Understanding Hearing Loss
Types of Hearing Loss
There are three types of hearing loss: conductive hearing loss, sensorineural hearing loss, and mixed hearing loss.
Conductive Hearing Loss
Conductive hearing loss results in a loss of loudness; sounds are just not loud enough to be well heard. Conductive hearing loss results from an abnormality of the outer or middle ear. This type of hearing loss can be permanent or temporary depending on the cause of the hearing loss. If there is fluid in the middle ear, the loss is temporary if given prompt medical attention. Other causes can be remedied by medical or surgical techniques or by amplifying sound with hearing aids. Some causes of conductive hearing loss are otitis media, wax impaction, perforated eardrum, and cholesteatoma.
Sensorineural Hearing Loss
A sensorineural hearing loss means there is a problem in the inner ear. Sensorineural hearing loss in young children can be caused by certain infections before birth, from genetic factors, or from a lack of oxygen during birth. There is typically no medical or surgical treatment to correct for sensorineural hearing loss, but hearing aids can help in most cases.
Sensorineural hearing loss can cause not only a loss of loudness, but also clarity of speech. Sometimes, sensorineural hearing loss is incorrectly referred to as “nerve deafness”. It is not completely possible to correct the lack of clarity that may be associated with a sensorineural hearing loss by amplifying sounds. It is important to be aware of the difference between a conductive and sensorineural loss. This is the reason why some people with hearing loss seem to benefit more from hearing aids than others. When it is determined that hearing aids provide little to no clarity for someone with sensorineural hearing loss, a cochlear implant can be considered.
Mixed Hearing Loss
Mixed hearing loss is a combination of conductive hearing loss and sensorineural hearing loss. Chronic ear infection can result in a defective eardrum or middle ear cavity, and often in addition to the conductive hearing loss, the individual may have a sensorineural hearing impairment. The optimal treatment for this type of hearing loss requires consideration of all of the factors involved and must be individualized for the patient. The option of hearing aids versus reconstruction of the middle ear hearing mechanism is considered on a case-by-case basis.
Degrees of Hearing Loss
Hearing loss is measured in decibels (dB) hearing level (HL). The hearing level represents the softest level heard and is used to determine the degree of hearing loss. Degree of hearing loss is classified as mild, moderate, moderately severe, severe, or profound. Hearing loss is more accurately defined by degree rather than a percentage. Hearing levels are not always the same in each ear or for all the frequencies tested. For example, some children have a high frequency hearing loss, which is when hearing is normal in the low to mid frequencies with hearing loss in the higher frequencies, resulting in the child “hearing” some sounds, but not hearing all the sounds needed for speech understanding. The degree of hearing loss is an important factor when choosing a hearing aid. Not all hearing aids will suit all degrees of hearing loss.
Children with normal hearing can usually hear sounds quieter than 15 dB. When hearing levels are outside the normal range, they are considered to have one of the following degrees of hearing loss:
Mild Hearing Loss (16 to 40 dB HL)
Children with a mild degree of hearing loss will have difficulty hearing sounds softer than 16 to 40 dB HL. With mild hearing loss, children cannot hear soft speech, whispering and distant speech. Understanding conversation in a noisy environment will also be challenging. A mild hearing loss is similar to blocking the ear with a finger; people can still be heard talking, but it sounds muffled and it’s even more difficult to understand the conversation if there is any background noise.
With hearing levels of 20 dB HL, the child may miss up to 10% of the speech signal when the speaker is at a distance greater than 3 feet. The percentage of speech missed will be greater whenever there is background noise. With hearing levels of 30 dB, the child may miss 25 to 40% of the speech signal. With hearing levels of 40 dB, the child may miss 50% of classroom discussions.
Hearing is not an all or nothing phenomenon. Even a mild hearing loss during the crucial years for language and speech development can cause a child to misunderstand speech sounds and may result in a delay of normal communication development, and difficulties learning early reading skills such as letter/sound associations. For mild hearing loss, hearing aids are beneficial, but are not always mandatory. Sometimes a Remote Microphone (RM) system can be used in a classroom setting rather than a hearing aid to provide access to speech sounds. However, it is important that the parents, pediatric audiologist, and physician consider the child’s configuration of hearing loss, age, speech and language development, school performance, behavioral concerns, and other factors prior to deciding whether or not to proceed with amplification; in cases where it is decided that the child not yet be fitted with hearing aids, it is especially important that the child’s hearing loss and abilities be monitored so that amplification can be provided as soon as concerns develop. When these children receive hearing aids or an RM system, they usually find that school is easier as they do not have to exert as much energy to listen.
Moderate Hearing Loss (41 to 55 dB HL)
Children with a moderate degree of hearing loss have problems hearing sounds softer than 41 to 55 dB HL. With a moderate hearing loss, children will have trouble hearing conversation at a normal level, especially in noisy situations. The TV and radio may have to be turned up in order to be heard. With hearing levels of 50 dB, the child may miss up to 80% of conversations.
Hearing aids are needed to understand speech. Even with hearing aids, if background noise is present, the child may miss some of the speech signal. Without early amplification, the child is likely to have delayed or disordered syntax, limited vocabulary, imperfect speech production, and flat voice quality.
Moderately Severe Hearing Loss (56 to 70 dB HL)
Children with a moderately severe degree of hearing loss will not hear sounds softer than 56 to 70 dB HL. Speech sounds will not be heard. Sounds that are loud to a normal hearing person will be a whisper to the child. Children with this amount of hearing loss can hear and understand only a loud voice very close to them. They usually do not develop speech and language on their own, and if they do, their speech will be poor. Consistent use of hearing aids will help these children hear conversation and learn to speak clearly.
Severe Hearing Loss (71 to 89 dB HL)
Children with a severe degree of hearing loss have problems hearing sounds softer than 71 to 89 dB HL. Speech sounds will not be distinguishable, no matter how close the child is to the speaker. The child may respond to a loud sound such as a door slam or siren, but other loud sounds such as a phone ringing or a dog barking may not be heard.
With the help of hearing aids or cochlear implants and therapy, a child with this degree of hearing loss often can understand some speech sounds; however, with hearing aids, only a portion of the clues available in speech sounds will be provided. Children with severe hearing loss can learn to understand and speak, even though they will not hear speech the way children with normal hearing do.
If hearing loss is not identified and appropriately managed during infancy, it is likely that spoken language will be delayed; the earlier the child begins consistent use of amplification with rigorous language intervention, the greater the child’s chances are that speech, language and learning will develop at a fairly normal rate. Individual ability and intensive intervention prior to 6 months of age will determine the extent that sounds detected will be understood by the brain and processed as meaningful input.
Profound Hearing Loss (> 90 dB HL)
Children with a profound degree of hearing loss cannot hear sounds softer than 91 dB HL. With profound hearing loss, children will receive very little auditory information; speech sounds will not be audible and even some very loud environmental sounds will not be heard. Even with hearing aids, the child may not be able to understand all speech sounds. However, a cochlear implant and therapy can help the child learn speech and language. Most children with a profound hearing loss will need help at home and school to improve their speech and language. Some children may still need to use visual cues to help them understand spoken conversation.
Causes of Hearing Loss
It is normal as a parent to need to know why your child has a hearing loss. Sometimes the cause of hearing loss can be determined and sometimes it cannot. 25% of infant hearing losses are due to unknown causes. Sometimes the hearing loss is caused by a combination of factors. A physician will guide you through the process to determine the cause of your baby’s hearing loss. The process begins by the physician reviewing your family history, your baby’s birth history, and an examination of your child. The physician may order medical and lab testing to help determine the cause.
Permanent childhood hearing loss can be congenital, delayed-onset, progressive, or acquired. Hearing loss from birth, referred to as congenital hearing loss, is often identified through a newborn hearing screening. Some hearing loss in childhood is delayed-onset or progressive in nature. As a result, it is important to monitor hearing over time for children who are considered to be at risk for hearing loss.
Congenital and Genetic Causes
Genetic Factors
Nongenetic Factors
Delayed-Onset and Progressive Causes
Large Vestibular Aqueduct
Large vestibular aqueduct (LVA), a congenital enlargement of the cochlear aqueduct, is the most common malformation of the inner ear associated with sensorineural hearing loss. This condition is referred to as large vestibular aqueduct syndrome (LVAS). The vestibular aqueduct is the bony canal that travels from the vestibule into the temporal bone. Inside the vestibular aqueduct is a tube known as the endolymphatic duct that carries endolymph fluid from the inner ear to the endolymphatic sac. When the vestibular aqueduct is enlarged, the endolymphatic sac and duct enlarge to fill the space. It is thought that the endolymphatic sac and duct help regulate the concentration of ions in the cochlear fluids and this enlargement may result in a chemical imbalance, disrupting the transmission of hearing and balance nerve signals to the brain. LVA can result from abnormal or delayed development of the inner ear (non-syndromal) or may be associated with syndromes such as Pendred syndrome, brancio-oto-renal syndrome, CHARGE syndrome, or Waardenburg syndrome.
LVAS is diagnosed through magnetic resonance imaging (MRI), which is useful in visualizing the endolymphatic duct and sac soft tissues. LVAS is typically bilateral and almost always leads to some degree of progressive or fluctuating hearing loss. Although LVAS is a congenital condition, hearing loss may not be present from birth. Typically, the hearing loss does not occur until after a minor or major head injury or an upper respiratory infection. Even active play like jumping can shake the head enough to result in hearing loss if LVAS is present. Generally, the hearing loss occurs in a series of steps; with each minor event, the hearing loss progresses until reaching a level of profound hearing loss.
With LVAS, it is important to protect the residual hearing by avoiding scuba diving and activities that could lead to head injury, and by wearing a helmet when bike riding, skateboarding, or skiing. Parents are often challenged to find a middle ground between allowing their child to enjoy the typical physical activities of childhood and preventing future hearing loss.
Due to LVAS’ progressive nature, the hearing loss should be monitored frequently. It is difficult to predict what will ultimately happen in any one case of LVAS because the condition follows no typical course. No relationship exists between the size of the large aqueduct and the amount of hearing loss. Children with LVAS can benefit from hearing aids; if the hearing loss progresses to a severe to profound degree in both ears, a cochlear implant can be considered.
Acquired Causes
Acquired hearing loss occurs after birth. Conditions that may cause permanent acquired hearing loss in children include ototoxic medications, encephalitis, mumps, measles, meningitis, large vestibular aqueduct, head injury, and noise exposure.
Cholesteatoma
Cholesteatoma is a tumor like growth in the middle ear. They are generally formed from the skin cells on the outside of the eardrum that have become folded into the middle ear as a result of ear infections or with a perforation of the eardrum. The squamous epithelium, or skin layer, of the outside of the eardrum is continuously replaced and the old skin elements are meant to come out through the ear canal. When these skin elements become trapped behind the eardrum in the middle ear or mastoid, it is called a cholesteatoma. Cholesteatoma typically grows very slowly and begins to cause symptoms as it compresses and erodes the structures of the middle ear and surrounding areas. Often the debris is infected with bacteria or other organisms, causing drainage and a foul smell.
Acquired cholesteatoma, the type that generally occur as a result of infection, is the most common type of cholesteatoma. This type of cholesteatoma may occur at any age. The other type of cholesteatoma is congenital cholesteatoma, which is much less common. In this type, skin cells are trapped in the middle ear from birth. These skin cells grow in the middle ear and have no way of coming out of the middle ear cavity because of the intact eardrum. The typical age of presentation for a congenital cholesteatoma is 4 to 6 years old.
Management of Cholesteatoma
A cholesteatoma is treated surgically with a primary goal of total eradication of the disease to obtain a safe and dry ear. The surgical procedure used is designed for each individual case according to the extent of the disease. More extensive disease will usually dictate a more aggressive surgical approach. The second objective is restoration or maintaining the functional capacity of hearing.
Childhood Noise Exposure
One of the most common and yet completely preventable causes of permanent sensorineural hearing loss is exposure to sound levels that are excessively loud. High noise levels first cause temporary hearing loss and then permanent damage to the sensory hair cells within the cochlea. Even young children may be exposed to sounds that could be damaging to their hearing. Noise produced by various modes of transportation (airplanes, subways, trains) and home appliances (stereo speakers, power tools, lawn mowers, hair dryers) may be damaging to hearing depending upon the exposure time and distance to the noise source. Even some toys can produce intense sound and certainly sound levels at some music concerts can damage hearing.
Monitor the level of noise your child is exposed to. If speech must be raised to communicate, most likely the noise is excessive and possibly damaging. Ringing in the ears known as tinnitus after noise exposure indicates excessive sound levels. Children should be told about the dangers of noise exposure and the use of ear protection (ear plugs, ear muffs). Children should be protected from excessive noise exposure whenever possible.
Hearing Protection
Some Common Hearing Problems in Children
Children will experience one or some of the most common hearing problems with the most common being otitis media, a condition of the middle ear. Discussed below are some causes of common hearing problems. For more information or if you have any concerns, contact us at 469-803-5555 to schedule an appointment with one of our physicians.
Wax (Cerumen)
Foreign Objects
Swimmer’s Ear
Otitis Media
Otitis media is the most common cause of conductive hearing loss in children. Otitis media, also known as glue ear, is a general term used to describe various conditions of the middle ear. More than 85% of all children will have at least one ear infection in childhood. Ear infections are second only to well-baby checks as the reason for office visits to a physician, accounting for approximately 30 million office visits annually in the United States. While some children appear to suffer no negative consequences from otitis media, others may be delayed in speech development and later academic problems.
Forms of Otitis Media
There are different forms of otitis media. An Acute Otitis Media (AOM) episode sometimes known as suppurative otitis media is characterized by a sudden onset of ear pain that may be associated with fever, restlessness and some hearing loss. The ear infection will usually respond to medical treatment, but in some rare cases, AOM may result in a rupture or perforation of the eardrum with drainage into the outer ear. If left untreated, ear infections may lead to more severe ear conditions.
Another form, Otitis Media with Effusion (OME), is characterized by persistent fluid in the middle ear and usually follows an episode of AOM. The fluid in the middle ear can impede the movement of the eardrum and of the middle ear bones. Depending on the thickness of the fluid, mild to moderate conductive hearing loss can result. This may prevent the child from being able to hear all speech sounds, which is particularly harmful during the early years of language learning.
Causes of Otitis Media
There are various causes of otitis media. The most frequent cause is eustachian tube dysfunction. The adenoids, which sit behind the nose at the opening of the eustachian tube, may obstruct the eustachian tube. More often, the adenoids become infected and the bacteria contribute to middle ear infections.
Ear infections may also result from upper respiratory infections (URIs). It is more common for middle ear problems to occur during the winter months. The risk of ear infections increases when smoking occurs in the home. Children with poor immune systems or respiratory allergies can have a greater incidence of otitis media.
Diagnosis and Treatment of Otitis Media
To diagnose an ear infection, the physician can use a pneumatic otoscope to see the appearance of the eardrum and examine movement in response to small changes in air pressure.
Treatment of acute otitis media typically includes antibiotics and sometimes additional medications prescribed by the physician. Often the condition subsides spontaneously or responds to medical treatment without prolonged hearing loss or other complications; however, when the OME is unresolved and hearing loss in both ears is present, ventilation or pressure equalizing (PE) tympanotomy tubes may be necessary. These tubes remain in the ear for several months or even a few years and often when the tubes fall out, the eustachian tube has further matured and begun to function better. In cases when the fluid and hearing loss return, a new set of tubes can be placed. Tubes can restore hearing to normal, prevent fluid from recurring, decrease the number of acute ear infections, and prevent damage to the middle ear bones as well as other more serious ear complications.
If you are concerned that your child might have one of the above problems, contact us at 469-803-5555 to schedule an appointment with one of our physicians.