By Dr. BPS Tyagi In this article, the term hearing loss, used by itself, denotes any or all levels of severity of hearing difficulty. These levels of hearing impairment comprise mild HL (26-40 decibel hearing level, dB), moderate HL (41-60 dB), severe HL (61-80 dB), and profound HL (81 dB or greater)1. Hearing loss is the most frequent sensory deficit in human populations, affecting more than 255 million people2,3 in the world (2002). Consequences of hearing impairment include inability to interpret speech sounds, often producing a reduced ability to communicate, delay in language acquisition, economic and educational disadvantage, social isolation and stigmatization2.
Most congenital and childhood onset hearing loss is included as sequel to various disease and injury causes already included in the Global Burden of Disease Study. Examples include otitis media, meningitis, rubella, congenital anomalies and non-syndromal inherited hearing loss2.
Those 192 million people with adult-onset loss (age 20 years and above) and 63 million people with childhood-onset loss make up almost 4.1 percent of the world’s population and just over 40 percent of all people globally with hearing loss of any severity. Numbers with childhood-onset hearing loss by cause have so far not been estimated separately but are included among sequel of other diseases (for example, infectious diseases such as meningitis, otitis media, congenital conditions).
Causes and Characteristics
Hearing loss is grouped according to International Classification of Diseases and Related Health Problems, 10th revision, version for 2003 (ICD-10) into conductive and Sensorineural loss and other hearing loss, ICD-10 codes 90-91(WHO 2003).
Chronic otitis media (COM) includes chronic suppurative otitis media and otitis media with effusion. These forms of otitis media, together with some other middle ear diseases, such as perforation of the tympanic membrane, cholesteatoma, and otosclerosis, are the major causes of conductive hearing loss1.
Conductive hearing loss is caused by anything that interferes with the transmission of sound from the outer to the inner ear. Below are some possible causes of conductive hearing loss.
1. Middle ear infections (otitis media).
2. Collection of fluid in the middle ear (“glue ear” in children).
3. Blockage of the outer ear, most commonly by wax.
4. Otosclerosis.
5. Damage to the ossicles.
Sensorineural hearing loss is due to damage to the pathway that sound impulses take from the hair cells of the inner ear to the auditory nerve and the brain. Below are some possible causes.
1. Age-related hearing loss (presbyacusis).
2. Acoustic trauma (injury caused by loud noise) can damage hair cells.
3. Meningitis can lead to loss of hair cells or other damage to the auditory nerve.
4. Meniere’s disease.
5. Acoustic neuroma. This is a benign tumor affecting the auditory nerve.
Deafness in children
If a pregnant woman gets rubella, the baby is at risk of being born with profound deafness (among other possible birth abnormalities). This is one reason why vaccination against rubella, available in the UK as the MMR (measles, mumps and rubella) vaccine, is so important. Cytomegalovirus is a common and relatively harmless virus in healthy adults, but if a woman gets exposed to it for the first time while pregnant, it can cause significant hearing loss in the unborn child.
Statistics Data Hearing Loss
Total world population at the end of 2008 is 6.75 billion. There is 6-8% deaf population suffering from Moderate to Severe Hearing loss. According to WHO, There are 255 million (4.25%) deaf people out of total 6 billion (Census, IDB) world population. There are approx. 500 million (AHAA) deaf people round the world. By the year 2015 the figure is estimated to be 700 million (Hear-it) (Figure1). (Source: WHO & Hear-it)
(Figure-1: Percentage of Deaf People Worldwide)
More than 50% deaf people are in Asia region. The elderly were more likely than any other age group to have hearing problems. Persons 50 years and older are eight times more likely to have hearing impairment than persons ages 16-35 (Figure-2, Figure-3).
(Figure-2, Worldwide Deafness, Source:
www.wrongdiagnosis.com census (IDB))
(Figure-3, Source: RNID, Annual Survey Repot, 2005) The prevalence of hearing loss differs according to gender. The overall prevalence is 10.5 percent for males and 6.8 percent for females. While males at all ages are more likely than females to be deaf or hard-of-hearing, the gap widens after age 18 (Figure-4, (Source: National Academy of Aging Society).
Of the estimated 500 million deaf and hard-of-hearing people, 23.4% report that their loss is due to some sort of noise.
1. Otosclerosis.
2. Damage to the ossicles.
Sensorineural hearing loss is due to damage to the pathway that sound impulses take from the hair cells of the inner ear to the auditory nerve and the brain. Below are some possible causes.
1. Age-related hearing loss (presbyacusis).
2. Acoustic trauma (injury caused by loud noise) can damage hair cells.
3. Meningitis can lead to loss of hair cells or other damage to the auditory nerve.
4. Meniere’s disease.
5. Acoustic neuroma. This is a benign tumor affecting the auditory nerve.
Deafness in children
If a pregnant woman gets rubella, the baby is at risk of being born with profound deafness (among other possible birth abnormalities). This is one reason why vaccination against rubella, available in the UK as the MMR (measles, mumps and rubella) vaccine, is so important. Cytomegalovirus is a common and relatively harmless virus in healthy adults, but if a woman gets exposed to it for the first time while pregnant, it can cause significant hearing loss in the unborn child.
Statistics Data Hearing Loss
Total world population at the end of 2008 is 6.75 billion. There is 6-8% deaf population suffering from Moderate to Severe Hearing loss. According to WHO, There are 255 million (4.25%) deaf people out of total 6 billion (Census, IDB) world population. There are approx. 500 million (AHAA) deaf people round the world. By the year 2015 the figure is estimated to be 700 million
(Hear-it) (Figure1).
(Source: WHO & Hear-it) % report that their loss is due to some sort of noise.
Another 28% report that their loss is due to age, while 12.2% report that it is due to infection or injury. Only 4.4% report the presence of hearing loss at birth (Figure-5). (Figure-4: Percentage of Deaf in Gender, Age wise)
(Figure-5, Causes of Hearing Loss, Source: National Centre for Health Statistics)
Conclusion
Hearing loss and deafness are serious disabilities that can impose a heavy social and economic burden on individuals, families, communities and countries. Children with hearing impairment often experience delayed development of speech, language and cognitive skills, which may result in slow learning and difficulty progressing in school. In adults, hearing impairment and deafness often make it difficult to obtain, perform, and keep employment. Its big challenge to our society is to help and support the deaf people who are unable to afford and are uncapable to take of own health.
In India, there is around 6.0% incidence of hearing loss, out of which approximately 50% suffer from conductive hearing loss. The universal screening t is a long way, even to the high-risk group, which is due to asphyxias, premature birth, hyperbilirubinemia, low birth weight, and others. Facility of brainstem evoked response audiometry (BERA) is scarcely available. Certainly, auditory BERA tells us about the hearing status of a child on a pass/fail basis, and technically, automated BERA is a simple and reliable screening test, but in a country that is still struggling to spread its wings in controlling deafness, the cost of equipment will definitely be a deterrent to its provision. Auditory steady state response (ASSR) or oto-acoustic emission (OAE) cannot be thought of for routine testing in India. In BERA, in the initial phase below the age of 2 years in all cases, bone conduction (click and tone pip) should be used to fully evaluate the hearing status of the child.
For terminology purpose and to properly divide subgroups, first 4 weeks’ (28 days) baby is considered as neonate, up to the age of 3 years is considered as infant, from 3 years to 5 years is considered as preschool, and up to 16 years is considered as school-age child. While assessing the hearing acuity and overall physical and mental development, one has to keep in mind the gestational age, which is the time period between conception and birth. Hence, in premature babies, delayed response is expected. As the baby grows his responsiveness to sound increases and gets mature to adult level at the age of 10 years.
In behavioral observation audiometry (BOA), we assess the baby’s response to different frequency intensity and duration of sounds presented. While performing BOA, we have to keep in mind [1] that the individual ear cannot be tested. [2] The judgment of the audiologist may be biased [3] on repeated testing or the baby may be habituated or exhausted [4] The responsiveness varies with the age for the same intensity. Hence, a chart must be made displaying the guidelines of the test and the response expected.
Although the newborn baby responds to 70 db noise by eye blink, eye widening or startle, and between 6 weeks and 16 weeks by arousal, eye blink or eye shift, BOA is more useful between the age of 4 months and 3 years. Above the age of 4 months, baby responds to sound stimuli above 50 db hearing loss (HL) generated by a toy or in free field audiometry. This is the age where BOA can be more useful in our Indian scenario than physiological testing by evoked potential (EP) (BERA).
The infant is able to localize the sound of 50 db at horizontal level between 4 and 7 months. The 10 and 15-month-old baby can localize the sound by downward and upward eye or head movement, respectively. The only caution to be taken is that the baby mimics for every action; hence, family member should not be present and attendant has to be trained not to respond or point during the test. [5]
The child response is enhanced at this age if the toy is lit up or moves with the sound. Again, the duration of the sound is important with the maturation; shorter the duration better is the response. During the test, the child is seated on a clean carpet/floor. There should be a collection of different colorful toys, but out of reach and out of sight of baby. As per the requirement, toy should be used and examinee must keep in mind the comfort level of the baby along with exhaustion and habituation. Usually three out of four tests are suggestive of a positive test. A break of 10 minutes increases the total number of positive responses at the age of 1 year.
The physiological test EP (BERA) is difficult to perform because at times babies do not cooperate and require sedation. The child may be having a conductive hearing loss, which should be assessed by bone conduction (both click as well as tone pip) to assess the high frequency and low frequency, respectively.
I conclude that behavioral enforcement audiometry screening should be a part of the training program of all paramedical workers, specifically auxiliary nurse midwife and American Speech and Hearing Association (ASHA). This is a simple test that can easily be mastered with negligible equipment. In all suspected cases apart from air conduction BERA, bone conduction BERA and tympanometry with acoustic reflex should be performed. Every parent must be made aware about the residual hearing and development of speech with an early use of hearing aid. Signboard display should be placed in every hospital or public place to make the parents aware of early deafness.
A multi-cluster study (survey) was carried out by department of ENT KG Medical University, Lucknow from July 2003 to August 2004 in rural and urban population of Lucknow district to estimate prevalence and causes of hearing impairment in the community. Data included audiological profile and basic ear examination that was analysed through EARFORM software program of WHO. Overall hearing impairment was seen in 15.14% of rural as opposed to 5.9% of urban population. A higher prevalence of disabling hearing impairment (DHI) in elderly and deafness in 0-10 years age group was seen. The prevalence of sensorineural deafness necessitating hearing aids was 20% in rural and 50% in urban areas respectively. The presence of DHI was seen in 1/2 urban subjects and 1/3rd of rural counterparts. The incidence of cerumen / debris was very common in both types of population and the need of surgery was much more amongst rural subjects indicating more advanced / dangerous ear disease.
To prevent congenital deafness due to premature birth, birth asphyxia, and low birth weight and infentile pneumonia, adequate supplemental of vitamin D in all pregnant woman should be considered
The Deafening Silence…in India
There are three million deaf children in India
25000 children, on an average, are born deaf each year
Only one in ten deaf children goes to school in India and 90% of deaf children in
school, live in urban settlements
50% of deaf children in school drop out at the age of 13A highly complex system requiring extensive research, it is developed only by few nations’
“The Defence Research and Development Organisation [DRDO] has developed an indigenous and affordable cochlear implant which will be available for clinical trials within four months,” said former President A.P.J. Abdul Kalam here on Saturday.
He was speaking at the inauguration of a workshop on ‘Transcanal Technique for Cochlear Implants’ at Dr. B. L. Kapur Memorial Super Speciality Hospital.
FINAL LABORATORY EVALUATION
“Cochlear implant is a highly complex system requiring extensive research. Owing to this, the implant could only be developed by few countries. In India, the Naval Science and Technological Laboratory [NSTL] at Visakhapatnam, which is a unit of DRDO, has taken the lead and developed this cochlear implant which is undergoing final laboratory evaluation,” said Dr. Kalam.
APPRECIATION FROM KALAM
He also appreciated the work being done by other centres and noted that after multicentre trials at five centres across the country, the indigenous cochlear implant will go into production.
The former President also urged volunteer cochlear implant specialist doctors to come forward to take on the societal mission of implanting indigenously developed system.
The cochlear implant is a surgically implanted electronic device that provides a sense of sound to a person who is profoundly deaf or severely hard of hearing due to loss of sensory hair cells in their cochlea. In India, there are nearly a million people who need cochlear implants. Every year, about 9,000 to 10,000 children are born deaf.
Unfortunately, the imported cochlear implant is very expensive and priced at Rs. 7 lakh to Rs. 10 lakh, which only the affluent can afford.