Conductive Hearing Loss

With a conductive hearing loss, the inner ear hair cells and the auditory nerve and higher pathways are all normal.  The problem is that sound cannot be conducted to the inner ear.  That means that a conductive hearing loss is related to problems in the outer or middle ear.  There are several possible causes of a conductive loss and an audiologist can help your referring physician diagnose the cause of your loss and therefore prescribe the proper treatment to get you hearing well.  These disorders can be either temporary or permanent.  Many types of conductive hearing loss can be helped medically or surgically.

Symptoms of Conductive Hearing Loss:

People who experience this condition may find that voices and sounds appear faint, muffled or non-existent. Therefore other people may notice that they need to constantly repeat what they have said. Some types of conductive loss can cause pain in and around the ear.  Patients may also experience tinnitus (ringing in the ears) or hear their own pulse more easily because they do not hear normal external sounds well.  Normal everyday sounds often cover up or mask tinnitus or normal body sounds.  People may start to withdraw from social activities and can lead to embarrassment or even depression.

Types of Conductive Hearing Loss:

Atresia:

Atresia is a condition where the out ear lobe {pinna} can be deformed or actually missing all together.  With atresia the ear canal is often completely closed or nonexistent.

In congenital aural atresia, the external auditory canal (EAC) and structures in the middle ear fail to develop completely. Development of the ear canal and middle ear may be arrested at any point in the process. Therefore, the clinician may encounter varying degrees of severity of this malformation. In the severe form of the disorder, no identifiable ear canal exists (complete atresia), and the middle ear and its structures (ossicles, or ear bones) may be absent or show significant underdevelopment. If a semblance of an external auditory meatus is present, the ear canal may end in a shallow blind pouch. In less severe forms of the disorder, the ear canal may be stenotic with a pinpoint aperture leading into the medial ear canal and, possibly, a rudimentary tympanic membrane. The tympanic membrane in these cases may or may not be attached to the ear bones (the ossicular chain).

Cerumen:

Another very common problem is a build up of ear wax (cerumen) in the ear canal. Often the cerumen is mixed with dead skin and can completely occlude the ear canal causing a conductive loss.  Below is a normal looking ear canal and eardrum as seen through a video otoscope.  As you can see, the canal and eardrum are very clean and healthy so that sound entering the ear canal actually reaches the eardrum and sets in to motion.  The first bone (Malleus) of the ossicular chain is quite visible where it is attached on the other side of the eardrum.

The picture below shows an ear canal nearly occluded with cerumen and dead skin.  If the ear becomes completely occluded, then a significant hearing loss can develop.  If the person wears a hearing aid, the receiver tube of the hearing aid can be blocked by the cerumen and the patient may think that their hearing aid is broken.

Otitis Media:

Fluid behind the eardrum is another common cause of conductive hearing loss.  The fluid in the middle ear behind the eardrum is usually caused by bacteria (or viruses) that enter from the nose or throat and ascend the Eustachian tube to reach the middle ear. This occurs when the Eustachian tube is not functioning properly often because the Eustachian tube is inflamed from a cold, sinus or throat infection, or an allergy attack.  The opening of the Eustachian tube is in the naospharynx so it is easy for the bacteria or virus to find its way into the Eustachian tube and then into the middle ear.

The middle ear is lined with mucous membrane and it absorbs oxygen from the middle ear space.  If fresh oxygen cannot travel through the Eustachian tube to replace the oxygen that has been absorbed, then negative pressure can develop in the middle ear.  The negative pressure can be quite severe and that causes the eardrum to be retracted inward toward the middle ear space.  The retracted ear drum does not transmit sound waves coming into the ear canal be the eardrum is “rigid” and the sound wave energy bounces off the eardrum rather than being transferred on to the inner ear.  This of course leads to hearing loss.

If the fluid in the middle ear is not infected then it is called serous otitis media.  However, if the fluid is infected with bacteria that has travelled through the Eustachian tube, then matters can get much worse.  Infection in the middle ear causes earache, a red inflamed eardrum, and a build up of pus and mucus behind the eardrum.  If the pressure builds enough, the eardrum will actually rupture.  You may find drainage on your pillow or feel it running out of your ear.  A ruptured eardrum is nature’s way of relieving the pressure.  However, you want to receive treatment for this long before it reaches that point if you can.  Below is a picture of an eardrum.  You can also see the fluid behind the eardrum.  Its like looking at the water level in a glass.  This fluid is clear and represents serous otitis media.

                                From:  http://distractible.org/wp-content/uploads/2007/09/still2-thumb.jpg

Below is a middle ear with acute otitis media.  Because of the buildup of pus, the eardrum is bulging outward and may eventually rupture.

                                                               Source: David P. Skoner, MD

                                     From http://www.pediatricsupersite.com/view.aspx?rid=35968

If you are suspicious of a problem with your middle ear, then you should communicate with your primary care physician quickly.  Your physician may recommend you to an audiologist for a hearing exam including a tympanogram.  The tympanogram will measure not only the movement of your eardrum but also the pressure in your middle ear.

Treatments for serious otitis media include the use of antibiotics.  With serous otitis media the condition may improve without an medical intervention so your physician will simply monitor the situation to see if it improves before prescribing anything.  With acute otitis media, your physician may decide to use antibiotics immediately since infection in the middle ear is present.  Your physician may treat each case differently depending of a variety of factors.

In extreme cases of acute otitis media, your physician will probably refer you to an ear, nose and throat (ENT) specialist.  If antibiotics have been unsuccessful the ENT physician may insert tubes in the ear drums.  They will first remove the pus and then insert the tube in the eardrum.  The tube will help keep middle ear pressure the same as the outside pressure in the ear canal which is what the Eustachian tube is supposed to do then it is functioning properly.  Below is a picture of an eardrum with a tube in place.

                                       From: http://img.medscape.com/article/730/700/730700-fig1.jpg

Again, the tube will keep the middle ear pressure the same as atmospheric so negative pressure in the middle ear should never be a problem.  However, cerumen can plug the small hope in the tube, or drainage from the middle ear can become crusty and also plug the tube.  In either case, that situation is the same as having no tube at all because the middle ear is a closed cavity again and negative pressure could reoccur.  Some of the tubes are designed to fall out on their own.  Some are designed to stay in much longer.  The type of tube is chosen by the ENT physician.  If the tube falls out on its own, there is usually no harm to the patient’s ear canal.  It will sometimes fall completely out of the ear canal and the patient doesn’t even know about it.  Occasionally the tube may be surrounded by cerumen in the canal and it removed when the ear is cleaned.

Foreign Objects:

Children usually place things in their ear canal because they are bored, curious, or copying other children. Sometimes one child may put an object in another child’s ear during play. It is important for parents to be aware that children may cause themselves or other children great harm by placing objects in the ear. There may also be a link between chronic outer ear infections (otitis externa)  and children who tend to place things in their ears. Insects may also fly into the ear canal, causing potential harm. Any child with a chronically draining ear should be evaluated for a foreign body.

Some of the items that are commonly found in the ear (usually the canal) of young children include the following: food, insects, toys, buttons, pieces of crayon, and small button-shaped batteries. Teenagers sometimes have objects imbedded in the ear lobe due to an infection from a pierced ear or a poorly healed piecing.  The picture below shows a bug which has decided to visit someone’s ear canal.  It is warm and moist inside so he probably feels right at home!

                                             From: http://orl.ifps.org.pl/jedn_chor/graph/corp_al1.jpg

Adults also have problems with foreign bodies in their ear canal.  I personally have witnessed this in my own office.  Adults with dementia have inserted hearing aids directly into their own ear canals.  The obviously confused the battery with the actual hearing aid.  Even adults that do not have dementia have forgotten about those cotton balls that they put in their ears months ago when they went hunting.  Since they forgot about them, they sometimes used Q-tips and pushed the cotton in further and further.  One patient who had done this noticed that every time he took a shower, his ears remained plugged for several hours.  The cotton balls were probably absorbing water that ran into his ears which would completely occlude the ear canal until the cotton balls dried out.  Below is a picture of a patient who broke off a small twig from a tree that actually perforated the eardrum.

                               From: http://www.entusa.com/Ear_Photos/20050330-stick-eardrum-1.jpg

Of course, if this happens to you  or a child, you should contact a physician. The following are some of the techniques that may be used by the physician to remove the object from the ear canal:  They may use instruments to pull out the object.  They may even use magnets if the object is metal.  Irrigating the ear with water is another method that may be used.  Filling the ear with mineral oil may be used to suffocate an insect,  a suction machine may be used help pull the object out.  After the object is removed, antibiotic drops for the ear may be prescribed to treat any possible infections.