Abstract
Background: This study aims to evaluate speech production outcomes and auditory performance in children with post-meningitis deafness who were treated with cochlear implants. Additionally, the study assesses the impact of electrode insertion depth on surgical outcomes.“. Methods: We conducted a study on 66 pediatric patients with bilateral postmeningitis hearing loss who were being prepared for cochlear implantation at four tertiary referral academic institutions. The speech intelligibility rating (SIR) and categories of auditory performance (CAP) were evaluated after the first and second years following implantation. The patients were divided into two groups based on electrode insertion depth: one group had full electrode insertion (more than two-thirds), while the other had partial electrode insertion (less than two-thirds). We compared the SIR and CAP scores between the two groups to assess the impact of electrode insertion depth on outcomes. Results: Before implantation, the median CAP score was one, but it improved significantly to six within two years after the procedure (P-value < 0.001). Similarly, the median SIR score before implantation was one, but it improved significantly to three within two years after surgery (P-value < 0.001). However, there was no significant difference between the partial and full electrode insertion groups in terms of CAP and SIR scores during the follow-up evaluations conducted after the first and second years. Conclusion: The study found that cochlear implantation significantly improved speech production skills and auditory performance in children with postmeningitis deafness. Importantly, the amount of electrode insertion at the time of implantation did not have a significant impact on the outcomes.
Keywords: Meningitis, Cochlear implant, Auditary perception, Language developement
Introduction
Meningitis is a common cause of acquired profound hearing loss in young individuals [1]. The infection can rapidly spread to the cochlea through the cochlear aqueduct and internal auditory canal within hours of clinical symptom onset [2]. The resulting damage to inner ear structures, including the organ of Corti, can result in the irreversible sensorineural hearing loss. Streptococcus pneumoniae is known to cause the most severe ear damage among the bacteria that cause meningitis [3], leading to cochlear ossification and partial or complete blockage of cochlear blood flow. While some individuals may experience limited ossification in the scala tympani near the entrance of the cochlear aqueduct, severe cases can lead to entire cochlear ossification within weeks of meningitis [4]. Cochlear implantation surgery may be complicated by cochlear ossification. Therefore, this retrospective study aims to evaluate the effectiveness of cochlear implantation in improving hearing in deaf children with a history of meningitis.
Materials and Methods
This retrospective, multicenter study examined children under the age of ten who underwent cochlear implantation between 2005 and 2020 at four different nationwide cochlear implant facilities and developed hearing loss due to meningitis. The study received approval from the ethics committee under the ethical code IR.MUMS.MEDICAL.REC.8.786, and written informed consent was obtained from the parents of all patients. All patients included in the study had a documented history of bacterial meningitis resulting in severe to profound bilateral hearing loss.
The diagnosis of post-meningitis deafness was conducted using auditory brainstem response (ABR) and auditory steady-state response (ASSR). High-resolution computed tomography scans and magnetic resonance imaging (MRI) of the temporal bone were performed to assess the anatomy of the inner ear, bone anatomy, and cochlear fluid intensity. To ensure data integrity, children with a history of otologic or neurologic disorders, preexisting suspicion of hearing loss, total ossification in CT or MRI, surgical complications preventing implantation of the device, and those who failed to complete the one-year follow-up after surgery were excluded from the study.
Additionally, children above ten years of age at the time of implantation were excluded from the study because our intention was to analyze the effectiveness of hearing aid amplification in younger children.
The cochlear implantation team at each center selected the appropriate device for each child from a range of prosthetic devices, including Cochlear Nucleus Contour Advance TM (Cochlear Ltd., Centennial, USA), HifocusTM (Advanced Bionics LLC, Valencia, USA), and Sonata TM (MED-EL Corporation, Innsbruck, Austria) electrodes. CI fitting was performed one month after surgery.
The children’s ability to hear and produce speech was evaluated using the categories of auditory performance (CAP) test and the speech intelligibility rating (SIR) scale before implantation and at 12 and 24 months after the procedure. These assessments were conducted by a speech therapist and are summarized in Table 1 [5, 6].
Table 1.
The classes of auditory performances (CAP), and Speech intelligibility rating (SIR) scoring
| Classes of auditory performances (CAP) | Speech intelligibility rating (SIR) scoring |
|---|---|
| No awareness of environmental sounds | 1. Connected speech is not comprehensible. Pre-identifiable words in spoken language. A manual primary mode of communication is essential. |
| The awareness of environmental sounds | 2. Connected speech is not comprehensible. Intelligible speech is developed in single words if lip-reading and context cues exist. |
| Response to speech sounds | 3. Connected speech is comprehensible to a listener by concentrating and lip-reading |
| The identification of environmental sounds | 4. Connected speech is comprehensible to a listener with less experience in the speech of a deaf person |
| The discrimination of some speech sounds without lip-reading | 5. Connected speech is comprehensible to all listeners. The child is easily understood in daily contexts |
| Understanding common phrases without lip-reading | |
| Understanding conversation without lip-reading | |
| Using telephone with a known listener |
The cochlear implantations were performed by qualified surgeons under general anesthesia at four collaborating CI centers located in Mashhad, Shiraz, and two centers in Tehran. The surgical procedure involved simple mastoidectomy, retroauricular approach, posterior tympanotomy, and insertion either via trans-round-window or cochleostomy. The surgeons reported any difficulties encountered during electrode installation in a structured manner. Most patients had their implants placed through the scala tympani, while others had them placed via alternative routes. The position of electrodes was confirmed via post-operative imaging, and any complications during surgery were recorded.
The first fitting was conducted one month after surgery, and ultimate programming approaches were obtained six months after activation of the device for all children. The study evaluated speech and hearing outcomes using SIR and CAP ratings, while patient ages at surgery and diagnosis were analyzed based on a retrospective file review. Statistical analysis was performed using SPSS (V.16, SPSS Inc., Chicago, USA). Normal continuous variables were summarized using mean ± SD, while SIR and CAP scores were reported using interquartile ranges and medians (IQRs). Improvement in CAP score at each follow-up was calculated as the difference between the CAP scores at the follow-up time and the previous CAP score for the same subjects. Similarly, improvement in SIR score was evaluated. The Wilcoxon signed-rank test and Mann-Whitney U test were used to assess outcome improvements, with statistical significance defined as P < 0.05.
Results
A total of 68 children with post-meningitis hearing impairment met the study’s inclusion criteria and were enrolled. However, two patients had to be removed from the trial because the electrode array could not be placed due to complete ossification of the cochlea. The remaining 66 cases included 25 girls (37.9%) and 41 boys (62.1%). The mean age at the time of meningitis was 18.29 ± 16.2 months (age range: 1–84 months), while the average age at the time of implantation was 42.38 ± 19.86 months (age range: 13–108 months).
The subjects were divided into two groups based on their electrode insertion status: Group 1 (n = 55, 83.3%) consisted of cases that received a cochlear implant with full electrode insertion (at least two-thirds of the length inserted), while Group 2 (n = 11, 16.7%) included patients who underwent CI surgery with partial electrode insertion (less than two-thirds inserted). It’s worth noting that none of the participants had less than 50% of active electrodes.
Post-operative imaging verified the electrodes’ placement, and the procedure and recovery were uneventful. Pre-op CAP scores had a median value of 1 on a scale from 0 to 1. In Group 1 (full electrode insertion) and Group 2 (partial electrode insertion), the pre-op median CAP scores were 1 (IQR: 0–1) and 0 (IQR: 0–1), respectively. CAP scores were evaluated at one and two years post-operation, as shown in Table 2. A comparison of the median pre- and post-CAP scores revealed a significant change in CAP scores for both groups after surgery (P-value < 0.001). The median improvement in CAP scores after the first- and second-year follow-ups was 4 (IQR: 3-4.5) and 1 (IQR: 0.5-1), respectively.
Table 2.
CAP score evaluation after surgery
| CAP | Pre-operative Median (IQR) |
One year after surgery Median (IQR) |
Two years after surgery Median (IQR) |
|---|---|---|---|
| Group I | 1(0–1) | 5(4-5.75) | 6(5–7) |
| Group II | 0(0–1) | 4(4-4.63) | 5.5(4.75-6) |
| Total | 1(0–1) | 5(4–5) | 6(5–6) |
*group I: full electrode insertion, group II: Partial electrode insertion Med (IQR): medians and interquartile range
Table 3 shows that there were no significant differences between two groups in terms of changes in median CAP scores one and two years after surgery. This suggests that the depth of insertion (with a minimum of 50% active electrodes) was not a significant influential factor in this study’s population.
Table 3.
CAP score Improvement after surgery
| CAP improvement | Group I Med(IQR) |
Group II Med(IQR) |
p-value |
|---|---|---|---|
| First Year | 4(3–5) | 4(3–4) | 0.381 |
| s year | 1(0.5-1) | 1(0.38-2) | 0.773 |
| Total time of Follow up(2 years) | 5(4–6) | 5(4-5.25) | 0.715 |
*group I: full electrode insertion, group II: Partial electrode insertion Med (IQR): medians and interquartile ranges
Table 4 presents the results of SIR score evaluations. The median pre-operative SIR score was 1 with an interquartile range (IQR) of 0–1. The median SIR score in Group 1 (full electrode insertion) before surgery was also 1 (IQR: 0–1). In contrast, the median SIR score for Group 2 (partial electrode insertion) was two (IQR: 1–2).
Table 4.
SIR score evaluation after surgery
| SIR | Pre-operative Med(IQR) |
One year after surgery Med(IQR) |
Two years after surgery Med(IQR) |
|---|---|---|---|
| Group I | 1(0–1) | 2(2–3) | 3(2.5-4) |
| Group II | 2(1–2) | 3.5(2–4) | 4(2.88–4.25) |
| Total | 1(0–1) | 2.25(2–3) | 3(2.5-4) |
*Group I: full electrode insertion, Group II: Partial electrode insertion
In group 1 the median improvement in SIR score after the first-year follow-up was 1 (IQR: 0.5-2), while during the second-year follow-up, the median SIR enhancement was 1 (IQR: 0.5-1). Also in group 2 the median improvement in SIR score after the first-year follow-up was 1 (IQR: 0.75-2), while during the second-year follow-up, the median SIR enhancement was 1 (IQR: 0–1).Table 5 shows that there were no significant differences between two groups in terms of changes in median SIR scores one and two years after surgery.
Table 5.
SIR Improvement after surgery
| SIR improvement | Group I Med(IQR) |
Group II Med(IQR) |
p-value |
|---|---|---|---|
| First Year | 1(0.5-2) | 1(0.75-2) | 0.399 |
| s year | 1(0.5-1) | 1(0–1) | 0.758 |
| Total time of Follow up(2 years) | 1.75(1–3) | 2(1–3) | 0.807 |
*Group I: full electrode insertion, Group II: Partial electrode insertion
The patients were divided into two groups: Group A (better outcome), which had a final (after two years) SIR score of ≥ 3 and CAP score of ≥ 5 (42 patients), and Group B (poorer outcome), which had a final SIR score of < 3 and CAP score of < 5 (24 patients). The ages of those who had meningitis, the period that passed before either group underwent cochlear implantation, or their SIR or CAP scores, were all factors that were compared. Table 6 shows that with the exception of the pre-operative SIR score, none of these factors substantially linked with the result.
Table 6.
The comparison of groups with different outcomes
| variable | Final Improvement group* | Mean ± SD | Med(IQR) | p-value |
|---|---|---|---|---|
| Age at Meningitis | Group B | 15.91 ± 10.28 | 14(10–20_ | 0.836 |
| Group A | 19.59 ± 18.66 | 12(8-24.75) | ||
| Time from Meningitis to CI | Group B | 22.91 ± 14.72 | 20(10–32) | 0.989 |
| Group A | 23.93 ± 18.23 | 20.5(10–33) | ||
| Pre-op SIR score | Group B | 1.17 ± 0.49 | 1(1–1) | 0.046** |
| Group A | 1.56 ± 0.95 | 1(1–2) | ||
| Pre-op CAP score | Group B | 0.67 ± 0.70 | 1(0–1) | 0.91 |
| Group A | 1.13 ± 1.12 | 1(0–2) |
* Group A: Patients with final (after two years) SIR ≥ 3 and CAP ≥ 5. Group B: Patients with final SIR < 3 and CAP < 5.**Significant at level 0.05
Discussion
This study presents the outcomes of cochlear implantation (CI) surgery in children with hearing loss following meningitis. Nikolopoulos et al. reported that all children with various degrees of hearing loss due to meningitis who received cochlear implantation benefited from the treatment, with results similar to those seen in children with normal anatomical ears. [7] A systematic review by Singhal et al. in 2020 showed that cochlear implantation significantly improved speech perception in patients with post-meningitis hearing loss. However, limited conclusive results were attributed to differences in outcome measurement tests and small sample sizes of primary studies. The review identified two limiting factors: the various measures used in different studies and the small number of participants for statistical analysis. [8]
Bille et al. conducted a retrospective study to assess the results of cochlear implants in 22 deaf children after meningitis. They reported an average post-operative SIR score of 4.00 and an average post-operative CAP score of 6.00. [9].
Our findings suggest that many people who had cochlear implantation surgery benefited from the procedure. Two years after surgery, the median CAP score was 6.00, indicating that the children could comprehend common sentences without lip reading, and the median SIR score was 3.00, indicating that the child’s speech was understandable to a listener who lip-reads and focuses within a familiar setting. The Category of Auditory Performance (CAP) is a global measure used to evaluate the daily hearing development of hearing-impaired children. This observation scale can assess short- and long-term results after cochlear implantation and offers higher inter-user reliability and repeatability compared to other measures.
This research assessed the effects of ossified cochleas on the activation of selected sensory components, as they have fewer electrodes than normal cochleas. Our findings showed no discernible difference between the two groups. This could be due to several effective parameters, such as the patient’s background hearing and speech development at the time of hearing loss, the number of activated electrodes, and the post-operative intensive rehabilitation program and follow-up for two years. In contrast, a study conducted by Rotteveel et al. found that patients with partial electrodes in the cochlea had lower auditory outcomes than those with full electrodes. [10].
Panda et al. examined the factors contributing to poor SIR and CAP scores following cochlear implantation. They found that low SIR and CAP scores were linked to greater implantation age, low socioeconomic status, moderate cognitive impairment, and poor compliance with rehabilitation programs. In their multivariate study, they did not discover a negative association between ossification and the CAP and SIR scores. [11] Similarly, previous studies have not found significant differences in results related to the degree of ossification. [12] Moreover, other studies have also reported no correlation between the time after meningitis and ossification development. [13].
Studies conducted by Nichani et al. and Taskin Tokat have reported similar findings to ours, showing that children with post-meningitis who underwent cochlear implantation had good auditory outcomes. These studies also found no significant difference between full-electrode and partial-electrode patients [14].
Several studies suggested that MRI is the gold standard for early screening of patients after meningitis for ossification signs [15]. However, ossification can occur within a few months after meningitis, making electrode insertion difficult or even impossible. Therefore, our study included all cases with full or partial insertions.
In our case, we have identified two individuals diagnosed with autism, two individuals diagnosed with attention deficit hyperactivity syndrome (ADHD), one patient with hydrocephalus, and three patients who have been receiving inadequate rehabilitation due to parental neglect, resulting in poor progress. Besides the process of bone formation, the existence of neurological consequences presents notable difficulties in the rehabilitation of cochlear implants. Individuals with extra disabilities encounter delayed advantages from the implant as they take more time to acquire speech perception and may have additional behavioral or emotional issues that can complicate their speech development. Therefore, it is crucial to establish practical anticipations with parents and patients before the insertion procedure. Individuals experiencing neurological complications should undergo a comprehensive assessment prior to and following the implantation process to detect and manage any further challenges that may arise. Moreover, they necessitate specialized ongoing care and additional focused auditory training to maximize the advantages of the device. The aural rehabilitation program, both in educational settings and at home, should be personalized, rigorous, continuous, and regularly assessed to enhance results for every patient. [16].
There are a few limitations to this research. Due to its retrospective nature and the fact that it included many centers, not all patients had complete data available. Furthermore, we lacked sufficient data for individuals who were ineligible for cochlear implantation. The degree of ossification in the cochlea, as observed in MRI or CT scans, can have an impact on hearing outcomes and can be assessed in further studies. While SIR and CAP are global indicators used to evaluate the effectiveness of cochlear implants in children, these scores may not have the sensitivity to represent subtle differences in speech and auditory performance.
Conclusion
The findings of the current study suggest that cochlear implant surgery significantly improves the speech production skills and auditory performance (SIR and CAP) of patients with post-meningitis deafness. Moreover, our results indicate that the depth of electrode insertion at the time of implantation did not appear to have a significant impact on these outcomes.
Authors’ Contributions
Mohsen Rajati: Designed the study, interpreted the patient data, managed the patient and co-wrote the paper, supervised the research and revised the manuscript. Mohamad Reza Afzalzadeh: Interpreted the patient data, managed the patient and co-wrote the paper. Ahmad Daneshi: Designed the study, managed the patients, collected and interpreted the data. Mohammad Ajalloueyan: Designed the study, managed the patients, collected and interpreted the data. Seyed Basir Hashemi: Designed the study, managed the patients, collected and interpreted the data. Navid Nourizadeh: Designed the study, managed the patients, collected and interpreted the data. Mohammad Mahdi Ghasemi: Designed the study, managed the patients, collected and interpreted the data. Ali Moradi :Revised the manuscript. Mohammad Farhadi: Designed the study, managed the patients, collected and interpreted the data. Alimohamad Asghari: Designed the study, managed the patients, collected and interpreted the data. Saleh Mohebi: Designed the study, managed the patients, collected and interpreted the data.
Funding
None.
Declarations
Conflict of interest
None.
Footnotes
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