Is There Any Correlation between Spread of Excitation Width and the Refractory Properties of the Auditory Nerve in Cochlear Implant Users?

BACKGROUND: The spread of excitation (SOE) and auditory nerve recovery function (REC) are objective measures recorded by neural response telemetry and may interfere in cochlear implant (CI) stimulation. OBJECTIVE: To analyze and correlate SOE with the refractory periods in subjects with pre- and postlingual deafness implanted with different electrode arrays. METHODS: This was a retrospective study of 323 ears separated by perimodiolar or straight arrays and by pre- or postlingually deaf recipients. Measures were collected intraoperatively on electrode 11. The SOE width was measured in millimeters at the 0.75 point of the curve, and the relative (tau) and absolute (t0) refractory periods were measured in microseconds. RESULTS: There was a statistical correlation between the SOE and the t0 in the patients with postlingual deafness implanted with the perimodiolar array. The SOE width was statistically different between the straight and perimodiolar arrays and between the pre- and postlingual groups in the perimodiolar array. Tau was statistically different between the pre- and postlingual groups with the straight array and the t0, between the pre- and postlingual groups with the perimodiolar array. Neural response threshold and amplitude of the neural response were not statistically different among groups. CONCLUSION: There was a correlation between SOE width and t0 only in patients with acquired deafness. The findings suggest that different factors influence SOE and REC, considering SOE is different according to the electrode array and REC being different according the onset of deafness.

Are There Cochlear Dead Regions Involved in Hearing Loss after Cisplatin Ototoxicity?

BACKGROUND: The most common complaint of patients affected by chemotherapy-induced hearing loss is difficulty understanding speech in noisy environments despite the use of hearing aids. Cochlear dead regions, those areas with damaged or absent inner hair cells and dendrites, may account for this type of hearing loss. However, it is unknown whether this condition is associated with cisplatin agents. OBJECTIVE: The aim of this study was to determine whether cisplatin is associated with hearing loss and cochlear dead regions. METHODS: This prospective cross-sectional study was conducted in patients participating in routine audiological monitoring during and after chemotherapy treatment. Adults undergoing audiological evaluation who had completed chemotherapy treatment were invited to participate. Patients were divided into 3 groups according to pure tone thresholds. Group 1 patients had thresholds over 70 dB (HL) at 2,000 Hz and higher frequencies. Group 2 patients had thresholds below 70 dB (HL) up to 2,000 Hz. Patients in the control group had normal thresholds at all frequencies. The threshold equalizing noise test (TEN[HL]) was used to identify cochlear dead regions by repeating thresholds in the presence of TEN noise played from a compact disc. The presence of cochlear dead regions was established when the masked threshold was 10 dB or greater above the TEN level and 10 dB or greater above the absolute threshold at any frequency. RESULTS: Twelve patients were included in study group 1, 10 patients in study group 2, and 7 patients in the control group. Cochlear dead regions were present in all patients with hearing loss and in none of the control group. For groups 1 and 2, mean differences between absolute and masked thresholds were 21 and 16 dB at 500 Hz; 22 and 15 dB at 1,000 Hz; 31 and 17 dB at 2,000 Hz; 32 and 20 dB at 3,000 Hz; and 31 and 21 dB at 4,000 Hz, respectively. Nevertheless, analysis of variance testing with Bonferroni analysis showed a difference between groups 1 and 2 only at 2,000, 3,000, and 4,000 Hz. CONCLUSION: We found unresponsive or dead cochlear regions in patients who had undergone cisplatin chemotherapy even among patients with mild to moderate hearing loss.

Evaluation of ototoxicity in children treated for retinoblastoma: preliminary results of a systematic audiological evaluation.

BACKGROUND: The objective of this study was to identify the ocurrence of hearing loss in children treated for retinoblastoma using a multidisciplinary approach. PATIENTS AND METHODS: Thirty-two children were evaluated pre- and post-treatment. Eleven children were treated exclusively with enucleation, fifteen with carboplatin and six with cisplatin. Otoacoustic emissions were performed with the ILO 88, before and after the treatment. RESULTS: In our study we found 5 children (24%) with hearing loss among the 21 evaluated. However in the group of children treated with carboplatin (N=15), 1 case (6.6%) presented hearing loss, while among those treated with cisplatin (N=6) we found 4 cases (66.6%) with hearing loss (p=0.0114). CONCLUSION: We concluded that patients who are treated with cisplatin are at risk for developing hearing loss.