ELIOS

Transient Otoacoustic Emissions (TEOAE)

Otoacoustic emissions (OAE) are low intensity sounds generated by the outer hair cells (OHC) of the inner ear. When we speak about otoacoustics emissions, we primarily think about transient otoacoustic emissions also called TEOAE which are most used in clinical examination. OAE are recorded by a small probe place in the external ear canal. Detection of transient otoacoustic emissions (TEOAE) is a real asset in the series of hearing tests.

User Tips:

• Make sure that ear canal is not obstructed by earwax.
• Choice of eartip is the most important point for the quality of the measurement.
• Eartip should not be pressed against a side of the ear canal.
• Eartip must be sealed to prevent acoustic leaks and isolate to surrounding noise.

Measure specifications:

• Per click
• Sound intensity: 84dB HL

Aimed diseases: objective diagnosis of hearing loss, monitoring of cochlear damage.

Method: The TEOAE are otoacoustic emissions by click, which means that we are going to test patient ear with frequencies between 2000 and 4000 Hz. The result is represented by a curve that simply shows whether otoacoustic emission is present or not. This is an objective test because he does required cooperation of the patient. This test is very important, in especially in the examination of newborns, because if the acoustic otoemissions are present it means that hearing of newborn does not present deafness superior to 30-40 dB. It is a screening test routine, more and more used in examination of newborns.

Distortion Products of otoacoustic emissions (DPOAE)

Distorsion product otoacoustic emission phase shift (Shift-OAE)

This measure, based on the collection of distortion products, records the response time of external ciliate cells of the cochlea. Our exclusive clinical studies have shown that the measured time is the image of the pressure in the perilymph (apex). Monitoring Shift-OAE can observe reproducible or isolated pressure changes from the cochlea and thus highlight a cochlear hydrops.

User tips:

• Make sure that ear canal is not obstructed by earwax.
• Choice of eartip is the most important point for the quality of the measurement.
• Eartip should not be pressed against a side of the ear canal.
• Eartip must be sealed to prevent acoustic leaks and isolate to surrounding noise.

Measure specifications:

• Acoustic stimulation from 1kHz to 3kHz
• Sound intensity from 50 to 75dB SPL

Aimed diseases: Hydrops, vertigoes, Non invasive diagnosis of the Ménière’s disease.

Method: In the case of record of distortion products, bitonal acoustic stimulation is applied (simultaneous sending of two pure tones). These two sounds exciting, called primary, with the respective frequencies f1 and f2 will cause the emission of a characteristic distortion product in human beeing at frequency 2f1-f2. In healthy subjects as subjects with endolymphatic hydrops, postural tests, (from standing to lying position) cause an increase of intra-cochlear pressure (exaggerated in the context of Meniere’s disease). Indeed, during postural tests there is a change in the distribution of cerebrospinal fluid that spreads to the cochlea via the cochlear aqueduct.
Monitored, the cochlear physiological parameter allows real time monitoring of the evolution of intra-cochlear pressure.

Auditory Brainstem Response (ABR)

Auditory brainstem response (ABR), are routinely used in the field of neurological and otological investigation. Non-invasive electrophysiology technique based on the principle of electroencephalography (EEG), ABR provide objective information, reproducible in the hearing function from the cochlea to the brainstem. They help to reveal the electrical activity of peripheral auditory pathways, through the application of acoustic stimulation (usually a click), in the overall activity of the EEG.

User tips:

• Make sure that ear canal is not obstructed by earwax.
• With an abrasive gel, clean skin surface where electrodes will be attached. It decreases skin impedance.
• Patient must be settled comfortably to avoid any excessive muscle tension.

Mesure specifications:

• 50 clicks/sec
• Alternating clicks / burst
• Contralateral masking
• 0 to 100dB HL
• Impedance tests

Aimed diseases: acoustic neuroma screening, hearing loss threshold, auditory neuropathy.

Method: There are two different types of auditory evoked potential tests.
The ABR latency are widely used to explore the nerve conduction in the auditory pathways. The dysfunction auditory pathways are highlighted by analyzing a time signal during tests at fixed intensity (greater than 80 dB HL). Typical ABR tracings consist of several waves numbered I to V. In the situation of ABR latency (neurological testing), the waves I, III and V must be clearly identified in a context of normality, with a variability from presence for waves II and IV. These waves should appear in a range of normality. Any lengthening from the latency for waves suspects a conduction disorder and suggests further investigation.
Moreover, applying acoustic stimuli of decreasing intensity, the ABR threshold can objectify the auditory threshold of each ear. Determining the auditory threshold is identified at the disappearance of wave V.

ASSR (Auditory Steady-State Responses)

The Auditory Steady-State Responses (ASSR) is an electrophysiology measurement used to determine the hearing loss degree with a specificity in frequency.

User tips:

• Make sure that ear canal is not obstructed by earwax.
• With an abrasive gel, clean skin surface where electrodes will be attached. It decreases skin impedance.
• The patient should be comfortably properly installed in order to avoid muscle tension and discomfort, which are factors that disrupt the
  measurement.

Mesure specifications:

• Stimulation AM2
• Carrier frequencies: 500Hz, 1000Hz, 2000Hz, 4000Hz
• Modulation frequency: 40Hz or 80Hz
• 10 to 90 dB HL
• Impedances test

Aimed diseases: hearing loss threshold

Method: The sound stimuli (500Hz, 1000Hz, 2000Hz and 4000Hz) are presented with modulation frequencies sufficiently spaced so that their physiological responses do not interfere with each other. The presentation frequency (or modulation frequency) of the stimulation signal will be analyzed on an electroencephalogram (EEG) in order to determine the hearing threshold of the corresponding stimulus (LINS & Picton, 1995; Lins et al., 1996).
The response presence is determined by statistical tests which analyze the coherence of the signal (amplitude and phase) between the different samples collected during the measurement. These tests provide objective responses with a previously known rate of false positive. This is why they are commonly called “objective response detection” techniques (ORD) (Melges et al., 2009).
The objective nature and the possibility to stydy a hearing threshold for each frequency indicate the ASSR as an important tool for audiological assessment, mainly for non-collaborative individuals (children, cognitive impairment, legal procedures).

Vestibular Evoked Myogenic Potentials (VEMP)

Otolithic Evoked Potential (OEP) or Myogenic Vestibular Evoked Potential (VEMP) are sacculo-collique reflex recorded in response to an acoustic stimulation. They study the sacculo-spinal way: the sacculo, inferior vestibular nerve from the sterno-cleido-mastoid (SCM) ipsilateral, via cervico spinal cord. The OEP or VEMP are recently used in the battery of cochleovestibular investigation tests and reinforce the aid diagnostic in addition to other tests such as audiogram and Auditory Brainstem Response (ABR).

User tips:

• Muscle must be contracted at the time of the registration of the OEP. One of the preferential positions adopted by the authors is the patient lying supine with a head position elevated.
• With an abrasive gel, clean skin surface where electrodes will be attached. It decreases skin impedance.

Mesure specifications:

• 50 clicks/sec
• Alternating clicks/ burst
• Contralateral masking
• 40 to 110dB HL
• Impedance tests

Aimed diseases:Meniere’s disease, vestibular neuritis, perilymphatic fistula, dehiscence syndrome of semicircular superior canal (Mino syndrome), vestibular neuroma.

Method: Sounds stimulations of high intensity (90-100 dB) activate primary vestibular neurons innervating the saccule and secondary vestibular neurons of nucei inferior and side vestibular. In practice short sounds clicks (100 microseconds) or short tone bursts from 90 to 100 dB are unilaterally issued by using an acoustic stimulation at 1 KHz or 500 Hz frequency. OEP are collected at the two SCM muscles through skin electrodes placed at the 1/3 superior part of these two muscles. During recording, patients are placed lying supine with a head position elevated to increase the SCM muscle contraction. Sometimes it’s useful to turn the head on the opposite side of the stimulation to increase the muscle contraction. Indeed it’s a necessary condition because the evoked potentials amplitude is correlated with the SCM muscle contraction amplitude. VEMP are then amplified, filtered and averaged on 500 stimulations. Saccule being innervated by inferior vestibular nerve, such as posterior CCS, results is complementary to choose obtained by using caloric tests, which in testing the external canal, evaluate the function of the higher vestibular nerve. This test assesses the functioning of saccule receptors and sacculo-spinal channels.

Cochlear Microphonic Potential Phase Shift (DPMC)

With its knowhow and its collaboration with the Clermont-Ferrand Sensory Biophysics Laboratory, ECHODIA Company developed a Cochlear microphonic potential phase shift measure (DPMC). This world exclusive measurement belonging to ECHODIA, records the response time from external ciliate cells of the cochlea, electrophysiologically, following an acoustic stimulation called toneburst. Our exclusive clinical studies have shown that the measured time is the image of the pressure in the perilymph (base). Monitoring DPMC can observe reproducible or isolated pressure changes from the cochlea and thus highlight a cochlear hydrops.

User tips:

• Make sure that the ear canal is not obstructed by a wax plug.
• Clean the surface of the skin where the electrodes will be attached with abrasive gel. This decreases the impedance of the skin.
• The patient must be settled comfortably to avoid any excessive muscle tension.
• Use of saline water is recommended to improve the conductivity of the electrode placed in the ear.

Measure specifications:

• Acoustic stimulation from 900Hz to 1100Hz
• Specific eartip
• Impedance tests
• Configurable rejection
• Sound intensity from 40 to 90dB SPL

Aimed diseases: hydrops, vertigoes, Non-invasive diagnosis of the Ménière’s disease.

Method: The cochlea, peripheral organ of hearing, contains the external ciliate cells (ECC) which have a role in amplifying acoustic signals through their contractile properties. By applying acoustic stimulation to the ear, particularly a tone burst (1kHz frequency), it will stimulate the sensitive part of the ECC at this frequency.
The ECC will thus be stimulated to contract in resonance with the same frequency as the stimulation frequency (1 kHz). As a muscle contraction ECC generates an electric specific potential: Cochlear Microphonic Potential (CMP).
In healthy subjects as subjects with endolymphatic hydrops, a postural test (transition from standing to lying down) causes an increase in intra-cochlear pressure (exaggerated in the context of Meniere’s disease). Indeed, during the postural test, there is a change in the distribution of the cerebrospinal fluid that spreads to the cochlea via the cochlear aqueduct. Monitored for some time, the physiological parameter cochlear allows real-time monitoring of the intra-cochlear pressure change.

Electrocochleography (ECochG)

Among the short latencies auditory evoked potential, auditory evoked potentials (AEP) and cochlear potential or electrocochleography (ECochG) are included. Historically, ECochG was performed under anesthesia through a trans-tympanic invasive electrode placed on the promontory. With its expertise in electrophysiology, ECHODIA Company developed a noninvasive technique for routine use, without anesthesia, using a gold coated electrode gently inserted into the ear canal.

User tips:

• Make sure that the ear canal is not obstructed by a wax plug.
• Clean the surface of the skin where the electrodes will be attached with abrasive gel. This decreases the impedance of the skin.
• The patient must be settled comfortably to avoid any excessive muscle tension.
• Use of saline water is recommended to improve the conductivity of the electrode placed in the ear.

Measure specifications:

• 50 clicks/sec
• Alternating clicks / burst
• Contralateral masking
• 0 to 100dB HL
• Impedance tests

Aimed diseases: Search for auditory thresholds in addition to ABR, search for a cochlear residual activity (as part of a review of cochlear implant, for example), evaluation of the cochlear function in auditory neuropathy.

Method: The cochlear potential include the microphonic cochlear potential (MPC), the summating potential (SP) and the action potential of the auditory nerve (AP).
In addition to ABR, the ECochG can be used for the revealing of wave “I” which is difficult to identify on ABR tracing, search for hearing thresholds, search for residual cochlear activity (as within the framework of an assessment of cochlear implant), evaluation of the cochlear function within the framework of hearing neuropathies (existing MPC, flat ABR), per-operating monitoring in the surgery of the acoustic neuroma, intraoperative monitoring in surgery for acoustic neuroma. One of the common indications of ECochG is an assessment of the SP / AP, which is increased in diseases associated with endolymphatic hydrops.

Pure tone audiometry

Pure-tone Audiometry is the basic review of the hearing. This test allows a quick check of the transmission chain of sound to the brain. The measure is obtained through the issuance of a sound wave frequency calibrated whose it will lower the power until the patient hears. The sounds are emitted by a helmet above the ear in one ear then in the other with a mask-side.

User tips:

• Make sure that the ear canal is not obstructed.
• Check the status of the eardrums.
• To obtain quality results, the patient should be comfortably settled in a quiet place, devoid of surrounding noise.

Mesure specifications:

• Air conduction: 125 to 8 000Hz / -10 to 110dB HL
• Bone conduction: 250 to 8 000Hz / -10 to 70dB HL
• Dual channel
• Contralateral masking

Pathologies visées : surdité de transmissions (courbe osseuse meilleure que l’aérienne), surdité de perception (courbes aérienne et osseuse identiques), surdité mixte (mélange des deux).

Different types of deafness: Light deafness (loss between 20 and 40 dB), moderate deafness (loss between 40 and 70 dB),significant deafness (loss between 70 and 90 dB), deep deafness (loss up to 90 dB), total deafness (no measurable hearing).

Method: Pure-tone Audiometry allows searching hearing thresholds for each ear in a frequency range from 125Hz to 12 kHz. While bone conduction evaluates performance of the inner ear and the auditory nerve, the air conduction tests all of the acoustic function of the external ear to the auditory nerve. Interpretation of the audiogram, measures the degree of hearing loss and type of deafness. The pure-tone also allows the determination of threshold of discomfort, or looking for any frequency of tinnitus.

Speech audiometry

Speech audiometry is a complementary review of air and bone conduction. This test doesn’t record the perception threshold, but the language understanding threshold and the phonetic discernment. This test confirms pure tone audiometry and allows estimating the ability to understand words.

User tips:

• Make sure that the ear canal is not obstructed.
• Check the status of the eardrums.
• To obtain quality results, the patient should be comfortably settled in a quiet place, devoid of surrounding noise.

Measure specifications:

• Fournier’s disyllabic list
• Choice of the voice (female/male)
• Word list selected randomly

Aimed diseases: help in the diagnosis of retro cochlear pathologies (tumor of the acoustic nerve, auditory neuropathies).

Method: the test consists of asking the patient to repeat a series of words that he hears. By varying words elocution, a curve appears relating the percentage of discrimination in function of power. Well known by the hearing professionals for the ability to refine settings of hearing prosthesis, this test is also used for retro-cochlear pathologies diagnosis, like neuropathies or acoustic neuromas.