Assessment of the efferent auditory system in children with suspected auditory processing disorder: the Middle ear muscle reflex and contralateral inhibition of OAEs.

OBJECTIVE: To determine whether children aged 7 to 12 years with listening difficulties show objective evidence for efferent auditory function based on measurements of medial olivo-cochlear and middle ear muscle reflexes. DESIGN: Click-evoked otoacoustic emissions recorded with and without contralateral broadband noise and ipsilateral and contralateral tonal (1000, 2000 Hz) middle ear muscle reflex thresholds were examined. STUDY SAMPLE: 29 children diagnosed with suspected auditory processing disorder (APD) and a control group of 34 typically developing children participated in this study. RESULTS: Children with suspected APD had poorer performance on auditory processing tests than the control group. Middle ear muscle reflex thresholds were significantly higher at 2000 Hz in the suspected APD group for contralateral stimulation. MOC inhibition effects did not differ between APD and control groups. CONCLUSIONS: This research supports earlier studies showing altered acoustic reflexes in children with APD. No group differences were found for the MOC reflex measures, consistent with some earlier studies in children with APD.

Addressing variability in the acoustic startle reflex for accurate gap detection assessment.

The acoustic startle reflex (ASR) is subject to substantial variability. This inherent variability consequently shapes the conclusions drawn from gap-induced prepulse inhibition of the acoustic startle reflex (GPIAS) assessments. Recent studies have cast doubt as to the efficacy of this methodology as it pertains to tinnitus assessment, partially, due to variability in and between data sets. The goal of this study was to examine the variance associated with several common data collection variables and data analyses with the aim to improve GPIAS reliability. To study this the GPIAS tests were conducted in adult male and female CBA/CaJ mice. Factors such as inter-trial interval, circadian rhythm, sex differences, and sensory adaptation were each evaluated. We then examined various data analysis factors which influence GPIAS assessment. Gap-induced facilitation, data processing options, and assessments of tinnitus were studied. We found that the startle reflex is highly variable in CBA/CaJ mice, but this can be minimized by certain data collection factors. We also found that careful consideration of temporal fluctuations of the ASR and controlling for facilitation can lead to more accurate GPIAS results. This study provides a guide for reducing variance in the GPIAS methodology - thereby improving the diagnostic power of the test.

Assessment of cochlear nerve deficiency and its effect on normal maturation of auditory tract by diffusion kurtosis imaging and diffusion tensor imaging: A correlational approach.

OBJECTIVE: The use of diffusion kurtosis imaging (DKI) and diffusion tensor imaging (DTI) was evaluated in assessing cochlear nerve deficiency (CND) and its effect on normal maturation of auditory tract. METHODS: 25 CND patients and 25 controls (age matched: 2months to 17years, gender matched) were evaluated by mean kurtosis (MK), axial kurtosis, and radial kurtosis and compared against fractional anisotropy (FA), axial and radial diffusivities in internal auditory canal (IAC), lateral lemniscus (LL) and inferior colliculus (IC). The age related changes of auditory tract were studied through Pearson correlation between estimated indices and age of both CND and control populations. RESULTS: Significant loss of MK (IAC: 10.71%, IC: 10.87%, LL: 15.63%) was observed in CND cases as against moderate reduction in FA (IAC: 8.57%, IC: 10%, LL: 7.69%) in all three anatomical locations. Similarly, substantial decline is observed in radial kurtosis (IAC: 27.03%, IC: 33.33%, LL: 31.43%) in comparison to moderate increase in radial diffusivity (IAC: 13.46%, IC: 24.39%, LL: 24%) in CND cases. No statistically significant change was seen in both axial kurtosis and diffusivities. In control populations, MK (r=0.473, p=0.011) and radial kurtosis (r=0.418, p=0.016) correlate positively with age and had no correlation in case of CND cases. FA (r=0.356, p=0.019) minimally correlated with age in control population but showed no statistically significant correlation in CND cases (r=0.198, p=0.036). CONCLUSION: DKI metrics performed better than DTI in assessing microstructural changes of CND. In particular, MK and radial kurtosis are found to be more sensitive enough to differentiate the normal maturation of cochlear nerve from CND cases.

Assessment of responses to cochlear implant stimulation at different levels of the auditory pathway.

This paper reviews characteristics of both the electrically evoked compound action potential (ECAP) and analogous measures of cortically evoked responses (CAEP) to electrical stimulation in cochlear implant users. Specific comparisons are made between the two levels of processing for measures of threshold, growth of responses with increasing stimulus level, changes in stimulation electrode and, finally, in temporal response properties. The results are interpreted in a context that ECAPs primarily reflect the characteristics of the electrode-neural interface for an individual ear. CAEPs clearly are dependent on those peripheral responses but also reflect differences in central processing among individual implant users. The potential applicability of combined measures in clinical situations is discussed. This article is part of a Special Issue entitled .

Neurofunctional assessment in a stroke patient with musical hallucinations.

We reported a case of an elderly female patient affected by musical hallucinations (MHs) as the unique symptom of a right temporal ischemic stroke. A functional magnetic resonance imaging examination was performed in the patient and in five age- and sex-matched normal controls (NC) to detect the complex neural substrate subserving MHs in such a context. Although an activation pattern involving the primary auditory cortex and the temporal associative areas bilaterally was found in the patient and NC, a significant increased activation mostly located in right temporal cortex (in the ischemic area), was observed in the patient. Further functional neuroimaging studies should be performed to detect the complex neural pathways underlying MHs and to find out differences between these hallucinations and real music perception.

Assessment of cochlear and auditory pathways in patients with migraine.

PURPOSE: In this study, we aimed to determine the function of the cochlea and peripheral and central auditory pathways with migraine. MATERIALS AND METHODS: Fifty-eight patients with migraine and 40 healthy subjects were assessed using routine diagnostic audiometry along with transient evoked otoacoustic emissions (TOAEs), distortion product otoacoustic emissions (DPOAEs), and auditory brainstem response (ABR) at high and low repetition rate frequencies. RESULTS: Nearly two thirds of patients with migraine had one or more abnormalities in electrophysiological testing. Compared with control subjects, patients reported significant lowering of TOAEs amplitude at frequencies of 1 kHz (right: P = .0003; left: P = .002), 3 kHz (right: P = .025), and 4 kHz (right: P = .019); prolonged wave III latency (right: P = .009); and I-V interpeak latency (IPL) (left: P = .024) at high repetition rate frequencies. Significant correlations were identified between age, duration of illness and frequency of migraine and TOAEs total response and at amplitude of 4 kHz, amplitudes of DPOAEs at 1, 1.5, 2, 3, and 5 kHz and I, III and wave latencies and I-V IPL of ABR at high rate frequencies. CONCLUSIONS: These data suggest that subclinical changes in cochlear function and auditory pathways are associated with chronic migraine. It is possible that migraine could be accompanied by compromise of blood supply of auditory system.

Assessment of hearing organ activity in a group of neonates with central nervous system impairment.

OBJECTIVE: Hypoxic-ischemic encephalopathy, primary subarachnoid hemorrhage in term newborns as well as periventricular leukomalacia and intraventricular hemorrhage in premature newborns are the major consequences of perinatal asphyxia. Intrauterine hypoxia and labor prolongation can also affect the hearing organ in newborns causing reversible or irreversible changes in the cochlea, brainstem or cortex. The aim of the study was to carry out the objective assessment of the cochlea and hearing pathway activity using CEOAEs and ABR; to find relationships between hearing status and parameters effecting on nervous system in neonates with central nervous system impairment occurring following perinatal asphyxia. METHODS: To the investigation 36 newborns with hypoxic-ischemic encephalopathy, periventricular leukomalacia or intraventricular hemorrhage were included. The control group encompassed 32 health newborns matched as to the age. In all newborns otoscopic examination, CEOAEs after birth and CEOAEs with ABR 3 months later were performed. Perinatal anamnesis, general pediatric status, results of trans-fontanel ultrasonography and biochemical test results were taken into account in statistical analyses. RESULTS: The mean amplitudes of CEOAEs in the first days of life were significantly reduced in investigation group comparing to control babies. 3months later the recorded responses significantly increased but did not reach values of control group. No differences were found between latencies of waves I and II. ABR latencies of waves III, IV, V and interpeak latencies I-III, III-V, I-V were delayed in investigation group when compared to control patients. Also morphology of ABR recordings in investigation group has slightly changed. Perinatal aspyxia leading to hypercapnia, low gestational age, prolonged artificial ventilation and meningitis were the main risk factors related to disturbances in ABR recordings. CONCLUSIONS: The combined use of CEOAEs and ABR in neonates with central nervous system impairment involvement revealed the existence of abnormalities in cochlear micromechanics and retrocochlear auditory pathway. Etiology seems to be multifactoral.

Assessment of tinnitus-related impairments and disabilities using the German THI-12: sensitivity and stability of the scale over time.

OBJECTIVE: To evaluate the reliability, dimensionality, predictive validity, construct validity, and sensitivity to change of the THI-12 total and sub-scales as diagnostic aids to describe and quantify tinnitus-evoked reactions and evaluate treatment efficacy. DESIGN: Explorative analysis of the German tinnitus handicap inventory (THI-12) to assess potential sensitivity to tinnitus therapy in placebo-controlled randomized studies. Correlation analysis, including Cronbach's coefficient α and explorative common factor analysis (EFA), was conducted within and between assessments to demonstrate the construct validity, dimensionality, and factorial structure of the THI-12. STUDY SAMPLE: N = 618 patients suffering from subjective tinnitus who were to be screened to participate in a randomized, placebo-controlled, 16-week, longitudinal study. RESULTS: The THI-12 can reliably diagnose tinnitus-related impairments and disabilities and assess changes over time. The test-retest coefficient for neighboured visits was r > 0.69, the internal consistency of the THI-12 total score was α ≤ 0.79 and α ≤ 0.89 at subsequent visits. Predictability of THI-12 total score and overall variance increased with successive measurements. The three-factorial structure allowed for evaluation of factors that affect aspects of patients' health-related quality of life. CONCLUSIONS: The THI-12, with its three-factorial structure, is a simple, reliable, and valid instrument for the diagnosis and assessment of tinnitus and associated impairment over time.

Auditory pathways and processes: implications for neuropsychological assessment and diagnosis of children and adolescents.

Neuroscience research on auditory processing pathways and their behavioral and electrophysiological correlates has taken place largely outside the field of clinical neuropsychology. Deviations and disruptions in auditory pathways in children and adolescents result in a well-documented range of developmental and learning impairments frequently referred for neuropsychological evaluation. This review is an introduction to research from the last decade. It describes auditory cortical and subcortical pathways and processes and relates recent research to specific conditions and questions neuropsychologists commonly encounter. Auditory processing disorders' comorbidity with ADHD and language-based disorders and research addressing the challenges of assessment and differential diagnosis are discussed.

Behavioral assessment and identification of a molecular marker in a salicylate-induced tinnitus in rats.

Tinnitus is a non-observable phantom sensation. As such, it is a difficult condition to investigate and, to date, no effective treatment has been developed. To approach this phantom sensation, we aimed to develop a rat behavioral model of tinnitus using salicylate, an active component of aspirin known to induce tinnitus. We also aimed to establish a molecular marker of tinnitus by assessing the expression of transient receptor potential cation channel superfamily V-1 (TRPV1) in the rat auditory pathway during salicylate-induced tinnitus. Animals were trained to perform "an active avoidance task": animals were conditioned by electrical footshock to move to the other side of the conditioning box when hearing a sound. Animals received a single injection of saline or salicylate (400 mg/kg i.p.) and false positive responses were measured 2 h after injection as the number of movements during a silent period. The number of responses in salicylate-treated animals was highest when the conditioned stimulus was 60 dB sound pressure level (SPL) and 16 kHz. This indicates that animals could feel tinnitus 2 h after salicylate injection, equivalent to that induced by 60 dB SPL and 16 kHz. By means of real-time PCR and western blot analysis, TRPV1 expression was significantly upregulated in spiral ganglion cells 2 h after salicylate injection and this upregulation together with the increase in the number of false positive responses was significantly suppressed by capsazepine (10 mg/kg i.p.), a specific antagonist of TRPV1. This suggests that salicylate could induce tinnitus through activation of TRPV1 in the rat auditory pathway.

Steady state responses: electrophysiological assessment of sensory function in schizophrenia.

Persons with schizophrenia experience subjective sensory anomalies and objective deficits on assessment of sensory function. Such deficits could be produced by abnormal signaling in the sensory pathways and sensory cortex or later stage disturbances in cognitive processing of such inputs. Steady state responses (SSRs) provide a noninvasive method to test the integrity of sensory pathways and oscillatory responses in schizophrenia with minimal task demands. SSRs are electrophysiological responses entrained to the frequency and phase of a periodic stimulus. Patients with schizophrenia exhibit pronounced auditory SSR deficits within the gamma frequency range (35-50 Hz) in response to click trains and amplitude-modulated tones. Visual SSR deficits are also observed, most prominently in the alpha and beta frequency ranges (7-30 Hz) in response to high-contrast, high-luminance stimuli. Visual SSR studies that have used the psychophysical properties of a stimulus to target specific visual pathways predominantly report magnocellular-based deficits in those with schizophrenia. Disruption of both auditory and visual SSRs in schizophrenia are consistent with neuropathological and magnetic resonance imaging evidence of anatomic abnormalities affecting the auditory and visual cortices. Computational models suggest that auditory SSR abnormalities at gamma frequencies could be secondary to gamma-aminobutyric acid-mediated or N-methyl-D-aspartic acid dysregulation. The pathophysiological process in schizophrenia encompasses sensory processing that probably contributes to alterations in subsequent encoding and cognitive processing. The developmental evolution of these abnormalities remains to be characterized.

Electrophysiologic assessment of central auditory processing by auditory brainstem responses in children with autism spectrum disorders.

In addition to aberrant features in the speech, children with Autism Spectrum Disorder (ASD) may present unusual responses to sensory stimuli, especially to auditory stimuli. We investigated the auditory ability of children with ASD by using Auditory Brainstem Responses (ABR) as they can directly judge both hearing status and the integrity of auditory brainstem pathways. One hundred twenty-one children (71: ASD; M 58/ F 13, mean age; 41.8 months, 50: control group; M 41/ F 9, mean age; 38 months) were included in the study. As compared with the values in the control group, the latency of wave V, wave I-V, and wave III-V inter-peak latencies were significantly prolonged (p<0.05) in the ASD group. The findings indicate that children with ASD have a dysfunction or immaturity of the central auditory nervous system. We suggest any children with prolonged III-V inter-peak latencies, especially high functioning children should be further evaluated for central auditory processing to set up a more appropriate treatment plan.

General review of tinnitus: prevalence, mechanisms, effects, and management.

Tinnitus is an increasing health concern across all strata of the general population. Although an abundant amount of literature has addressed the many facets of tinnitus, wide-ranging differences in professional beliefs and attitudes persist concerning its clinical management. These differences are detrimental to tinnitus patients because the management they receive is based primarily on individual opinion (which can be biased) rather than on medical consensus. It is thus vitally important for the tinnitus professional community to work together to achieve consensus. To that end, this article provides a broad-based review of what is presently known about tinnitus, including prevalence, associated factors, theories of pathophysiology, psychological effects, effects on disability and handicap, workers' compensation issues, clinical assessment, and various forms of treatment. This summary of fundamental information has relevance to both clinical and research arenas.

Mechanisms of intraoperative brainstem auditory evoked potential changes.

Brainstem auditory evoked potential (BAEP) changes during intraoperative monitoring may reflect damage to or potentially reversible dysfunction of the ear, the eighth nerve, or the brainstem auditory pathways up to the level of the mesencephalon. They may also be caused by other physiologic mechanisms such as anesthesia, hypothermia, and acoustic masking from drilling noise, or they may result from technical factors that prevent proper stimulus delivery or recording of an evoked potential that is actually present. Cochlear ischemia or infarction resulting from compromise of the internal auditory artery and inner ear damage during temporal bone drilling will affect all BAEP components, including wave I. Direct mechanical or thermal trauma to the eighth nerve will delay, attenuate, and possibly eliminate waves III and V, but wave I, which is generated at the cochlear end of the eighth nerve, may be preserved. During scraping of tumor off the eighth nerve, force applied in an ear-toward-brainstem direction can avulse the fragile fibers of the distal eighth nerve at the area cribrosa. Prolonging the I-to-III interpeak interval during retraction of the cerebellum and brainstem reflects stretching of the eighth nerve, and is often reversible. Vasospasm within the eighth nerve can cause similar, potentially reversible BAEP changes. Damage to the brainstem auditory pathways at or below the level of the mesencephalon will delay and attenuate or eliminate wave V. Wave III is affected similarly if the damage is at or caudal to the region of the superior olivary complex. These BAEP changes may reflect direct mechanical or thermal damage to the brainstem, brainstem compression, or ischemia or infarction resulting from vascular compromise. During BAEP monitoring, examination of the pattern of BAEP changes, analysis of their correlation with surgical maneuvers, and investigation for possible contributory technical factors can help to determine the cause of the BAEP changes and provide the appropriate information to the rest of the surgical team.

Towards optimal recording and analysis of the mismatch negativity.

In this paper, the conceptual and practical issues related to the measurement of mismatch negativity (MMN) are discussed from the viewpoint of cost-efficiency. First, various criteria for efficiency or optimality of measurements are described, including reliability and signal-to-noise ratio. Then a critical look is taken at some currently used concepts and data analysis methods. Practical guidelines for the measurement and analysis of MMN are given, complementing the earlier reviews on the subject. Finally, reliability studies on MMN are critically reviewed.

Stereological assessment of the glial reaction to chronic deafferentation of the cochlear nuclei in the macaque monkey (Macaca fascicularis).

Neurectomy of the auditory nerve produces a massive deafferentation of the cochlear nuclei (CN) in the brainstem. Degenerating primary afferents are removed in the acute phase, and this is followed by a synaptic reorganization in the CN. As part of an ongoing study on the effect and applicability of auditory brain implants in the CN of Macaca fascicularis monkeys, we studied the chronic response of astrocytes in the CN to bilateral deafferentation of the VIIIth cranial nerve. Four control and five deafferentated animals were employed. The treated animals had a bilateral extradural section of the VIIIth cranial nerve and a survival of 3 months. Animals were euthanized and perfused, and the brainstem was serially sectioned. The astrocyte population of the CN was studied by glial fibrillary acidic protein (GFAP) immunohistochemistry and quantified by unbiased stereological methods. The total length of astrocyte processes, L(proc), was estimated as the product of nuclear volume V(nuc), which was estimated by the Cavalieri method, times the ratio L(V)(proc, nuc) of process length to nuclear volume. Mean nuclear volume was significantly lower in deafferented animals, whereas the mean ratio L(V)(proc, nuc) was higher (albeit no statistical significance was reached). However, the mean total astrocytic process length was virtually the same in both groups. The absence of a length increase in the glial processes indicates a decrease of the astrocytic reaction after the acute phase. No glial scar is present in the CN of the monkey after long-term deafferentation, so the usefulness of auditory brain implants to stimulate CN neurons directly as a means to overcome deafness resulting from direct damage to the VIIIth cranial nerve (i.e., acoustic neuromas) is plausible.

Assessment of functional recovery after spinal cord injury in rats by reticulospinal-mediated motor evoked responses.

Auditory startle reflexes (ASR) and cortico-myoelectric evoked potentials (CMyEP) were investigated as possible tests of descending motor function in a rat spinal cord injury model. ASR, which consist of stereotyped myoelectric responses recorded in limb and axial muscles to brief loud tones, were found to provide a simple, objective, and reliable measure of motor recovery after spinal cord injury (SCI). While ASR are easily recorded in awake rats, they are blocked by anesthetics, and thus cannot be recorded during the acute injury period. ASR were compared with CMyEP, which can be recorded while the animal is anesthetized. CMyEP were found to produce large myoelectric responses in the vastus lateralis and tibialis anterior hindlimb muscles of the rat similar to ASR except that latencies were approximately 3 msec earlier. Both ASR and CMyEP tended to be bilaterally symmetric regardless of the stimulus configuration, and threshold for responses were the same for both muscles in both hindlimbs. The results suggest that CMyEP may be related to ASR and thus mediated partly by reticulospinal pathways. Evidence supporting this hypothesis is reviewed.

Limits of ABR and contribution of transtympanic electrocochleography in the assessment of cerebellopontine angle tumours.

Auditory brainstem responses (ABR) and transtympanic electrocochleography (ECochG) were analysed for 63 patients with tumours of the cerebellopontine angle (CPA) and/or internal auditory meatus (IAM). ABR recordings indicated a clearly prolonged wave I-V interval (above 4.3 ms) in half of the patients, hence suggesting a retrocochlear disorder. For the remaining patients ABR alone was not sufficient for clear diagnosis and ECochG was therefore used in addition. When the latency of wave V was uncertain due to the absence of wave I, the latency of wave N1 was always measurable by ECochG. The NI-V interval evaluated in this way was always significantly prolonged (above 4.5 ms) relative to a control group of patients with a sensorineural hearing loss. In 9 of the 13 subjects without any discernible ABR, an ECochG response could be recorded and its threshold was often better than the mean pure tone audiogram. This study confirms the validity of transtympanic ECochG in the diagnosis of retrocochlear disorders. The time difference observed between wave N1 (ECochG) and wave I (ABR) in CPA tumours is discussed and a possible explanation is proposed.

Electrophysiologic assessment of auditory pathways in high risk infants.

This study evaluated auditory processing in a group of 59 infants at risk for subsequent hearing and language disorders due to low birthweight and/or perinatal asphyxia. Auditory system integrity was evaluated electrophysiologically by recording the auditory brainstem response (ABR), middle latency response (MLR) and the cortical auditory evoked potential (CAEP). 63% of the babies had normal peripheral function or slight unilateral impairment; 84% had normal brainstem auditory system function; 82% showed normal MLRs; and 81% showed normal CAEPs. Fifty-three percent of the babies were normal on all tests and only 3% were deviant on all tests. The remaining infants showed diverse patterns of peripheral, brainstem and cortical abnormalities.