Auditory perception in pediatric cochlear implant users with cochlear nerve hypoplasia

OBJECTIVES

The objectives of this study were to assess auditory perception and speech intelligibility outcomes in children with cochlear nerve (CN) hypoplasia who received cochlear implants (CIs) using Categories of Auditory Performance II (CAP II) and Speech Intelligibility Rating (SIR) scales.

METHODS

In total, 40 children who received CI and who were aged between 3 and 18 years were included in this study. The study group included 20 children with CN hypoplasia at least one ear, while the control group included 20 children with normal cochleas and cochlear nerve structures. All children in the study and control groups who participated were evaluated using the CAP II and the SIR scale. Demographic data were collected.

RESULTS

Significant differences were found between the study and control groups' CAP II and SIR scores (p < 0.001). It was found that CAP II scores were positively correlated with SIR scores in the study (r = 0.743, p < 0.001) and control (r = 0.601, p < 0.001) groups. In the study group, significant negative correlations were found between SIR scores and age at implantation (r = -0.674, p = 0.004) and between CAP II scores and age at implantation (r = 0.751, p = 0.003). In the control group, a significant negative correlation was found between age at implantation and CAP II scores (r = -0.805, p = 0.001). Similarly, a significant negative correlation was found between age at implantation and SIR scores (r = -0.702, p = 0.007).

CONCLUSION

Even for children with severe inner ear malformation and CN hypoplasia, CI is an effective treatment modality for auditory perception and speech production. However, it should be noted that CN hypoplasia affects auditory performance negatively in children with CI.

A Comparison of Surgical Auditory Nerve Response and Speech Outcomes in Patients with Post-meningitic Deafness and Without Cochlear Osteogenesis Who Underwent Cochlear Implantation

Objective

Patients with post-meningitis deafness remain challenging candidates for cochlear implantation (CI) which can be difficult due to fibrosis or ossification of the inner ear, and their outcomes remain doubtful. We assessed the surgical and audiological outcomes of CI in patients with profound sensorineural hearing loss caused by meningitis and compared those outcomes to patients without cochlear ossification.

Methods

This retrospective cross-sectional study was carried out at King Fahad General Hospital, Jeddah, Saudi Arabia. Among 246 patients who underwent cochlear implantation, 13 patients with post-meningitic deafness were identified (Group 1). A matched control group, including patients with deafness due to other causes who did not have cochlea osteogenesis, was selected (Group 2). For all patients, data were collected from medical records, including surgical and audiological outcomes.

Results

Sclerosis of the cochlea was high in Group 1 (46.2%). There were no postoperative surgical complications in either group. Responses of the auditory nerve action potential obtained through auditory response telemetry (ART) or the neural response telemetry (NRT) were recorded. There was no significant difference between the two groups regarding the intraoperative and the postoperative ART or NRT at selected electrodes representing the entire cochlea. Likewise, no significant difference regarding the speech recognition test (SRT) was detected.

Conclusions

Cochlear implantation is a safe procedure without surgical complications in post-meningitis patients. Furthermore, early CI in children was associated with favorable outcomes in terms of preservation of the auditory nerve response, restoration of speech discrimination, and recognition to levels comparable to patients with deafness due to other causes. Early audiological assessment in meningitis patients is recommended to identify hearing loss and eventually to offer CI.

Transient Hearing Loss Within a Critical Period Causes Persistent Changes to Cellular Properties in Adult Auditory Cortex

Sensory deprivation can induce profound changes to central processing during developmental critical periods (CPs), and the recovery of normal function is maximal if the sensory input is restored during these epochs. Therefore, we asked whether mild and transient hearing loss (HL) during discrete CPs could induce changes to cortical cellular physiology. Electrical and inhibitory synaptic properties were obtained from auditory cortex pyramidal neurons using whole-cell recordings after bilateral earplug insertion or following earplug removal. Varying the age of HL onset revealed brief CPs of vulnerability for membrane and firing properties, as well as, inhibitory synaptic currents. These CPs closed 1 week after ear canal opening on postnatal day (P) 18. To examine whether the cellular properties could recover from HL, earplugs were removed prior to (P17) or after (P23), the closure of these CPs. The earlier age of hearing restoration led to greater recovery of cellular function, but firing rate remained disrupted. When earplugs were removed after the closure of these CPs, several changes persisted into adulthood. Therefore, long-lasting cellular deficits that emerge from transient deprivation during a CP may contribute to delayed acquisition of auditory skills in children who experience temporary HL.