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PubMed2006

Short- and long-term outcome of severe neonatal nonhemolytic hyperbilirubinemia.

We studied the effects of hyperbilirubinemia on brainstem auditory pathways and neurodevelopmental status in 99 full-term neonates with severe nonhemolytic hyperbilirubinemia (total serum bilirubin level = 301 to 500 micromol/L) born between 1995 and 2000. These were divided into three groups: group 1, moderate hyperbilirubinemia (n = 30; mean maximum total serum bilirubin = 320.7 micromol/L or 18.9 mg%); group 2, severe hyperbilirubinemia (n = 63; mean maximum total serum bilirubin = 369.0 micromol/L or 21.7 mg%); and group 3, super hyperbilirubinemia (n = 6; mean maximum total serum bilirubin = 457.2 micromol/L or 26.9 mg%). All received phototherapy, and three neonates also had exchange transfusion. Initial brainstem auditory evoked potentials were recorded in all at the mean age of 3.1 months (range 1-9 months). At initial assessment, only nine neonates (9.1%) had abnormal brainstem auditory evoked potentials. All except two returned to normal at 2 years. These two children had a hearing threshold at 50 nHL. We then compared serial brainstem auditory evoked potentials until 2 years for these nine cases with initial abnormal brainstem auditory evoked potentials, and nine cases with initial normal brainstem auditory evoked potentials were recruited for comparison. All 99 children had regular physical, neurologic, visual, and auditory assessments every 3 to 6 months until the age of 3 years. There was no significant correlation between demographic factors (gender, gestational age, or birthweight), maximum total serum bilirubin, and total serum bilirubin at discharge with an abnormal brainstem auditory evoked potential. There was no significant difference in the rate of brainstem auditory evoked potential abnormalities between the three groups: moderate (10%), severe (7.9%), and super (16.7%). All had normal neurodevelopmental status at 3 years. Only two children had transient mild motor delay and hypotonia, and both had normal brainstem auditory evoked potentials. There was no relationship between the abnormalities of the brainstem auditory evoked potentials and neurodevelopmental status. None of the three children receiving exchange transfusion had abnormal brainstem auditory evoked potentials or neurodevelopmental outcome. With the neurophysiologic and clinical outcomes in our cohort with severe nonhemolytic hyperbilirubinemia, we propose that the toxic effect of hyperbilirubinemia on auditory brainstem pathways might be transient provided that prompt treatment is initiated.

Auditory Pathways↗
PubMedDate not supplied

Cochlear and brain stem responses in hearing loss following neonatal hyperbilirubinemia.

The site of lesion in hearing loss following neonatal hyperbilirubinemia is unclear. Histopathological studies have implicated the brain stem auditory nuclei while other investigations have hinted at a lesion in the cochlea. In order to clarify this issue, attempts were made to record responses from the auditory pathway in 13 patients with hearing loss following neonatal hyperbilirubinemia. The neural response from the auditory nerve was absent in 11 of the 13 patients and present only in response to high intensity stimuli in 2 patients. However, the response of the cochlear hair cells (cochlear microphonic potential) was present in 9 of the 13 patients. In most other cases of sensorineural hearing loss, with no history of hyperbilirubinemia, the hair cell response was absent. This is functional evidence for auditory nerve damage in cases of hearing loss following neonatal hyperbilirubinemia while the hair cells are spared.

Adult↗
PubMedDate not supplied

Detectability of auditory evoked response components in preterm infants.

In determining the detectability of brainstem, middle latency and cortical auditory evoked responses in preterm newborns, one has to deal with the ongoing maturation of the auditory system. In the preterm period the detectability of evoked responses is closely related to the appearance of the individual evoked response components. The detectability of the individual evoked response components in preterm infants is important, because low detectability rates make the absence of a particular evoked response component irrelevant with respect to the clinical-neurophysiological correlation. In a longitudinal study we determined the detectability and cumulative detectability, i.e. the presence of individual evoked response components in one or more recordings of evoked response components in 37 low risk preterm infants between 30 and 41 weeks conceptional age (CA). On the basis of their detectability it is concluded that evoked response components, determined between 30 and 34 weeks CA, are generally of limited use for clinical application, except for auditory brainstem response (ABR) components I, IIn, V and Vc and middle latency response (MLR) component Na. Our study made clear that improvement can be achieved by performing more than one examination within a period of approximately 4 weeks between the recording sessions. The cumulative detectability rates after two recordings showed improvement for all components involved in this study. The cumulative detectability rates of ABR components I, II, IIN, III, V, IIc, IIINc, Vc, MLR components Na and P0, and auditory cortical response (ACR) components PbP1 and N2p are sufficient to use as measures in the neurophysiological judgement of functional integrity of the central auditory pathway in preterm infants.

Auditory Cortex↗
PubMed1984

Brainstem auditory evoked potential and blink reflex in multiple sclerosis.

Brainstem auditory evoked potential (BAEP) and blink reflex (BR) were abnormal in 40% and 26% of 130 patients with MS. Overall, BR was affected in 53% of patients with abnormal BAEP involving I-III and 41% of those involving III-V interval. In 23 patients with unilateral BR involvement, BAEP was affected ipsilaterally in 10, contralaterally in 0 and bilaterally in 8. In 12 patients with bilateral BR abnormalities, BAEP was involved unilaterally in 1 and bilaterally in 8. We conclude: (1) pontine lesions may prolong either I-III or III-V interwave latency of BAEP, and (2) unilateral abnormalities of BAEP tend to implicate the uncrossed auditory pathways.

Adolescent↗
PubMed1986

'Switching-off' of an auditory interneuron during stridulation in the acridid grasshopper Chorthippus biguttulus L.

In freely moving grasshoppers of the species Chorthippus biguttulus compound potentials were recorded from the neck connectives with chronically implanted hook electrodes. The spikes of one large auditory interneuron, known as the G-neuron (Kalmring 1975a, b) were clearly distinguishable in the recordings and the neuron was identified by its physiology and morphology. In quiescent grasshoppers the G-neuron responds to auditory and vibratory stimuli, but responses to both stimuli are suppressed during stridulation in males. When a male's wings were removed so that the stridulatory movements of its hindlegs produced no sound, the suppression of the G-neuron response still occurred. When proprioceptive feedback from the hindlegs was reduced, by forced autotomy of the legs, the switching-off remained incomplete (production of stridulatory patterns was inferred on the basis of electromyograms from the relevant thoracic musculature). Imposed movement of the hindlegs, on the other hand, suppressed the G-neuron response in a graded fashion, depending on the frequency of the movement. These experiments suggest that the switching-off is brought about by a combination of proprioceptive feedback and central efferences. The switching-off phenomenon could either protect the grasshopper's auditory pathway from undesired effects of overloading by its own intense song (e.g. self-induced habituation as described by Krasne and Wine 1977) and should therefore apply for most auditory neurons. Alternatively it could prevent escape reflexes from being triggered by stridulatory self-stimulation and consequently might apply only for neurons involved in such networks (as the G-neuron might be).

Animals↗
PubMedDate not supplied

Improvement in auditory brainstem response of hyperbilirubinemic infants after exchange transfusions.

Auditory brainstem response tests were performed before and after exchange transfusions in 6 infants with hyperbilirubinemia. The latencies of Waves I, II, and V decreased significantly after the exchange transfusions (p less than .05, p less than .02, p less than .005, respectively) and I-V interpeak latencies also were decreased (p less than .01). However, the latencies of Wave I both before and after exchange transfusions were within normal limits. The central conduction times were prolonged by hyperbilirubinemia, but the peripheral auditory pathways were not impaired. These auditory brainstem response abnormalities became normal with decreased serum bilirubin concentration. Neonatal hyperbilirubinemia is associated with transient brainstem lesions which are reversible in the early stages. Auditory brainstem response testing is an effective and readily available technique for detecting bilirubin neurotoxicity.

Brain Stem↗
PubMed2006

Midbrain pathways for prepulse inhibition and startle activation in rat.

The midbrain is essential for prepulse inhibition (PPI) of the startle reflex, but the exact neural circuits for PPI are not yet determined. Electrical stimulation of the superior colliculus (SC) or pedunculopontine tegmentum was used to characterize the neurons and pathways that mediate PPI and the activation of startle that also occurs at higher currents in the same sites. Startle was inhibited by prepulses in most, but not all SC sites, with the lowest intensity sites in intermediate layers of SC. PPI latencies in SC sites were 4-6 ms longer than in inferior colliculus, intercollicular nucleus or pedunculopontine sites. Contrary to previous serial models, there must be two parallel midbrain pathways for PPI, a faster auditory pathway from inferior colliculus to pedunculopontine tegmentum, and a slower multimodal SC output for PPI. Double-pulse stimulation of SC sites shows that PPI results from direct stimulation of neurons with moderate refractory periods (0.4-1.0 ms), similar to SC neurons that mediate contraversive turning responses. By contrast, startle activation occurring at higher currents in all SC sites (even sites where PPI could not be elicited) results from stimulation of very short refractory period neurons (0.3-0.5 ms) and very long refractory period neurons (1.0-2.0 ms), with startle inhibition often found from 0.5-1.0 ms. Startle activation appears to result from stimulation of short refractory period neurons in deep SC layers that mediate fear-potentiated startle, plus long refractory period substrates in more dorsal SC sites.

Animals↗
PubMed2004

[Contribution of cognitive and behavioral therapy for patients with tinnitus: implication in anxiety and depression].

OBJECTIVES: Tinnitus is a common otologic symptom but, despite important advances in the evaluation and management of such symptom, ENTs often fail to address tinnitus properly. Some tinnitus patients report that tinnitus interferes with activities of daily living, such as reading, social interactions, sleep, concentrating on complex tasks. Anxiety and depression are current major disorders associated with tinnitus. Many theories exist regarding mechanisms of tinnitus origin. A number of publications favors the theory of discordant dysfunction of inner or outer hair cells of the organ of Corti. Nevertheless, some authors insist on the possible role of the central auditory pathways. Multiple functional connections between auditory system, limbic system, autonomic nervous system seem crucial in the development of tinnitus. The aim of this paper is to present a new approach in France of tinnitus treatment by cognitive-behavioral therapy (CBT). MATERIAL AND METHODS: 96 patients with chronic and intense tinnitus were included in the study (38 females, 36 males, mean age 48 years). A CBT was developed after a clinical evaluation based on standardized questionnaires. RESULTS: The two main results are: (i) the importance of anxiety and depression in this population, (ii) the amelioration of tinnitus perception in 750f the included patients. CONCLUSION: CBT shows promise as a treatment of tinnitus-related distress.

Anxiety↗
PubMed2006

Neural plasticity in tinnitus.

Two distinctly different kinds of tinnitus occur: objective and subjective tinnitus. Objective tinnitus is caused by sounds generated in the body while subjective tinnitus is caused by abnormal neural activity that is not evoked by sound. This chapter discusses subjective tinnitus. Subjective tinnitus has many forms. In most forms of tinnitus the anatomical location of the physiological abnormality is in the central nervous system, although the sensation is often referred to one ear or both ears. The cause of most forms of subjective tinnitus is the changes that have occurred as a result of expression of neural plasticity, thus a form of reprogramming of the brain that is not to the benefit of the individual person. Tinnitus often occurs together with hearing loss, indicating that the expression of neural plasticity has been evoked by deprivation of input. Tinnitus is often accompanied by hyperacusis, and sometimes phonophobia and depression, indicating altered processing of auditory information or rerouting of information. Several studies have brought evidence that some forms of tinnitus are associated with an abnormal involvement of the nonclassical (extralemniscal, diffuse, or polysensory) auditory pathways that bypass the primary auditory cerebral cortex and provide subcortical connections to limbic structures among others. There is no general treatment for tinnitus, but there are several treatments that can alleviate or reduce the tinnitus in some patients.

Humans↗
PubMedDate not supplied

Reduction of acoustic reflex threshold in neonates without auditory risk.

UNLABELLED: The auditory sensitization, a tool used in the investigation of acoustic reflex, allows the decrease of acoustic reflex thresholds from a facilitating stimulus. It may be presented before or simultaneously with the elicitor tone. The thresholds after and before the facilitating stimulus are compared and it is expected to see the decreased threshold. From the study of the acoustic reflex it is possible to obtain information about the auditory pathways, such as structures of the brainstem, since the acoustic reflex pathway is related to the auditory nuclei in this site. They are also involved in auditory processing. Thus, alterations of the acoustic reflex could be related to deficits in auditory processing skills. AIM: This study aims at investigating the acoustic reflex sensitization from a high-frequency facilitating tone (6 kHz) in newborns without risk factors to hearing impairment. RESULTS: The acoustic reflex threshold decreased in males and females for all studied frequencies. CONCLUSION: A high-frequency facilitating tone presented simultaneously produced a decrease of the acoustic reflex threshold in newborns without risk factors to hearing impairment.

Acoustic Impedance Tests↗
PubMedDate not supplied

ECochG, CNAP and ABR monitoring during vestibular Schwannoma surgery.

Identification of the specific pathophysiological processes and correlation with post-operative hearing are the prerequisites for utilizing electrophysiological audio monitoring techniques in preventing damage to auditory structures during vestibular Schwannoma (VS) surgery. The present paper compares the value of auditory brainstem responses (ABRs), electrocochleography (ECochG) and directly recorded cochlear nerve action potentials (CNAPs) in detecting damage to auditory structures during VS surgery and predicting post-operative hearing. Eighteen consecutive patients operated on for VS, in an attempt at hearing preservation, participated in the investigation. The ipsilateral hearing level (pure tone average [PTA] 0.5-3 kHz) ranged from 10 to 50 dB HL (mean: 30.7 dB HL), with a speech discrimination score equal to or better than 50 per cent. CNAPs furnished the highest predictive score for post-operative hearing. In particular, when a permanent loss of CNAPs occurred the sensitivity and specificity were 100 per cent. The discrepancies between the ECochG and CNAP findings were attributable to high prevalence of cochlear nerve damage, capable of 'disconnecting' the ear from the central auditory pathways, causing persistence of peripheral auditory function and no propagation of the neural input. ABR monitoring was highly sensitive in detecting auditory damage but its prognostic utility was marred by its poor specificity.

Adult↗
PubMed2000

A pilot study of the relationship between Down's syndrome and hearing loss.

OBJECTIVE: Hearing loss is one of the most common disabilities in children with Down's syndrome. The objective of this study is to investigate the incidence and types of hearing loss in Down's syndrome patients. METHODS: Twenty-six subjects with Down's syndrome aged between 2 and 17 year old were evaluated during the year 1998, referred randomly by the Pediatric Department and the Down's Syndrome Centre. Screening audiological procedures were used to evaluate these patients, which include behavioral audiometry, play and pure tone audiometry, tympanometry and ABR, which is the measurement of the activity of the auditory pathway structures from the distal auditory nerve to the midbrain using clicks or tonepips. RESULTS: The study showed that 35% were found to have normal hearing compared to 4% found to have sensorineural hearing loss, while the majority of patients were found to have a conductive hearing loss (50%). CONCLUSION: Hearing evaluation of children with Down's syndrome revealed a high prevalence of conductive hearing loss. This study proposed that this might be attributed to eustachian tube dysfunction and middle ear ciliary malfunction. Further diagnostic studies need to be carried out.

Acoustic Impedance Tests↗
PubMedDate not supplied

[Mid-latency auditory evoked potential].

AIMS: Given the diversity of criteria regarding the use of the midlatency auditory evoked potential (MLAEP) for diagnostic purposes, we carry out a review of the subject and highlight areas such as the generators of fundamental components, the conditions in which responses are obtained, factors that can modify results and the clinical uses that have been reported. DEVELOPMENT: There seems to be a strong tendency towards considering areas of the primary and secondary auditory cortex as generators of the response, with the subcortical structures playing a moderating role. Factors such as age, the method of stimulation used and the monitoring conditions can all exert an influence on the characteristics of this evoked response and modify its capacity for detection and repetition. Clinical uses of this potential range from the detection of the hearing threshold, monitoring the depth of anaesthesia, the functional evaluation of cochlear implants, and the diagnosis of neurological disorders, among others. CONCLUSIONS: MLAEP is a technique that is widely used in the study of the most rostral segments of the auditory pathway and this information complements that provided by short latency responses and increases the diagnostic sensitivity of auditory evoked potentials.

Acoustic Stimulation↗
PubMed2004

Superior olivary contributions to auditory system plasticity: medial but not lateral olivocochlear neurons are the source of cochleotomy-induced GAP-43 expression in the ventral cochlear nucleus.

A unilateral cochlear lesion induces expression of the growth and plasticity-associated protein 43 (GAP-43) in fibers and their varicosities on specific types of postsynaptic profiles in the ventral cochlear nucleus (VCN), suggesting the induction of synaptic remodeling. One candidate population from which GAP-43 might emerge was neurons of the lateral olivocochlear (LOC) system residing in the lateral superior olive (LSO). Upon cochleotomy, these neurons express GAP-43 mRNA and GAP-43 protein. However, retrograde axonal tracing with Fast Blue or biotinylated dextran amine from VCN revealed that the number of 6.8 +/- 1.3 neurons in the whole ipsilateral LSO labeled in normal adult rats was distinctly small and did not rise after cochleotomy. Concluding that LOC neurons cannot be the source of GAP-43 in the VCN, we reinvestigated the pattern of GAP-43 in situ hybridization and found that, after cochleotomy, shell neurons in the regions surrounding the LSO and medial olivocochlear (MOC) neurons in the ventral nucleus of the trapezoid body up-regulated GAP-43 mRNA. We then lesioned these regions by means of stereotaxic injections of kainic acid. Destruction of shell neurons preceding an ipsilateral cochleotomy did not change the emergence of GAP-43 immunoreactivity in the VCN. However, if the contralateral MOC system was lesioned, the rise of GAP-43 immunoreactivity in VCN on the side of the cochleotomy was significantly reduced. We conclude that, after cochlear dysfunction, MOC neurons are the major (if not exclusive) source of synaptic reorganization in the VCN that could possibly entail compensatory activation of the affected ascending auditory pathway.

Animals↗
PubMed1997

Compatibility between auditory and articulatory representations of vowels.

Auditory-articulatory linkage in our brain plays an essential neurobiological role in human speech communication. Speech-specific sensorimotor organization is basically a genetically transmitted program, whereas its ontogenetic outcome may strongly reflect the unique form of human vocal organs. In this study, electromyographic data from the four extrinsic tongue muscles were processed to derive motor targets of vowels in a two-dimensional space representing muscle force equilibrium. The result shows evidence that the motor pattern of tongue muscles in vowel production is compatible with the acoustic pattern of vowels: the distribution of intended targets of tongue movement resembles the vowel distribution in the auditory (F1 vs. F2) space. This coincidence suggests a co-evolution of the human vocal tract and vowel system that facilitates the development of efficient auditory pathway for processing speech sounds.

Auditory Pathways↗
PubMed1994

Auditory temporal resolution in multiple sclerosis.

Disturbances of hearing in multiple sclerosis patients have been variably reported, likely because standard audiologic testing emphasizes assessment of peripheral, rather than central, auditory function. This study investigated a group of patients with multiple sclerosis (MS), prospectively selected on the basis of magnetic resonance imaging (MRI) scans. Five of these patients had demyelinating lesions that included the rostral auditory fibre tracts, while another seven patients had lesions restricted to brainstem auditory sites. A further four had no lesions in the distribution of their auditory pathways. A comprehensive battery of audiometric tests, including standard audiometry and retrocochlear testing, was performed. In addition, their findings on electrophysiologic testing, including auditory brainstem responses (ABR) and middle latency responses (MLR), were studied. Finally, their performances in gap detection and speech recognition in continuous and interrupted background noise were examined to assess their auditory temporal resolution. The MS patients were found to be selectively impaired under the interrupted masker of this speech-in-noise paradigm, confirming a temporal processing defect. Furthermore, these patients' performances suggested a predominant role of forebrain pathways in mediating auditory temporal resolution.

Adult↗
PubMed2003

Evolutionary aspects of bat echolocation.

This review is yet another attempt to explain how echolocation in bats or bat-like mammals came into existence. Attention is focused on neuronal specializations in the ascending auditory pathway of echolocating bats. Three different mechanisms are considered that may create a specific auditory sensitivity to echos: (1). time-windows of enhanced echo-processing opened by a corollary discharge of neuronal vocalization commands; (2). differentiation and expansion of ensembles of combination-sensitive neurons in the midbrain; and (3). corticofugal top-down modulations. The second part of the review interprets three different types of echolocation as adaptations to ecological niches, and presents the sophisticated cochlear specializations in constant-frequency/frequency-modulated bats as a case study of finely tuned differentiation. It is briefly discussed how a resonant mechanism in the inner ear of constant-frequency/frequency-modulated bats may have evolved in common mammalian cochlea.

Acoustic Stimulation↗
PubMedDate not supplied

Ipsilateral and contralateral recordings of auditory brainstem responses to monaural stimulation.

The developmental changes of the ipsilateral and contralateral auditory brainstem responses (ABRs) were studied in 105 normal infants and children. In both ipsilateral and contralateral recordings, the peak and interpeak latencies shortened with increasing age, while the amplitudes of wave V had a tendency to become higher. Contralateral ABR amplitudes were always smaller than those of ipsilateral ABRs. In the contralateral recording, wave I was absent and the contralateral wave II and wave III complex began to separate after birth (25%); separation percentage reached 80-100% at 7 months of age. Our results suggest that the contralateral recording of ABRs is a useful measure of developmental changes in infant auditory pathways.

Acoustic Stimulation↗