My four-month-old grandson does not react with a startle when loud noises are made behind him. He does not turn to them, yet he interacts with big smiles and lighted eyes when you talk to him as you stand before him. My daughter-in-law's parents have brought this to her attention. The baby's parents don't seem to be extremely concerned, perhaps in denial. If he is hearing impaired, are there remedies? What kind?

Abraham

Your observations are very consistent with a significant hearing loss in both ears. In fact, I can think of no other explanation for his behavior. If this is not diagnosed and treated soon, your grandson's speech and language development will eventually be impaired.

Excellent techniques are available to test hearing in infants, even in newborns. For very young babies, a method called ABR (for auditory brainstem evoked response, also referred to as BAER, for brainstem auditory evoked response) can be used to test hearing. This method measures the electrical activity of the cochlear nerve (hearing nerve) and nerve pathways in the brainstem in response to sound. It is safe, painless and accurate, but your grandson may need to be sedated for the test.

Older infants can be tested by behavioral observation. The audiologist "trains" the infant to associate a sound with the appearance of a pleasant visual stimulus (a light will shine on the mother's smiling face, or a light will shine on a favorite toy). Infants learn that when they hear the sound, they can look in a particular direction to see the pleasant sight. Eventually, they will look in that direction purely in response to sound. The audiologist can then play the sound at a lower and lower volume in order to test hearing sensitivity.

An examination by an ear, nose and throat doctor (ENT) would also be necessary. An ENT could examine your grandson's ears to determine whether there are any structural problems. For example, some babies are born with extremely narrow ear canals. In some cases, the ear canals may not even exist. Some babies develop fluid behind the eardrums, even at very young ages. These problems are easy to detect.

If there is a structural problem with the outer ear or middle ear, there are safe, effective surgical procedures to correct these problems. If, on the other hand, he has nerve deafness, then hearing aids are the only option. (Yes, infants CAN use hearing aids.) If his hearing loss is so severe that hearing aids will not work, then he may be a candidate for cochlear implants. These are devices that electrically stimulate the inner ear in response to sound. They are effective in cases where a hearing aid would be useless.

Clinical research in this area has demonstrated that EARLY intervention is essential in order to avoid significant speech and language impairment. Thus, time is of the essence. I encourage you to copy this column and share it with your grandson's parents.