The process by which sounds in our environment are collected, translated into nerve signals, and interpreted by our brains is nothing short of incredible. Hearing loss can arise from an issue in any part of this hearing sequence, and it’s helpful to understand the mechanisms underlying it.
Sound waves begin by entering your outer ear, called the pinna. It funnels these waves through your ear canal and into your middle ear, which are separated by the tympanic membrane, also known as the eardrum. This flexible membrane begins to move when sound vibrations hit it, which in turn starts to move the ossicles, three small bones in the middle ear. They are named the malleus (hammer), incus (anvil), and stapes (stirrup). These bones work together to amplify the sound waves and move them to your inner ear. Hearing loss may begin in the inner ear, so it’s important that all of these moving parts are free of damage.
The inner ear is full of fine hair-like cells, replete with nerve endings, within a spiral-shaped organ called the cochlea. These tiny hair cells collect information from sound vibrations coming in from the middle ear and transmit those vibrations into nerve impulses, via the auditory nerve, to your brain. The brain processes and interprets these signals as sounds, allowing us to hear the noises around us.
If you suffer from hearing loss, it means that one of the above sections isn’t working quite right. Our hearing evaluation is designed to diagnose which type of hearing loss is present, and enables us to identify the most effective solution for you.
There are four types of hearing loss:
1. Sensorineural Hearing Loss
2. Conductive Hearing Loss
3. Mixed Hearing Loss
4. Auditory Processing Disorders
Sensorineural Hearing Loss
Sensorineural hearing loss is the most common type of hearing loss and is the result of a problem in the inner ear or auditory nerve. It occurs when the tiny hair-like cells in the cochlea and/or the auditory nerve are missing or damaged, as both result in weakened nerve signals being sent to the brain.
Common causes of sensorineural hearing loss are:
- Drugs that are toxic to hearing (ototoxicity)
- Head trauma
- Malformation of the inner ear
- Exposure to loud noise
Conductive Hearing Loss
Conductive hearing loss results from a problem in the outer or middle ear that prevents sound from reaching the inner ear. Conductive hearing losses are relatively uncommon and are typically temporary. Most cases of conductive hearing loss can be treated with medication or surgery. When it cannot be treated with those means, most people benefit from the use of a hearing aid.
Common causes of conductive hearing loss are:
- Fluid in the middle ear from colds
- Ear infections
- Perforated eardrum
- Impacted cerumen (earwax)
- Benign tumors
- Swimmer’s Ear
- Foreign object in ear
- Absence or malformation of the outer ear, ear canal, or middle ear
Mixed Hearing Loss
Mixed hearing loss is a combination of conductive hearing loss and sensorineural hearing loss. When there is damage to either the outer or middle ear and the inner ear or auditory nerve, mixed hearing loss occurs. The sensorineural hearing loss is permanent while the conductive hearing loss may be reversible. Mixed hearing loss typically occurs when the ear sustains some type of trauma or injury, but can also result from a combination of the possible causes listed above.
Auditory Processing Disorders
Auditory Processing Disorder (APD) is different from the other types of hearing loss as it’s not the inability to hear—it’s the inability to interpret, organize, or analyze what’s heard. All the parts of the outer, middle, and inner ear are working well, but parts of the brain are not. APD occurs when the auditory centers of the brain are affected by injury, disease, tumor, heredity or unknown causes. While the symptoms can be similar, hearing loss is not always present with APD and the treatment for APD is different than for hearing loss.