Interpeak Latencies Research Articles

AUDITORY BRAINSTEM RESPONSE ABNORMALITIES IN SCHIZOPHRENIC PATIENTS WITH AUDITORY HALLUCINATIONS

Background : although the exact pathogenesis of auditory hallucinations is not yet known, some suggested the impairment of perception and processing of auditory information as a possible explanation. So, the aim of this study is to evaluate auditory pathways of schizophrenic patients using auditory brainstem responses (ABR). Methods : schizophrenic patients with auditory hallucinations and age and sex matched healthy non-relative controls were recruited in this case-control study. Scale for assessment of positive symptoms (SAPS) was used for rating the severity of hallucinations. Then, ABR recorded from all participants and the latencies of waves I, II, III, IV, V and inter-peak latencies (IPL) of waves I-III, III-V were analyzed on both sides. Chi squire and independent t tests were applied for statistical analysis. P-value≤0.05 was considered significant. Results : 39 patients and 35 controls were included. Latencies of waves III and V and IPL of III-V were significantly prolonged on the left side. Disease duration had no influence on the results. Conclusion : there is a link between abnormal ABRs and auditory hallucinations in schizophrenic patients that indicates dysfunction and abnormal asymmetry of auditory pathways in these patients.

Hearing and Kidney: Effects of Chronic Kidney Disease on Various Auditory Parameters – Results from a Tertiary Care Hospital in India

Background: An association between chronic kidney disease (CKD) and hearing loss was first described in patients with Alport syndrome. Patients with CKD develop sensorineural hearing loss with the progression of the disease. Studies using BAER as an index of auditory function among patients with CKD showed evidence of various degrees of auditory dysfunction.
 Materials and methods: 100 adult CKD patients (stage 3 – 5 and 5D) and 50 controls were included in the study. Clinical and biochemical parameters were assessed and all the patients and controls underwent Pure Tone Audiometry (PTA) and Brainstem Auditory Evoked Response (BAER) evaluation.
 Results: When hearing thresholds were compared between the patients and controls PTA showed an increase in hearing threshold in all patient groups. This increase was more noticeable at higher frequencies (4 and 8 kHz). Compared with healthy controls, a highly significant delay was observed in CKD patients in both absolute and interpeak latencies in BAER in the present study.
 Conclusion: The present study provides a concrete evidence to the otherwise disputed relation of auditory function in CKD proving that hearing is permanently affected by ESRD at all levels of the auditory neural pathway.
 J MEDICINE JAN 2020; 21 (1) : 31-35

Effects of Caffeine on Auditory- and Vestibular-Evoked Potentials in Healthy Individuals: A Double-Blind Placebo-Controlled Study.

Background and ObjectivesThe blockage of adenosine receptors by caffeine changes the levels of neurotransmitters. These receptors are present in all parts of the body, including the auditory and vestibular systems. This study aimed to evaluate the effect of caffeine on evoked potentials using auditory brainstem responses (ABRs) and cervical vestibular-evoked myogenic potentials (cVEMPs) in a double-blind placebo-controlled study.Subjects and MethodsForty individuals (20 females and 20 males; aged 18-25 years) were randomly assigned to two groups: the test group (consuming 3 mg/kg pure caffeine powder with little sugar and dry milk in 100 mL of water), and the placebo group (consuming only sugar and dry milk in 100 mL water as placebo). The cVEMPs and ABRs were recorded before and after caffeine or placebo intake.ResultsA significant difference was observed in the absolute latencies of I and III (p<0.010), and V (p<0.001) and in the inter-peak latencies of III–V and I–V (p<0.001) of ABRs wave. In contrast, no significant difference was found in cVEMP parameters (P13 and N23 latency, threshold, P13-N23 amplitude, and amplitude ratio). The mean amplitudes of P13-N23 showed an increase after caffeine ingestion. However, this was not significant compared with the placebo group (p>0.050).ConclusionsIt seems that the extent of caffeine’s effects varies for differently evoked potentials. Latency reduction in ABRs indicates that caffeine improves transmission in the central brain auditory pathways. However, different effects of caffeine on auditory- and vestibular-evoked potentials could be attributed to the differences in sensitivities of the ABR and cVEMP tests.

The effect of hypoxia on hearing function

Background/aimThis study was conducted to determine the critical partial oxygen pressure (pO2) value that would impair hearing function by evaluating the effects of hypoxia on hearing function in subjects diagnosed with chronic obstructive pulmonary disease (CPOD).Materials and methodsThe study included 25 male and 5 female patients referred to our clinic who were diagnosed with COPD, according to spirometry and PaO2 values, and who did not show pathology upon autoscopic examination. The control group consisted of 14 female and 16 male patients who had no lung disease and were in the same age range as the COPD group.ResultsA statistically significant difference was found between the two groups for distortion-product otoacoustic emission (DPOAE) (P < 0.001). The COPD group was divided into two groups according to pO2 levels (pO2 ≤ 70 and pO2 > 70) in order to find a critical pO2 level which might cause significant change at a certain audiological extent.ConclusionHypoxia causes long-term decline in hearing thresholds, deterioration of DPOAE results, and prolongation of I–V interpeak latency in auditory brainstem response. However, the critical oxygen level that disrupts hearing function could not be determined.

A study of auditory brainstem evoked responses in type 1 and type 2 diabetes mellitus patients with normal hearing

&lt;p class="abstract"&gt;&lt;strong&gt;Background:&lt;/strong&gt; Diabetes mellitus (DM) is one of the most common metabolic disorders with millions of cases world-wide. Its effect on functioning of the central nervous system (CNS) and the peripheral nerves is a matter of current neurological research. Our study aimed to find out changes in auditory brainstem responses if any, in patients with type 1 and type 2 DM patients with apparently normal hearing.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Methods:&lt;/strong&gt; 50 cases each of type 1 and type 2 diabetic patients with normal hearing were chosen along with 50 healthy controls. Pure tone audiometry and brainstem evoked response audiometry (BERA) was performed in all cases. The BERA results were interpreted for the latencies of waves I, II, III, IV and V and inter-peak latencies I-III, I-V and III-V. &lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Results:&lt;/strong&gt; Significant delay in absolute latency of wave I, III, IV, V and inter-peak latencies I-V and III-V was seen in Type 1 diabetic patients. In Type 2 diabetic patients, latencies of waves I, II, III, IV and V and inter-peak latencies I-III, I-V and III-V were significantly delayed. There was no statistically significant difference in latency delay between type 1 and type 2 DM. No relation was found with the duration of DM.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Conclusions:&lt;/strong&gt; BERA is a non-invasive and easy to perform test that can detect minor CNS changes and can be used to detect peripheral (auditory nerve) and central neuropathy in diabetics even in absence of clinical signs and symptoms of deafness.&lt;/p&gt;

Auditory and vestibular dysfunction in patients with Parkinson\u2019s disease

BackgroundMotor dysfunction in patients with Parkinson disease (PD) is just the tip of the iceberg. Auditory and vestibular dysfunction in patients with PD gained much attention owing to them being one of the nonmotor symptoms.AimTo explore abnormalities of pure tone audiometry (PTA), brainstem auditory evoked potentials (BAEPs), vestibular evoked myogenic potential (VEMP), and videonystagmography (VNG) in patients with PD and their correlation with motor and cognitive dysfunction.Patients and methodsThe study was conducted on 20 patients with PD and 15 controls. Selected patients were subjected to evaluation of motor symptoms using Unified Parkinson’s Disease Rating Scale (UPDRS) and cognitive function using Parkinson disease-Cognitive Rating Scale (PD-CRS). PTA, BAEPs, cervical VEMPs, and VNG were carried out for all patients and controls.ResultsPatients with PD show higher mean hearing thresholds at all PTA frequencies in both ears than controls. Analysis of BAEP demonstrated that patients with PD have significantly prolonged absolute latencies of wave III and wave V and interpeak latencies of I–III and I–V in both ears than controls. VEMP findings revealed that patients have significantly delayed P13 and N23 latencies and smaller P13–N23 amplitude in both ears than controls. VNG findings showed canal paresis in 60% of patients with PD and nystagmus in 60% of patients with PD. Correlative results revealed statistically significant correlations between VEMP parameters and UPDRS as well as PD-CRS, but there were no statistically significant correlations between PTA frequencies or BAEP latencies and UPDRS or PD-CRS.ConclusionAuditory and vestibular dysfunction is common in PD but cannot be totally correlated with the motor and cognitive symptoms.

Auditory brainstem responses in weaning pigs and three ages of sows.

Piglet crushing is a devastating welfare concern on swine farms; however, some sows appear unresponsive to a piglet’s call. Sow hearing ability is rarely considered despite the extensive body of research performed on crushing. In this study, pigs of four age groups (weaning, n = 7; gilts, n = 5; 2nd and 3rd parity, n = 5; 5th parity and up, n = 5) were anesthetized and auditory brainstem responses (ABRs) were performed to measure if pig hearing diminishes with age in a mechanically ventilated barn. Before testing, pigs were placed in a sound dampening box. ABRs were performed on animals using 1,000 clicks at two decibel (dB) levels: 90 and 127 dB sound pressure level. Latencies and amplitudes of waves I–V were measured and interpeak latencies for waves I–III, III–V, and I–V were calculated. Five pigs (three 2nd and 3rd parity, and two 5th parity and above) had no detectable waves at either decibel. Sows in 2nd and 3rd parities had very few distinguishable waves, with only wave I and II present in two sows. Amplitudes of waves I and V increased with increased dB (P < 0.001). Increasing dB decreased the latency of each of the recorded waves (P < 0.01). The vast majority of commercial swine are raised in noisy barn environments; it is possible that these environments directly affect the ability for pigs to hear and normal hearing development in this population of animals. Hearing has a significant effect on swine welfare as hearing is integral to successful animal handing and during moments of animal-to-animal communication. Hearing is a considerable welfare issue on farms and ways to decrease pig hearing loss should be considered.

The value of ABR- and ASSR-based hearing estimation in young children with congenital monaural malformation (atresia)

Background: The electrophysiology of auditory nerve mature is particularly important for unilateral hearing loss.Objectives: To assess the hearing status in young children with congenital monaural malformation and evaluate their potential for practical use in the functional maturation parameters of the auditory pathway.Materials and methods: ABR (auditory brainstem responses) and ASSR (auditory steady-state responses) threshold measurements were performed in 21 young children with congenital monaural atresia.Results: The average electrophysiologic thresholds for the ABR were 65 dB nHL ± 1.20 in malformed ears and 25 dB nHL ± 0.48 in normal ones. All 21 atretic ears presented with typical conductive hearing loss. There was no statistic positive correlation in hearing-impaired ears between the methods of ABR and ASSR responses (r = 0.12, 0.20 and 0.17). The IPL (interpeak latency) of I–III, III–V and I–V of atretic ears in ABR test was decreased relative to normal ears. Furthermore, a shortening of the IPLs I–III, III–V, I–V can be observed with increasing age of the children in malformed ears.Conclusions and significance: The ABR- and ASSR-based hearing evaluation in young children with congenital monaural malformation should be viewed as complementary technologies. Besides, there was no delay of functional maturation at brainstem level although unilateral hearing was deprived during their early years of life.

Peripheral and central auditory function in adults with epilepsy and treated with carbamazepine

Purpose of the study: Epilepsy is a chronic medical disease in one third of patients. Chronic epilepsy and its antiepileptic drugs (AEDs) therapy are commonly associated with comorbid adverse somatic conditions. This study aimed to evaluate auditory function in patients with idiopathic epilepsy and on treatment with carbamazepine (CBZ).Methods: This is a cross-sectional case-control study. It included 50 patients with idiopathic epilepsy (mean age = 34.56 ± 7.11 and duration of illness = 17.84 ± 7.21years) and 40 healthy subjects. Hearing was evaluated using pure tone audiometry and brainstem auditory evoked potentials (BAEPs) analyses.Results: Mild bilateral hearing impairment and abnormal acoustic reflex (but normal tympanometry) were reported in more than one third of patients. Compared to controls, BAEPs of patients had prolonged waves I, III, V latencies and I–III, III–V and I–V interpeak latencies (IPLs) particularly at high repetition frequencies. Significant correlations were identified between CBZ dose, serum level and duration of treatment with waves I, III and V and I–III, III–V and I–V latencies at high repetition frequencies.Conclusions: Long-term treatment with CBZ may result in delayed auditory conduction within the peripheral pathways and brainstem. This should be taken into account during drug selection and monitoring of patients with epilepsy.

A cross sectional study of effects of mobile phone exposure on Brainstem evoked response audiometry (BERA)

Human physiology creates a framework for understanding how the human body adapts to stresses, physical activity and disease. Best example is usage of mobile phones for daily routine. An attempt was made to study the effect of exposure to mobile phone on functions of ear. Hence, the objective of our study was to find out the effects of exposure of mobile phones on BERA in mobile phone users for long time. 18–30 years aged 100 normal healthy volunteers were considered for the study. Two groups of 50 each participant, who used mobile phones for 4 years for 60 minutes in each day and who used mobile phones since a year for 60 minutes per day respectively. Concise click acoustic stimuli alternating in polarity were presented by an earphone on the ear with 40 and 90 dB intensities. Recording of peak BERA latencies (I, III and V) and calculation of interpeak latency I - V were done. Analysis reveals significant prolongation of latencies in wave III and wave V in Group I participants and also significant prolongation of inter peak latency I - V in Group I participants. On comparison of various latencies of BERA in participants of both the groups, in Group I, a significant increase in latencies of the wave III and V was observed. This damage to the ear can be at various levels of auditory pathway and can be proportional to the amount and duration of exposure. Keywords: BERA, Interpeak latencies, Auditory pathway.

P35-F Brainstem auditory evoked potentials in patients with primary Sjögren’s syndrome

Background Primary Sjogren’s syndrome (pSS) is a chronic autoimmune exocrinopathy characterized by dysfunction of exocrine glands. Central nervous system (CNS) involvement is estimated to be present in 3–60% patients with pSS. The aim of our study was to evaluate parameters of brainstem auditory evoked potentials (BAEP) in pSS patients without clinical neurological deficit, and without otolaryngological abnormalities. Material and methods 36 patients with pSS (35 women, 1 man, mean age 49.3 years old) and 40 healthy controls, sex and age-matched were studied. They did not suffer from disease that could have affected the brain electrical activity. Clinical neurological and otolaryngological examinations, laboratory parameters (C3 and C4 component, ANA antibodies, RF levels), brain imaging (CT or MRI) and BAEP were performed. Statistical analysis was performed using the Statistica 10.0 PL software. Results In none of the patients were the abnormalities on brain imaging found. Abnormal BAEP were recorded in 6 patients (16.6%). pSS patients had a longer mean wave I and V latency and mean wave III-V and I-V interpeak latencies than the controls. There were no correlations between BAEP parameters and laboratory tests. Conclusions 1. In pSS patients without clinical central nervous system impairment the auditory pathway disturbances could be found. 2. Disorders of the brain bioelectrical activity in the course of pSS may be associated with an ongoing autoimmune process. item The analysis of BAEP may be useful methods of assessment of the CNS in patients without clinical neurological symptom.

Hidden hearing deficits in military service members with persistent post concussive symptoms

Individuals with persistent symptoms after mild traumatic brain injury (mTBI) often have auditory complaints. In this study, we used the auditory brainstem response (ABR) to determine whether cochlear synaptopathy could explain auditory symptoms. 69 adult military service members with mTBI and 25 adults without brain injury (NCT01611194 and NCT01925963) completed pure-tone audiometry, ABR, and central auditory processing tests. All participants were male, ages 21-50. 37/69 mTBI participants had measurable hearing loss, while another 20%-30% had hearing complaints or tinnitus. While mTBI participants with measurable hearing loss had reduced wave I and III amplitude and decreased III-V interpeak latency, those with no measurable hearing loss did not significantly differ from controls on any ABR parameter. Those with measurable hearing loss were also more likely to have abnormal central auditory processing. mTBI participants with no measurable hearing loss but who reported hearing concerns had some ABR findings (III-V interpeak latency, I and V amplitudes, V/I amplitude ratio) more like the measurable hearing loss mTBI group than normative controls. Cochlear synaptopathy may have contributed to some of the auditory impairment in service members with mTBI with measurable hearing loss. However, these results are likely confounded by cochlear hair cell damage.

Characteristics of short-patent auditory evoked potentials in children with cerebral palsy

Background. In children with cerebral palsy, high risk of cognitive impairments connected with sensory disintegration – delayed visual and auditory perception.The objective – assessment of temporary and amplitude characteristics brainstem auditory evoked potentials of children with cerebral palsy.Materials and methods. Neurological examination, retrospective analysis of magnetic resonance imaging data of brain and 2-channel brainstem auditory evoked potentials registration with left- and right-ear stimulation and analysis was performed for 60 children aged 4–17 years, with mean age 11.80 ± 0.56 years.Results. There are no significant difference in brainstem auditory evoked potentials latencies of children’s with cerebral palsy age subgroups. A significantly increasing of III–V peak latencies of brainstem auditory evoked potentials and also I–III and I–V interpeak latencies was observed in children with cerebral palsy in comparison of control group. Latencies of different brainstem auditory evoked potentials peaks were significantly higher in children with uni- and bilateral form of cerebral palsy and speech impairment. Group with periventricular leucomalation (on magnetic resonance imaging) is characterized by significantly increased brainstem auditory evoked potentials latencies and normal interpeak intervals. These abnormalities may be linked to non-progressive impairment of brainstem acoustic afferentation.Conclusion. Impairment of brainstem auditory evoked potentials maturation and it’s difference in various cerebral palsy forms may be potentially clinical applicable for assessment of the children and early detection of sensory impairment.

Multimodal Evaluation of TMS - Induced Somatosensory Plasticity and Behavioral Recovery in Rats With Contusion Spinal Cord Injury.

Introduction: Spinal cord injury (SCI) causes partial or complete damage to sensory and motor pathways and induces immediate changes in cortical function. Current rehabilitative strategies do not address this early alteration, therefore impacting the degree of neuroplasticity and subsequent recovery. The following study aims to test if a non-invasive brain stimulation technique such as repetitive transcranial magnetic stimulation (rTMS) is effective in promoting plasticity and rehabilitation, and can be used as an early intervention strategy in a rat model of SCI.Methods: A contusion SCI was induced at segment T9 in adult rats. An rTMS coil was positioned over the brain to deliver high frequency stimulation. Behavior, motor and sensory functions were tested in three groups: SCI rats that received high-frequency (20 Hz) rTMS within 10 min post-injury (acute-TMS; n = 7); SCI rats that received TMS starting 2 weeks post-injury (chronic-TMS; n = 5), and SCI rats that received sham TMS (no-TMS, n = 5). Locomotion was evaluated by the Basso, Beattie, and Bresnahan (BBB) and gridwalk tests. Motor evoked potentials (MEP) were recorded from the forepaw across all groups to measure integrity of motor pathways. Functional MRI (fMRI) responses to contralateral tactile hindlimb stimulation were measured in an 11.7T horizontal bore small-animal scanner.Results: The acute-TMS group demonstrated the fastest improvements in locomotor performance in both the BBB and gridwalk tests compared to chronic and no-TMS groups. MEP responses from forepaw showed significantly greater difference in the inter-peak latency between acute-TMS and no-TMS groups, suggesting increases in motor function. Finally, the acute-TMS group showed increased fMRI-evoked responses to hindlimb stimulation over the right and left hindlimb (LHL) primary somatosensory representations (S1), respectively; the chronic-TMS group showed moderate sensory responses in comparison, and the no-TMS group exhibited the lowest sensory responses to both hindlimbs.Conclusion: The results suggest that rTMS therapy beginning in the acute phase after SCI promotes neuroplasticity and is an effective rehabilitative approach in a rat model of SCI.

Effects on auditory function of chronic exposure to electromagnetic fields from mobile phones

The widespread use of mobile phones has given rise to apprehension regarding the possible hazardous health effects of high-frequency electromagnetic fields (EMFs) on auditory function. We conducted a study to investigate the effects of long-term (>4 yr) exposure to EMFs emitted by mobile phones on auditory function. My study population was made up of 40 healthy medical students—31 men and 9 women, aged 20 to 30 years (mean 22.7). Of this group, 31 subjects typically held their phone to the right ear and 9 to the left ear; the non–phone-using ear served as each subject’s control ear. The phone-using subjects were also split into two groups of 20 based on the duration of their daily phone use (≤60 min vs. >60 min). All subjects underwent pure-tone audiometry, speech audiometry, impedance audiometry, and brainstem evoked response audiometry (BERA), and comparisons were made between the phone-using ear and the control ear and between the shorter and longer duration of daily use. We found no statistically significant differences in high-frequency pure-tone average between the phone using ears and the control ears (p = 0.69) or between the shorter- and longer-duration phone-using ears (p = 0.85). Moreover, statistical analysis of BERA findings revealed no significant differences between the phone-using ears and the control ears in terms of wave I-III, III-V, and I-V interpeak latencies (p = 0.59, 0.74 and 0.44, respectively). None of the subjects reported any subjective symptoms, such as headache, tinnitus, or sensations of burning or warmth behind, around, or on the phone-using ear. I conclude that long-term exposure to EMFs from mobile phones does not affect auditory function.

Brainstem auditory evoked potentials (BAEP) in dairy calves

Brainstem auditory evoked potentials (BAEP) are useful to diagnose neurologic and genetic disorders in cattle but normal parameters and its application to detect changes in hearing are not demonstrated. The aims of this study were to develop a protocol for obtaining BAEP in Holstein calves and to establish the normal parameters of peak latencies, interpeak latencies (IPL) and waveforms of BAEP in this species. Ten male Holstein calves, aged 2.5 months and weighting 90.7 ± 4.0 kg were used. All animals were previously sedated with 0.08 mg/kg xylazine hydrochloride administered intramuscularly. The BAEP analysis was recorded using the IHS SmartEP-ASSR program connected with electrode needles placed on the standardized locations of the animal's head. Monoaurally presented broadband click stimuli (0.1 ms) were used for BAEP stimulation, with contralateral masking of 30 dB SPL. Stimuli were presented at a rate of 35.5 pulses per second (PPS) and evoked responses were collected and averaged 450–1500 times for each sound intensity. Earphones were inserted into the ear canal to present the acoustic stimulus and to attenuate environmental noise. Peak latencies, IPL, waveforms and auditory thresholds were recorded and analyzed in the right ear and were like those described in previous papers in adult male bulls. Auditory thresholds obtained in all animals were 33 ± 1.5 dB SPL. Peak latencies were 1.4 ± 0.07 ms (Peak I), 2.4 ± 0.10 ms (Peak II), 3.3 ± 0.10 ms (Peak III), 4.4 ± 0.19 ms (Peak IV) and 5.6 ± 0.28 ms (Peak V). IPL were 1.9 ± 0.12 ms (IPL I-III), 4.1 ± 0.29 ms (IPL I-V), 2.2 ± 0.19 ms (IPL II-V) and 2.2 ± 0.19 ms (IPL III-V). Brainstem auditory evoked potentials are a minimally-invasive method to evaluate level of audition in Holstein calves. In addition, BAEP is a method that can be applied in young calves and it would work on-farm to select the animals with better conditions.

Changes in Auditory Brainstem Response in very preterm and late preterm infants

AimAim of this study was to compare the absolute and interpeak latencies of Auditory Brainstem Responses (ABR) in very preterm and late preterm infants at 1 month and 3 months of corrected age. Methodology: ABR traces were obtained from 80 preterm infants (40 very preterm and 40 late preterm) at 1 month and 3 months of corrected age in a prospective, comparative cohort study. Auditory click stimuli at 70 dBnHL and 30 dBnHL, with repetition rate of 11.1/s were used. Absolute latencies of peak I, III, V and interpeak latencies of peak I-V, I-III and III-V were analyzed and compared between preterm groups at 1 month and 3 months of corrected age. Wilcoxon Signed Ranks test was used to compare the ABR variables. Mann Whitney test was used to make inferences between groups. ResultsThere was a statistically significant difference in absolute latencies and interpeak latencies between very preterm and late preterm infants at 1 month of corrected age (p < 0.05). Absolute latency of peak I was similar among both groups of preterms. Absolute latencies of peak III, V and interpeak latencies I-III, III-V and I-V were prolonged in very preterm infants at 1 month of corrected age. However, these latencies were significantly reduced at 3 months of corrected age. This indicated accelerated maturation/myelination of the central auditory nervous system in very preterm infants. Absolute latencies of peak III and V and interpeak interval I-V was reduced in late preterm infants at 3 months of corrected age and this was statistically significant. This reduction in latency was considered to be a normal age dependent change. ConclusionFindings of the current study revealed that there was no deviation in the pattern of auditory maturation among preterms; it followed the typical ‘caudal to rostral’ form of maturation. Very preterm infants have less mature neuronal development compared with late preterm infants at 1 month of corrected age which catches up at 3 months of corrected age.

Effect of neonatal hyper bilirubinemia on brain stem auditory evoked response

Introduction: Neonatal hyperbilirubinemia is a major cause of morbidity in neonates. The long term neurological sequel can be prevented and reversed by timely and aggressive management of hyperbilirubinemia. Brain stem auditory evoked response (BAER) is an assessment tool to help predictimpeding bilirubin neurotoxicity. This study was conducted to evaluate the effect of hyperbilirubinemia on auditory system of newborn and the effect of therapy on BAER. Materials and Methods: In this case control study, 50 term neonates with hyperbilirubinemia (total serum bilirubin > 15 mg/dl) were included in the study group and 25 normal term neonates were taken as controls. Baseline BAER was recorded in study group before therapy and after therapy. Results were compared with controls and intra group comparison was also done. Continuous data with normal distribution was analysed by student t-test, and categorical data was analysed using chi-square test. Results: Most common BAER abnormality noted in jaundiced neonates was prolonged latency of wave V (42%) andprolonged inter wave interval I–V (32%). Significant increase in the absolute latencies of waves III and V was noted in hyperbilirubinemic neonates as compared to controls (p<0.05). I-III and I-V inter-peak latencies were also significantly prolonged in neonates with hyper bilirubinemia (p<0.05). There was significant improvement in the latency of wave III and wave V, I – III inter- peak latency and I – V inter-peak latency after treatment (P<0.05). Conclusion: Results of our study demonstrate the importance of early ABR screening as an efficient tool for monitoring the neonates at risk of bilirubin neurotoxicity. Diagnosing the early changes in ABR caused by hyperbilirubinemia before appearance of clinical abnormality will help prevent bilirubin neurotoxicity.

Early Phototherapy at Lower Total Serum Bilirubin Can Decrease Auditory Neuropathy Disorder

Background: Neurologic dysfunctions, specifically hearing impairments due to hyperbilirubinemia are ranked among the main concerns in medicine. Objectives: This study evaluates the prevalence of acute auditory neuropathy (AN) disorders in term neonates with mild to moderate hyperbilirubinemia and low bilirubin-induced neurological dysfunction (BIND) score and the roll of early treatment on reducing their incidence. Methods: Fifty one term jaundice neonates with normal newborn exam and total serum bilirubin (TSB) ≥ 15 mg/dL after the third day of birth with normal otoacoustic emission (OAE) test were enrolled. The BIND score assessment for severity of neurologic dysfunction was done. Neonates with low BIND score were divided into two groups based on their TSB levels at the time of admission (15 - 18 mg/dL: Mild-moderate hyperbilirubinemia and ≥ 19 mg/dL: Severe hyperbilirubinemia). ABR was performed within the first 12 hours of their admission and the second ABR was performed before discharge. Results: The 30.60% of neonates with TSB < 19 mg/dl had abnormal ABR. Latency of V, III waves and interpeak interval latency of I-III, I-V waves were detected. Mean latency of wave V and I-V interpeak latency after phototherapy were significantly decreased compared to pre-treatment (P < 0.001). Conclusions: With the prevalence of auditory neuropathy (AN) at lower TSB concentrations (that have traditionally been considered safe) it can be concluded that more attention should be given to this group despite the absence of neurologic signs, and it also shows the sensitivity of early phototherapy to lower bilirubin level.

Morphology variations of click-evoked auditory brainstem response with low and high rate stimuli in rat

Background and Aim: The auditory brainstem response (ABR) is one of the most common obj­ective hearing tests conducting in animal and human. The purpose of this study was evalua­ting the morphology variations of ABR wave­forms in rats with low and high rate click sti­muli. Methods: First, rats with ABR thresholds hig­her than 55 dB SPL were excluded and total 81 ears remained in study. Absolute and interpeak latencies of wave I, II, IV were evaluated at low (17.7 Hz) and high rate (88.7 Hz) for click sti­muli at 120 dB SPL.. Results: At low rate stimuli, ABR waveforms showed different morphologies. The most com­mon complex for waves II to IV was wave III placed on downward slope of wave II (71% of cases). Almost the same morphologies were seen at higher rate; but in some waves, it rou­nded and decreased amplitude. For waves IV-V, the most common morphology was equal amp­litude of wave IV and V in low and high rates (35% vs 56%, respectively). Generally, the high rate stimuli didn’t severely change morphology patterns except for later waves. Conclusion: Normal click-evoked ABR could result in different waveforms. Using click sti­muli at low and high rate result in different mor­phology patterns. Recognizing morphology var­iations of ABR waveforms are essential for det­ecting any pathological conditions. The high rate stimuli increased latencies, especially for later waves.