Session 2: Sensory Development

Transcription

1 Module: Developmentally Appropriate Orientation and Mobility Session 2: Sensory Development Handout K: Hearing Testing and Hearing in Children With Visual Impairments Greeley, J.C., & Gearhardt, C. (1995, September). Hearing testing in children with visual impairments. The National Newspatch. Part 1: Hearing testing Hearing testing in children is almost always challenging. Between birth and 18 months, reflexive reactions to sound are consistent enough that the audiologist can interpret the infant s or toddler s response accurately. At different developmental stages, young children can be expected to become aware of, and alert to various sounds at different intensity levels. When the no stage hits, usually between 1-1/2 and 2-1/2 years, children are cognitively able to override their reflexes, but are often unable to muster enough cooperation to respond well, and testing can be very difficult. Around the age of 3 years, cooperation usually improves, earphones can be introduced (sometimes successfully!), and children can respond more consistently, usually in the context of play. There are several different kinds of hearing tests. Behavioral testing, where a child is asked to cooperate, or at least respond volitionally to a sound stimulus. Stimuli used are usually pure tones consisting of single frequency tones or beeps, and speech including words, sentences, or other speech stimuli. Testing can be done either with headphones for older children, or, for children who are not ready to tolerate headphones, with speakers positioned near the child (this is called sound field testing by audiologists). The softest pure tone or speech that a child can hear (the threshold) is measured. For anyone, but particularly in children younger than four, if there is a discrepancy between the speech measure and the pure tone measure, the speech measure is usually considered more reliable. In behavioral testing, the audiologist often uses visual reinforcement such as a lighted or moving animal to condition the child. The child hears a sound, and responds by looking at the stimulus he expects to light up or move. This is particularly useful for children who do not find the small beep-beep of pure tones to be very interesting. Many visually impaired children find the tones even less interesting than normally sighted children and are less than impressed by visual reinforces, so salient and interesting sounds become even more important stimuli. Because voice and music evoke consistent responses in many children, a variety of different voices (a mother talking, a baby crying), types of music, and toys with realistic sounds are useful EIVI-FPG Child Development Institute Page 1 of 5

2 measuring tools. Responses to these stimuli vary. Children who have developed language skills often respond by naming a sound they hear ( I hear the bird or computer ), while younger children will often smile or reach out when they recognize a familiar sound. Earphones are particularly difficult to use with many visually impaired children, probably because they interfere with a more reliable sensory system, and feel funny as well. One introduction to the test procedure might include holding the child on a (trusted) adult s lap and holding one earphone on one ear, to help him/her understand the task and know what to expect. Although testing with speakers does not always result in an accurate picture of how each ear functions, the child s overall functional hearing with both ears can be assessed with a minimum of difficulty. Tympanometry (or impedance) measures how well the eardrum moves and can determine if there is fluid or another unusual condition present. (Parents of children with ear infections quickly become familiar with tympanometry testing.) It is a quick measurement, performed by inserting a probe into the ear canal and measuring the pressure. It does not require the cooperation of the child, other than sitting still, and usually introduces a momentarily unusual, but not painful sensation. Tympanometry is a reliable measurement of eardrum function, and many pediatricians offices have the equipment to do this testing. It is often used to verify otoscopy (looking at the eardrum and visually monitoring the movement). ABR, or Auditory Brainstem Response. Audiometry is a relatively newer test which requires no cooperation from the child, other than remaining calm. Children older than 23 months who are unable to fall asleep or stay calm are usually sedated. This test involves pasting three or four electrodes on the scalp and ears, and introducing a series of clicks into the ear via earphones. The response of the child s nervous system is measured, and hearing levels can be determined. In older children, this test is done when: a hearing loss is suspected, other methods of testing (behavioral) are consistent with the presence of a hearing loss or are inconclusive, or behavioral testing is difficult due to inconsistent responses from the child. Newborn hearing screening often uses ABR screenings to determine which children hear generally within normal limits. If an infant fails the newborn screening, it does not mean there is a hearing loss; it simply means that further testing is necessary. In that instance, a regular ABR test is done to determine the presence or absence of a hearing loss. Although ABR has limitations, it accurately determines general levels of hearing. EIVI-FPG Child Development Institute Page 2 of 5

3 Part II: Hearing testing in visually impaired children Early Intervention Hearing tests in young visually impaired children require adjustment of the usual testing procedures. In addition to visual impairment, other conditions (e.g., motor difficulties) affect a child s ability to respond consistently to sound, and a child s developmental age may lag behind his/her actual age. Attention needs to be paid to the way a child is able (or unable) to pair auditory and visual stimuli, and how much a child relies on his/her hearing to compensate for lack of visual information. Some visually impaired children will reflexively search for and turn to a sound even when they cannot see the source, and this searching can take different forms. A child may put his head down in a thinking (or listening ) posture, or tilt his head backward to concentrate on the direction of the sound, or may actually turn toward a sound source. A child may be unable to search due to motor difficulties, but may be able to lean or move his entire body toward a sound. Another child may not try to localize at all, and show no obvious response, but will become quiet and his breathing rate may change. All these children will, of course, need additional time to respond to the stimulus. Some children need to touch and explore a noisemaker so it gains significance for them before that noisemaker can be moved out of their reach and used to test hearing. Many of these same children often do not respond well to sounds outside their immediate reach ( If I can t touch it, it isn t there ). For some visually impaired children, sound becomes so important that they are hypersensitive, and cannot help attending to every sound in the environment. Much noise or many different sounds or voices can over stimulate these children (shopping malls, parties, etc.). They might startle easily to loud sounds, and have distinct preferences and dislikes (e.g., the bass or low frequency end of the piano versus the treble or high frequency end). Especially for children who had prolonged postnatal courses in the neonatal intensive care unit (where it was always noisy), all sounds, even loud ones, may be ignored or blocked out. Special care must be taken to make environmental sounds real to them again (e.g., by feeling water running from a faucet, hearing Dad s voice over the telephone after it rings). It is important to understand that there is a difference between actual hearing tests and hearing screenings. Passing a hearing screening does not mean that a child hears normally, particularly if that pass is based upon a caregiver s saying, He hears everything. Children with a high frequency hearing loss, for example, appear to hear everything because they can hear and respond to low frequency sounds, such as the dog barking, door slamming, or someone calling to them. They do not hear the high frequency consonants well, especially s, sh, f, v, th (as in this), and th (as in thing), and will have difficulty understanding speech and eventually learning to talk. Babies who are anoxic (experience a lack of oxygen) at birth are at high risk for this type of hearing loss. Otitis media, or ear infections, are another source of hearing loss. Thick fluid in the middle ear can create as much as a 45/50 db, or moderate hearing loss, which isolates a child from the world. The loss is usually temporary and reverses as the fluid EIVI-FPG Child Development Institute Page 3 of 5

4 disappears, but the hearing loss can fluctuate significantly while the fluid remains. Speech and language learning become difficult for the child who hears inconsistently from day to day. While no child can afford to have this hearing loss, especially during the critical language learning early years, otitis media can represent a very significant obstacle to visually impaired children who rely on their hearing as a major means of contact with the world. Otitis media is most often treated with a 10-day course of antibiotics. In the case of a persistent infection, a different antibiotic is used for a second 10-day course. Several antibiotics may be used for particularly stubborn infections, followed by a prophylactic course of antibiotics to prevent the infection from recurring. Surgical intervention for otitis media involves the placement of small PE (polyethylene) tubes in the eardrum. These tubes allow air to reach the middle ear and Eustachian tube, facilitating more normal function. In recent years, there has been much discussion about whether PE tubes are placed too often, too soon, or unnecessarily. In making the decision to get tubes, both the health of the ears and the healing are considered. Therapists who have worked with young children who get PE tubes can vouch for the effectiveness of this intervention, but it is the parents who are the most enthusiastic about the changes they see in their children. Audiologists often hear I wish I had known (what a difference the tubes would make); I d have done this sooner, He s sleeping through the night now and not cranky anymore, She s talking more now, and more clearly. In view of the benefits, tubes often do not deserve the bum rap they have gotten lately. A parent in doubt about a physician s recommendation to have PE tubes placed owes it to the child to get a second opinion. In the first year that the hearing of infants at the Anchor Center for Blind Children was tested, 80% were found to have minor hearing problems, usually from low-grade chronic otitis media which was not serious enough to cause the child enough visible discomfort to warrant a doctor s visit, but serious enough to disrupt auditory function. For visually impaired children, this represents a major impediment to learning. Although standard hearing testing might not be an option with some children, there are ways to adapt testing to determine the functional hearing of a child, and a variety of adaptations are acceptable. Parents and teachers of visually impaired children can be aware of the different ways their children (students) respond, and pass the information on to the audiologist. An audiologist who has experience working with children, and with differently abled children, recognizes the difficulties and adaptations necessary, and will usually be able to determine the learning strengths and functional hearing of a given child. Several test sessions may be necessary, and a great deal of patience is required on the part of all involved. What a small price to pay to ensure that a visually impaired child has a strong avenue of communication with the world! EIVI-FPG Child Development Institute Page 4 of 5

5 Effects of hearing loss Degree of loss Slight db Mild db Moderate db Moderate/ severe db Severe db Profound 91 db or greater Potential effects Person can hear faint speech within a close range. Person may not experience any appreciable difficulty with communication. Speech is not likely to be affected. May have difficulty hearing faint or distant speech. A child with mild loss may miss up to 10% of speech signal when the speaker is at a distance greater than three feet, or if the environment is noisy. The child is likely to experience some difficulty in communication and education settings. The child understands conversational speech at a distance of 3-5 feet. Amplification may enable listener to hear and discriminate all sounds. Without amplification, 50% to 100% of speech signal may be missed. Speech may be affected unless optimally amplified all sounds. Conversation must be very loud to be heard without amplification. A 55 db loss can mean 100% of the speech signal is missed. The child may have difficulty in settings requiring verbal communication, especially in large groups. Delays in spoken language and reduced speech intelligibility are to be expected without intervention and amplification. If loss is pre-lingual, spoken language and speech may not develop spontaneously, or could be severely delayed unless modifications and interventions are taken. With optimal amplification, should be able to detect all the sounds of speech and identify environmental sounds. Without amplification, the individual is aware of loud voices about one foot from ear and likely to rely on vision for communication. Person is aware of vibrations more than tonal pattern. Many rely on vision rather than hearing as the primary avenue for communication and learning. Speech and oral language will not develop spontaneously without modifications and intervention. Speech intelligibility often greatly reduced and atonal voice quality likely. Residual hearing can benefit from amplification. EIVI-FPG Child Development Institute Page 5 of 5