Auditory-evoked Responses Research Articles

Comparison of the sedative and cardiovascular effects of medetomidine and medetomidine-vatinoxan, combined with butorphanol, in pediatric dogs undergoing brainstem auditory-evoked response testing

Comparison of the sedative and cardiovascular effects of medetomidine and medetomidine-vatinoxan, combined with butorphanol, in pediatric dogs undergoing brainstem auditory-evoked response testing

An observational study of auditory-evoked potential mismatch negativity response in individuals at high genetic risk for schizophrenia

Objectives: This study presents a novel approach by investigating the abnormal mismatch negativity (MMN) found during response to auditory-evoked potential (ERP) in schizophrenia (SZ) patients. Our unique focus is on the genetic high-risk (GHR) for SZ, comparing it with healthy controls (HC). In addition, we aim to illuminate the interrelationship of MMN with socio-occupational functioning in the GHR group, a novel aspect of our research. Material and Methods: We conducted this study with a rigorous methodology, ensuring the reliability and validity of our findings. Thirty first-degree relatives of SZ patients (GHR) who met the inclusion and exclusion criteria were recruited by purposive sampling and compared with thirty HCs. We collected sociodemographic and clinical data from all study participants, which were assessed by the Family Interview of Genetic Studies. GHR was evaluated for current socio-occupation functioning using the Social and Occupational Functioning Assessment Scale (SOFAS). All the participants underwent 128-channel electroencephalographic recording using an auditory-evoked responses paradigm. The MMN was calculated at the frontal electrode clusters, ensuring accurate and reliable data collection. Results: The study revealed a statistically significant difference in frontal MMN latency between GHR and HC. Moreover, a positive relationship was noted between the SOFAS score and MMN amplitude, and a negative relationship was found between the latencies at the frontal region. Conclusion: Our research has made a significant breakthrough in understanding SZ. Our findings reveal that individuals with a genetic susceptibility to SZ exhibit a unique response in a particular test known as MMN. This test measures the automatic auditory change detection mechanism, which detects minor alterations in the acoustic environment and is referred to as MMN. This newfound insight could prove instrumental in developing more effective diagnoses and treatments for SZ.

Neural Delays in Processing Speech in Background Noise Minimized after Short-Term Auditory Training.

Background noise disrupts the neural processing of sound, resulting in delayed and diminished far-field auditory-evoked responses. In young adults, we previously provided evidence that cognitively based short-term auditory training can ameliorate the impact of background noise on the frequency-following response (FFR), leading to greater neural synchrony to the speech fundamental frequency(F0) in noisy listening conditions. In this same dataset (55 healthy young adults), we now examine whether training-related changes extend to the latency of the FFR, with the prediction of faster neural timing after training. FFRs were measured on two days separated by ~8 weeks. FFRs were elicited by the syllable "da" presented at a signal-to-noise ratio (SNR) of +10 dB SPL relative to a background of multi-talker noise. Half of the participants participated in 20 sessions of computerized training (Listening and Communication Enhancement Program, LACE) between test sessions, while the other half served as Controls. In both groups, half of the participants were non-native speakers of English. In the Control Group, response latencies were unchanged at retest, but for the training group, response latencies were earlier. Findings suggest that auditory training can improve how the adult nervous system responds in noisy listening conditions, as demonstrated by decreased response latencies.

Developmental Windows for Effects of Choline and Folate on Excitatory and Inhibitory Neurotransmission During Human Gestation.

Choline and folate are critical nutrients for fetal brain development, but the timing of their influence during gestation has not been previously characterized. At different periods during gestation, choline stimulation of α7-nicotinic receptors facilitates conversion of γ-aminobutyric acid (GABA) receptors from excitatory to inhibitory and recruitment of GluR1-R2 receptors for faster excitatory responses to glutamate. The outcome of the fetal development of inhibition and excitation was assessed in 159 newborns by P50 cerebral auditory-evoked responses. Paired stimuli, S1, S2, were presented 500 msec apart. Higher P50 amplitude in response to S1 (P50S1microV) assesses excitation, and lower P50S2microV assesses inhibition in this paired-stimulus paradigm. Development of inhibition was related solely to maternal choline plasma concentration and folate supplementation at 16 weeks' gestation. Development of excitation was related only to maternal choline at 28 weeks. Higher maternal choline concentrations later in gestation did not compensate for earlier lower concentrations. At 4 years of age, increased behavior problems on the Child Behavior Checklist 1½-5yrs were related to both newborn inhibition and excitation. Incomplete development of inhibition and excitation associated with lower choline and folate during relatively brief periods of gestation thus has enduring effects on child development.

Brainstem auditory evoked responses in newly diagnosed untreated hypothyroid females

Background: Hypothyroidism stands as a prevalent endocrine disorder, affecting females more than males. Among the array of otolaryngological manifestations linked with thyroid dysfunctions, sensorineural hearing loss emerges as the most frequently encountered issue. Evoked potentials serve as valuable tools extensively utilized in studying brain disturbances. Among these evoked potentials, Brainstem Auditory Evoked Response (BAER) stands out as one of the methods employed for assessing the pathology within the brainstem auditory pathway. Aims and Objectives: The aim of the study is to evaluate the auditory sensory process in the brainstem using BAERs in newly diagnosed untreated hypothyroid individuals. Materials and Methods: Forty newly diagnosed untreated hypothyroid females of 20–50 years were taken as cases and forty age-matched females were considered controls. The hypothyroidism was diagnosed by estimating the serum levels of free T3 (fT3), free T4 (fT4), and thyroid-stimulating hormone. After getting informed written consent, the absolute latencies and interpeak latencies of BAER were recorded using NeuroPerfect EMG 2000 system with installed BAER in the research laboratory, Department of Physiology, Coimbatore Medical College, Coimbatore, and the data were analyzed by student unpaired t-test. Results: The absolute latencies I, III, V and interpeak latencies I- III, III- V, I – V were significantly prolonged in newly diagnosed untreated hypothyroid females (P < 0.0001) and also there was a direct correlation between thyroid profile changes and the BAER latencies. Conclusion: The results of the present study suggest that hypothyroidism impacts the auditory pathway diffusely and early identification of auditory pathway involvement in thyroid hormone deficiency can be achieved using BAER. Prolonged BAER latencies observed in newly diagnosed untreated hypothyroid females are attributed to defective myelination of neural pathways and diminished cerebral metabolism. Hence, integrating BAER recordings into screening protocols could enhance the accuracy and early assessment of neurological involvement in hypothyroid females.

A Comparative Study on Brainstem Auditory-Evoked Response between Dogs and Cats

A Comparative Study on Brainstem Auditory-Evoked Response between Dogs and Cats

Limiting parameter range for cortical-spherical mapping improves activated domain estimation for attention modulated auditory response

BackgroundAttention is one of the factors involved in selecting input information for the brain. We applied a method for estimating domains with clear boundaries using magnetoencephalography (the domain estimation method) for auditory-evoked responses (N100m) to evaluate the effects of attention in milliseconds. However, because the surface around the auditory cortex is folded in a complicated manner, it is unknown whether the activity in the auditory cortex can be estimated. New MethodThe parameter range to express current sources was set to include the auditory cortex. Their search region was expressed as a direct product of the parameter ranges used in the adaptive diagonal curves. ResultsWithout a limitation of the range, activity was estimated in regions other than the auditory cortex in all cases. However, with the limitation of the range, the activity was estimated in the primary or higher auditory cortex. Further analysis of the limitation of the range showed that the domains activated during attention included the regions activated during no attention for the participants whose amplitudes of N100m were higher during attention. Comparison with existing methodWe proposed a method for effectively limiting the search region to evaluate the extent of the activated domain in regions with complex folded structures. ConclusionTo evaluate the extent of activated domains in regions with complex folded structures, it is necessary to limit the parameter search range. The area of the activated domains in the auditory cortex may increase by attention on the millisecond timescale.

Distinguishing Fine Structure and Summary Representation of Sound Textures from Neural Activity.

The auditory system relies on both local and summary representations; acoustic local features exceeding system constraints are compacted into a set of summary statistics. Such compression is pivotal for sound-object recognition. Here, we assessed whether computations subtending local and statistical representations of sounds could be distinguished at the neural level. A computational auditory model was employed to extract auditory statistics from natural sound textures (i.e., fire, rain) and to generate synthetic exemplars where local and statistical properties were controlled. Twenty-four human participants were passively exposed to auditory streams while the electroencephalography (EEG) was recorded. Each stream could consist of short, medium, or long sounds to vary the amount of acoustic information. Short and long sounds were expected to engage local or summary statistics representations, respectively. Data revealed a clear dissociation. Compared with summary-based ones, auditory-evoked responses based on local information were selectively greater in magnitude in short sounds. Opposite patterns emerged for longer sounds. Neural oscillations revealed that local features and summary statistics rely on neural activity occurring at different temporal scales, faster (beta) or slower (theta-alpha). These dissociations emerged automatically without explicit engagement in a discrimination task. Overall, this study demonstrates that the auditory system developed distinct coding mechanisms to discriminate changes in the acoustic environment based on fine structure and summary representations.

Auditory function in humans at high altitude. A scoping review.

High-altitude (HA) affects sensory organ response, but its effects on the inner ear are not fully understood. The present scoping review aimed to collect the available evidence about HA effects on the inner ear with focus on auditory function. The scoping review was conducted following the guidelines of the Preferred Reporting Items for Systematic Review and Meta-Analysis extension for scoping reviews. PubMed, Scopus, and Web of Science electronic databases were systematically searched to identify studies conducted in the last 20 years, which quantified in healthy subjects the effects of HA on auditory function. The systematic search identified 17 studies on a total population of 888 subjects (88.7% male, age: 27.8 ± 4.1 years; median sample size of 15 subjects). Nine studies were conducted in a simulated environment and eight during real expeditions at HA. To quantify auditory function, six studies performed pure tone audiometry, four studies measured otoacoustic emissions (OAE) and eight studies measured auditory evoked responses (AER). Study protocols presented heterogeneity in the spatio-temporal patterns of HA exposure, with highly varying maximal altitudes and exposure durations. Most studies reported a reduction of auditory function with HA in terms of either elevation of auditory thresholds, lengthening of AER latencies, reduction of distortion-product and transient-evoked OAEs. Future studies in larger populations, using standardized protocols and multi-technique auditory function evaluation, are needed to further characterize the spatio-temporal pattern of HA effects along the auditory pathways and clarify the pathophysiological implications and reversibility of the observed changes.

Delirium is associated with loss of feedback cortical connectivity.

Post-operative delirium (POD) is associated with increased morbidity and mortality but is bereft of treatments, largely due to our limited understanding of the underlying pathophysiology. We hypothesized that delirium reflects a disturbance in cortical connectivity that leads to altered predictions of the sensory environment. High-density electroencephalogram recordings during an oddball auditory roving paradigm were collected from 131 patients. Dynamic causal modeling (DCM) analysis facilitated inference about the neuronal connectivity and inhibition-excitation dynamics underlying auditory-evoked responses. Mismatch negativity amplitudes were smaller in patients with POD. DCM showed that delirium was associated with decreased left-sided superior temporal gyrus (l-STG) to auditory cortex feedback connectivity. Feedback connectivity also negatively correlated with delirium severity and systemic inflammation. Increased inhibition of l-STG, with consequent decreases in feed-forward and feed-back connectivity, occurred for oddball tones during delirium. Delirium is associated with decreased feedback cortical connectivity, possibly resulting from increased intrinsic inhibitory tone. Mismatch negativity amplitude was reduced in patients with delirium. Patients with postoperative delirium had increased feedforward connectivity before surgery. Feedback connectivity was diminished from left-side superior temporal gyrus to left primary auditory sensory area during delirium. Feedback connectivity inversely correlated with inflammation and delirium severity.

A Comparative Study of the Brainstem Auditory-Evoked Response during Medetomidine, Propofol and Propofol-Isoflurane Anesthesia in Dogs

A Comparative Study of the Brainstem Auditory-Evoked Response during Medetomidine, Propofol and Propofol-Isoflurane Anesthesia in Dogs

Decoding auditory-evoked response in affective states using wearable around-ear EEG system

Objective. In this paper, an around-ear EEG system is investigated as an alternative methodology to conventional scalp-EEG-based systems in classifying human affective states in the arousal-valence domain evoked in response to auditory stimuli. Approach. EEG recorded from around the ears is compared to EEG collected according to the international 10–20 system in terms of efficacy in an affective state classification task. A wearable device with eight dry EEG channels is designed for ear-EEG acquisition in this study. Twenty-one subjects participated in an experiment consisting of six sessions over three days using both ear and scalp-EEG acquisition methods. Experimental tasks consisted of listening to an auditory stimulus and self-reporting the elicited emotion in response to the said stimulus. Various features were used in tandem with asymmetry methods to evaluate binary classification performances of arousal and valence states using ear-EEG signals in comparison to scalp-EEG. Main results. We achieve an average accuracy of 67.09% ± 6.14 for arousal and 66.61% ± 6.14 for valence after training a multi-layer extreme learning machine with ear-EEG signals in a subject-dependent context in comparison to scalp-EEG approach which achieves an average accuracy of 68.59% ± 6.26 for arousal and 67.10% ± 4.99 for valence. In a subject-independent context, the ear-EEG approach achieves 63.74% ± 3.84 for arousal and 64.32% ± 6.38 for valence while the scalp-EEG approach achieves 64.67% ± 6.91 for arousal and 64.86% ± 5.95 for valence. The best results show no significant differences between ear-EEG and scalp-EEG signals for classifications of affective states. Significance. To the best of our knowledge, this paper is the first work to explore the use of around-ear EEG signals in emotion monitoring. Our results demonstrate the potential use of around-ear EEG systems for the development of emotional monitoring setups that are more suitable for use in daily affective life log systems compared to conventional scalp-EEG setups.

Comparative study of Automated Auditory Brainstem Response (AABR) and Brainstem Evoked Response Audiometry (BERA) for Hearing Loss Detection in High Risk Infants delivered in Dhulikhel Hospital

Background & Objective: Brainstem evoked response audiometry (BERA) is most specific and sensitive test for brain stem dysfunction. It is most important objective method for evaluating peripheral auditory system in neonates, infants, sedated and comatose patients and other person who doesn’t understand the language. Objective of the study was to evaluate correlation BERA with other audiological tests in different types of hearing loss. Material and Methods: This was a hospital based retrospective observational analytic study that used a cross-sectional approach. The sampling used was consecutive sampling until the minimum size fulfilled from 1st September 2021 to 30th September 2022. All high-risk infants aged 0–3 months who suffer from asphyxia, sepsis, LBW, premature, and hyperbilirubinemia, the baby was stable and transportable, the patient’s parents were willing to participate were taken. Results: Out of 46 high risk infants of 0 - 3 months, male:female ratio of 1.7:1 with mean age of 31 days, the most common high risk factor was low birth weight and hyperbilirubinemia i.e 23(50%). 64% of infants were pass in AABR 2nd test in comparison to 71% pass in BERA test. Conclusion: There was no difference between AABR and BERA results for HL detection in high-risk infants at NICU.

Chiari-like malformation in Cavalier King Charles Spaniels impacts brainstem auditory-evoked response latency results.

To evaluate hearing loss in Cavalier King Charles Spaniels (CKCS), breed-specific brainstem auditory-evoked response (BAER) testing parameters are needed to help assess the Chiari-like malformation (CM) grade. The purpose of this study was to establish breed-specific BAER data and to determine if BAER indexes differed based on the CM grade. We hypothesized that there would be latency differences based on the CM grade. 20 CKCS without apparent hearing abnormalities as assessed by the owners. Under general anesthesia, CKCS underwent a CT scan (to assess the middle ear), BAER testing, and MRI (to assess the grade of CM). No CKCS had CM0. Nine (45%) CKCS had CM1; 11 (55%) had CM2. All had at least 1 morphologic abnormality in waveforms. Absolute and interpeak latencies were reported for all CKCS and compared between CM grades. The median threshold for CKCS with CM1 was 39 and for CM2 was 46. Absolute latencies for CKCS with CM2 were consistently longer than those for CKCS with CM1 with the exception of waves II and V at 33 dB. Significant differences were found for wave V at 102 dB ( P = .04) and wave II at 74 dB (P = .008). Interpeak latency comparisons were inconsistent between CM1 and CM2. Breed-specific BAER data for CKCS with CM1 and CM2 were established. The results suggest that CM impacts BAER latency results, but the influence of the malformation is not always statistically significant or predictable.

Possibility of additive effects by the presentation of visual information related to distractor sounds on the contra-sound effects of the N100m responses

Auditory-evoked responses can be affected by different types of contralateral sounds or by attention modulation. The present study examined the additive effects of presenting visual information about contralateral sounds as distractions during dichotic listening tasks on the contralateral effects of N100m responses in the auditory-evoked cortex in 16 subjects (12 males and 4 females). In magnetoencephalography, a tone-burst of 500 ms duration at a frequency of 1000 Hz was played to the left ear at a level of 70 dB as a stimulus to elicit the N100m response, and a movie clip was used as a distractor stimulus under audio-only, visual-only, and audio-visual conditions.Subjects were instructed to pay attention to the left ear and press the response button each time they heard a tone-burst stimulus in their left ear. The results suggest that the presentation of visual information related to the contralateral sound, which worked as a distractor, significantly suppressed the amplitude of the N100m response compared with only the contralateral sound condition. In contrast, the presentation of visual information related to contralateral sound did not affect the latency of the N100m response. These results suggest that the integration of contralateral sounds and related movies may have resulted in a more perceptually loaded stimulus and reduced the intensity of attention to tone-bursts. Our findings suggest that selective attention and saliency mechanisms may have cross-modal effects on other modes of perception.

Dépistage et diagnostic de la surdité chez le chien

Screening and diagnosis of deafness in dogs is based on Brainstem Auditory Evoked Response or BAER recording. Deafness is usually classified according to five criteria : determinism, onset, severity, symmetry, and anatomical-functional stage reached. In breeds at risk for hereditary deafness, with white or piebald robes (Dalmatian Dogo argentino, Bull terrier, Australian cattle dog, etc.) or merle (Border collie, Australian shepherd, etc.), screening of breeding animals and newborns should be encouraged to reduce the prevalence of deafness in these breeds. In dogs with acute deafness, hearing impairment should be confirmed by BAERs recording and lesions should be in-vestigated by medical imaging (CT-scan and/or magnetic resonance imaging). Acquired causes of deafness are nu-merous : inflammatory (especially otitis media), toxic (or ototoxicity), traumatic, degenerative (or presbycusis). In acute deafness in dogs, total bilateral deafness is most often irreversible.

Intensity and inter-stimulus-interval effects on human middle- and long-latency auditory evoked potentials in an unpredictable auditory context.

It is not known how Auditory-Evoked Responses (AERs) comprising Middle Latency Responses (MLRs) and Long Latency Responses (LLRs) are modulated by stimulus intensity and inter-stimulus interval (ISI) in an unpredictable auditory context. Further, intensity and ISI effects on MLR and LLR have never been assessed simultaneously in the same humans. To address this important question, thirty participants passively listened to a random sequence of auditory clicks of three possible intensities (65, 75, and 85 dB) at five possible ISI ranges (0.25 to 0.5s, 0.5 to 1s, 1 to 2s, 2 to 4s, 4 to 8s) over four to seven one-hour sessions while EEG was recorded. P0, Na, Pa, Nb, and Pb MLR peaks and N1 and P2 LLR peaks were measured. MLRs P0 (p=.005), Pa (p=.021), and Pb (p=<.001) were modulated by intensity, while only MLR Pb (p=<.001) was modulated by ISI. LLR N1 and P2 were modulated by both intensity and ISI (all p values < .001). Intensity and ISI interacted at Pb, N1, and P2 (all p values < .001), with greater intensity effects at longer ISIs and greater ISI effects at louder intensities. Together, these results provide a comprehensive picture of intensity and ISI effects on AER across the entire thalamocortical auditory pathway, while controlling for stimulus predictability. Moreover, they highlight P0 as the earliest MLR response sensitive to stimulus intensity and Pb (~50 ms) as the earliest cortical response coding for ISIs above 250 ms and showing an interdependence between intensity and ISI effects.

Brainstem auditory-evoked responses among children afflicted by severely hypoxic CHD.

To electrophysiologically determine the impact of moderate to severe chronic hypoxia (H) resulting from a wide array of CHD (HCHD) conditions on the integrity of brainstem function. Applying brainstem auditory-evoked response methodology, 30 chronically afflicted HCHD patients, who already had undergone heart surgery, were compared to 28 healthy control children (1-15 yo) matched by age, gender and socioeconomic condition. Blood oxygen saturation was clinically determined and again immediately before brainstem auditory-evoked response testing. Among HCHD children, auditory wave latencies (I, III and V) were significantly longer (medians: I, 2.02 ms; III, 4.12 ms, and; V, 6.30 ms) compared to control (medians: I, 1.67ms; III, 3.72 ms, and; V, 5.65 ms), as well as interpeak intervals (HCHD medians: I-V, 4.25 ms, and; III-V, 2.25ms; control medians: I-V, 3.90 ms and, III-V, 1.80 ms) without significant differences in wave amplitudes between groups. A statistically significant and inverse correlation between average blood oxygen saturation of each group (control, 94%; HCHD, 78%) and their respective wave latencies and interpeak intervals was found. As determined by brainstem auditory-evoked responses, young HCHD patients manifestly show severely altered neuronal conductivity in the auditory pathway strongly correlated with their hypoxic condition. These observations are strongly supported by different brainstem neurological and image studies showing that alterations, either in microstructure or function, result from the condition of chronic hypoxia in CHD. The non-altered wave amplitudes are indicative of relatively well-preserved neuronal relay nuclei.

Greater tau pathology is associated with altered predictive coding.

Altered predictive coding may underlie the reduced auditory mismatch negativity amplitude observed in patients with dementia. We hypothesized that accumulating dementia-associated pathologies, including amyloid and tau, lead to disturbed predictions of our sensory environment. This would manifest as increased reliance on ‘observed’ sensory information with an associated increase in feedforward, and decrease in feedback, signalling. To test this hypothesis, we studied a cross-sectional cohort of participants who underwent PET imaging and high-density EEG during an oddball paradigm, and used dynamic casual modelling and Bayesian statistics to make inferences about the neuronal architectures (generators) and mechanisms (effective connectivity) underlying the observed auditory-evoked responses. Amyloid-β imaging with [C-11] Pittsburgh Compound-B PET was qualitatively rated using established criteria. Tau-positive PET scans, with [F-18]MK-6240, were defined by an MK-6240 standardized uptake value ratio positivity threshold at 2 standard deviations above the mean of the Amyloid(–) group in the entorhinal cortex (entorhinal MK-6240 standardized uptake value ratio > 1.27). The cross-sectional cohort included a total of 56 participants [9 and 13 participants in the Tau(+) and Amyloid(+) subgroups, respectively: age interquartile range of (73.50–75.34) and (70.5–75.34) years, 56 and 69% females, respectively; 46 and 43 participants in the Tau(−) and Amyloid(−) subgroups, respectively: age interquartile range of (62.72–72.5) and (62.64–72.48) years, 67 and 65% females, respectively]. Mismatch negativity amplitudes were significantly smaller in Tau+ subgroup than Tau− subgroup (cluster statistics corrected for multiple comparisons: P = 0.028). Dynamic causal modelling showed that tau pathology was associated with increased feedforward connectivity and decreased feedback connectivity, with increased excitability of superior temporal gyrus but not inferior frontal regions. This effect on superior temporal gyrus was consistent with the distribution of tau disease on PET in these participants, indicating that the observed differences in mismatch negativity reflect pathological changes evolving in preclinical dementia. Exclusion of participants with diagnosed mild cognitive impairment or dementia did not affect the results. These observational data provide proof of concept that abnormalities in predictive coding may be detected in the preclinical phase of Alzheimer’s disease. This framework also provides a construct to understand how progressive impairments lead to loss of orientation to the sensory world in dementia. Based on our modelling results, plus animal models indicating that Alzheimer’s disease pathologies produce hyperexcitability of higher cortical regions through local disinhibition, mismatch negativity might be a useful monitor to deploy as strategies that target interneuron dysfunction are developed.

Approach and solutions to congenital hearing impairment in Cameroon: perspective of hearing professionals

ObjectivesTo bring out the diagnostic attitude of hearing professionals in Cameroon towards congenital hearing impairment (CHI), assess availability of tests, neonatal screening, and create a national map of availability of treatment opportunities.MethodsWe conducted a cross-sectional online-based survey from June to December 2021, concerning ear–nose–throat (ENT) specialists, hearing care professionals, speech therapists and ENT nurses. A Google Forms online questionnaire was used to collect data, filled by eligible professionals involved in hearing care in Cameroon.ResultsA total of 93 professionals working in 31 different health facilities participated. A cumulative percentage of 79.9% of ENTs were found in just two out of 10 regions. Specialists sought by ENTs for assessment of patients with CHI included neurologists/neuro-pediatricians (96.8%), pediatricians (47.6%), other ENTs (34.9%), and psychologists (3.2%). Investigations requested included auditory-evoked brainstem response (ABR; 87.3%), otoacoustic emissions recording (OAE; 71.4%), and tympanometry (66.7%). There were eight OAE and nine ABR machines in the country. Twenty-five (88.6%) out of 31 facilities with otolaryngologists did not carry out systematic neonatal screening. Reasons included unavailability of equipment (21; 84%), and administrative delays (14; 56%). Sixteen (51.6%) facilities had ENTs with additional training in otologic surgery and 11 (35.5%) were equipped to perform ear surgery. Three centers (9.7%) specialized in hearing aid provision and maintenance services. Three hospitals (9.7%) had performed cochlear implantation.ConclusionOur results show scarcity and overt unevenness in distribution of specialists, equipment and solutions to CHI in Cameroon. A serious negative health care consequence of this shortage is the unavailability of universal newborn hearing screening and implementation programs.