Vestibular disease

Extended vestibular aqueduct

This information is intended as a general introduction to this topic. As everyone is affected differently by balance and dizziness problems, you should speak to your doctor for individual advice.

For reasons of better readability, the generic masculine is used and the simultaneous use of the language forms male, female and diverse (m/f/d) is dispensed with. Unless otherwise indicated, the personal designations used in this patient information refer to all genders.

What is an extended vestibular aqueduct?

The vestibular aqueduct is a narrow channel that runs from the inner ear deep into the skull. It contains the endolymphatic duct, which connects the inner ear with the endolymphatic sac. The endolymph is the fluid in the inner ear.

Normally, the vestibular aqueduct is very narrow: at half its length it is less than 1 mm wide - about the width of a pin. In some people, however, the vestibular aqueduct is wider, measuring between 1.5 mm and 8 mm. This is known as an extended vestibular aqueduct (EVA).

People with EVA often have sensorineural hearing loss, with or without vertigo and balance problems. These problems often begin in childhood; between 5-15% of children with sensorineural hearing loss have EVA. These problems are more common in girls than boys and are more common on both sides (bilaterally) than on one side. As a rule, hearing deteriorates over time.

EVA was first discovered in 1791, but the link between EVA and hearing loss was not described until 1978.

Summary

What causes a dilated vestibular aqueduct?

EVA appears to occur before birth, while the fetus is still developing. EVA does not appear to cause hearing loss. Instead, the researchers believe that both EVA and hearing loss are caused by an underlying genetic problem.

Many people with EVA and hearing loss also have other structural changes in the inner ear. For example, EVA is most commonly associated with incomplete partition type 2 (Mondini dsyplasia).

This anomaly consists of:

  • a cochlea (part of the inner ear that looks like a snail) with only 1.5 instead of the usual 2.5 turns
  • Enlarged vestibular organ with normal semicircular canals
  • dilated vestibular aqueduct containing a dilated endolymphatic sac

Connection with other faults

EVA sometimes occurs alone and sometimes in combination with other disorders. For example, about 1 in 4 people with EVA and hearing loss have Pendred syndrome, which also causes thyroid problems. Mutations in a gene called SLC26A4 can cause EVA and Pendred syndrome. But not everyone with EVA has these mutations. Other causes of EVA are being investigated.

Other conditions that are sometimes associated with EVA are:

  • CHARGE syndrome
  • Distal renal tubular acidosis
  • Waardenburg syndrome
  • X-linked inherited mixed deafness
  • Branchio-Oto-Renale (BOR) syndrome
  • Oto-facio-cervical syndrome

 

Both hearing and balance disorders can occur with an EVA.

Sometimes the symptoms are only noticed or worsen after a head injury.

  • The hearing impairments of EVA can include:

    • Sensorineural hearing loss, such as difficulty distinguishing words or a child who does not respond when their name is called
    in children: speech and language delays

EVA balance disorders can include:

  • Dizzy spells that last for varying lengths of time
  • Balance problems
  • in children: Delays in crawling or walking

Diagnosis of a dilated vestibular aqueduct

EVA is most commonly diagnosed in young people, from infants to young people in their 20s.

EVA can be diagnosed by a pediatrician, but more often by a specialist, such as an ENT specialist.

The doctor will take a thorough medical history, perform a neurological examination and various tests to assess the function of your vestibular system.

Your child will probably undergo some of the following diagnostic tests:

  • Hearing tests and vestibular function tests
  • Imaging tests such as magnetic resonance imaging (MRI) or computed tomography (CT); these tests can show whether the vestibular aqueduct is larger than usual and whether there are other abnormalities in the temporal bone

Treatment of an enlarged vestibular aqueduct

To date, there is no treatment that reduces or slows down hearing loss in people with EVA. It is important to identify hearing loss as early as possible so that children and their caregivers can develop skills to help them communicate. These skills include sign language and spoken language, which uses hand signals and other visual signs to make the 'building blocks' of speech (phonemes) visible.

You or your child will need to have regular check-ups to monitor their hearing and see if there have been any changes. This is especially important for very young children who may not yet be able to tell you if something is wrong. Hearing aids are recommended for severe hearing loss.

Therapy option

Operation

Surgery to drain excess fluid or to remove the enlarged endolymphatic duct and endolymphatic sac is not helpful. It often leads to severe hearing loss.

Some people with hearing loss and EVA gradually lose their hearing to a degree where hearing aids are no longer helpful. They may become candidates for cochlear implants. Surgery for cochlear implants is associated with some risk. People with EVA are more likely to leak cerebrospinal fluid (CSF) during surgery. CSF is the fluid that surrounds the brain and spinal cord. It is important to carefully consider the risks and benefits of surgery and discuss them with the surgeon.

 

 

Therapy option

Prevention of injuries

About 1 in 3 people with EVA suffer a hearing loss after a minor head injury or barotrauma (sudden, extreme change in air pressure). For this reason, people with EVA are often advised to protect their hearing by

  • Avoid contact sports
  • wear head protection during activities such as cycling or skiing
  • Avoid loud noises
  • Avoid situations that lead to extreme, rapid changes in air pressure (e.g. diving)
  • avoid playing wind instruments
  • take decongestants when flying if the sinuses or nose are blocked

The risk seems to be higher in people whose hearing changes (fluctuates) a lot. Talk to your doctor about whether certain activities are risky.

What happens next?

What you can expect in the future.

In many people with EVA, hearing changes dramatically or suddenly gets worse. It is not possible to predict who will experience these sudden changes, so regular monitoring is important.

Researchers are investigating the factors that cause EVA and hearing loss. In the future, we may know more about what causes EVA and how it can be prevented.

 

In order to keep this patient information as short as possible, we have not included a detailed list of references. However, this can be requested at any time at info@ivrt.de.

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