Types of Hearing Loss

The process by which sounds in our environment are collected, funnelled into the ear canal, translated into nerve signals, and interpreted by our brains is nothing short of incredible. Your ear is made up of three parts, the outer ear, the middle ear, and the inner ear. Hearing loss can arise from an issue in any part of this hearing sequence, and it is helpful to understand the mechanisms underlying it.

There are four types of Hearing Loss

Sound waves begin by entering the outer ear, called the pinna. The pinna funnels these waves through the ear canal and into the 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 the inner ear. Hearing loss may begin in the inner ear, so it is important that all these moving parts are free of damage.

Sensorineural Hearing Loss

Sensorineural hearing loss refers to any reduction in hearing sensitivity or sound clarity that is caused by damage to the delicate structures of the inner ear or the nerve pathways that carry the sound signal from the inner ear to the auditory processing area of the brain. Sensorineural hearing loss is the most common type of hearing loss. 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.

Hearing aids are the primary treatment for sensorineural hearing loss as medical or surgical intervention is rarely possible. Correctly fitted hearing aids stimulate the affected nerves in the inner ear to help forward sound processing along the auditory pathway to the brain. Today’s hearing aid technology can even address ‘high-frequency’ sensorineural hearing losses that were once thought to be un-treatable.

Common causes of sensorineural hearing loss are:

• Illnesses
• Drugs that are toxic to hearing (ototoxicity)
• Genetics
• Aging
• Head trauma
• Malformation of the inner ear
• Exposure to loud noise

Prevention:

Not withstanding the fact that sensorineural hearing loss can have many causes, exposure to high noise level is often the causative factor. I would highly recommend the use of custom hearing protection if you are exposed excessive noise levels.

Conductive Hearing Loss

A conductive hearing loss occurs when there is a problem with one or more of the parts of the ear that conduct sound into the inner ear. The ear canal, ear drum, and the tiny bones in the middle ear make up the conductive system and any hearing loss caused by a problem in one or more of these areas is called a conductive hearing loss. Unlike a sensorineural hearing loss, a conductive hearing loss occurs because the sound entering the ear is reduced or dampened by the obstruction; there is no damage to the delicate nerves in the inner ear. A conductive hearing loss can often be partially or completely reversed with medical intervention.

Common causes of conductive hearing loss are:

• Fluid in the middle ear from colds
• Ear infections
• Allergies
• Perforated eardrum
• Abnormal bone growth in middle ear
• Poor Eustachian tube dysfunction
• Impacted cerumen (earwax)
• Benign tumours
• Swimmer’s Ear
• Foreign object in ear
• Absence or malformation of the outer ear, ear canal, or middle ear

Treatment Options:

Treatment for conductive hearing loss varies based on the circumstances. Antibiotics or antifungal medications are usually prescribed for ear infections, whereas surgery is usually an option for malformed or abnormal outer or middle ear structures and other physical problems. Hearing aids are often the best answer when surgery is not possible, because they significantly improve hearing and are convenient.

Mixed Hearing Loss

When both conductive and sensorineural hearing loss are present at the same time and at the same ear, it is referred to as mixed hearing loss or ‘combined –type’ hearing loss. In this case, there is likely to be damage to the outer or middle ear as well as to the inner ear or auditory nerve.

Potential Causes:

Causes of mixed hearing loss vary wildly. Typically, the sensorineural hearing loss is already present, and the conductive hearing loss develops later and for an unrelated reason. As with sensorineural and conductive hearing losses, only a thorough diagnostic hearing and medical evaluation can identify a specific cause.

Treatment Options:

Medication or surgery may be the answer to the conductive portion of the mixed hearing loss, but these interventions cannot treat the sensorineural portion of the hearing loss. Many people who suffer from a mixed hearing loss will receive medical treatment for the conductive hearing but will have to use hearing aids to treat the remaining sensorineural component of their hearing loss. Mild to severe sensorineural hearing loss can be helped by using hearing aids.

Auditory Processing Disorders

Auditory Processing Disorder (APD) is different from the other types of hearing loss as it is not the inability to hear—it is the inability to interpret, organize, or analyse what is 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 centres of the brain are affected by injury, disease, tumour, 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.