Monthly Archives: December 2017

Types of Hearing Loss: Conductive, Sensorineural, and Mixed

What Kind of Hearing Loss Do You Have?

As described in our last blog post, the human ear can be divided into three general parts: the outer ear, the middle ear, and the inner ear. Hearing loss can occur in any, or multiple, parts of the pathway from the ear to the brain. Depending on where the hearing loss is occurring, hearing loss can be classified into three different types: conductive hearing loss, sensorineural hearing loss, and mixed hearing loss.

Note that in order to determine the type and degree of hearing loss, an audiologist would perform a hearing test and graph the results on an audiogram. In addition, different types of hearing loss require different types of intervention. Make sure to discuss all of your options with a medical provider.

  • Conductive hearing loss occurs when sound cannot be transmitted from the outer ear, to the ear drum, and into the middle ear space (where the smallest bones in the human body, the ossicles, are located). This type of hearing loss can often be corrected medically or surgically. Common causes of a conductive hearing loss may include:
    • Middle ear infection (otitis media)
    • Earwax (cerumen) impaction
    • Fluid or pressure in the middle ear from colds or allergies
    • Poor Eustachian tube function
    • Perforation in the eardrum
    • Head trauma
    • Swimmer’s ear (otitis externa)
  • Sensorineural hearing loss happens when there is damage to the inner ear (the cochlea) or to the nerve pathways from the inner ear to the brain. This is the most common type of permanent hearing loss. And even when speech is loud enough to hear, it may still be unclear or sound muffled. Common causes of a sensorineural hearing loss can include:
    • Aging
    • Exposure to loud noise
    • Genetics (hearing loss that runs in the family)
    • Drugs that are toxic to hearing
  • Mixed hearing loss occurs when a conductive hearing loss happens in combination with a sensorineural hearing loss. In other words, there may be damage in the outer or middle ear as well as damage in the inner ear or auditory nerve. Common causes of a mixed hearing loss can include any combination of the other issues listed above.

 

All About Ear Anatomy

Anatomy and Physiology of the Auditory System

The auditory system consists of several main parts that help carry sounds/signals to the brain. Although hearing seems like a simple feat, the transduction of a signal through the auditory system up to the brain is quite complex.

The Outer Ear

Beginning with the outer portion of the ear, the pinna helps pick up sounds and funnel them into the ear canal, anatomically known as the external auditory canal. The pinna helps individuals localize where sounds are coming from. Sound then travels down the ear canal where it eventually reaches the eardrum, or the tympanic membrane. The tympanic membrane is a thin membrane of skin that vibrates with sound stimulation.

The Middle Ear

Once sound vibrates the tympanic membrane, sound is transferred across three bones (ossicles) in the air filled middle ear space. These ossicles are the tiniest bones in the body known as the malleus, the incus, and the stapes. The stapes bone is shaped like a stirrup and has a round footplate. These three bones work together as a lever system to mechanically transduce sound through the middle ear to the inner ear. As sound reaches the stapes, the footplate pushes on what is referred to as the oval window. This window is the beginning of the inner ear system.

The Inner Ear

After sound reaches the oval window, the stimulation causes fluid in the inner ear system to move. The inner ear is a fluid filled space and therefore sound is hydromechanically transduced. Within the inner ear is an important hearing organ called the cochlea. The cochlea is a snail-shaped organ which has many tiny receptor hair cells embedded in a basilar membrane which respond to certain frequencies of sound. This is known as tonotopic organization in which the base of the membrane in the cochlea responds to higher pitches and the apex responds to lower pitches. As the hair cells are stimulated by the fluid moving in the cochlea, neurons attached to the hair cells receive the signal then send the auditory signal along the auditory nerve and up to the auditory cortex in the temporal lobe of the brain. Although we perceive and interpret sound within milliseconds, the pathway that sound travels to get to the brain is very complex, as detailed above.

There is much more detail related to the process of hearing and understanding, but the above is a basic overview of how individuals hear and interpret a signal. For a more in depth explanation, watch the links below.

The Connection between Hearing and Balance

Why Test My Hearing If I Have Vertigo?

As our name suggests, Jacksonville Hearing and Balance Institute helps patients with hearing and balance/dizziness issues. But how are hearing loss and dizziness related? If you have scheduled an appointment because of your dizziness, why would you need to have your hearing evaluated?

The answer to the above questions lies within the anatomy of our inner ear. The hearing and balance organs are both housed in the inner ear. The cochlea is necessary for hearing and the semicircular canals are part of our balance system.

There are multiple disorders that can cause disruptions in our hearing and balance. The type and configuration of hearing loss can help our providers better diagnose your dizziness. Meniere’s disease is one example of a disorder that is defined by the dizziness you are experiencing and the type of hearing loss that you may have. A patient with Meniere’s disease can experience dizziness for 30 minutes to multiple hours and have fluctuations in their hearing accompanied by a roaring tinnitus. Semi-circular Canal Dehiscence is another disorder that can be accompanied with hearing loss. A patient with SCCD may have a slight conductive component present on the audiogram even though they may not perceive a hearing deficit.

Jacksonville Hearing and Balance provides a comprehensive evaluation to help diagnose and treat your hearing loss and/or dizziness. For questions or to schedule an evaluation, you can reach us at (904)351-1904.