Download Hearing Loss 2/17/11 Continuity Lecture

Hearing Loss
Mary Beth Palomaki, MD
February 17, 2011
Outline
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Review anatomy and physiology of hearing
Etiology of hearing loss
Hearing screening
Evaluation of hearing loss
Treatment of hearing impairment
Anatomy of the Ear
Hearing Loss
• Conductive
– Obstruction of sound to inner ear
• Sensorineural
– Problem in inner ear, cochlea, auditory nerve
• Mixed (both conductive and sensorineural)
• Central
– Problem in auditory centers in brain
Causes of Congenital Conductive
Hearing Loss
• Microtia
– Absence or malformation of auricle
• External ear canal atresia/stenosis
– Most often unilateral
– Usually with other craniofacial abnormalities
• Treacher-Collins sndrome
• Robin sequence
• Crouzon syndrome
• Tympanic membrane abnormality
• Ossicular malformation
– Most common is stapes malformation/atresia
– Osteogenesis Imperfecta
Causes of Acquired Conductive
Hearing Loss
• Otitis Externa
– Bacteria, fungi
• Otitis media with effusion
– Fluid obstructs TM movement
– Effusion persists after therapy
• Asymptomatic effusion is present in 40% of patients 1 month post
treatment
• Fluid present in 10% of patients 3 months post treatment
– Hearing loss is 25dB and persists until fluid disappears
Causes of Acquired Conductive
Hearing Loss
• Foreign body
– cerumen
• Cholesteatoma
– Benign growth made of cells and keratin
– As it enlarges, it compresses ossicles, and occludes
external auditory canal
• Trauma
– Temporal bone fractures
– TM perforation
• Otosclerosis
– Overgrowth of bone (near stapes usually)
Causes of Congenital Sensorineural
Hearing Loss
• Prenatal infections
– CMV infection
• Leading cause of sensorineural hearing loss
• Usually progressive/delayed onset
– Toxoplasmosis
• Delayed hearing loss
• Can be prevented by treating with pyrimethamine and
sulfonamide
– Rubella
• Usually bilateral
– Syphilis
• Hearing loss usually occurs around 2 years of age
• Can be prevented by treatment of disease before 3 months of age
Causes of Congenital Sensorineural Hearing Loss
• Genetic Abnormalities
– Autosomal Recessive (80% of genetic causes)
• Syndromic: Alport syndrome, Usher syndrome, Pendred syndrome,
Jervell-Lange-Nielsen syndrome, Albinism, Hurler syndrome
• Nonsyndromic: >30 loci identified; most common on connexin 26
gene on chromosome 13
– Autosomal Dominant (20% of genetic causes)
• Syndromic: Waardenburg syndrome, neurofibromatosis I and II,
branchio-oto-renal syndrome, Jervell-Lange-Nielsen syndrome
• Nonsyndromic: immediate onset or delayed onset; 2 genes
identified for delayed onset
– Potassium channel in outer hair cells
– Transcription factor
– X-linked
• Hunter syndrome, Alport syndrome, x-linked congenital hearing
loss
Causes of Congenital Sensorineural
Hearing Loss
• Anatomic abnormalities
– Michel: complete lack of inner ear
– Mondini: partial development and malformation inner ear
– Scheibe: membranous cochleosaccular degeneration of
the inner ear
– Alexander: malformation of the cochlear membranous
system
• Prenatal exposure to ototoxic drugs
Causes of Acquired Sensorineural
Hearing Loss
• Prematurity
– Hypoxia, acidosis, incubator noise
• Hyperbilirubinemia
– Bilirubin toxic to cochlear nuclei and central auditory
pathways
• Ototoxic drugs
– Aminoglycosides:
gentamycin>tobramycin>amikacin>neomycin
– Chemotherapy: cisplatin, 5-FU, bleomycin, nitrogen
mustard
– Salicylates, quinines (reversible)
Causes of Acquired Sensorineural
Hearing Loss
• Infection
– Bacterial meningitis
• Trauma
– Blunt or penetrating trauma to the temporal bone
• Radiation to head and neck
• Tumor: acoustic neuroma
• Neurodegenerative/demyelinating disorders
Causes of Acquired Sensorineural
Hearing Loss: Noise Exposure
• Noise causes direct damage to cochlear
structures
• Noise causes over-stimulation of cochlear
structures
– increased metabolic demand causes increased
nitric oxide release--toxic to hair cells
– Increased metabolic demand causes generation of
free radicals
Degrees of Hearing
• Normal: 0-15 dB: detects all speech
• Minimal: 16-25 dB: misses up to 10% speech, may
respond inappropriately, social interaction affected
• Mild: 26-40 dB: may miss up to 50% of speech
• Moderate: 41-55 dB: misses 50-100% of speech,
speech quality poor, limited vocabulary
• Severe: 56-90 dB: 100% normal speech volume lost,
delayed speech, social isolation
• Profound: 90+ dB: sound vibrations felt rather than
heard, need visual cues for communication
Evaluation of Hearing Loss
• History
• Physical exam
• Newborn screening
– Auditory Brainstem Response
– Otoacoustic Emissions testing
• In office screening
– Rinne, Weber tests
– Pure tone audiometry
• Formal audiologic evaluation
– Tympanometry
– Behavioral audiometry
– Speech audiometry
– Imaging
History: Risk Factors for Hearing
Loss
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Neonate:
– Family History
– In utero infections
– Birth weight <1500g
– Apgar score <3 at 5 minutes, <6 at 10 minutes
– Mechanical ventilation x 10 days or more
– hyperbilirubinemia
After 28 days of age:
– Parental concern
– Persistent otitis media > 3 months
– Head trauma
– Bacterial meningitis
– Demyelinating disorders
– Syndromes
Gifford, KA et al. Hearing Loss in Children. Peds in Review 2009;30: 207-215.
Universal Newborn Hearing Screening
• Started in 1990’s due to availability of
screening tools
• United States Preventative Services Task Force
recommended universal newborn hearing
screening in 2008
• Universal screening improves language
outcomes
USPSTF Recommendations
• All newborns should be screened before 1
month of age
• If the newborn fails screening, the newborn
should have audiologic assessment by 3
months of age
• Intervention should be given to families by 6
months of age for hearing impaired children
US Preventive Services Task Force. Universal screening for hearing loss in newborns:
US Preventive Services Task Force recommendation statement. Pediatrics 2008
Jul;122(1):143-8
Newborn Hearing Screening
• Auditory Brain Stem Response
– Screening test
– Click stimulus near ear
– Electrodes on forehead, nape of neck, mastoid
– Measurement of action potentials from 8th cranial
nerve
– Can detect conductive and sensorineural hearing
loss
– Duration: 4-15 min
– Is appropriate for infants up to 9 months
Newborn Hearing Screening
• Otoacoustic emissions
– Screening test
– A sound is made by the baby’s ear
– Cochlear hair cells generate sound waves (otoacoustic
emission) in response to the sound
– A tiny microphone by the baby’s ear detects the
otoacoustic emissions
– Duration: 5-8 minutes
– Vernix should be cleaned out of ear canal prior to
testing
– Babies at risk for developing sensorineural hearing
loss need to have ABR screening
– Appropriate for all ages
Child Hearing Screening
• No recommendations for screening after
newborn screen up to age 4
– Unless risk factors present
• Recommended age for screening: 4,5,6,8,10
yrs
• No screening in NYC schools
NY City School Hearing Screening
Discontinued in Fall 2009
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“The Office of School Health has discontinued hearing screening in
elementary schools. This decision follows the recommendation of The
United States Preventive Services Task Force, the group charged by the
federal government with making recommendations on screening and
preventive health services.
The reasons behind this recommendation are as follows:
– 1) There are no high quality research trials which demonstrate that hearing
screening in this age group leads to better functional or educational outcomes
– 2) The vast majority of children who fail a hearing screen have hearing loss due
to fluid in the middle ear or wax in the external ear canal. These are temporary
conditions.
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In addition, because of the State requirement for universal neonatal hearing
screening, (since 2000) most severe hearing deficiencies are detected in
infancy. This is important because the impact of hearing loss is greatest in
the 0-3 age group when children are acquiring basic language skills.”
NYC department of education website:
http://schools.nyc.gov/Offices/Health/HearingVisionScreening/default.htm. Accessed February 13. 2011
Pure Tone Audiometry
(Conventional Audiometry)
• Tests air and bone conduction at different frequencies, from
250 Hz-8000 Hz
• Measured in decibels
• Tones played into ear to measure air conduction
• An oscillator on the mastoid is used to measure bone
conduction
• Relies on patient response, typically raising a hand
• Gives ear-specific results
• It is appropriate for older children, adolescents (age 4 and up)
• Can be done in pediatric office
Tympanometry
• Compliance of the TM is measured as air pressure in
the external ear canal is varied
• Used to detect abnormalities of the tympanic
membrane and middle ear
• Can help differentiate between conductive and
sensorineural hearing loss
– Is normal in SNHL
– Tests function of TM, not hearing
• Most useful when combined with pneumatic
otoscopy
• Appropriate for all ages except neonates
Linden-Jerger Classification
Speech Audiometry
• Speech threshold: decibel level at which
patient can repeat 50% of words accurately
– Test uses spondee words
• Speech discrimination: percent of words a
patient can identify at approximately 40 dB
above threshold
• Can help determine central
lesions/neuropathies
Behavioral Testing: Behavioral
Observation Audiometry
• Auditory stimulus provided
– Voice
– Warbled tones
• Response to stimulus is observed
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Startle
Movement of limb
Cessation movement, e.g. sucking pacifier
cry
• No reinforcement of behaviors
• Appropriate for infants up to 8 months, patients with
multiple handicaps
Behavioral Testing: Visual
Reinforcement Audiometry
• Child placed between two speakers with lightup toys
• Child is conditioned to look towards active
speaker by a toy that lights up when patient
looks toward correct speaker
• Patient is rewarded visually for looking at the
active speaker
• Appropriate for ages 9 mo-2.5 years
Behavioral Testing: Play
Audiometry
• Patient is conditioned to perform a certain
play action in response to an auditory stimulus
– Drop a block in a cup
– Place peg in board
• Similar to pure tone audiometry: varying
frequencies and or oscillation on mastoid
• Appropriate for children ages 2.5-4 years
Imaging
• CT scan:
– Inner ear abnormalities
– Tumors
– Bony structure abnormalities: temporal bone and
ossicles
• MRI
– tumor
Treatment of Hearing Loss
• Team effort:
– Audiologists
– Otolaryngologists
– Speech pathologists
– Geneticists
– Educational specialists
– Pediatric ophthalmologist
Hearing Aids
• Types: analog, digital
– Digital has better sound quality, flexible settings
– Digital more expensive
• Style: bone conduction, behind-the-ear, in-the-ear,
completely-in-the-canal
– Behind-the-ear are easiest as child grows; the aid can be
re-molded
– In-ear models appropriate for mild-moderate hearing loss
only
• Adjustment:
– Computer programs can tell if hearing aid is correct fit and
volume
– Not necessary to rely on child reporting
Hearing Aids
Assistive listening devices
• Person talking has a microphone
• An FM transmitter wirelessly sends sound to
receiver
• Listener wears receiver
• Provides sound amplification
• Eliminates background noise
• Most commonly used for educational
purposes
Bone Conduction Hearing Devices
• For children with air
conduction hearing loss
(atresia, chronic infections)
• Types:
– Steel headband
• Uncomfortable, poor sound
quality
– Implantable
• “bone-anchored implantable
hearing aid system”
– BAHA
• Titanium screw in skull
attaches to hearing aid
Cochlear Implants
• Prosthetic device that stimulates the cochlear nerve
• For patients with severe-profound hearing loss
• All models approved for children > 18 months
– One model approved in 12 month old children
• How does it work?
– Microphone receives sound (placed in external ear canal)
– A speech processor arranges/selects sounds (above skinlooks like hearing aid)
– Receiver coil (placed below scalp) converts sounds to
electrical impulses
– Electrical impulses transmitted to electrode in
cochlea/auditory nerve
Cochlear Implant
Cochlear Implants
• Patients learn to hear sounds in environment
• Require extensive therapy to learn
interpretation of sounds, words
• Early implantation puts children at risk of
losing any remaining cochlea function but can
improve language outcomes
Development in Children with
Hearing Loss
• Children with hearing loss who are not diagnosed appropriately:
– lack sensory stimuli from sounds of language
– fail to develop synapses in auditory and language centers of the brain
• Development of language is related to timing of intervention
• If child is identified before 6 months, no connection exists between level
of hearing loss and degree of language development
• If child is identified before 6 months of age, language is related closely to
cognitive abilities
• Children diagnosed late, suffer from delayed language skills in relation to
cognitive abilities, poor overall academic achievement, and poor social
skills
Healthy People 2010 initiative
• 1. Increase the percent of newborns screened
for hearing loss by 1 month of age
• 2. Increase the number of at-risk patients
evaluated by audiologist by 3 months of age
• 3. Increase the number of children with
hearing loss enrolled in special services by 6
months of age
Which of the following statements regarding
hearing loss in infants and children is true?
• A. Children born with external ear anomalies
experience SNHL more commonly than conductive
hearing loss
• B. Cholesteatoma is the most common cause of
conductive hearing loss
• C. Language delay does not occur unless hearing loss
is severe or profound
• D. Newborn screen is reserved for preterm infants or
those who have a positive family history
• E. Parental concern regarding language delay or
hearing loss is sufficient cause for auditory testing
Answer
• E
References
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NIDCD.nih.gov/hearing/coch. Accessed 2 Feb 2011.
Tierney, CD and Brown, PJ. Development of children who have hearing impairment. Peds in Review 2009;
29: e72-73.
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NYC department of education website:
http://schools.nyc.gov/Offices/Health/HearingVisionScreening/default.htm. Accessed February 13. 2011
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US Preventive Services Task Force. Universal screening for hearing loss in newborns: US Preventive
Services Task Force recommendation statement. Pediatrics 2008 Jul;122(1):143-8
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Sanford, B and Weber, P. Treatment of hearing impairment in children. www.UpToDate.com. Access 16
Feb 2011.
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Sanford B and Weber P. Etiology of hearing impairment in children. www.UpToDate.com. Access 7 Feb
2011
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Adcock, L and Freysdottir, D. Screening the newborn for hearing loss. www.uptodate.com Access 6 Feb
2011.
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Recommendations for Preventitive Pediatric Health Care. AAP.org. Access 13 Feb 2011.
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Gifford, KA et al. Hearing Loss in Children. Peds in Review 2009;30: 207-215.