They are testing two different things. Normally sound travels down the ear canal and hits the eardrum, the ear drum vibrates and this vibration is passed through the tiny bones of the middle ear and into the cochlea (inner ear) where it is transduced to neural signals that are interpretted by the brain.
Given that your child passed the ABR, their hearing at the level of the inner ear, their “true” hearing, is normal. If there are no particular risk factors (i.e. the birth history was uncomplicated and there are no genetic, syndromic, or disease concerns) then it is VERY unlikely that your child will develop hearing loss (in childhood, who knows what their hearing will be when they are 80). There are genetic mutations that result in children having normal hearing at birth and progressive loss later on, but they are very rare and not really worth worrying about unless particular concerns arise.
The pressure test is testing the movement of the ear drum. The middle ear space connects through the eustachian tube to the nose and throat. The eustachian tube’s normal job is to open and close to maintain appropriate pressure in the middle ear space. When we’re born, it is very flat and small and it is tremendously common for it to get plugged up, and when it gets plugged up you can get a fluid build up in the middle ear space that stops the eardrum from moving. This may be referred to as abnormal middle ear function or middle ear dysfunction, because the eardrum and bones of the middle ear aren’t moving the way they should be (because of the fluid). This can cause a temporary hearing loss–the inner ear hears normally but the sound is not transmitting through the middle ear properly. Note that it doesn’t always cause clinical hearing loss–sometimes the eardrum isn’t moving well, but there are negligible impacts on hearing.
Most children just grow out of this, the fluid clears on its own, the eardrum starts moving normally and hearing returns to normal. Where we are concerned is when it does NOT clear on its own and the temporary, mechanical hearing loss impacts language development because there is a critical window for language development between the age of 0 and 4. As a result, kids with chronic middle ear dysfunction are sent along to the ENT to determine whether they should get PE tubes placed in their eardrums to clear the fluid. In many cases, one set of tubes is all it takes and the child doesn’t have trouble again. Some children get multiple sets of tubes. Some children might also need their adenoids/tonsils assessed.
It sounds like your child has middle ear dysfunction, but only in one ear, and it’s not clear that it is really impacting your child’s hearing much at this time. As a result, your child is not currently at risk for language delays BUT the audiologist wants to keep monitoring to make sure that the middle ear dysfunction clears up on its own and doesn’t become a chronic concern.
Extra note: Many children are fine at birth, or have temporary middle ear dysfcuntion that clears up on its own, but start having problems again between the ages or 2-5, often when they are entering daycare or preschool and picking up viruses all the time. This is another point where you want keep an eye on how they are hearing in case they might need reassessment or rereferral. Children with multiple ear infections in a year will also typically be referred on to the ENT. All of this is super common and kids who get PE tubes generally grow up to be adults with completely normal ears.
