Central Hearing Loss
In central hearing loss the damage is situated in the central nervous system at some point between the auditory nuclei (in the medulla oblongata) and the cortex of the brain. Formerly, central hearing loss was described as a type of “perceptive deafness,” a term now obsolete. Knowledge about the subject still is limited.
Although information about central hearing loss is accumulating, it remains somewhat a mystery in otology (the medical specialty of ear and medicine surgery); a sub-specialty of otolaryngology. Physicians know that some patients cannot interpret or understand what is being said and that the cause of the difficulty is not in the peripheral mechanism but somewhere in the central nervous system. In central hearing loss the problem is not a lowered pure-tone threshold but in the patient’s ability to interpret what he or she hears. Obviously, it is a more complex task to interpret speech than to respond to a pure-tone threshold; consequently, the test necessary to diagnose central hearing impairment must be designed to access a patient’s ability to handle complex information. Most of the tests now available were not created specifically for this purpose, and, so, it still requires a very experienced and almost intuitive judgement on the physician’s part to make an accurate diagnosis.
One common central condition frequently leads people to think they have hearing loss when their hearing is actually normal. It is called a central auditory processing disorder. Despite the fact that this problem is extremely common and present in many highly successful people, it is actually classified as a learning disability. Basically, the problem involves a person’s inability to filter out competing auditory signals. People with central auditory processing disorders have difficulty “hearing” when there are several conversations going on, can’t study with the radio or television on, have difficulty reading if someone turns on a vacuum cleaner or any air conditioner near them, and generally miss the first sentence from people talking to them if they are involved in an auditory attention task (such as watching television). Although such people (and their families and friends) frequently suspect that they have a hearing loss, the function of the ears is usually normal, and routine hearing tests are normal. Naturally, people with this condition may also develop hearing loss from other causes which sometimes makes it even more difficult for them to function under everyday circumstances. There is no good treatment for central auditory processing disorders other than educating the patient, family and friends, and trying to control the environment. This is especially important for children whose grades may go from F to A if they are provided with a silent place in which to do their homework!