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What is the ASSR test?

A steady-state auditory response (ASSR) is an electrophysiological response elicited by a repetitive (rapid) auditory input. Typically, an ASSR employs frequency-specific stimuli (0.5, 1, 2, 4 kHz) to generate an approximated audiogram. In other words, it’s a test for figuring out what the cutoff point is.

Unlike the auditory brainstem response (ABR), which measures the reaction’s amplitude and latency in the time domain, the ASSR measures the response’s amplitudes and phases in the frequency domain. Responses are recognized using a mathematical detection technique based on statistics to identify whether or not a response is there. Another distinction is that, with frequency-specific threshold ABR, only one frequency per ear may be tested at a time. ASSR enables binaural testing; four frequencies are delivered simultaneously to each ear (eight simultaneous presentations).

Why the ASSR test?

ASSR is an objective technique based on statistical probability rather than a subjective evaluation of response waveforms. ASSR’s primary audiological use is to estimate the pure tone audiogram employed in rehabilitation.

ASSR demonstrates frequency-specific thresholds and is an extremely important technique for programming hearing aids for little infants, for whom behavioral audiometry is not practicable. A clinician may better grasp the amount of gain that should be applied at a certain frequency and determine which kind of hearing aid or amplification device would be most appropriate for the youngster.

ASSR also plays a significant part in determining who should have Cochlear Implantation. It enables us to readily assess whether the residual hearing is inside or under the speech banana on an audiogram and whether hearing aids give only limited improvements after trial.

Our ASSR test procedure:- 

We ensure a smooth and hassle-free experience of patients during the ASSR test. Take a look at the tired and tested procedure followed by our audiologists.

1. Patient population

ASSR, like ABR, is used to estimate hearing thresholds for people who are unable or unwilling to take standard behavioral tests. As a result, newborn newborns for screenings and follow-up diagnostic assessments, babies in the neonatal intensive care unit (NICU), comatose patients, ototoxicity monitoring, and others would be key candidates for ASSR. For persons who cannot or will not participate in traditional behavioral assessments, ASSR can be used to estimate hearing thresholds.

2. Patient preparation:

We perform otoscopy and impedancemetry prior to ABR and ASSR recording to rule out cerumen impaction, acute or serous otitis media, or tympanic perforation. The patient is only examined if he or she has no respiratory problems: not only would this preclude premedication, but simple nasal congestion causes facial and thoracic movements, resulting in muscle artifacts.

3. Electrode placement

To achieve an acceptable low skin impedance, the electrode locations are prepped and cleansed. The two active electrodes are located at or near the vertex and the ipsilateral earlobe/mastoid, respectively, while the ground electrode is located on the low forehead. When the instrument collects data from both ears simultaneously, a two-channel preamplifier is utilized to take advantage of the binaural electrode montage. A single channel recording device is utilized to identify activity generated by a binaural presentation and a common reference electrode at the nape of the neck is used. 

4. Performing measurement

The electrode impedance is tested before the ASSR measurement begins. A “play” button displays in the footer when the impedance is within an acceptable range (below 12 k). If the impedance value is less than 6 k, the color of the impedance value will turn green to signify good impedances. If a response is detected, the ASSR recording will come to a halt. If there is no response, the set averaging time is required. The highest stimulus level will be used to begin the measurement. All levels of stimuli are put to the test. When the current measurement’s significance is reached, the Algorithm will move on to the next stimulus level.

5. ASSR Stimulation

Each manufacturer designs (and may alter) the stimulus and recording parameters and procedures. Broadband (i.e., frequency nonspecific) or frequency-specific stimuli can be used to measure ASSR. Clicks, sounds, amplitude modulated noise, and chirps are examples of broadband stimuli.

Filtered clicks, band-limited chirps, narrow-band noise bursts, tone bursts, amplitude modulated narrow-band noise, or amplitude and frequency modulated pure tones are examples of frequency-specific stimuli.

6. ASSR vs ABR

There are also significant discrepancies between ASSR and ABR. Rather than relying on amplitude and latency, ASSR employs spectral (frequency) amplitudes and phases. Rather than peak detection across a time versus amplitude waveform, ASSR relies on peak detection over a spectrum (see John and Picton1). ABR is elicited by brief sounds provided at a low repetition rate, whereas ASSR is elicited by repetitive sound stimuli presented at a high repetition rate.