Causes of Hearing Loss in Children
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.
Acquired Hearing Loss
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.
Genetic factors make up about 50% of infant hearing loss. A genetic factor can be inherited or non-inherited and refers to the “code” that determines the unique characteristics of a child. Hearing loss from genetic causes can be congenital or develop later in life. The two types of genetic hearing loss are nonsyndromic hearing loss and syndromic hearing loss. A nonsyndromic hearing loss means that the hearing loss occurs without involvement of other systems in the body. Connexin 26 is the most common type of nonsyndromic genetic hearing loss. A syndromic hearing loss means that the hearing loss is in addition to a recognized set of characteristics. About 20% of genetic hearing losses are related to syndromes. Examples of genetic disorders that include hearing loss are Down syndrome, Usher syndrome, Treacher Collins syndrome, Crouzon syndrome, Alport syndrome, Sickle cell disease, Tay-Sachs disease, Waardenburg syndrome, Pendred syndrome, Goldenhar syndrome, and CHARGE syndrome.
25% of infant hearing losses are non-genetic. Permanent hearing loss that is non-genetic can be a result of maternal infections (e.g., rubella, cytomegalovirus, herpes simplex virus, syphilis, toxoplasmosis, chickenpox), prematurity, low birth weight, lack of oxygen (anoxia), hyperbilirubinemia, maternal diabetes, toxins such as drugs and alcohol consumed by the mother during pregnancy, or inner ear malformations (e.g., Mondini’s malformation, large vestibular aqueduct).
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.
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.
As a parent, you can set examples for your child on hearing conservation. If hearing and the use of hearing protection are important to you, it will also be important to your child. When using power tools or mowing the lawn, use hearing protection and if your child is playing nearby, make him or her also use hearing protection. Using hearing protection will protect both your hearing and your child’s hearing. If you are interested in custom hearing protection for you or your child, contact us at 469-803-5552.
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.
An excessive amount of wax in the ear canal can block sound waves from going to the eardrum. Wax softening drops can help the wax exit the canal. A physician can irrigate the canal or remove the wax. Parents should never use Cotton swabs in an attempt to remove wax. The cotton swab may actually push the wax deeper into the canal or damage the eardrum.
Foreign objects such as beads and food items impede sound and can damage the eardrum. The ear canal may become inflamed if the object damages the surface lining.
Another common condition affecting the outer ear canal is called “swimmer’s ear.” This external ear canal infection may be painful and cause the ear canal to swell, resulting in temporary hearing loss. In most cases, it is a bacterial infection that develops in an ear canal that stays wet after bathing or swimming.
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.