Brainstem Auditory Evoked Response

We were at the hospital this past Tuesday for Matthew's scheduled BAER (Brainstem Auditory Evoked Response) test. He had to be sedated for the test and we were told that the test would take anywhere from 1 to 4 hours depending on how well the test was going. He was not to have anything to eat after midnight and allowed only clear liquids (water, Sprite, apple juice) until 5am with the hearing test at 8am.

We woke Matthew at 5:45am. He wasn't mad that we woke him up, just confused but more than happy to get into the car. (He loves car rides.) We left the house at 6am and arrived at the hospital at 7am and checked in at the Pediatric Outpatient Sedation Unit. A pediatric nurse took Matthew's vitals and administered Versed mixed with a small amount of apple juice. Matthew loves apple juice but he drank this reluctantly, tasting the medicine in it.

The audiologist and anesthesiologist met with us before the test to give us a run down of what was going to happen before, during and after the test and to answer any other questions we had about the test. The plan was to administer general anesthesia via a gas mask and start with two other hearing tests - a tympanogram and an OAE (Otoaccoustic Emissions) test - before proceeding with the BAER.

At 8am, the nurse took a very drowsy Matthew to the testing room. The wait began for Bill and I. We had left Elizabeth home with my mom so we took the opportunity to eat a decent breakfast and nap.

What is BAER?
Brainstem auditory evoked response (BAER) is also known as Auditory Brainstem Response (ABR). The BAER is done under general anesthesia with younger patients. It is a painless test to measure the brain wave activity that occurs in response to clicks or certain tones conducted through earpieces in the ear canals. Sticky pad electrodes are attached to the scalp to track sound moving through the ear to the brain. The anesthesiologist and pediatric nurse are present during the whole procedure to monitor breathing and vitals. Matthew was intubated (breathing tube down his throat) to help with his breathing during the test.

We opted for a diagnostic BAER for Matthew, also upon his ENT's (doctor) suggestion, to find out how well he was hearing. The literature on Down syndrome points out that up to 80% of individuals with Down syndrome have hearing issues. Matthew has proven that he can hear quite well, being able to hear a doorknob turn even if he was two rooms away. And except for his speech delay and occasional fluid in his middle ears, there was no specific indication that he had any significant hearing loss.

The BAER would answer questions we had: Can he hear different pitches/ sound frequencies well? Can he not hear some pitches? What decibels (loudness & softness of sound) can he hear? It would also give us a good idea of how well Matthew is hearing various sounds, especially in relation to speech. For example, the letter "a" is a high frequency sound/ pitch compared to "d", which is a low frequency/ pitch. If Matthew wasn't hearing some tonal pitches, then I think that would significantly slow down his speech development. Of course, there may be other causes of speech delay, such as verbal apraxia, and we want to check what we can to either rule them out or determine the best possible strategy to overcome it.

Other Hearing Tests
Matthew has never had a BAER test before. As a newborn, he passed the OAE (Otoaccoustic Emissions), which is a routine hearing test done on sleeping newborns before they are discharged from the hospital. The OAE test measures the weak echo sounds made by the ear as soon as it hears. If no echo sounds are detected through this test, there may be possible hearing loss.

When he was about 6 months old, he had a tympanogram, which is another type of hearing test but it measures movement of the eardrum only in response to a sound. The result of a tympanogram is charted by a computer. A peak in the chart indicates movement of the eardrum. A flat line on the chart is an indication of no eardrum movement and fluid in the ear. There may be some degree of hearing loss or hearing distortion depending on how much fluid is present. After the first couple tympanograms, he got tubes in both ears when he was 8 months old. He had fluid in his ears. Both tubes fell out after about a year or so. He has had several tympanograms since then and they've always been flatliners. This was another reason why we wanted a BAER done as it is known to be more accurate and can get more information compared to the OAE and tympanogram.

The Results
The test took 2-1/2 hours and the results were discussed with us immediately after. According to the tympanogram, Matthew has fluid in both ears. We came to the hospital with the knowledge that he had fluid in one ear since his June 2010 visit with his ENT. Having fluid in both ears isn't good especially if it doesn't drain well into his eustachian tubes, making him susceptible to ear infections, which could in turn affect his hearing. The tympanogram doesn't detect how much fluid is present so we'll need to schedule an appointment with his ENT within the next month or two.

According to the BAER, Matthew can hear all pitches and decibels tested within normal hearing levels. So perhaps there isn't a lot of fluid in his ears if the audiologist successfully used a BAER to test his hearing. But the only way to tell for sure is to have the ENT look into both ears with a microscope to determine if Matthew will need another set of ear tubes.

Recovery
Matthew was out of sorts and mad after waking from the anesthesia. The anesthesiologist explained that this was expected. He was taking in very (scary) deep noisy breaths every few minutes - also expected since his was intubated and under general anesthesia. We were to give him clear liquids if he wanted to drink. We stayed at the hospital until Matthew was feeling a little better, probably another 30 minutes, before heading home.

Once home, Matthew had some lunch and kept everything down. He was still a little unstable on his feet. After his afternoon nap, he was back to his usual playful self.