Current Status of Pediatric Hearing Loss Cases in Oita University Hospital From 2016 to 2019

Abstract

Objective:

The importance and effectiveness of Newborn hearing screening (NHS) have been widely recognized. However, there are a few cases of false-negative NHS results. Hearing loss in children causes various disorders. Therefore, attention should be paid to pediatric hearing loss in clinical otolaryngology. We examined the multiple causes of children referred for detailed hearing loss examination.

Methods:

This retrospective study included 154 patients, 68 males and 86 females, 3 to 12 years old, referred to our outpatient department between January 2016 and December 2019. We reviewed data on reasons for consultation, newborn hearing screening results, and diagnosis.

Results:

Seventy-one patients (46.1%) were identified during the health examinations. Seventy-five patients (48.7%) were referred for hearing loss, and 8 (5.2%) were referred for language delay or dysarthria. Most cases are not diagnosed by newborn hearing screening. There were 33 (21.4%) patients who had no hearing loss, 54 (35.1%) had functional hearing loss, 24 (15.6%) had severe-to-profound unilateral hearing loss, 24 (15.6%) had mild to moderate unilateral hearing loss, and 18 (11.7%) had mild to moderate bilateral hearing loss. Of the 66 patients with substantial hearing loss, 40 (61%) had unknown causes and 26 (39%) had middle or inner ear malformations.

Conclusions:

Appropriate diagnostic imaging is essential in pediatric cases of hearing loss to assess for middle or inner ear malformations. Strategies to address false-negative results in neonatal hearing screening, functional hearing loss, and severe to profound unilateral hearing loss remain important challenges for future clinical practice.

Introduction

Hearing loss in children causes various disorders such as speech development, articulation, emotion, and learning disabilities^{1 -5}; therefore, otolaryngological practice requires caution. Newborn hearing screening (NHS) was introduced in Japan 20 years ago. ⁶ The importance and effectiveness of NHS have been widely recognized. However, there are a few cases of false-negative NHS results. Important issues regarding pediatric hearing loss in children who pass newborn hearing screening include delayed-onset and progressive hearing loss,^7,8 insufficient follow-up, ⁸ and inherent limitations of the screening methods. ⁹ Oita University Hospital is the only one in Oita prefecture capable of conducting detailed audiological examinations, so pediatric hearing loss cases requiring audiological evaluation are referred to us. However, we do not have a clear understanding of the current situation at our facility. We investigated the demographic profile, patient background, results of various otologic examinations, imaging studies, otological diagnoses, and post-diagnosis course of pediatric hearing loss cases referred to our department. The purpose of this study is to clarify the diagnosis and frequency of pediatric hearing loss cases and to identify issues with diagnostic methods and management approaches.

Methods

This retrospective study reviewed the medical records of 154 patients, 68 males and 86 females aged 3 to 12, referred to our outpatient department for hearing loss investigation between January 2016 and December 2019. Our outpatient clinic operates on a strict referral-only basis and covers all pediatric hearing loss cases referred during the study period. The target age group was 3 years because health examinations, including hearing, were conducted on children aged 3 in Japan. Children under 3 years of age were excluded because of assessment limitations. The upper limit was set at 12 years of age, as this was up to primary school age.

The data reviewed included (i) age and sex, (ii) reasons for consultation, (iii) awareness of hearing loss, (iv) NHS results, (v) diagnosis, (vi) auditory ossicle malformations, and (vii) inner ear malformations.

The degree of hearing loss was determined using an audiometric test and summarized using average thresholds of 500, 1000, 2000, and 4000 Hz on pure tone audiometry (PTA). Hearing loss severity was categorized follows: slight impairment (25-39 dB), moderate impairment (40-69 dB), severe impairment (70-89 dB), and profound impairment (⩾90 dB or greater).

Awareness hearing loss was assessed through parent-reported.

Distortion product otoacoustic emissions (DPOAEs) were recorded using an Interacoustics Titan system (Interacoustics A/S, Denmark). Primary tones were presented at levels of L1 = 65 dB SPL and L2 = 55 dB SPL with an f2/f1 ratio of 1.22. DPOAEs at 2f1–f2 were measured at f2 frequencies ranging from 1 to 8 kHz. Measurements were performed in a sound-treated room, and responses were considered present when the signal-to-noise ratio exceeded 6 dB.

Auditory brainstem responses (ABRs) were recorded using a Neuropack S1 system (Nihon Kohden, Tokyo, Japan). Click stimuli of rarefaction polarity were delivered monaurally through headphones at 10 dB intervals from 90 to 30 dB with a click duration of 0.1 ms. Responses were amplified and band-pass filtered from 100 to 3000 Hz. The analysis time window was set to 10 ms, and 1000 sweeps were averaged for each recording. Recordings were obtained in an electrically shielded, sound-attenuated room while the subjects were resting quietly. Hearing was evaluated based on the threshold of wave V, and measurements were confirmed by waveform reproducibility.

Computed tomography (CT) was performed on patients with hearing loss who provided informed consent and did not require sedation. Abnormal findings on CT were defined as cases where structural abnormalities were observed. CT scans were obtained using 3 scanners (Aquilion ONE GENESIS [320-row detector], Aquilion CX [64-row detector], and Aquilion ONE [320-row detector]; all from Canon Medical Systems, Otawara, Japan) with a slice thickness of 0.5 to 1.0 mm.

Cases showing a discrepancy between PTA and objective hearing test findings (those with hearing loss on PTA but within the normal range on DPOAE and ABR) were classified as functional hearing loss. Stenger test, masked audiometry, or psychological evaluation were not used. Cases of functional hearing loss were also examined regarding their course after diagnosis.

Ossicular malformations were evaluated based on Funasaka’s classification. ¹⁰

Inner ear malformations were classified based on the classification by Sennaroglu and Saatci. ¹¹

Results

Age and Sex

Sixty-one (39.6%) patients were aged ⩽6 years, and 93 (60.4%) were aged ⩾7 years, that is, elementary school students. There were 68 (44.2%) males and 86 (55.8%) females; males were more common in those aged <6 years and females were more common in those aged ⩾6 years (Figure 1).

Figure 1.

Age and gender.

Reasons for Consultation

The results were shown in Table 1. Seventy-one of 154 patients (46.1%) were pointed out during the health examinations. Of these 71 patients, 54 patients were identified during the school physical examination. Seventy-five of 154 patients (48.7%) were referred for hearing loss, and 8 (5.2%) were referred for language delay or dysarthria. Two kindergarten patients with hearing loss were referred to our department after visiting other hospitals. (Table 1).

Table 1.

Summary of Reasons for Consultation, Awareness of Hearing Loss and Diagnosis.

Reasons for consultation		Awareness of hearing loss		Diagnosis
		Presence	Absence	Normal hearing	Functional hearing loss	Severe to profound unilateral hearing loss			Mild to moderate unilateral hearing loss			Mild to moderate bilateral hearing loss			Unevaluable
Health examination for children of 3 y of age	3	1	2	3
Health examination for children starting school age	12	2	10	6	4	2	Inner ear malformation	1
							Unknown	1
School physical examination	54	19	35	10	22	8	Deafness following mumps (suspected)	1	8	Auditory ossicle malformation	5	6	Inner ear malformation	1
							Unknown	7		Unknown	3		Unknown	5
Language delay dysarthria	8	4	4	5					1	Inner ear malformation	1	1	Otitis media	1	1	Autism	1
Pointed out in kindergarten	2	1	1	1									1	Unknown	1
Unilateral hearing loss	46	42	4	3	11	14	Auditory neuropathy (suspected)	1	13	Sudden deafness	3	5	Inner ear malformation	1
							Inner ear malformation	1		Auditory ossicle malformation	2		Otitis media	2
							Deafness following mumps (suspected)	1		Otitis media	1		Unknown	2
							Unknown	11		Unknown	7
Bilateral hearing loss	29	24	5	5	17				1	Unknown	1	6	Inner ear malformation	1
													Otitis media	3
													Unknown	2
Total	154	93 (60.4%)	61 (39.6%)	33 (21.4%)	54 (35.1%)	24 (15.6%)			24 (15.6%)			18 (11.7%)			1 (0.6%)

Numbers refer to the number of cases.

Awareness of Hearing Loss

The results were shown in Table 1. The result showed that 93 (60.4%) patients were aware of their hearing loss, and 61 (39.6%) were not. Among the cases identified during the health examination, there were more patients without awareness of hearing loss than those with awareness of hearing loss (Table 1).

Results of NHS

In 1 case, unilateral hearing loss have been identified as refer for 1 ear through NHS and diagnosed through detailed examination. However, in this case, the patient was referred to our department because of hearing loss on the opposite side. Except for this case, none of the patients had been diagnosed with hearing loss by the NHS. Unfortunately, the screening procedures used in our cases were unclear.

Diagnosis

The results were shown in Table 1. PTA was performed on 137 (89.0%) patients. Sixteen patients (10.3%) who could not undergo PTA were diagnosed with either DPOAE or ABR. Conditioned play audiometry was not used. There were 33 (21.4%) patients whose audiograms were within the normal range at the time of consultation, 54 (35.1%) with functional hearing loss, 24 (15.6%) with severe to profound unilateral hearing loss, 24 (15.6%) with mild to moderate unilateral hearing loss, and 18 (12.3%) with mild to moderate bilateral hearing loss (Table 1). Hearing could not be assessed in 1 patient (0.6%) with autism because sedation was ineffective, and an auditory brainstem response (ABR) could not be performed.

CT and MRI were performed in 52 cases where consent was obtained and sedation was not required. CT alone was performed in 43 cases, MRI alone in 5 cases, and both in 4 cases. CT was performed for 47 patients. Detailed information of 47 cases is provided in Table 2. No abnormalities were found in any of cases underwent MRI.

Table 2.

The CT Results.

	Abnormal findings that cause hearing loss
Type of hearing loss	Presence	Absence
Functional hearing loss	0	4
Severe to profound unilateral hearing loss	2	17
Mild to moderate unilateral hearing loss	8	12
Mild to moderate bilateral hearing loss	3	3

Numbers refer to the number of cases.

Functional Hearing Loss

Although the cause of most cases of functional hearing loss is unknown, suspected causes included family (father’s absence, divorce, and sibling rivalry), school (accident, enrollment, bullying, and relationship with the homeroom teacher), character (accumulating stress and learning disability), and living environment (moving to a new location; Figure 2).

Figure 2.

Causes of functional hearing loss. Numbers refer to the number of cases.

Twenty (38%) patients with functional hearing loss were followed at the hospital, 11 (20%) were counseled at other institutions, 11 (20%) were followed at a referral clinic or hospital, and 12 (22%) were not followed at all. Half of the patients who were followed up at our hospital showed improved audiograms (Figure 3).

Figure 3.

Follow-up of functional hearing loss case. Numbers refer to the number of cases.

Severe to Profound Unilateral Hearing Loss

The cause was unknown in 19 of the 24 (79.2%) patients who presented with severe to profound unilateral hearing loss. Two patients (8.3%) had inner ear malformations, 2 (8.3%) had deafness following mumps, and 1 (4.2%) had suspected auditory neuropathy (Table 1, Figure 4).

Figure 4.

The causes of hearing loss. Numbers in the bar graph refer to the number of cases.

Mild to Moderate Unilateral Hearing Loss

The cause was unknown in 12 of the 24 (50.0%) patients with mild to moderate unilateral hearing loss. Seven (29.2%) patients had auditory ossicle malformations and 3 (12.5%) had sudden deafness, 1 had otitis media, and 1 had inner ear malformation (Table 1, Figure 4).

Mild to Moderate Bilateral Hearing Loss

Nine of the 18 (50.0%) cases with mild to moderate bilateral hearing loss had an unknown cause. Six (33.3%) patients had otitis media, and 3 (16.7%) had inner ear malformations (Table 1, Figure 4).

Auditory Ossicle Malformations

Auditory ossicle malformations were observed in 15% of the 47 patients who underwent CT scans (Table 3).

Table 3.

Cases With Auditory Ossicle Malformations.

Age	Sex	Average hearing level		Tympanogram		Stapedial reflex				Pathologic condition
		R	L	R	L	R IPSI	R CONTRA	L IPSI	R CONTRA
8	M	8.8	27.5							Left incudostapedial joint separation
7	F	11.3	43.7	A	Ad	+	+	−	−	Left incudostapedial joint separation
4	M	32.5	72.5	A	B	+	−	−	−	Left malleus and/or incus fixation
7	M	5.0	23.7	B	B	−	−	−	−	Left incudostapedial joint separation
6	F	48.8	36.3	Ad	A	−	−	+	+	Right incudostapedial joint separation
6	F	22.5	46.2	A	Ad	+	−	−	−	Left incudostapedial joint separation
8	F	32.5	8.8	Ad	A	−	+	+	+	Right incudostapedial joint separation

Inner Ear Malformations

Inner ear malformations were observed in 6 patients (Table 4). Three cases had unilateral deafness, and 3 cases had bilateral hearing loss. This represented 13% of the 47 patients who underwent CT.

Table 4.

Cases With Inner Ear Malformations.

Age	Sex	Average hearing level		DPOAE		ABR		Diagnosis	Pathologic condition	Note
		R	L	R	L	R	L
6	M	42.5	50.0	−	−	60	60	Bilateral sensorineural hearing loss	Bilateral dilated vestible bilaterala hypoplastic semicircular canal
11	M	41.2	115.0			30	90<	Right functional hearing loss left severe sensorineural hearing loss	Bilateral dilated vestible bilateral absent semicircular canal left stenosis of bony cochlear nerve canal	Developmental disorder left middle ear malformation The left ear was refer for newborn hearing screening.
7	M	45.0	43.7	+	+			Bilateral sensorineural hearing loss	Bilateral hypoplastic semicircular canal left dilated vestible
5	F	115.0	16.3	−	+	90<	30	Right severe sensorineural hearing loss	Right stenosis of bony cochlear nerve canal
6	M	103.8	8.8	±	+	90<	40	Right severe sensorineural hearing loss	Right enlarged vestibular aqueduct
6	M	42.5	50.0			80	30	Right severe sensorineural hearing loss	Bilaterala hypoplastic semicircular canal bilaterala hypoplastic vestible	Down syndrome

Discussion

Our basic policy for medical examination of pediatric hearing loss is as follows: PTA, tympanometry, stapes reflex, and distortion product otoacoustic emission at the initial visit. If hearing was normal, it was only observed at this point. An ABR test was performed to see if functional hearing loss was suspected or if hearing loss was present. Counseling is recommended when a patient is diagnosed with functional hearing loss. If a patient had hearing loss, hearing aids and CT were considered. If sedation was required for the CT, we waited until the patient was sufficiently old to undergo the procedure without sedation.

There were 33 (21.4%) patients whose audiograms were within the normal range at the time of consultation. In preschool and school-aged children, abnormal hearing test results obtained in primary care settings are not infrequently followed by normal findings at secondary or tertiary referral centers. Although few studies have directly examined this specific clinical pathway, existing literature^{12 -14} on childhood hearing test provides several plausible explanations. First, transient middle ear conditions, such as otitis media with effusion or temporary Eustachian tube dysfunction, are highly prevalent in children aged 3 years and older and may cause temporary conductive hearing loss at the time of test, which subsequently resolves before diagnostic evaluation. Second, hearing screening in primary care settings is often conducted in non–sound-treated environments, where ambient noise and equipment limitations can increase false-positive referral rates. Third, behavioral hearing screening methods, including pure-tone audiometry, are highly dependent on the child’s attention, comprehension, and cooperation; inconsistent responses are particularly common in younger preschool children and may mimic hearing impairment. Finally, differences in examiner experience and screening protocols between primary care and specialized audiology centers may further contribute to discrepancies between screening and diagnostic results. These factors collectively underscore the importance of cautious interpretation of abnormal screening outcomes in young children and highlight the value of confirmatory testing in specialized settings.

After excluding 1 patient whose hearing ability could not be evaluated, all of the 66 patients with hearing loss passed the NHS. False-negative NHS results and late-onset hearing loss should be considered in patients with hearing loss.

Differences in testing techniques are believed to cause false negative results. The combination of OAE and AABR testing significantly reduces the referral rate and should be considered a standard protocol for the NHS. ¹⁵ Regarding hearing loss due to congenital cytomegalovirus (cCMV) infection in Japan, it has also been reported that the bilateral pass rate of AABR is 22.2% in the NHS, whereas that of OAE is 50%. ¹⁶

The Japanese Society of Otorhinolaryngology Head and Neck Surgery has created an NHS manual for pediatric and obstetric departments, and examinations are generally conducted according to this manual. The equipment used is either OAE or AABR, with the assessment based on the results from each specific device. Cases where the NHS assessment in pediatrics or obstetrics indicates a “refer” result are scheduled for detailed examinations, such as ABR, at specialized institutions designated by the society in each prefecture.

NHS equipment varied by facility in our prefecture. Unfortunately, details were unclear regarding NHS equipment in this study. We believe it is necessary to investigate the status of screening procedures in our region for future study.

The risk factors for delayed hearing loss are shown in Table 5. ¹⁷ Among these, 2 suspected deafness following mumps cases and 1 suspected case of auditory neuropathy were observed as possible cases in this study. However, in most cases, the underlying causes remain unknown. The problem was thought to be delayed hearing loss due to the cCMV infection. Minami et al ¹⁶ reported that approximately 8% of individuals with unilateral or bilateral hearing loss of unknown etiology are positive for cCMV infection. cCMV-related hearing loss is highly heterogeneous and there is a high risk of missing this condition from the NHS. Although immediate cCMV screening is recommended for infants who do not pass the NHS, targeted cCMV screening does not detect infections that cause late-onset hearing loss. In addition, valganciclovir has been reported to be effective against congenital cytomegalovirus infection, ¹⁸ and it became available in Japan through health insurance. We have established a cooperative system with the Department of Pediatrics for the early detection of cytomegalovirus infection at our facility.

Table 5.

Risk Factors for Early Childhood Hearing Loss (Modified From Reference ¹⁷ ).

1	Family history of early, progressive or delayed onset permanent childhood hearing loss
2	Neonatal intensive care of more than 5 days
3	Hyperbilirubinemia with exchange transfusion regardless of the length of stay
4	Amynoglicoside administration for more than 5 days
5	Asphyxia or Hypoxic Ischemic encephalopathy
6	Extracorporeal membrane oxygenation (ECMO)
7	In utero infections, such as herpes, rubella, syphilis, and toxoplasmosis
	In utero infections with cytomegalovirus (CMV)
	Mother + Zika and infant with no laboratory evidence & no clinical findings
	Mother + Zika and infant with laboratory evidence of Zika + clinical findings
	Mother + Zika and infant with laboratory evidence of Zika – clinical findings
8	Certain birth conditions or findings: Craniofacial malformations including microtia/atresia, ear dysplasia, oral facial clefting, white forelock, and microphthalmia; Congenital microcephaly, congenital or acquired hydrocephalus; Temporal bone abnormalities
9	Over 400 syndromes have been identified with atypical hearing thresholds
10	Culture-positive infections associated with sensorineural hearing loss, including confirmed bacterial and viral (especially herpes viruses and varicella) meningitis or encephalitis
11	Events associated with hearing loss: Significant head trauma, especially basal skull/temporal bone fracture; Chemotherapy
12	Caregiver concern regarding hearing, speech, language, developmental delay and or developmental regression

Family history is a risk factor for delayed-onset hearing loss, ¹⁷ and hereditary hearing loss should be considered. Since 2012, the genetic diagnosis of hearing loss has become possible in Japan through health insurance facilities that meet these requirements. At our facility, we could not conduct tests during the survey period of this study; however, this is possible in 2025. However, our facility does not have sufficient data regarding hereditary hearing loss. A recent survey of 10 000 Japanese patients with late-onset hearing loss found that a significant proportion also had genetic components. Approximately 30% of the young-onset group (aged 6-39) identified the gene responsible for their hearing loss. ¹⁹ The inability to perform genetic testing during this study period is a limitation of this research.

In this study, functional hearing loss was the most common diagnosis observed. Many cases showed no subjective awareness of hearing loss, and the psychogenic cause remained unclear. Weisleder and Weisleder ²⁰ reviewed the diagnosis, differential diagnosis, and management of functional hearing disorder in children and highlighted the importance of identifying psychosocial stressors and recommends cognitive behavioral therapy (CBT) as a core treatment strategy. Yamazaki et al ²¹ analyzed developmental profiles, psychosocial backgrounds, and intervention outcomes in children with functional hearing loss. They demonstrated the association between functional hearing loss and developmental imbalance or psychological stress. They emphasized the role of multidisciplinary collaboration, including otolaryngologists, psychologists, and pediatricians. Schmidt et al ²² described the clinical and audiological features of nonorganic hearing loss in children and highlighted the importance of non-confrontational counseling. Although we recommend counseling when explaining the hearing test results, many patients do not want to receive counseling, partially because they are unaware of their hearing loss. Otolaryngologists should consider collaborating with child psychiatrists and school counselors, but this remains difficult to achieve given the current state of healthcare in our prefecture. There were not enough pediatric psychiatrists and clinical psychologists to handle the cases. It is ideal for otolaryngologists to acquire psychosomatic medical techniques for treatment, but in reality, this is considered difficult. We considered the extent to which otolaryngologists should intervene is a future issue.

Unilateral hearing loss was observed in 48 patients, half with severe to profound hearing loss. Children with unilateral hearing loss are said to exhibit delayed language development ²³ and lower academic performance. ²⁴ Cochlear implant (CI) surgery in children with severe congenital unilateral hearing loss has been reported to improve auditory quality and spatial cognition significantly. ²⁵ It has also been noted that the early placement of the cochlear implants can quickly restore bilateral auditory input to the auditory cortex, which is necessary for binaural hearing. ²⁶ Many of our patients with severe to profound unilateral hearing loss had unknown etiologies and may have been congenital. In Japan, cochlear implants have not yet been indicated for severe to profound unilateral hearing loss; however, there is hope for the future.

Inner ear malformations account for 10% of cases of hearing loss, which is not a large number, but a number that cannot be ignored. We consider CT is essential for diagnosing hearing loss in pediatric patients. No severe bilateral hearing loss, cochlear aplasia, or cochlear hypoplasia were observed. These cases were considered to have been identified as refer through NHS and diagnosed through detailed examination. Another report suggested that hearing loss on the affected side was progressive in patients with cochlear neural tube stenosis. ²⁷ We believe that mild inner ear malformations may progress to hearing loss even if newborn screening is negative.

Finally, this study has several limitations as follows: Unclear detailed NHS protocol, lack of exclusion criteria, small sample sizes in some subgroups, and only small number of cases underwent MRI.

Conclusions

Half of the children in this study did not exhibit substantial hearing loss. Cases of hearing loss were considered false-negatives in the neonatal hearing screening or acquired hearing loss. We thought it is important to improve the accuracy of the NHS and diagnostic accuracy of acquired hearing loss. The frequencies of middle and inner ear malformations were significant, suggesting the importance of diagnostic imaging in pediatric cases of hearing loss. Coping methods for functional hearing loss and severe to profound unilateral hearing loss are considered future issues.