What are vestibular aqueducts?

Vestibular aqueducts are narrow, bony canals that 

travel from the inner ear to deep inside the skull (see 

figure). The aqueducts begin inside the temporal bone, 

the part of the skull just above the ear. The temporal 

bone also contains two sensory organs that are part 

of the inner ear. These organs are the cochlea, which 

detects sound waves and turns them into nerve 

signals, and the vestibular labyrinth, which detects 

movement and gravity. These organs, together with 

the nerves that send their signals to the brain, work to 

create normal hearing and balance. Running through 

each vestibular aqueduct is a fluid-filled tube called the 

endolymphatic duct, which connects the inner ear to a 

balloon-shaped structure called the endolymphatic sac.

A vestibular aqueduct is considered enlarged if it 

is greater than 1.5 millimeters in size, roughly the 

diameter of the head of a pin. If a vestibular aqueduct 

is enlarged, the endolymphatic duct and sac usually 

grow large too. The functions of the endolymphatic 

sac and duct are not completely understood. Scientists 

currently believe that the endolymphatic sac and duct 

help to ensure that the fluid in the inner ear contains 

the correct amounts of certain chemicals called ions. 

Ions are needed to help start the nerve signals that 

send sound and balance information to the brain.

How are enlarged vestibular aqueducts 

related to childhood hearing loss? 

Research suggests that most children with enlarged 

vestibular aqueducts (EVA) will develop some degree 

of hearing loss. Scientists also are finding that five 

NIH Medical Arts

NIDCD Fact Sheet

Enlarged Vestibular Aqueducts 

and Childhood Hearing Loss

u.s. department of health & human services ∙ national institutes of health ∙ National Institute on Deafness and Other Communication Disorders hearing balance

to 15 percent of children with sensorineural hearing 

loss, or hearing loss caused by damage to sensory 

cells inside the cochlea, have EVA. However, scientists 

do not think that EVA causes hearing loss. Instead, 

scientists regard EVA as an important clue about 

hearing loss and its possible causes. This information 

helps physicians talk with families about how their 

child’s hearing loss may change over time. 

The presence of EVA can be a symptom of a 

genetic disorder called Pendred syndrome, a cause 

of childhood hearing loss. According to a study 

by the National Institute on Deafness and Other 

Communication Disorders (NIDCD), approximately 

one-third of individuals with EVA and hearing loss 
have Pendred syndrome. With Pendred syndrome, the 

hearing loss is progressive, which means that a child 

will have less hearing over time. Some children may 

become totally deaf. 

In addition to causing hearing loss, EVA may affect 

balance. However, the brain is very good at making 

up for a weak vestibular system, and most children 

and adults with EVA do not have a problem with their 

balance or have difficulty doing routine tasks.

What causes enlarged vestibular 

aqueducts?

EVA has many causes, not all of which are fully 

understood. The most well-known cause of EVA and 

hearing loss is mutations to a gene known as SLC26A4 

(also referred to as the PDS gene) on chromosome 7. 

Two mutations in the PDS gene can result in Pendred 

syndrome. Scientists believe that other, currently 

unknown genetic or environmental factors also may 

result in EVA.

How are enlarged vestibular aqueducts 

diagnosed?

Medical professionals use different clues to help them 

determine the cause of an individual’s hearing loss. 

Two tests that are often used to identify the cause of 

hearing loss are magnetic resonance imaging (MRI) 

and computed tomography (CT) imaging of a person’s 

inner ear. One or both tests are often recommended 

to evaluate a child with sensorineural hearing loss. This 

is particularly true when a child’s hearing loss occurs 

suddenly, is greater in one ear than the other, or varies 

or gets worse over time. Although most CT scans of 

children with hearing loss are normal, EVA is the most 

commonly observed abnormality.

NIDCD Fact Sheet

Enlarged Vestibular Aqueducts 

and Childhood Hearing Loss

hearingbalance

Can enlarged vestibular aqueducts be 

treated to reduce hearing loss?

No treatment has proven effective in reducing the 

hearing loss associated with EVA or in slowing 

its progression. Although some otolaryngologists 

recommend steroids to treat sudden sensorineural 

hearing loss, there are no scientific studies to show 

that this treatment is effective or ineffective when an 

individual also has EVA. In addition, surgery to either 

drain liquid out of the endolymphatic sac and duct or 

to remove the endolymphatic sac and duct is not only 

ineffective in treating EVA, it can be harmful. Research 

has shown conclusively that these surgeries can 

destroy hearing.

To reduce the likelihood of progression of hearing 

loss, individuals with enlarged vestibular aqueducts 

syndrome should avoid contact sports that might lead 

to head injury; wear head protection when engaged in 

activities that might lead to head injury (such as bicycle 

riding or skiing); and avoid situations that can lead to 

barotrauma (extreme, rapid changes in pressure), such 

as scuba diving or hyperbaric oxygen treatment.

Identifying hearing loss as early as possible is the best 

way to reduce its effect. The earlier hearing loss is 

identified in children, the sooner they can develop 

the skills that will help them learn and communicate 

with others. Children with permanent and progressive 

hearing loss, which often is linked with EVA, will 

benefit from learning other forms of communication, 

such as sign language or cued speech, or using 

assistive devices, such as a hearing aid or cochlear 

implant. 
What research is being conducted on 

enlarged vestibular aqueducts and 

hearing loss?

While mutations of the SLC26A4 gene are known 

to cause EVA, not all EVA cases are the result 

of an SLC26A4 mutation. Some cases may be 

caused by other genetic or environmental factors. 

For these reasons, NIDCD researchers are currently 

conducting a clinical trial to identify and understand 

the various factors that can lead to EVA and hearing 

loss. For more information on this study, visit 

www.clinicaltrials.gov and enter “enlarged vestibular 

aqueducts” in the search box. 

Where can I get more information?

NIDCD maintains a directory of organizations that can 

answer questions and provide printed or electronic 

information on enlarged vestibular aqueducts 

and childhood hearing loss. Please see the list of 

organizations at www.nidcd.nih.gov/directory.

Use the following keywords to help you search for 

organizations that are relevant to enlarged vestibular 

aqueducts and childhood hearing loss:

• Early identification of deafness in children

• Genetic diseases/disorders

For more information, additional addresses and phone 

numbers, or a printed list of organizations, contact:

NIDCD Information Clearinghouse

1 Communication Avenue

Bethesda, MD 20892-3456

Toll-free Voice: (800) 241-1044

Toll-free TTY: (800) 241-1055

Fax: (301) 770-8977

E-mail: nidcdinfo@nidcd.nih.gov

Improving the lives of people who have communication disorders
NIDCD supports and conducts research and research training on the 

normal and disordered processes of hearing, balance, smell, taste, 

voice, speech, and language and provides health information, based 

upon scientific discovery, to the public.

hearing, balancesmell, tastevoice, speech, language

NIDCD Fact Sheet: Enlarged Vestibular Aqueducts and 

Childhood Hearing Loss

NIH Publication No. 06-6053

Updated April 2007

For more information, contact:

NIDCD Information Clearinghouse

1 Communication Avenue

Bethesda, MD 20892-3456

Toll-free Voice: (800) 241-1044

Toll-free TTY: (800) 241-1055

Fax: (301) 770-8977

E-mail: nidcdinfo@nidcd.nih.gov

Internet: www.nidcd.nih.gov

The NIDCD Information Clearinghouse is a service of the 

National Institute on Deafness and Other Communication 

Disorders, National Institutes of Health, U.S. Department 

of Health and Human Services.