Abstract
[Editor's note: This Guest Editorial has been adapted with permission from an article entitled “Update on Pediatric Sensorineural Hearing Loss” that appeared in the Fall 2012 issue of Soundings,the Pennsylvania Academy of Otolaryngology-Head and Neck Surgery's newsletter.]
Pediatric hearing loss is a significant problem that still warrants further attention by otolaryngologists. Systematic efforts to identify hearing loss in children are relatively recent. For example, prior to the implementation of the universal newborn hearing screen passed in Pennsylvania in 2001, only 50% of children in that state with hearing loss at birth were identified by risk factors. Considering that about 1 in 300 children is born with a hearing impairment and that 90% of hearing impaired children are born to hearing parents, the importance of the newborn hearing screen is clear. It is also clear that early intervention in these children, particularly by 6 months of age, improves receptive and expressive language skills independent of other variables. It is critical for all otolaryngologists not only to identify children with hearing loss but also to work them up appropriately and refer them for appropriate services.
Approximately 25% of sensorineural hearing loss in children is from an acquired cause. Prematurity is perhaps the most significant perinatal risk factor, but other factors including NICU admission, intubation, low birth weight, low Apgar score, severe hyperbilirubinemia, and sepsis are all associated with sensorineural hearing loss. Infectious causes should also be explored, particularly intrauterine exposure to cytomegalovirus, herpes, rubella, syphilis, toxoplasmosis, and varicella, as well as meningitis in the postnatal period.
Maternal teratogens that are associated with hearing loss include alcohol or drug abuse, methyl mercury, and thalidomide. Maternal use or perinatal exposure to ototoxic medication also can cause hearing loss in a newborn. Most commonly this is aminoglycoside exposure, but loop diuretic and other ototoxic medications can be involved.
About 50% of sensorineural hearing loss is genetic in origin, with two-thirds nonsyndromic and one-third syndromic. Otolaryngologists should remember that not all children with sensorineural hearing loss have a family history of hearing loss at a young age. Most nonsyndromic genetic hearing loss is autosomal recessive, with mutation in the connexin 26 protein being the most common. About 80% of connexin hearing losses will be severe to profound, and they are usually bilateral. Variations in phenotype and laterality have been observed, however, particularly in certain ethnic populations.
Autosomal dominant hearing loss tends to be milder and occur later, often in the second to third decades of life. X-linked recessive hearing loss is only expressed in males, with the hallmark being no male-to-male transmission. Mitochondrial hearing loss is inherited maternally, and is often associated with a syndrome or other muscular disease. The A1555G mitochondrial mutation also predisposes to aminoglycoside ototoxicity, which should be considered when obtaining medical history. There are more than 500 syndromes associated with hearing loss.
As mentioned previously, about 25% of cases of hearing loss are acquired, and therefore a thorough history is all that is necessary for a diagnosis. Physical exam findings, particularly those that may be associated with syndromes, should be identified, such as the white forelock of Waardenburg syndrome.
In children without risk factors, there has been mild controversy about the workup for hearing loss. Historically, a “shotgun” approach was used, involving computed tomography (CT) and magnetic resonance imaging (MRI), an electrocardiogram (EKG), urinalysis, renal ultrasound, complete blood count, chemistries, a thyroid-stimulating hormone test, an erythrocyte sedimentation rate, a TORCH profile, and an FTA-ABS test for syphilis, among others. Recent data suggest, however, that imaging is most useful and that other testing should be reserved for those cases in which history or physical exam warrants it.
CT abnormalities have been reported in about 20 to 40% of cases of hearing loss. Whether to obtain a CT or MRI scan is still not clear, but CT scans are better at showing bony anatomy, are cheaper, and usually do not require sedation. The most common CT finding in pediatric sensorineural hearing loss is an enlarged vestibular aqueduct. MRI allows for better soft tissue/ nerve definition but usually requires sedation in children. However, in cases of meningitis, MRI is superior in assessing early fibrotic ossificans of the labyrinth, which is critical preoperatively in potential cochlear implant candidates.
Genetic workup in terms of syndromes is based on history, family history, and physical exam findings. Connexin testing should be offered in all cases of bilateral hearing loss in children, as it accounts for about 50% of nonsyndromic sensorineural hearing loss. Obviously, if parents have significant concerns and would like genetic counseling, referral to a geneticist can be considered.
About 50% of children with severe to profound hearing loss and about 20% of all children with hearing loss will have an ophthalmologic finding, and therefore strong consideration should be given to an ophthalmology evaluation in all children with hearing loss. Consideration can also be given to obtaining an EKG on all children with sensorineural hearing loss, given the morbidity and mortality associated with the prolonged QT interval in Jervell and Lange-Nielsen syndrome.
All children with hearing loss should be followed with serial hearing tests. Hearing aids should be prescribed early in appropriate cases. All infants with newly diagnosed hearing loss should be referred to Early Intervention for hearing and speech services. Older children can also be referred to Early Intervention until age 3, when they transition to programs within their school districts. Otolaryngologists should be familiar with local Early Intervention units and school programs and be prepared to advocate for the patients when necessary.
Children with hearing loss should avoid noise exposure, and families should be counseled to protect their child's hearing environment and to educate their children about the long-term need to avoid excessive noise exposure. Advice should include use of ear protection when participating in activities such as hunting, concerts, and fireworks. In addition, caution should be used to keep volume levels down with listening devices such as iPods. In patients with enlarged vestibular aqueducts, avoidance of contact sports such as football, wrestling, and soccer is prudent.
Optimizing listening environments is also encouraged, including speaking to the child at closer distances and limiting background noise if possible. In school-age children, preferential seating should be recommended. The use of a personal frequency modulation (FM) system, particularly in school, can also be considered in some cases. Finally, the parents should be counseled about the difficulties with sound localization that can occur with hearing loss, particularly as it relates to safety situations such as crossing the street and riding a bicycle. Children should be reminded to use visual cues in these settings, as auditory cues may be unreliable.
While much of the information in this editorial will not be new to many readers, it is important for all to remember the importance and complexity of pediatric hearing loss and the value of early diagnosis and intervention, and to be vigilant and aggressive in detecting and managing hearing impairment. The adverse consequences of delayed diagnosis, and of allowing progression of a potentially treatable hearing loss because of inadequate workup, may be devastating not only to the child and family, but also to society in general. Pediatric hearing loss should be an active concern for all otolaryngologists, and we should educate our colleagues in Pediatrics and Family Practice, as well as the general public, about its importance.