Treatments & Therapies

Brainstem Audiometry – Treatment, Effect & Risks

Brainstem Audiometry

In non-invasive brainstem audiometry , the neurologist or ear, nose and throat doctor carries out an objective hearing performance measurement using auditory stimulation using impulses from the auditory nerve pathways, which can be traced to the middle brainstem.

This procedure is one of the few procedures for the objective assessment of hearing performance that can also be carried out on small children or otherwise unwilling patients. The test method is used in particular for the differential diagnosis of cochlear and retrochlear damage to the hearing, in the assessment system and as part of the ERA, a hearing screening for newborns .

What is Brainstem Audiometry?

Brainstem audiometry is also known by the term BERA (brainstem evoked response audiometry) and is a non-invasive hearing test method. It is a neurological and ENT-medical examination method, which is intended to help above all in the differential diagnosis of hearing disorders .

In principle, the method uses acoustic stimulation to measure the brain waves to assess the objective hearing ability. The impulses of the auditory nerve tracts are tracked through a targeted transmission of stimuli to the middle brainstem and registered and recorded as individual waves. The evaluation of the measurement data refers to the latency of the waves, which can provide information about the origin of hearing damage. The recorded data of a brainstem audiometry are therefore mostly used for differential diagnostics in hearing disorders, but can also be collected during a general hearing screening.

Function, effect & goals

The ear, nose and throat doctor or neurologist uses brainstem audiometry primarily for differential diagnostics. A disturbed hearing function, which can be recognized by disturbed brain waves, could indicate, for example, hearing damage caused by multiple sclerosis or a tumor on the auditory nerve.The most common tumors of this type are, for example, the acoustic neuroma and the cerebellopontine angle tumor. In terms of differential diagnosis, BERA can be used to distinguish between cochlear and retrochlear hearing impairment. Another area of ​​application for the objective test method is the assessment system. Hearing thresholds can be detected with BERA without the patient’s help and can also be determined for children who are resisting the test.

Even hearing screening in newborns can be carried out using brainstem audiometry. The basic principle of the BERA is ultimately always the graphical representation of electrical potentials in waveform. Five to six waves are recorded during the exam. This recording only occurs when acoustic stimuli are successfully processed. The potentials shown thus illustrate normal or disturbed activity of the auditory pathway. Electroencephalography (EEG) derives the potentials from acoustic stimulation with a latency greater than or equal to 10 ms between the center of the vertex and the mastoid.

To do this, three adhesive electrodes are attached to the patient’s head . He wears an electrode on each side behind the ear and a neutral electrode in the middle of the forehead . The acoustic stimulation is carried out by means of clicks, which are given via headphones at regular intervals of 20 seconds. The response potential is derived via the electrodes and summed up, while other EEG signals are filtered out. Ultimately, only the response of the brainstem to the acoustic click signals is displayed.

Waves I, III and V can usually be clearly identified and are therefore suitable for determining the absolute latency of an acoustic stimulus. In addition, a so-called inter-peak latency is recorded. This is a latency difference between several waves that can provide information about retrocochlear processes. In adults, for example, inter-peak latencies with latency periods greater than or equal to 4.4 ms in waves I to V provide an indication of retrochlear damage caused by MS or tumors. For small children, a delayed latency period is generally considered the norm.

Risks, side effects & dangers

Since BERA does not require the patient’s help and can even be carried out in an anesthetized state, this procedure is one of the few hearing measurement procedures that can also be carried out on unwilling patients such as children.The BERA is often used as one of three components of the ERA (Evoked response audiometry) and is completed by ECochG and CERA. While the former method measures the potentials of the cochlea and auditory nerves, the latter measures the potentials of the cerebral cortex. In a comprehensive hearing screening, all hearing-relevant potentials are recorded with ECochG, CERA and BERA. For adults, brainstem audiometry is usually not associated with any additional precautions.

Before the measurement, however, the patient has to take part in an extensive information discussion, which is intended to ensure the correctness of the measurements. In this conversation, patients receive precise rules of conduct for the period of the measurement. For example, if you are not lying relaxed or are moving more, this can significantly falsify the results. Newborns and children usually have to be put under anesthesia for the measurement , as they rarely remain completely still.

Patients who are otherwise unwilling are also anesthetized. Complications are usually not to be expected. However, there is always a risk with anesthesia during the measurement, since the anesthesia itself is slightly risky. After the measurement, no special precautions need to be taken and the patient can go home again. Depending on the evaluation findings, however, further diagnostic procedures may be indicated in the following weeks, which further secure or rule out a possible diagnosis.

Lisa Newlon
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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.