoperative speech and tone perception, which supports our claim. In the future, it would be interesting to find measurable parameters during the implantation that could suggest the potential of cochlear injury and its effect on postoperative results.

5. Conclusions

Many factors co-affect the outcome of postoperative speech audiometry in patients with inserted CI. Despite controlled circumstances, the NRT threshold has proven not to be a predictive factor in the success rate of cochlear implantation. We found that, based on perioperative parameters alone, no conclusions can be drawn about the end results in terms of postoperative speech perception or the degree of residual hearing preservation in patients receiving a slim straight electrode through a round window into the scala tympani with a controlled duration of electrode insertion. However, knowing the exact influence of individual factors on cochlear implantation outcome is essential for the future optimization of each surgical procedure. At any rate, a positive NRT response tells us that the electrode is in the correct position for subsequent stimulation and presents a reference in case of complications.

Author Contributions

Conceptualization, J.R.; methodology, P.P.B. and D.G.; software, P.P.B.; validation, J.R. and P.P.B.; formal analysis, P.P.B.; investigation, T.G., J.D. and D.G.; resources, J.R.; data curation, T.G., J.D., D.G. and P.P.B.; writing—original draft preparation, T.G., J.D., D.G. and J.R.; writing—review and editing, J.R. and P.P.B.; visualization, P.P.B. and D.G.; supervision, P.P.B. and J.R.; project administration, T.G.; funding acquisition, J.R. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

The study was conducted in accordance with the Declaration of Helsinki and approved by the Ethics Committee of Maribor University Medical Centre (protocol code UKC-MB-KME-70/21, 15 December 2021).

Informed Consent Statement

Informed consent was obtained from all subjects that were involved in the study. Written informed consent has been obtained from the patient(s) to publish this paper.

Data Availability Statement

Data are available from the authors upon reasonable request.

Acknowledgments

The authors wish to express great appreciation to Borut Vnuk and Milan Brumec from the Hearing and Speech Centre Maribor for their assistance in tone audiometry, speech audiometry, and NRT measurements. Furthermore, we would like to thank all the participants who have made our work possible.

Conflicts of Interest

The authors declare no conflict of interest.

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Applsci 13 03292 g001 550
Figure 1. On the left there is an exposed round window membrane prepared for incision. On the right there is a slim straight electrode inserted through the round window in the same patient.
Figure 1. On the left there is an exposed round window membrane prepared for incision. On the right there is a slim straight electrode inserted through the round window in the same patient.
Applsci 13 03292 g001
Applsci 13 03292 g002 550
Figure 2. NRT threshold values measurements in different diagnosis.
Figure 2. NRT threshold values measurements in different diagnosis.
Applsci 13 03292 g002
Table
Table 1. Sample description.
Table 1. Sample description.
N (%)
GenderFemale14 (60.9)
Male9 (39.1)
Cochlear implant2 (8.7)
Cochlear implant + Hearing aid20 (87)
Cochlear implant on both ears1 (4.3)
DiagnosisOtosclerosis4 (17.4)
UsherSy1 (4.3)
SNHL18 (78.3)
Slow insertionYes12 (52.2)
No11 (47.8)
Mean ± SDMedian (95% CI)Min–Max
Age (years)63 ± 1566 (59, 7)22, 9
Electrode insertion depth (degrees)415 ± 54420 (405, 450)300, 495
Time between surgery and audiometry (days)542 ± 535316 (224, 533)163, 2096
Time from surgery to survey completion (days)1153 ± 810975 (565, 1654)199, 2751
Duration of hearing loss before ear surgery with a cochlear implant (years)20 ± 1220 (16, 28)2, 5
Duration of hearing loss before ear surgery without a cochlear implant (years)21 ± 1220 (15, 26)2, 5
External processor wear time (hours per day)13.4 ± 2.914 (12, 16)6.5, 16
Legend: UsherSy: Usher syndrome; SNHL: sensorineural hearing loss; SD: standard deviation; CI: confidence interval.
Table
Table 2. Average of NRT thresholds and audiometry results.
Table 2. Average of NRT thresholds and audiometry results.
Mean ± SDMedian (95% CI)Min, MaxN
Average of all NRT thresholds (microvolts)190.8 ± 17.9191.1 (181.6, 202.9)158.4, 231.223
Postoperative speech audiometry at 65 dB (%)75.2 ± 24.385 (70, 90)20, 10023
Preoperative average tone audiometry (dB)89.0 ± 15.892.5 (81.3, 102.5)56.3, 11523
Average postoperative tone audiometry (dB)104.5 ± 21.0112.5 (104, 120)56.3, 120.023
The difference between pre and postoperative tone audiometry (dB)−15.6 ± 15.7−16.3 (−18.8, −8.8)−45.0, 22.523
Legend: NRT: neural response telemetry; SD: standard deviation; CI: confidence interval.
Table
Table 3. Comparison of otosclerosis and SNHL groups.
Table 3. Comparison of otosclerosis and SNHL groups.
Otosclerosis (n = 4)SNHL (n = 18)
Mean ± SDMedian (95% CI)Min, MaxMean ± SDMedian (95% CI)Min, MaxTest Value (p)
Age (years)67.5 ± 7.966.5 (59, 78)59, 7861.2 ± 16.061 (57, 71)22, 89t = 0.759 (0.457)
Genderfemale N (%)2 (50.0%)12 (66.7%)(0.602) *
male N (%)2 (50.0%)6 (33.3%)
Electrode insertion depth (degrees)372.5 ± 44.1385 (310, 410)310, 410423.1 ± 54.2437.5 (405, 460)300, 495t = −1.733 (0.099)
Average of all NRT thresholds (microvolts)213.1 ± 16.0212.9 (195.4, 231.2)195.4, 231.2186.3 ± 15.0186.1 (179.0, 193.0)158.4, 209.9t = 3.069 (0.034)
Speech audiometry at 65 dB after
surgery (%)		78.8 ± 19.387.5 (50, 90)50, 9074.7 ± 26.485 (60, 90)20, 100U = 35.000 (0.931)
* Fisher exact test; p: p-value; t: t-test value; U: Mann–Whitney U test value; SD: standard deviation; CI: confidence interval.
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MDPI and ACS Style

Gabrovec, T.; Dragar, J.; Guzelj, D.; Bržan, P.P.; Rebol, J. Comparison of Perioperative Electrophysiological Measurements and Postoperative Results in Cochlear Implantation with a Slim Straight Electrode. Appl. Sci. 2023, 13, 3292. https://doi.org/10.3390/app13053292

AMA Style

Gabrovec T, Dragar J, Guzelj D, Bržan PP, Rebol J. Comparison of Perioperative Electrophysiological Measurements and Postoperative Results in Cochlear Implantation with a Slim Straight Electrode. Applied Sciences. 2023; 13(5):3292. https://doi.org/10.3390/app13053292

Chicago/Turabian Style

Gabrovec, Tina, Jana Dragar, Domen Guzelj, Petra Povalej Bržan, and Janez Rebol. 2023. "Comparison of Perioperative Electrophysiological Measurements and Postoperative Results in Cochlear Implantation with a Slim Straight Electrode" Applied Sciences 13, no. 5: 3292. https://doi.org/10.3390/app13053292

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