Especially if you have no family history of deafness, one of the first questions in your mind when your child is diagnosed with hearing loss might be ‘Why?’ Around 40-50% of the time, children’s hearing loss is unexplained, but in the other 40-50% of cases, a cause can be pinpointed. Below are some of the areas that will be investigated when looking into children’s hearing loss causes, as well as some tests that may be taken to help give you and your family answers.
When you see the doctor to talk through possible causes for your child’s hearing loss, they will ask you a series of questions. These are likely to begin with information on your child’s medical history including medications taken during pregnancy, and the mother’s health before, during and after the birth. They will also ask about any history of deafness on both sides of the family. They may ask if your child has had meningitis, measles, mumps or another other illnesses or if they have taken any prescribed medication. Especially for older children and toddlers, questions may be asked around speech and development milestones, exposure to loud noises, any instances of head injury, infection, sight or balance problems.
During a physical examination when looking into children’s hearing loss, the doctor will look and take measurements of your child’s head and face area. They will also check the neck, skin, arms, legs, chest, tummy, eyes, mouth, palate and ears for any signs that may help indicate a reason for deafness, including any syndromes that your child may have.
Blood tests will check infections and viruses, including CMV (cytomegalovirus) which is very common in the general population. This virus can affect a baby if the mother has it whilst pregnant, and the virus is the cause of hearing loss in 10-20% of deaf children in the UK. Deafness linked to CMV can get worse over time so especially in young babies, treatment can prevent further hearing loss. Blood tests can also test for other infections such as German measles, toxoplasma and syphilis.
Blood tests can also be used to test genetics but it’s important to know that not all ‘deafness genes’ are yet known. Around 50% of permanent hearing loss in children has a genetic cause, and in 30% of these cases, the gene is also linked to a syndrome. Finding out if children’s hearing loss causes are genetic can be important in establishing how the deafness should be treated, as for some forms of genetic deafness, certain medications can contribute to further hearing loss.
Imaging may be requested if your child’s deafness is changing over time, or if assessment to be fitted with a cochlear implant is required. Imaging can also be used to rule out certain syndromes that may have caused your child’s hearing loss and will also be carried out if your child has had meningitis. Sometimes other hospital tests can also be ordered to investigate aetiology of children’s hearing loss.
Your doctor may wish to carry out imaging in the form of an MRI scan to take a look at the formation and development of your child’s ears, including taking a look at the ossicles and cochlear. An MRI uses radio waves and magnets and there are no known side effects. Your child will need to be still for an MRI. If they are younger than three months, the test may be done whilst they are sleeping but for older children who are unable to keep still, they will normally be given a light sedative or short general anaesthetic.
Alternatively, a CT scan may be requested, which involves exposure to X-ray radiation, though levels are kept as low as possible to prevent damage to cells. The earlier your child is exposed to radiation, the greater the risk, but it is generally accepted that with one or few scans, the risk is minimal. Much like an MRI, children under three months can sleep during imaging, but older children who can’t remain still will likely be given a light sedative or short general aesthetic.
An ultrasound scan of the kidneys may be ordered by your doctor to rule out any rare syndromes that are suspected or if there is a history of kidney problems within your family. There are no health risks in taking an ultrasound scan.
There is a rare syndrome that links profound hearing loss to a heart problem, which can be treated. This syndrome is often familial so if there are suggestions it is present in your family’s medical history, an electrocardiography may be ordered by your doctor.
Around 40% of children with hearing loss also have eye problems, but ophthalmology (eye tests) can also diagnose a syndrome that may be related to your child’s hearing loss. Eye tests are really important for deaf children because they will rely on their eyesight even more than their peers.