Three-year-old Emily has had a stable, mild sensorineural hearing loss. However, her most recent audiological evaluation showed a decline of 10–15 dB HL in her hearing thresholds at 1,000, 2,000, and 4,000 Hz. This surprised her parents, as they did not notice any unusual behavior or response that might be associated with her hearing decline. After an extensive medical examination, Emily was diagnosed with progressive hearing loss associated with GJB2 mutations.
Emily's sudden hearing decline is an example of hearing fluctuation—a condition of reduced or improved hearing due to a variety of factors, including middle and outer ear problems, diseases, and noise exposure. One of the most common causes of hearing fluctuation is multiple episodes of otitis media with effusion, which could reduce hearing by at least 30–40 dB (Top Lang Disord. 1990;11:29). Moreover, children with enlarged vestibular aqueduct (EVA) syndrome or a deafness-causing mutation in GJB2 or mitochondrial 12s rRNA genes are also considered to have a high risk of developing unpredictable hearing reduction (Otol Neurotol. 2003;24:625; Arch Otolaryngol Head Neck Surg. 2010;136:81; PLoS ONE. 2011;6:e22314). In some cases, the hearing loss is temporary, particularly with immediate medical treatment.
Hearing fluctuation is especially challenging to ascertain among young hearing-impaired children like Emily, who are unable to precisely express their hearing needs. Undetected hearing fluctuations pose a significant threat to these children as they need sufficient auditory access to speech to develop their oral language skills. As such, close and constant monitoring of these children's hearing is important to readily identify fluctuations and prevent further hearing and language development issues.
CHECK HEARING FREQUENTLY
Observing children's response to speech and their speech intelligibility is the most common method to monitor children's hearing. Caregivers and parents must be aware of the usual indicators of reduced hearing, like when a child says “Huh?” or “What?” more often than before or when a child begins to speak louder. However, caregivers should not solely depend on these indicators; children experiencing subtle changes in hearing may exhibit any of these behaviors. Obtaining frequency-specific information is important to recognizing hearing fluctuation more efficiently. Speech sound tests using frequency-specific phonemes, such as the Ling Six Sound or the Chinese sound test, can be regularly done to examine a child's hearing (Ling. wAG Bell, 2002; JSLHR. 2016;59:349). These tests can be easily administered and integrated into a child's daily routine without any additional audiological equipment (Ling. In: Estabrooks, ed. AG Bell, 2012). Native speech sounds should be used as testing items to maintain frequency specificity and ensure the validity of test results (JSLHR, 2016). Hearing tests should be done about two or three times per week on children with fluctuating or progressive hearing loss.
USE DETECTION TASKS
Because each testing sound represents a specific frequency region, the inaudibility of a sound indicates the lack of auditory access to corresponding frequencies. For example, the sounds /sh/ and /s/ are normally used to check hearing ability in high frequencies. The speech sound tests can be used as a detection or an identification task to assess a child's listening abilities. Compared with identification performance, the detection threshold reflects the softest intensity level at which a listener is aware of a sound; it is therefore more sensitive for monitoring hearing fluctuation. In other words, if a child's detection performance differs from the baseline, caregivers or clinicians should be aware of sudden changes in hearing. For example, a child normally detects the sound /s/ from about 20 feet away but one day shows sound detection from only six feet. This clearly indicates a red flag of hearing drop at a high-frequency level. As such, each ear should be tested independently to avoid confounding binaural effects and identify a single-sided hearing decline over time.
RULE OUT FALSE ALARMS
With the vocal effort held constant and a careful control of distance, the inconsistency of responses normally indicates a change in hearing. However, hearing fluctuations are not always pathological and may be caused by other circumstances. For example, a decline in hearing could be due to a hearing device malfunction. It can also be that the child was bored or not in the mood to cooperate. Parents and caregivers should rule out other possible causes to avoid false alarms (Table). If a significant hearing reduction is observed, a hearing health professional must be contacted for further assessment and treatment.
Ensuring a hearing-impaired child's maximum hearing potential could be challenging. Tools such as speech sound tests and detection tasks help parents and caregivers systematically and regularly test for red flags suggesting hearing reduction. More intensive monitoring should be undertaken in certain situations, such as when a child catches a bad cold or sustains a head trauma (especially for children with EVA syndrome).
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