The Auditory Brainstem Response (ABR), Middle Latency Response (MLR), and Auditory Late Response (ALR) tests are non-invasive electrophysiological tests that assess the function of the auditory nerve and brainstem. This is done by placing several small, disc-shaped electrodes on the patient’s forehead and earlobes. Earphones will be placed in the patient’s ears and recordings of the auditory pathways will be measured in response to the sounds presented.
To begin, the patient will be asked to sit in a reclining chair. The audiologist will clean the areas where the electrodes will be placed with a mild scrub. This is done to remove light skin debris and make-up, and to ensure good contact between the electrode and the skin. The electrodes will then be placed on the patient’s forehead and ears. Medical tape is used to keep the electrodes in place. The audiologist will then place the earphones in the patient’s ears and begin the test.
The electrophysiologic assessment can take approximately 1 hour to complete. During that time the patient will be asked to be in a relaxed state. This will help reduce any artifact that can be caused from excessive movement and facial tension. It is acceptable for the patient to fall asleep while the ABR is being measured. For other tests (MLR and ALR), the patient will be asked to lie in a relaxed state but remain awake. During those tests the audiologist may ask the patient to think of numbers or letters. The patient will hear a loud clicking sound which is presented to stimulate the auditory nerve. There will be pauses throughout the testing where no sound will be presented.
Once the testing is completed the audiologist may need time to analyze the data collected before reviewing the test results. If the audiologist is unable to review the test results at the end of the appointment, the patient will be called to discuss the results.