Neuroanatomy and Neurophysiology Systems Auditorium

The ear is anatomically divided into the outer, middle, and inner ear. The outer ear itself consists of from leaf ear, hole ear until membrane timpani. Leaf ear consist of bone vulnerable elastin And skin Which squiggly And maintained on the place by muscle And ligaments. Curve leaf ear Which main is helix And antihelix, tragus and antitragus and concha. The concha is a funnel-like curve that leads to the meatus, while the only part of the ear that does not contain cartilage is the lobule. The cartilage of the auricle is continuous with the cartilage of the external ear canal. ⁴

The external acoustic canal (ECC) is approximately 2.5 – 3.5 cm long and is divided into two part that is: 1) Pars cartilaginous Which is one third part outside from KAE. 2) Pars ossea which is the inner two-thirds of the ear canal and is formed from pars timpani as well as pars squamous bone temporal. Liang ear part this bone curved to direction front And inferior as well as narrow in part middle forms the isthmus. The anterior part of the KAE is connected to the temporomandibular articulation, the posterior part is connected to the mastoid cells, the superior part is connected to the cranial fossa, and the superomedial part is connected to the mastoid antrum. ^4,5

The middle ear includes the area between the tympanic membrane and the inner ear capsule consisting of the tympanic cavity, the auditory bones and muscles and their supporting organs, the eustachian tube, and the mastoid air cell system. The tympanic cavity from superior to inferior is divided into the epitympanicum at the apex, the mesotympanicum, and the hypotympanicum. ^4,5

The part of the inner ear known as the labyrinth is divided into the cochlea which is the hearing part and the vestibule along with the semicircular canals which are the balance parts. The inferior part of the labyrinth is spiral-shaped with 2 ½ to 2 ¾ turns, with a total length of almost 35 cm. The structure of the cochlear duct and room periotic very complex, to form a system three room tubular that is vestibular scale, scale media And scale timpani.Scale vestibule And timpani contain perilymph, whose electrolyte composition is extracellular fluid. The scala media contains endolymph which is intracellular fluid. ^4.5

Duct scale media shaped triangle, limit near scale timpani to form an important attachment site which is a strong radial connective tissue extension of the spiral lamina of the part of the bone called the basilar membrane, which supports the end organs hearing that is organ corti on its surface. Limit between scale vestibule and the cochlear duct is formed by a fine membrane, namely Reissner's membrane. On the outside, a line of vascular areas extends along the cochlear duct, containing a layer of secretory type granular cells, namely the stria vascularis. The tip or apex of the cochlea is called the helicotrema, which connects the perilymph of the scala tympani and scala vestibula. ^4,5,6

Organ corti is a structure Which complex consists of from three part The main components are supporting cells, hair cells, and a gelatinous membrane connecting the tectorial membrane. The largest components of the organ of Corti are the outer hair cells, inner hair cells and supporting cells, the tectorial membrane and the reticular lamina complex. The tectorial membrane and the organ of Corti as a whole also have structural characteristics with variations that result in a characteristics duct cochlea. As consequence from characteristics This, a sound energy with high frequencies will be centered at the basal end of the cochlea, while low frequencies low Which more low And Next divided in a way progressive throughout organ of corti. Hair cells are arranged in a single row of inner hair cells, while outer hair cells are arranged in 3-5 rows as seen in. ^7,8

After reaching the cochlear nerve, the auditory pathway will continue through the central process structure of the first order of the cochlear nerve to the first relay of auditory input, namely to the ventral cochlear nerve and the dorsal cochlear nerve. The ventral cochlear nerve will branch into the posteroventral and anteroventral cochlear nerves. The anteroventral cochlear nerve is the main nucleus to the termination end of the cochlear nerve. ^9,10,11

The second order fibers from the cochlear nerve will rise ipsilaterally to the medial and lateral olivary nerves or crosswise, forming three different pathways, namely: the acoustic stria. dorsal, intermediate, And ventral. Fibers Which cross This forms a collection of fibers called the trapezoid corpus. The fibers from the trapezoid corpus will go to to contralateral that is n.medial corpus trapezoid, Which on Finally will towards the lateral superior olivary n., medial superior olivary n. Dorsal lateral lemniscus and inferior colliculus (via the contralateral lateral lemniscus). ^9,10,11

The second-order fibers from the posteroventral cochlear nerve will form the intermediate acoustic stria, adjacent ventral from fascicle longitudinal medial. Fibers it will be Then join to lemniscus lateral ipsilateral And contralateral For go on and ends in the ventral nerve of the lateral lemniscus and inferior colliculus bilaterally. ^9,10,11

The auditory cortex has a tonotopic representation frequency, namely neurons that respond to low frequencies will be located in the rostral area, while those that respond to high frequencies will be located in the caudal area. Auditory cortex primary arranged in a way 2 dimensions. One dimensions arranged by Column frequency, while another dimension is the binaural column. There are two types of binaural columns, namely the summation and suppression columns. Neurons located in the summation column respond to auditory stimuli that stimulate both ears simultaneously. Different as it is on Column suppression, neuron respond maximum against stimulus auditory Which stimulate One ear just, However respond minimum when both ears stimulated. Cortex auditory on each side will send projection to the contralateral side via the corpus callosum. The primary auditory cortex plays a role in detecting changes in sound patterns and localization. ^9,10,11

Area cortex auditory secondary to form connection Which reciprocal with primary auditory cortex. The secondary cortex plays a role in the interpretation of sound, and through connections with Wernicke's area plays a role in language comprehension. ^9,10,11

The potential at the BERA source begins with neuroelectric activity in sensory cells. In in cochlea, cell sensory the in the form of cell hair outside And in. If there is sound or movement of the basilar membrane increases by the outer hair cells, then the inner hair cells will release transmitters to the auditory nerve fibers. AEPs generated from the function of hair cells are cochlear microphonic and summating potential. ²¹

During depolarization, ion positive enter on region neuron And cause extracellular part on region the become negative (chart down). Flow entry ion This positive will come out in other regions of the cell, which causes the extracellular part to become positive (chart positive). Difference current This produce a condition dipole (two poles). In general draft, dipole like on battery, own end positive And negative. During the examination, the wave recording will look good if the electrode is placed at the end opposite the dipole. ²¹

Neural activity can be recorded directly from the brain nerves, nerve fiber tracts, brain stem nuclei, and cortical surfaces ( near field potential ). Recording can also be done from a place far from the source of activity ( far field potential ), namely on the scalp or ear that receives signals through brain tissue conductors, cerebrospinal fluid, bone skull, And skin head. Inspection BERA is type far-field. Far field potential reflect activity neural from One or more source dipole.

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When the neurotransmitter is released, the peripheral auditory nerve fibers stimulate the auditory branch of cranial nerve VIII and produce an action potential to be sent to the cochlear nucleus complex in the brainstem. The cochlear nucleus is where the auditory system begins. nerve auditory central. In throughout stem brain there is a number of nucleus auditory bilaterally (cochlear nuclear complex, superior olivary complex and inferior colliculus) and nerve fiber pathways (acoustic stria and lateral lemniscus). In the brainstem there are also several crossings of nerve fibers ( decussation ) from and to several nuclei. The first crossing begins at the level of the cochlear nucleus on its way to the superior olivary. The inferior colliculus receives about 99% of the synapses before moving upwards to the auditory system. After passing through the inferior colliculus, the sound signal will sent to structure midbrain to thalamus, Which called as medial geniculate bodies , Then going to to cortex auditory primary in cerebrum Which called girus Heschl's which is located supratemporally in both Temporal lobes. The primary auditory cortex is where auditory perception begins. ²¹

Hear just No Enough, For give meaning  from a sound/voice, further processing is required for the neural signals that occur in the secondary auditory cortex, which involves One or more posterior from girus Heschel Which called plane temporal which is also located in the Temporal lobe. Another important structure that is also related to the auditory system is the isthmus of the corpus callosum. The corpus callosum is a bundle consisting of on around 200 million fiber nerve myelinated as intermediary the occurrence exchange of information between the two cerebral hemispheres. ²¹

Brainstem Evoked Response Audiometry (BERA)

Brainstem evoked response audiometry (BERA) examination or often also called as auditory brain stem response (ABR) is Wrong One form auditory evoked potential (AEP) examination, which is a type of electrophysiological examination of hearing. ²¹

AEP is an examination of electrical activity in the auditory system by providing stimuli and assessing the effects of these stimuli on the auditory system. AEP is an electrophysiological response that arises from one or more sources along the peripheral and/or central auditory system in response to acoustic stimuli recorded at a specific location on the head or ear, resulting in a waveform with positive and negative voltage deflections at a specific time in succession. The deflection can be considered as a wave, peak, or component. The height or depth of a wave peak is the wave amplitude, while the time required for a peak to occur indicates the wave latency. ²¹

BERA is one type of examination that must be performed when examining a child's hearing. This examination is used more widely than with inspection subjective, Because can done on baby, child small, uncooperative patients, people who are ill or under sedation or anesthesia, and comatose patients. BERA also has better sensitivity and specificity than subjective examination. ²¹

Apart from BERA, there are several other examinations included in AEP, for example electrocochleography (EcochG) which assesses cochlear function and audiotry steady-state response (ASSR). ²¹

BERA is an important electrophysiological procedure for hearing evaluation. Development BERA own meaning  clinical on two area main: (1). Evaluation and diagnosis of disorders related to the peripheral auditory systemec. (2). Assessment of the integrity of the auditory nerve and auditory nerve pathways at the caudal level of the brain stem. ¹³ In the assessment of the auditory system, the most important BERA examination is to assess a person's hearing function as objectively as possible. ²¹

Base Inspection Brainstem Evoked Response Audiometry (BERA)

On function brain Which normal, there is activity neurophysiology spontaneous Which arise with or without external stimulation. The activity is clearly visible as an electroencephalogram (EEG). EEG functions to measure brain activity and can describe level vigilance somebody. If recording done on electrodes on the head, then the EEG activity will be recorded together with the AEP. Compared with the AEP, the EEG wave has a larger amplitude, so the AEP wave is covered and cannot be read. ²¹

Another signal that can be recorded is myogenic activity with large amplitudes. can happen with or without stimulation external. In general general, activity myogenic is often undesirable because it can contaminate the AEP recording. Eye blinks, eye movements jaw, swallow, And pressure on neck is example activity myogenic most frequently, but these waves can be reduced or even eliminated by proper electrode placement and appropriate patient instruction. ²¹

The neural source/generator in BERA involves structures in the brain stem and auditory nerve. After years of research, animal experiments and finally analysis wave brain man in a way direct, can concluded source each- each wave in BERA. Wave I comes from the distal part of the auditory nerve in the inner ear, wave II comes from the proximal part of the auditory nerve (end of the brain stem), wave III originate from a number of generator at a time, that is nucleus cochlear and part of the superior olivary complex, especially contralateral, wave IV originates from midline structures in the brainstem (can be from the acoustic stria, trapezoid bodies, and superior olivary complex), and wave V originates mainly from the lateral lemniscus in the inferior colliculus on the contralateral side. ²¹

Several instrumentation base needed For do recording BERA.

Computers are used to convert analog forms of EEG waves into digital form, as filters against unwanted signals or noise , and function to do signal averaging so that wave AEP can seen. Box amplifier used For deliver amplitude EEG And AEP to range voltage in computer. Electrode Which functioning as antenna For catch change voltage from below the surface of the skin which is delivered to the electrode box. There are also transducer devices that function to deliver stimuli, for example earphone inserts , supra-aural headphones , bone oscillators , and speakers . ²¹

There are several important things to note and can affect recording parameters. These things are stimulus type, stimulus polarity, stimulus intensity, rate stimulus or stimulation rate , type transducer, And placement electrode. ²¹

1. Type stimulus

There are several types of stimuli that can be used, namely click, tone burst, and chirp .

click stimulus is the most widely used and effective stimulus, in the form of a clicking sound that lasts for a short time so that it can cause simultaneous nerve synchrony. The click stimulus can assess whether or not there is synchronization of the auditory nerve. This stimulus has energy with a fairly wide frequency range ( broadband ) which will give stimulus maximum in area frequency 2000 - 4000 Hz. Click BERA is formed from activity across the frequency range of the cochlea. The click stimulus has the disadvantage that it cannot detect abnormalities at low pitch frequencies. This stimulus is the standard stimulus in BERA testing. For neurodiagnostic purposes, it will provide a clear wave peak for interpretation, but the BERA wave can not give description function hearing on certain frequencies, so it is not appropriate for the diagnosis of estimated hearing thresholds.

tone burst stimulus has a short duration, usually no more than 4-5 cycles at a frequency of 500 - 4000 Hz. The tone burst stimulus has the characteristic of being able to be performed at specific frequencies that can be used to see hearing loss at both low and high frequencies, so it can also be used to estimate hearing thresholds. The weakness of this stimulus is that the examination time required becomes longer. long. On use stimulus tone bursts, stimulation only happen in some auditory fibers in a region limited to the cochlea, so that the recorded AEP waves have a smaller amplitude compared to the click stimulus.

4. Stimulation rate

   Rule general on stimulation rate is No may There is more from one stimulus in one observation time unit ( time window ). For example, if a 10 msec time window is used, then one click stimulus can occur every 10 msec. In conventional BERA recording, stimuli generally have rate 10 - 40/sec, with amount odd And decimal (example: 27.7/s), to avoid multiple noise. For example, in BERA examination, generally time the window 10 msec, and the stimulus very clear (example 100 msec click). At high rates, it will produce smaller and longer waves (inversely).

5. Type transducer

Stimuli in BERA can be delivered via supra-aural or insert (tubal) earphones . The use of insert earphones is more recommended because of their position. Which near with membrane timpani so that reduce noise and artifacts from environment around. Besides That, insert earphone Also own

In addition to the parameters mentioned, there are also terms in recording. BERA. Time Windows is range time analysis between before And after stimulus presentation in recording. In BERA, a 10 msec time window is generally used . The signal to noise ratio (SNR) is how strong the signal that can be read is compared to noise or interference from the surrounding environment. The BERA wave has SNR Which more small compared to with EEG. Noise or noisy can comes from physiological and non-physiological noise sources. Physiological noise sources include spontaneous brain activity, electromyogenic potential, corneoretinal potential, and electrodermal potential. Some non-physiological noise sources include potentials that arise from noise in the environment, electromagnetic, internal noise from electronic devices And polarization electrode. Sweep is amount repetition stimulus. Amount sweep needed For look for average wave BERA. Generally needed sweep 1000 to 2000 for BERA. If the SNR is good, the clinician can stop and move to the next step, but if the SNR is poor, more sweeps are needed. ²¹

To reduce artifacts, average EEG waves, and amplify BERA waves, a digital signal processing ( DSP) process is performed. The DSP consists of averaging , filtering , and amplification . ²¹

Amplification has the purpose of reducing room noise during recording. During amplification, any signals (and noise) that are generally in the head on the positive and negative inputs will be reduced, while the different signals between the inputs will be amplified. Differential amplifiers are two single amplifiers that work like mirrors of each other ( mirroring ). One amplifier passes on the normal signal and one amplifier will force the signal coming at the input to be inverted.

Filtering is another technique to improve SNR. Since the desired signal may occur together with unwanted noise , filtering will cause emphasis ( suppressing ) noise on file frequency Which related with BERA. Based on definition, filter will pass signal Which searching for And reject noise ( noise ). An analog filter is a tool/instrument that records the (unlimited) numeric value of signal electric Which varies in voltage And time. Filter analog used in differential amplifier because the brain's electrical signals are continuous. Digital filters are numerical algorithms that are executed by computers. Digital filters are useful after AD conversion is performed and the numerical values are stored in memory. AD conversion is more relevant in the statistical average search process.

Through the process of signal averaging , EEG signals randomly cancel each other out, while BERA waves are added together. The basis for improving SNR with signal averaging is based on noise (example: EEG) which is not time-bound to external stimuli. The EEG will be summed randomly and balanced (averaged) statistically throughout the time interval until the process search average. Mark SNR depends from type signal Which must averaged and the amount of noise that occurs. For example, the BERA waveform requires sweeps of up to several thousand because it has a very small amplitude.

Analysis And Interpretation Wave Brainstem Evoked Response Audiometry

The morphology of BERA waves is almost always different in each individual, even between ear on individual Which The same, although own hearing normal And intact auditory nervous system. These interindividual differences are likely due to differences in anatomy and size. Some patients are quieter than other patient groups (motor and breathing activity), which will affect the SNR during the averaging process . ²¹

The classic BERA wave is a wave elicited by a 100µs click stimulus of moderate intensity after several positive to negative waves within 10 msec. after onset stimulus. Wave the given label with numbering Roman. Waves I, III and V are clinically very useful for neurodiagnostic purposes, and wave V is clinically very useful in estimating hearing thresholds. Waves II and IV are not always clearly visible. The waveforms vary over time, Can is at in line base, turn to direction positive or negative And can reach maximum point. This maximum point is called a “peak” or “ wave ”, sometimes also called a component. A negative peak is also called a valley. ²¹

On determination peak wave, often happen difficulty in determining wave IV/V. Sometimes the two waves are easy to distinguish, but sometimes united And doubtful For determine latency wave IV or V. Wrong One technique that can help with this situation is to measure the ipsilateral and contralateral BERA simultaneously. In addition, knowing the nature of the two waves that are often united, generally complex wave This followed by deflection Which very in. Fusion wave IV/V generally has a width/duration > 1.5 msec, while in single wave the duration is < 1.5 msec. ²¹

There are several analyses that can be performed on BERA wave results to assess pathological conditions, namely: ²¹

1. Count latency absolute wave I up to V

   Absolute latency is the time required from when a stimulus is given until emergence peak wave, generally measured in millisecond (msec).

Mark normal on stimulus click with intensity 75 dB SL: Absolute latency of wave I : 1.5 - 1.6 msec

Absolute latency period of wave III : 3.57 - 3.7 msec Period absolute latency of wave V : around 5.6 msec.The absolute latency of waves III and V is longer in children up to age 18 months and age 50-60 years.

2. Look for cochlear microphonics on malformed or absent BERA waves.

   Wave I must be distinguished from cochlear microphonic (CM). CM is an electrical wave. that happened in accordance frequency signal, which originates from the outer hair cells of the cochlea ( outer hair cells ). The emergence of CM follows the polarity of the signal, whereas response neural No, so that in a way theory CM can eliminated when the 2 waves are added. CM and wave I appear as separate peaks, especially if the artifact is small. The two waves can be distinguished by changing the polarity to the opposite polarity, in CM the polarity is will backwards, whereas wave I Possible will happen latency shift is slight, but the polarity does not change. As for the ways to get wave I Which more clear, that is put electrode in external acoustic canal, increasing stimulus intensity, and decreasing stimulus rate.

3. Calculating interwave/interpeak latency (IPL/IWL) of waves I-III, III-V and I- V

   Interpeak latency (IPL) or also called interwave latency interval is the duration of time between wave peaks, at the same voltage polarity. IPL duration is generally measured between waves I-III and III-V.

Mark normal: IPL wave I-III 2.06 msec

IPL wave III-V 1.96 msec IPL IV around 4 msec

with standard deviation between I-III And III-V is 0.2 msec.

Prolonged interwave latency is a sign of retrocochlear auditory dysfunction. IPL I-III is activity synchrony N.VIII And stem brain distal part, so this value is the best description for nerve VIII. Abnormal lengthening between the initial wave components (wave I to III), relate with with lesi fossa posterior Which involving nerves to VIII or stem brain part lower. IPL III-V describe all over activity

N.VIII and nuclei and tracts in the brainstem that are responsive to auditory stimuli. Mark This generally not influenced by nerve tumor VIII except when The tumor affects the brainstem. A prolonged IPL IV indicates intraaxial brainstem auditory dysfunction.

4. Count different latency between second ear ( interaural latency difference /ILD)

   Interaural latency is the difference in latency of wave V in both ears. ILD is the difference in latency of right and left IPL IV. ILD counted on the same intensity in both ears. The value is said to be abnormal if it is 0.4 ms or more. In peripheral hearing loss, ILD is not more than 0.4 msec. ILD assessment provides information to differentiate tumor and nontumor diagnostics. This assessment is not effective if you want to see brainstem involvement.

5. Count ratio amplitude wave V/I

   Normal BERA waves have an amplitude of: 0.1-1.0 µvolts. The amplitude of wave V must be greater than the amplitude of wave I, with a V/I ratio > 1.

6. Change in wave latency to changes in intensity ( latency intensity function )

   The stimulus is inversely proportional to the latency period and directly proportional to the amplitude. In recording, the lower the decibel, the lower the amplitude of the wave. will the more small And latency absolute wave the more elongated.

7. Evaluate wave morphology

8. Application Auditory Clinic Brainstem Response

BERA is the most frequently performed AEP examination, especially in children. This examination own application clinic that is estimate threshold hearing in children and uncooperative patients and detecting abnormalities in the auditory nerve, starting from cranial nerve VIII to the brainstem. ²¹

There is a number of use clinic main from BERA, that is:

1. Screening hearing in neonates

2. Inspection hearing threshold on baby, child, And patient malingering

3. Diagnosis acoustic tumor

4. Diagnosis neuropathy peripheral And lesi stem brain

5. Monitoring moment operation like appointment tumor acoustic, decompression vascular nerve VIII, vestibular nerve transection

6. Monitoring placement electrode on auditory implant brain stem

7. BERA with high-pass masking technique is used to detect Meniere disease/cochlear hydrops.

Newborns are indicated to undergo BERA examination to anticipate disturbance development talk And Language. If There is child Which experiencing speech disorders or being slow in speaking and having risk factors may be one of the reasons because the child is unable to receive sound stimulation due to disorders in the ear, especially the inner ear and the pathways of the vestibulocochlear nerve. ^2,13 Risk factors include premature birth, hyperbilirubinemia, craniofacial abnormalities, infection during pregnancy, family history of hearing loss, sepsis, hypoxia, and intracranial hemorrhage. ¹⁴

Inspection BERA relatively safe, No painful, And No There is effect side, so it is also commonly used for screening medical check ups and differentiating hearing disorders. consequence psychological or physique. BERA can used For evaluation employees in companies with noisy environments and to evaluate employees with suspected malingering. Although BERA is not the primary test for hearing in adults, it can be used to evaluate the auditory nerve and to help assess hearing thresholds objectively and non-invasively. ¹⁵

Inspection threshold BERA used For estimate amliang hear in the pediatric population, populations that are difficult to examine and those suspected of having non-organic hearing loss. Wave V identification is performed at each intensity using a descending method using click or tone burst stimuli until the wave the No identified Again. Wave V No can identified at or near the subject's hearing threshold. Click stimuli can provide estimates of hearing threshold sensitivity in the 1000 - 4000 Hz region. Tone burst stimuli can provide estimates at specific frequencies. ²¹

Stimulus tone burst uses a brief tone stimulus and is standard procedure. For get information frequency specific And ear specific on frequency 500, 1000, 2000 and 4000 Hz. This examination uses a decreasing intensity technique to look for wave V. Inspection This used For estimate threshold hear, but it should be remembered that evoked potentials analyze auditory function, not to measure hearing threshold.

The BERA threshold is 10 - 20 dB above the behavioral response, depending on the type of BERA computer used. The BERA threshold is 10 - 20 dB above the behavioral response, with variations in the different BERA computers used. ²¹

Objective main inspection BERA that is For determine disturbance hearing, whether in the cochlea or retrocochlear involvement, but not to determine the location lesi in a way specific. Inspection neurodiagnostics BERA depends on component recording wave I Which clear And Good. Wave I is benchmark For peripheral auditory function. While the latency between waves provides clues regarding the retrocochlear function (VIII nerve and brain stem) which is relatively unaffected by conductive or sensorineural hearing loss. ^3,13

The application of BERA in addition to determining a person's auditory status, is as a diagnostic tool and a tool for identifying neurological abnormalities. BERA has the sensitivity to predict the presence of lesions in N.VIII such as scwhanomma nerve VIII and lesions in the brain stem. This ability can not only assess a space-occupying lesion but also assess a vascular lesion and degenerative disease or demyelinating disease such as multiple sclerosis. Other uses of BERA include intraoperative monitoring and also as monitoring of neurological status in comatose patients in intensive care. BERA also has the ability to assess neurological disorders in high-risk neonates who are treated intensively. ^9,12

The BERA response can be used to identify retrocochlear abnormalities, such as neuroma acoustic or schwannoma vestibular with number accuracy until 95% in medium to large tumors. In some cases, BERA can accurately locate the lesion, although BERA is not the main indication for locating the lesion. However, with the development of MRI, retrocochlear tumor screening with BERA has become less popular. ²¹

BERA has been shown to be the best audiometric examination for the detection of acoustic tumors. This success is based on the fact that acoustic tumors compress or stretch nerve auditory, cause elongation latency BERA. This prolongation can occur in ears with normal hearing. In contrast, cochlear lesions have minimal effect on brainstem latency responses to high-intensity stimuli until hearing loss becomes severe. ²¹

When on wave I there is elongation latency on stimulus intensity high is characteristic for conduction or mixed hearing loss. Small or absent waves but latency between waves within normal limits (IV latency less than 4.6 ms), there is a possibility of high frequency sensorineural hearing loss (cochlear). ²¹

If wave II cannot be identified or is absent, this indicates hearing loss or brainstem dysfunction. In wave III, this wave will looks abnormal Good on ipsi or contralateral on condition pathology with asymmetric lesions. When wave This No can identified or No There is, matter This indicates the presence of disturbance hear or dysfunction stem brain. Wave IV influenced cerebrovascular disorder on midpons. Wave V is wave Which most big and clear from BERA. Elongation latency show existence dysfunction peripheral or auditory. The presence of latency shift is an indicator of retrocochlear pathology. Poor shape indicates high frequency sensory (cochlear) hearing loss. ²¹

Auditory Neuropathy Spectrum Disorder (ANSD) is type disturbance sensorineural hearing involving the cochlea and/or auditory nerve. ANSD is established in conditions of good outer hair cell function accompanied by an asynchronous auditory nerve response ( dyssynchronous ). In ASND there are OAE pass results and/or there is cochlear microphonic (CM) but No There is wave BERA. Inspection potential evoked Good and accurate interpretation is essential in identifying these patients and recommending intervention and referral strategies. ²¹

BERA is also not a test for hearing threshold. Although BERA provides information about hearing function and sensitivity, it cannot be used as a substitute for a formal hearing evaluation, and the results obtained must can connected with results audiometry Which used If available. ^9,10 Therefore, the results of the BERA examination cannot be used for hearing aid (ABD) fitting . ²¹

BERA reflects the synchronization of electrical currents in neurons in the auditory system. In BERA, the objective thing to note is that the response can be recorded properly. At least 2 consecutive measurements are carried out. If the response in the two examinations is different, then the examination protocol must be modified and technical problems must be resolved. If the response produced remains the same, can be replicated and confirmed, then the examination continues to assess the absolute latency of each wave component and the latency between waves. ²¹

Factors that influence BERA examination are age, gender, temperature body, And sensitivity hearing. Maturation own influence significant to morphology wave BERA, especially on age in lower 2-3 year, Which own longer latency. In neonates, the absolute latency period is slightly longer and will gradually shorten and achieve the value that The same with adults on age 12-18 months. There isn't any difference between second gender on interwove latency values, but men tend to have longer absolute latencies of waves I, III and V than women. Patients with low frequency hearing loss can own description BERA Which normal Because bias from energy stimulus click on the basal cochlea. Patients with high-frequency SNHL can show BERA with prolongation of wave V like an acoustic tumor, even though at low frequencies hearing is normal. ²¹

Of course, hearing examination is not enough with just one examination. BERA examination should be performed simultaneously/in a series with other audiological procedures. ²¹

Discussion

BERA examination can be used as a neurodiagnostic, this is approved and supported. by Balasubramanian. According to Balasubramanian that inspection BERA This also useful in identifying neonatal deafness, can be used as a screening tool for early detection of deafness in infants. This assessment involves recording all forms of electrical responses generated at the brainstem level in response to click impulses by placing electrodes. BERA can be used to detect demyelinating lesions and also tumors in the auditory pathway. It also helps neurosurgeons in intraoperative monitoring of the audio vestibular system during neurosurgical procedures involving large areas. ¹⁷

According to Hi et al. BERA This is method simple, non-invasive, And objective to evaluate the functional integrity of the auditory pathway.3 Wijana said that BERA can determine abnormalities that occur in the cochlea or retrocochlea by looking at wave I which is a benchmark for peripheral auditory function. While the latency between waves provides clues regarding retrocochlear function. (nerve VIII and brain stem) which are relatively unaffected by conductive or sensorineural hearing loss.

In the research, Wijana et al. stated that the BERA examination is a reliable hearing examination which aims to assess the synchronization of the auditory nerve. peripheral. Evaluation wave BERA consists of on identification Wave I up to V, time latent absolute, time latent between waves, differences time latent inter second ear, the ratio of the amplitude of the V and I waves and the function of stimulus intensity to the latency period. This study was conducted on children under five years old and was conducted at the ENT-KL polyclinic of Dr. Hasan Sadikin Hospital, Bandung during the period of December 2008 to June 2011. The results of the study showed that hearing loss problems were more common in children man compared to Woman. Matter This Also found on study Which conducted by Osama et al. ¹⁸

The previous BERA examination procedure, the patient's family was given education first. This is supported by Dr. Hiya Bhattacharya et al. that the patient's family was given education. about procedure inspection This, Then child the Also must shampoo on the day before inspection, wake child on Morning day moment day inspection so that the child falls asleep quickly, and remains asleep during the examination. BERA examination is an efficient examination performed on children who are at risk of neurotoxicity. ¹⁹

According to Wijana, the BERA assessment is based on the type of hearing loss, namely normal, conductive, sensory, And neural. Matter This supported with journal from Leigh Biagio who said that The results of BERA can determine the type hearing loss. Annanya said that BERA is an effective and non-invasive way to assess the functional status of the auditory nerve and brainstem auditory sensory pathways. BERA changes in patient with hyperbilirubinemia is lost One or more peak wave I- V, improvement latency wave I, III or V, or happen improvement peak intervals. BERA can detect subclinical bilirubin encephalopathy. In 30 cases, there were 10 cases (33.3%) that experienced changes in BERA in the form of prolonged latency. There is a correlation between changes in BERA and maximum bilirubin levels, increasing the risk of toxicity to the auditory tract. ²⁰

Conclusion

Brainstem Evoked Response Audiometry (BERA) is the most commonly used hearing test and is an objective electrophysiological method to assess the hearing process from the auditory nerve to the brain. This test can cause auditory potentials and can also be used to assess the auditory nerve within the first 10 ms (milliseconds) after the stimulus is given. The BERA test has seven waves of which waves I, III, and V are the most visible and can assess the results and clinical signs.

Brainstem Evoked Response Audiometry (BERA) is performed using a click sound stimulus that produces a response from the basilar region of the cochlea. Each ear can be evaluated separately, with a stimulus intensity of 35-40 db nHL. BERA stimulated by click sounds is closely related to hearing sensitivity in the frequency range of 1000-4000 Hz. The signal travels through the auditory pathway from the cochlear nuclear complex, proximal to the inferior colliculus. An active electrode is placed at a point on the head that allows for the recording of auditory evoked potentials from the auditory nerve and brainstem (early potentials in wave IV), and deeper auditory structures in the thalamo-cortex. BERA has a short latency (<10 ms), currently used clinically to test the auditory pathway up to the level of the inferior colliculus.

BERA refers to the potential generator that is generated by a short sound or tone special Which transmitted by transducer acoustic with use headset or headphones . The waveforms generated from these responses are assessed using surface electrodes that are usually placed on the vertex of the scalp and on the ear lobes.

Although the BERA test can be used to assess hearing thresholds, it is important to remember that this test is not a hearing test. Another major application of BERA is as a diagnostic tool and a tool for identifying neurological abnormalities. BERA can detect lesions in the eighth nerve, such as eighth nerve schwanoma, as well as lesions in the brain stem. In addition, the BERA test can also detect demyelinating diseases such as multiple sclerosis. Other uses of BERA include monitoring intraoperative And Also as monitoring status neurological on coma patient in intensive care.

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