BACKGROUND AND OBJECTIVES: Electrically evoked middle latency response (EMLR) has several advantages over electrically evoked auditory brainstem response (EABR). The major component peaks of EMLR lie outside the region of stimulus artifacts and it reflects the activation of a more significant portion of the auditory pathway than EABR. It is known that several conditions alter the general morphology, amplitude, and latency of the waveforms of EMLR. The purpose of this study was to record and evaluate the effects of stimulation rate and pulse duration on detectability, latency and amplitude of EMLR in the cat. MATERIALS AND METHOD: EMLR was recorded in response to 9 experimental conditions-3 conditions of pulse duration (150, 200, 250 micron sec biphasic) at each of 3 conditions of stimulation rate (2, 6 and 10/sec)-after electrical stimulation at the round window in 7 cats. RESULTS: PA was identified in all conditions. PB was obtained from 17 of the 63 waves. The latency of PA was significantly shorter and the amplitude of PA was significantly larger for the stimulation rate of 10/sec and the pulse duraion of 250 micron sec compared with other conditions. CONCLUSION: We found that based on the present data, the optimal stimultion condition for EMLR in our laboratory was the stimulation rate of 10/sec and the pulse duration of 250 micron sec. This data can provide a basis for the appropriate stimulation condition of EMLR in human.
Animals ; Artifacts ; Auditory Pathways ; Cats ; Cochlear Implantation ; Electric Stimulation ; Evoked Potentials, Auditory, Brain Stem ; Humans

Humans ; Auditory Pathways ; Hearing Loss, Sensorineural ; Cochlear Implantation ; Cochlear Implants ; Hearing Loss, Central ; Auditory Threshold ; Evoked Potentials, Auditory, Brain Stem

BACKGROUND AND OBJECTIVES: Auditory brainstem implantation (ABI) is another option for hearing rehabilitation in non-neurofibromatosis type 2 patients who cannot undergo cochlear implantation (CI). However, the average performance of ABI is worse than that of CI. We analyzed the psycho-electrical parameters of each electrode and psycho-acoustic response to different frequency sounds in nontumor patients with ABI. SUBJECTS AND METHOD: Sixteen patients with ABI from July 2008 to May 2013 were included in the study. They were followed up for 4 to 56 months. Among them, 12 were prelingual deaf with a narrow internal auditory canal or cochlear ossification. The remaining four were post-lingual deaf adults with severely ossified cochleae. We analyzed the electrical parameters [impedance, threshold level (T level), and dynamic range] of each of the 12 electrodes. We also evaluated the sound field pure-tone threshold, Ling 6 sound detection-identification test (Ling 6 test), and pitch ranking data of these patients. RESULTS: The impedance, T level, and dynamic range did not significantly differ among electrodes. However, the pure-tone threshold to sound field stimulation was elevated in the high tone area, where more variables were found than in the low frequency area. Patients could not identify /S/ and /Sh/ sounds in the Ling 6 test. The mean T level and the dynamic range of the three highest pitch-perceiving electrodes in each patient was higher and narrower, respectively, than those of the three lowest pitch-perceiving electrodes. CONCLUSION: The nontumor patients with ABI have difficulty perceiving high pitch sound. More sophisticated penetrating type electrodes and, if possible, bimodal stimulation with CI, could be considered.
Adult ; Auditory Brain Stem Implantation* ; Auditory Brain Stem Implants* ; Cochlea ; Cochlear Implantation ; Cochlear Implants ; Electric Impedance ; Electrodes ; Hearing ; Humans ; Methods ; Rehabilitation

BACKGROUND AND OBJECTIVES: Recently, functional studies for auditory cortex are being watched with interest in accordance with development of many radiologic equipments and surgical devices for sensorineural hearing loss. Moreover, it is well known that the function of central auditory pathway is essential for hearing rehabilitation. There are some papers that reported about the functional or metabolic changes of auditory cortex in deafness and in patients with cochlear implantation. The aim of this study was to investigate indirectly the metabolic changes of primary auditory cortex and visual cortex in the c-fos immunoreactivity in an experimentally induced permanent threshold shift animal model. MATERIALS AND METHOD: Ototoxic drugs (kanamycin and furosemide) and noise were used for the induction of permanent threshold shift. Cochlear damages were evaluated with auditory brainstem responses (ABR) and morphologic studies. The c-fos immunoreactivity was observed with a lapse of time after deafening. RESULTS: After the administration of ototoxic drugs and noise exposure, ABR threshold shifts were not recovered until after three months. Cochlear damages were observed in broad areas of cochlea. The c-fos immunoreactivity in the primary auditory cortex was increased during the acute period but it was decreased after one month. In addition, it was recovered again within the level of control three months later. In the visual cortex, increased and sustained immunoreactivities were observed after the drug and noise exposure. CONCLUSION: This result shows the plasticity of auditory cortex and possibility of some kinds of auditory-visual cross modal plasticity.
Animals ; Auditory Cortex ; Auditory Pathways ; Cochlea ; Cochlear Implantation ; Cochlear Implants ; Deafness ; Evoked Potentials, Auditory, Brain Stem ; Guinea ; Guinea Pigs ; Hearing ; Hearing Loss, Sensorineural ; Humans ; Noise ; Plastics ; Visual Cortex

BACKGROUND AND OBJECTIVES: We aim to explore the effects of residual auditory steady state response (ASSR) on cochlear implantation (CI) outcomes in children lacking auditory brainstem responses (ABRs). SUBJECTS AND METHODS: We retrospectively reviewed the data of child CI recipients lacking ABRs. All ears were divided into two groups: with residual ASSR and without ASSR. For each frequency, the T- and C-levels and the electrical dynamic ranges of postoperative 3-month and 1-year mappings were compared between the groups. To evaluate speech perception, patients who received simultaneous bilateral CIs were divided into two groups: group 1 exhibited responses at all frequencies in both ears; in group 2, at least one ear evidenced no response. The Categories of Auditory Perception (CAP) and Infant-Toddler Meaningful Auditory Integration Scale (IT-MAIS) scores were compared between the groups. RESULTS: We enrolled 16 patients. At 2 kHz, the postoperative 3-month and 1-year T-levels of patients with residual hearing were lower than those of hearing loss group (p=0.001, p=0.035). In residual hearing group, the ASSR threshold correlated positively with the postoperative 1-year T-level (p=0.012, R² =0.276) and C-level (p=0.002, R² =0.374). Of 10 simultaneous bilateral CI recipients, 5 exhibited ASSRs at all frequencies and the other 5 showed no response at ≥1 frequency. The latter had higher CAP scores at the postoperative 1-year (p=0.018). CONCLUSIONS: In children exhibiting hearing loss in ABR testing, residual hearing at 2 kHz ASSR correlated positively with the post-CI T-level. Those with ASSRs at all frequencies had significantly lower CAP scores at the postoperative 1year. CI should not be delayed when marginal residual hearing is evident in ASSR.
Auditory Perception ; Child ; Cochlear Implantation ; Cochlear Implants ; Ear ; Evoked Potentials, Auditory ; Evoked Potentials, Auditory, Brain Stem ; Hearing Loss ; Hearing Loss, Sensorineural ; Hearing ; Humans ; Retrospective Studies ; Speech Perception

Patients with neurofibromatosis type 2 (NF2) develop bilateral vestibular schwannomas that can cause binaural progressive hearing loss in most individuals. Auditory rehabilitation for bilateral profound sensorineural hearing loss in patients with NF2 poses a great therapeutic challenge. An auditory brainstem implantation may be an option after tumor excision, but its hearing results are still relatively unsatisfactory. A cochlear implantation (CI) may be another option in those cases where the cochlear nerve has been left intact after tumor excision or in those cases that have been kept stable after treating with Gamma-Knife. Here we report a case of undergoing CI after having been treated with Gamma-Knife in NF2 and showing improved open-set speech perception.
Auditory Brain Stem Implantation ; Auditory Brain Stem Implants ; Cochlear Implantation* ; Cochlear Implants* ; Cochlear Nerve ; Hearing ; Hearing Loss ; Hearing Loss, Sensorineural ; Humans ; Neurofibromatosis 2* ; Neuroma, Acoustic ; Radiosurgery ; Rehabilitation ; Speech Perception

Child ; Cochlear Implantation ; Cochlear Implants ; Evoked Potentials, Auditory, Brain Stem ; Hearing Loss, Central ; physiopathology ; Humans ; Vestibulocochlear Nerve Diseases ; physiopathology

OBJECTIVE: To introduce a rat model for use in cochlear implant related research. METHOD: Five deafened Hooded-Wistar rats were implanted with a scala tympani electrode array using a new surgical method. Electrically evoked brainstem responses (EABRs) using bipolar stimulation were recorded and cochlear history was assessed. RESULT: Electrically evoked brainstem responses with normal configuration confirmed the functional status of the cochlear implantation. There was no evidence of severe insertion-induced damage of intra-cochlear structure. CONCLUSION The surgical method established in the rat model is a safe and effective procedure for acute or chronic cochlear implantation.
Animals ; Cochlear Implantation ; methods ; Cochlear Implants ; Evoked Potentials, Auditory, Brain Stem ; Male ; Models, Animal ; Rats ; Rats, Wistar

OBJECTIVE: To evaluate the electrophysiological characteristics of electrically evoked auditory brainstem responses (EABR) and its application in cochlear implantation, especially in evaluating acoustic nerve survival. METHOD: An auditory evoked potential instrument was used to record responses and Cochlear Nucleus 24CA implants were used to generate electrical stimulation. We measured EABR in 23 patients with cochlear implants and compared EABR with behavioral measures and neural response telemetry (NRT). RESULT: EABR III-V waveforms were recognized in all of the 23 patients. The characteristics and origins of EABR waveforms were similar to those of ABR. The average EABR threshold was (172.61 +/- 14.61) CL. At 20 CL above threshold, the average latencies of Wave III, V were (2.93 +/- 0.18)ms, (4.80 +/- 0.28)ms which were 1-2 ms shorter than ABR latencies. But III-V intervals remained at (1.86 +/- 0.18)ms. EABR thresholds were strongly correlated with behavioral performance and NRT thresholds, while EABR input-output function is correlated with behavioral dynamic range (DR). CONCLUSION EABR is such an effective method to objectively evaluate the function of auditory pathway which can estimate residual spiral ganglion cell count. This is consistent with the foreign study leading to the conclusion that DR reflects spiral ganglion cell survival.
Auditory Threshold ; Child ; Child, Preschool ; Cochlear Implantation ; Cochlear Nerve ; physiopathology ; Deafness ; physiopathology ; surgery ; Evoked Potentials, Auditory, Brain Stem ; physiology ; Female ; Humans ; Infant ; Male

Aged ; Auditory Brain Stem Implantation ; instrumentation ; methods ; Female ; Humans ; Male ; Middle Aged ; Neurofibromatosis 2 ; diagnosis ; rehabilitation ; surgery ; Speech Perception ; Speech Therapy