In order to understand hearing, or the auditory system, and the ability to perceive sound and understand speech, it is best to consider the ear as being divided into 3 parts: the external ear, the middle ear, and the inner ear.
The external ear consists of the auricle and the ear canal. These structures direct sound towards the eardrum.
The middle ear is the space that lies between the external ear and inner ear. The middle ear is made up of the eardrum and the air-filled space behind it which contains the 3 small hearing bones which are called the ossicles. The ossicles are referred to as the malleus (the hammer), the incus (the anvil), and the stapes (the stirrup). Once sound hits the eardrum the ossicles vibrate and transmit sound to the inner ear. They essentially convert sound vibrations to fluid waves in the inner ear. The only connection between the middle ear and the outside of the body is through the eustachian tube which connects to the back of the throat. The eustachian tube is a narrow channel that allows air pressure to equalize behind the eardrum. Yawning or swallowing opens the eustachian tube. For example, when flying on a plane or diving in the ocean, blowing air into the nose with the nostrils plugged causes the eustachian tube to open allowing equalization of the pressure behind the eardrum. This is commonly referred to as “popping” the ears.
The inner ear, also known as the cochlea, is a fluid-filled structure surrounded by bone, located within the skull, just under the brain. This portion of the ear contains microscopic hairs that transmit sound to nerve endings which in turn transmit nerve impulses along the hearing nerve to the brain where sound is processed and interpreted as words or music or laughter, for example.
There are 2 main types of hearing loss: conductive and sensorineural. Patients can also have both a conductive and sensorineural hearing loss referred to as mixed hearing loss.
A conductive hearing loss can be caused by anything that affects or impairs the transmission of sound from the external and middle ear to the inner ear. This can be caused by a variety of processes such as wax buildup in the ear canal, fluid behind the eardrum, a hole in the eardrum, or any number of conditions that can affect how the hearing bones vibrate and transmit sound to the inner ear. In cases where only the conduction of sound is affected, the nerve hearing remains normal, but increased volume is required to hear sounds and speech because their transmission to the inner ear is dampened. In other words, amplifying the sound as it enters the ear canal can many times overcome the effects of a conductive hearing loss.
Having sensorineural hearing loss simply means that the nerve portion of hearing, which involves the inner ear and hearing nerve, is damaged in some way. The most common cause of sensorineural hearing loss is exposure to loud noise. It is also common to gradually lose hearing as we age, usually in the higher frequencies first. There are a variety of other conditions related to genetics, medications, and general health, which can also lead to hearing loss.
A conductive hearing loss can sometimes be corrected or treated with both medical and surgical treatments depending on the cause. In that sense it can be considered reversible in some cases. Conductive hearing loss can also be treated with hearing aids depending on the underlying condition. On the other hand, sensorineural hearing loss is usually not reversible. It can be helped with the use of a hearing aid once the hearing loss progresses enough to affect normal social functions and daily activities. Interestingly, with either conductive or sensorineural hearing loss, if the onset is gradual over several years, the patient is often the last one to know they have a hearing problem.
If hearing loss is a concern, scheduling an appointment to have the hearing fully evaluated by one of the doctors of audiology at CornerStone Ear, Nose & Throat, PA, is encouraged. CornerStone Ear, Nose & Throat physicians and doctors of audiology work together closely to assess and treat all of the various causes of hearing loss. If there is any suspicion of a medical or surgical problem, a CornerStone Ear, Nose & Throat physician will be consulted, allowing patients the convenience of proficient comprehensive audiologic care and expert medical or surgical treatment in one location.