What is Syndromic Sensorineural Hearing Loss?
Congenital hearing loss, or being born with hearing loss, affects 1 to 3 out of every 1000 babies. For many of these children, the only issue they have is the hearing loss, which is known as nonsyndromic hearing loss. On the other hand, children with syndromic hearing loss have hearing loss as well as other health problems. Among those children whose hearing loss is caused by genetic abnormalities, around 20% also have other disorders along with their hearing loss. This article discusses further on syndromic sensorineural hearing loss (SNHL), which is a type of hearing loss caused by issues with the vestibulocochlear nerve, which is responsible for hearing and balance.
What Causes Syndromic Sensorineural Hearing Loss?
About half of all babies with deafness from birth, or congenital hearing loss, have it due to environmental reasons, and the other half due to genetic problems. When we say ‘environmental factors’, we’re talking about influences from the surroundings, like certain conditions during pregnancy or infections at the time of birth that can affect a baby’s hearing. ‘Genetic problems’ refer to changes in genes inherited from parents that can cause hearing loss.
Interestingly, from 70% to 80% of all congenital hearing loss cases are ‘non-syndromic’, which means that the hearing loss is a standalone issue and not part of any other medical condition. In nearly half of these non-syndromic cases, a mutation or change in a specific gene is responsible – the gene that creates a protein called connexin 26.
Connexins are proteins that act like bridge between cells allowing exchange of nutrients and ions. Within the inner part of the ear, connexin 26 is crucial in managing the right level of potassium inside the cells. If there is any disruption in this protein, it can result in hearing loss.
Lastly, about 20% of children who are born with hearing loss have ‘syndromic losses’, meaning their hearing loss is associated with or part of other medical conditions or characteristics.
Risk Factors and Frequency for Syndromic Sensorineural Hearing Loss
Congenital hearing loss, or hearing loss present at birth, affects about 1 to 3 in 1,000 babies. Normal hearing levels are between 0 to 20 decibels. However, at least 3 out of every 1,000 children will have a hearing loss greater than 20 decibels. Approximately 1 in every 1,000 infants will have severe to profound hearing loss (more than 70 decibels). The chance of having hearing loss is 10 times higher in infants who have one or more risk factors associated with hearing loss compared to those without any risk factors.
- Risk factors include a family history of inherited childhood hearing loss.
- Physical abnormalities of the head or face.
- Being born with a weight less than 1500 grams.
- Experiencing high levels of bilirubin in the blood.
- Having bacterial meningitis.
- A low APGAR score, which is a quick measure of the physical health of a newborn, of 0 to 4 at 1 minute or 0 to 6 at 5 minutes after birth.
- Needing 5 or more days of mechanical ventilation.
- Also, there are certain infections known by the acronym TORCH that can be transmitted from the pregnant mother to the baby and increase the risk. These include toxoplasmosis, rubella, cytomegalovirus, herpes simplex virus, and other viral infections.
Signs and Symptoms of Syndromic Sensorineural Hearing Loss
When figuring out a family’s history of medical issues, it’s crucial to check for hearing loss, eye problems, and heart defects present from birth. Also, you should look into the health of the mother during pregnancy. This includes whether she had infections like TORCH, gestational diabetes, or hypothyroidism. It’s also key to check whether she consumed drugs, alcohol, or tobacco when she was pregnant.
A thorough examination of the head and neck must be conducted, observing for any anomalies. These may include:
- Small or abnormally shaped ears
- Blocked or absent ear canal
- Skin tags around the ear
- Indentations in the front of the neck
- Eye problems (vision issues, eye color, distance between the eyes)
- Cleft lip or palate (opening or split in the upper lip or roof of the mouth)
- Irregular skull size or unevenness
- Extra or missing fingers or toes
- Areas of skin that are either lighter (hypopigmentation) or darker (hyperpigmentation) than normal, including cafe au lait spots (light-brown skin marks)
During the ear examination, the ear might appear normal. However, the presence of fluid in the middle ear needs to be pointed out.
Testing for Syndromic Sensorineural Hearing Loss
It’s crucial to detect hearing problems as soon as possible, as early detection can lead to better outcomes. In every US state, newborn babies are tested for hearing issues during their first three months. The American Academy of Pediatrics suggests these tests should be done by one month, the diagnosis confirmed by three months, and any necessary treatments started by six months.
There are a couple of different hearing tests that are used for this initial screening. These include the Auditory Brainstem Response test, or the Otoacoustic Emissions test. If a baby doesn’t pass these initial screenings, additional tests are recommended to confirm the issue. In some cases, an MRI or CT scan may also be done to evaluate the bones in the ear and the inner ear canal. While CT scans were originally used, MRIs are now becoming more popular due to the benefits they offer. However, it’s not certain when these imaging tests should be carried out and which patients should have them.
If the hearing loss is associated with a certain syndrome, this could warrant extra testing. Genetic consultations are usually recommended in such cases. A major part of diagnosing severe hearing loss that affects both ears now tends to involve testing for specific gene mutations. Other family members may also need to undergo hearing tests. Routine lab tests for children with hearing loss in both ears haven’t shown to be exceptionally useful, but they may be undertaken to look for signs of past or present infections.
If there’s a family history of fainting, an EKG might be needed. If there are concerns about an underactive thyroid, tests may be done to study thyroid function. A recent study found that over half of children with hearing loss linked to a certain syndrome have significant eye issues. It’s therefore advised that children with severe hearing loss affecting both ears should also see an eye doctor.
Treatment Options for Syndromic Sensorineural Hearing Loss
Treating hearing loss that comes with other medical conditions depends on how severe it is, when it started, and whether one or both ears are affected. The options for treatment can be standard hearing aids, bone-anchored hearing aids (BAHA implants which are attached to your skull and sends sound directly to your inner ear), or cochlear implants (which are placed in your cochlea, a part of your inner ear, and send sound signals directly to your brain) if the hearing loss in both ears is severe.
What else can Syndromic Sensorineural Hearing Loss be?
People can have increased blood clotting due to various health conditions. These include:
- Arteriosclerosis (hardening of the arteries)
- Diabetes (high blood sugar)
- Hypothyroidism (underactive thyroid)
- Leukaemia (type of cancer affecting white blood cells)
- Macroglobulinemia (a type of blood cancer)
- Polycythemia Vera (a disease that causes your body to make too many red blood cells)
- Sludging due to hyperviscosity (thickening of the blood leading to slower flow)
What to expect with Syndromic Sensorineural Hearing Loss
In instances of hearing loss present at birth, the outlook improves greatly when the condition is identified and treated early, even with severe or profound hearing deficits. Starting rehabilitation for your hearing earlier can lessen the negative impact of hearing loss on the development of speech and language skills.
Preventing Syndromic Sensorineural Hearing Loss
If your newborn’s hearing test results are not normal, it’s important to get educated about congenital hearing loss as soon as possible. Starting the care process for these babies and their families during the first few days after birth can help avoid the negative impacts of a late diagnosis. This way, any potential hearing problems are tackled early on.
