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Objective: The purpose of this study is to investigate the early myelination patterns of brainstem auditory nuclei and pathway on magnetic resonance imaging compared with past histological research. We aimed to identify the time course difference in myelination of the brainstem auditory nuclei and pathway between magnetic resonance imaging and histological research results., Methods: Subjects were 192 infants ranging in age from -4 to 224 corrected postnatal weeks. Images were obtained using a 1.5 T magnetic resonance unit. In four sites (cochlear nucleus, superior olivary nucleus, lateral lemniscus, inferior colliculus) of the brainstem auditory nuclei and pathway on four cross-sections obtained perpendicular to the long axis of the brainstem, signal changes of T1- and T2-weighted magnetic resonance images were analyzed using a region-of-interest methodology according to corrected postnatal age., Results: The cochlear nucleus and superior olivary nucleus showed myelinated intensity change from -3 to 13 corrected postnatal weeks on T2-weighted images. The lateral lemniscus showed myelinated intensity change from -3 to 8 corrected postnatal weeks on T1-weighted images and from -1 to 13 corrected postnatal weeks on T2-weighted images. The inferior colliculus showed myelinated intensity change from -2 to 39 corrected postnatal weeks on T2-weighted images., Conclusions: Magnetic resonance imaging revealed the signal intensity change by myelination 11-18 weeks later than those reported in the histological literature. This time lag suggests that apart from histological research, the necessity for the milestones of auditory pathway maturation using MRI is suggested to evaluate the development of brainstem auditory pathway using MRI. This result suggests that myelination does not take place suddenly but happens gradually, so definite myelination, namely the complete change of myelin sheath ingredients, loss of water, and gain of lipids, is needed to be detected by magnetic resonance imaging.

Copyright of Acta Oto-Laryngologica is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Oto-Laryngologica is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Oto-Laryngologica is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: The electrically evoked auditory brainstem response (eABR) during cochlear implantation in common cavity (CC) deformity has not been clinically well studied. Aim/Objective: To investigate the eABR wave configuration during cochlear implantation, the postoperative development of hearing, and educational settings in infants with CC deformity. Materials and Methods: Nine infants who were congenitally deaf and found to have CC deformity and suspected cochlear nerve deficiency by temporal bone CT and MRI were studied. All of them underwent sequential and unilateral cochlear implantation and their eABRs were recorded during the surgery. The postoperative development was followed up. Results: eABRs of all the nine infants with CC deformity showed that the mean peak of the evoked wave V (eV) was the same as that in controls at latencies but was twofold higher than that in controls at thresholds and their postoperative hearing thresholds improved markedly. Conclusion and Significance: The brainstem auditory pathways of the infants were considered intact on the basis of the eV peak latencies in the eABRs. The postoperative development of their speech and hearing abilities and their educational settings varied, probably because of the twofold higher thresholds of their eABRs and limited number of auditory neural units. [ABSTRACT FROM AUTHOR]

Objectives: We sought to determine how the pathology altered electrically evoked auditory brainstem responses (EABRs) in patients with hearing loss by evaluating EABRs in auditory neuropathy patients with OTOF mutations comparing with various types of congenital deafness. Methods: We included 15 patients with congenital hearing loss, grouped according to pathology: OTOF mutations (n = 4), GJB2 mutations (n = 4), SLC26A4 mutations (n = 4), or cytomegalovirus infections (n = 3). EABRs were recorded when patients underwent cochlear implantation surgery. We evaluated the latencies and amplitudes of the recorded EABRs and compared them statistically between four groups. Results: The EABR latencies of Wave III and Wave V, and of the interval between them, were significantly longer in the OTOF mutation group than in the GJB2 and SLC26A4 mutation groups (Wave III) and in all three other groups (Wave V and Wave III‐V latency); amplitudes were not significantly different between groups. Conclusions: Our results suggest OTOF mutations cause delayed (or slowed) postsynaptic neurotransmission, although the presumed mechanism involved reduced presynaptic transmission between hair cells and spiral ganglion neurons. Level of Evidence: Mainly a case report [ABSTRACT FROM AUTHOR]

Conclusions:EABR is a reliable and effective way of objectively confirming device function and implant-responsiveness of the peripheral auditory neurons up to the level of the brainstem in cases of inner ear malformation.Objective:To investigate the usefulness of measuring the intra-operative electrically evoked compound action potential (ECAP) and electrically evoked auditory brainstem response (EABR) in patients with and without congenital inner ear anomalies during cochlear implantation.Method:Thirty-eight consecutive children (40 ears) aged 5 or younger with congenital profound hearing loss. Twenty-four (25 ears) lacked congenital inner ear anomalies. The 14 patients (15 ears) with a malformation had common cavities (four ears), incomplete partition type I (three ears), cochlea hypoplasia type III (three ears), enlarged vestibular aqueduct (four ears), and cochlear nerve canal stenosis (one ear). Main outcome measures are ECAP and EABR responses.Results:Of the 25 ears lacking any malformation, 21, three, and one showed ‘Good’, ‘Variable’, and ‘No’ ECAP responses, respectively, and 24 and one showed ‘Good’ and ‘Variable’ intra-cochlear responses, respectively. Of the 15 ears with a malformation, two showed ‘Good’ ECAP responses, nine had ‘Variable’ ECAP responses, and four showed ‘No’ ECAP responses. Moreover, five showed ‘Good’ EABR responses and 10 showed ‘Variable’ EABR responses. [ABSTRACT FROM PUBLISHER]

Pelizaeus-Merzbacher disease (PMD) is a white matter dystrophy of the brain. Most children with PMD require comprehensive nursing care. Their speech and language abilities are poor or absent. Therefore, evaluating hearing ability is difficult in children with PMD. We have followed up two patients with PMD since early childhood. Patient 1 is an 11-year-old boy, and patient 2 is a 15-year-old adolescent boy in whom horizontal nystagmus was recognized after birth. Magnetic resonance imaging showed diffuse dysmyelination of the cerebral white matter. Auditory brainstem response recordings showed only waves I and II and the absence of all subsequent components. However, conditioned orientation reflex audiometry showed a threshold of 20-30 dB. Both patients can converse orally and have auditory perception and speech abilities better than those of most patients with PMD in the literature. We report on the development of their hearing and speech abilities. [ABSTRACT FROM AUTHOR]

A 27-year-old female showed auditory agnosia after long-term severe hydrocephalus due to congenital spina bifida. After years of hydrocephalus, she gradually suffered from hearing loss in her right ear at 19 years of age, followed by her left ear. During the time when she retained some ability to hear, she experienced severe difficulty in distinguishing verbal, environmental, and musical instrumental sounds. However, her auditory brainstem response and distortion product otoacoustic emissions were largely intact in the left ear. Her bilateral auditory cortices were preserved, as shown by neuroimaging, whereas her auditory radiations were severely damaged owing to progressive hydrocephalus. Although she had a complete bilateral hearing loss, she felt great pleasure when exposed to music. After years of self-training to read lips, she regained fluent ability to communicate. Clinical manifestations of this patient indicate that auditory agnosia can occur after long-term hydrocephalus due to spina bifida; the secondary auditory pathway may play a role in both auditory perception and hearing rehabilitation. [ABSTRACT FROM AUTHOR]

Conclusion: We regard spontaneous otoacoustic emission (SOAE) as a unique phenomenon due to spontaneous outer hair cell hyperactivity during the infantile period in these two infants. Objectives: We report the cases of SOAEs in two infants, which were audible to their parents. We were able to hear continuous sounds from these two infants' ears. We studied their hearing and the emitted sounds objectively. Patients and methods: Patient 1 was a 5-month-old girl and patient 2 was an 11-month-old girl. Their parents heard continuous sounds emanating from their infants' ears. Audiological examinations and frequency analysis were conducted. Results: The distortion-product otoacoustic emissions (DPOAEs) and auditory brainstem responses (ABRs) of the two patients were normal. Analysis of the continuous sounds demonstrated frequencies of 4.2 and 6.5 kHz for patient 1 and 6.7 kHz for patient 2. These audible sounds were diagnosed as SOAEs. The SOAEs in these infants did not disappear with their development in the last 2 years. [ABSTRACT FROM AUTHOR]

Conclusion. The early diagnosis of deafness and the early fitting of hearing aids in multiply handicapped children are recommended for language development in these children even when their neurological or mental status is poor. Subjects and methods. The subjects consisted of 5 hearing-impaired infants with no other problems and 28 hearing-impaired children with multiple handicaps. Behavioral audiometry and auditory brainstem responses were used for evaluating hearing impairment. The 5 hearing-impaired infants with no other problems underwent hearing aid fitting at approximately 1 year of age and the 28 hearing-impaired children with multiple handicaps underwent hearing aid fitting at various times from 1 to 5 years of age. The effects of their hearing aids were compared on the basis of auditory behavioral changes. The developmental scale of auditory behaviors in infancy that we proposed was introduced to evaluate the development of auditory behaviors. Results. The auditory behaviors of the hearing-impaired children with no other problems showed constant changes with age after hearing aid fitting. However, among the 28 hearing-impaired children with multiple handicaps, 17 showed improvement in auditory behaviors, 5 showed no improvement in auditory behaviors because of the associated severe motor and mental retardation, and epilepsy, and 6 were unable to adapt to wearing hearing aids. [ABSTRACT FROM AUTHOR]

Three young adult males with Pelizaeus–Merzbacher disease have been followed up since childhood. This disease is thought to be a dysmyelinating disorder of the brain during the prenatal period caused by gene mutations. The patients manifested horizontal nystagmus and severe rigidity of the extremities. Although the patients showed only waves I and II in auditory brainstem responses, they had relatively good hearing ability at ≈30  dB. They could not speak words at all but could hear well and enjoy listening to conversation and music. One of them had a normal hearing threshold in pure-tone audiometry and a normal speech discrimination rate in speech audiometry. This can be explained by a nerve conduction blockade through dysmyelinated axons or the desynchronization of neurons and nerves responsible for the waves following waves I and II. At present, all three patients are living with their families. We report their present hearing, speech and language abilities. [ABSTRACT FROM AUTHOR]

Auditory brainstem implants (ABI) that electrically stimulate the surface of cochlear nucleus have been clinically used for the rehabilitation of deaf patients with bilateral vestibular schwannomas. The change of pitch perception with an active electrode location is not as clear in ABIs as in cochlear implants, a factor which might play a role in poorer speech performance in ABIs. The objective of present work was to develop an animal ABI model that could provide physiological data for future ABI development and optimization. The experimental system included a penetrating microelectrode array for microstimulation of the cochlear nucleus and a surface microelectrode array for mapping evoked potentials over the auditory cortex. We first obtained tone-evoked cortical activation patterns, which represented a place code of the frequency and intensity of test tones, i.e., the amplietonotopic organization, and compared the patterns with those evoked by cochlear nuclear microstimulation. Our experimental results demonstrated that microstimulation of both the dorsal and ventral cochlear nucleus (DCN and VCN) could access the cortical ampli-tonotopic organization as acoustic stimuli did. We also found that the cortical dynamic range was wider for the DCN than VCN stimulation and for the low-frequency than for the high-frequency pathway. The present results have great implications for improved ABI performance. [ABSTRACT FROM AUTHOR]

Abstract: We reported two cases of Pelizaeus-Merzbacher disease. Both cases visited our hospital manifesting horizontal nystagmoid movements present from birth, and delayed motor development. Magnetic resonance imaging of the brain showed diffuse dysmyelination of the cerebral white matter, and auditory brainstem response showed waves I and II but absence of all subsequent components. Conditioned orientation reflex (COR) audiometry showed poor reactions in an infantile case whose development was severely retarded, and who spoke no meaningful words. Auditory steady-state response (ASSR) was a helpful tool for identifying her auditory ability; thereafter, her communication skills improved naturally. The other case was mildly developmentally retarded, and the results of COR audiometry and ASSR were considered the same level. The discrepancy between results of these hearing tests may arise under the influence of developmental level of the case. [Copyright &y& Elsevier]

Bilateral bone-conducted auditory brainstem responses (BC-ABRs) were recorded in children with atresia of the external auditory canal bilaterally (AECB) in order to compare the response characteristics to normal hearing adults. The binaural interaction component (BIC) of the ABR occurs when the sum of the monaural-evoked ABR amplitudes are different in amplitude when compared to the binaural-evoked ABR amplitude. Previous electrophysiological work from our lab has shown that children with AECB lateralize bone-conducted (BC) sound. Furthermore, we have found in normal-hearing adults that BICs exist using BC clicks. In adults, BC-BIC occurred in the latency region corresponding to waves IV–VI, whereas for children with AECB corresponding peak latencies occurred earlier. Same as normal-hearing adults, BC-ABR IV–V complex peak amplitudes for sum of the BC-monaural right and BC-monaural left ears were different from binaural response amplitude. Individual peak latencies were similar in children with AECB when compared to normal-hearing adults except for shorter latencies for BIC. These results indicate that: (1) BC-BI is present in children with AECB as well as normal-hearing adults; (2) the gross response properties of BIC are similar in children with AECB and normal-hearing adults; (3) fitting of a bilateral BC hearing aids might be a feasible method to optimize binaural hearing and sound lateralization. [Copyright &y& Elsevier]