Hearing Loss

1. Hearing Loss Mary Beth Palomaki, MD February 17, 2011

2. Outline • Review anatomy and physiology of hearing • Etiology of hearing loss • Hearing screening • Evaluation of hearing loss • Treatment of hearing impairment

3. Anatomy of the Ear

5. 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

6. 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

7. 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

8. 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)

9. 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

10. 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

11. 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

12. 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)

13. 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

14. 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

15. 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

16. 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

17. History: Risk Factors for Hearing Loss • 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.

18. 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

19. USPSTF Recommendations 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 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

20. 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

21. 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

22. 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

23. NY City School Hearing ScreeningDiscontinued in Fall 2009 • “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. • 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

25. 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

26. 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

27. Linden-Jerger Classification

28. 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

29. Behavioral Testing: Behavioral Observation Audiometry • Auditory stimulus provided • Voice • Warbled tones • Response to stimulus is observed • 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

30. Behavioral Testing: Visual Reinforcement Audiometry • Child placed between two speakers with light-up 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

31. 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

32. Imaging • CT scan: • Inner ear abnormalities • Tumors • Bony structure abnormalities: temporal bone and ossicles • MRI • tumor

33. Treatment of Hearing Loss • Team effort: • Audiologists • Otolaryngologists • Speech pathologists • Geneticists • Educational specialists • Pediatric ophthalmologist

34. 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

35. Hearing Aids

36. 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

37. 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

38. 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 skin-looks like hearing aid) • Receiver coil (placed below scalp) converts sounds to electrical impulses • Electrical impulses transmitted to electrode in cochlea/auditory nerve

39. Cochlear Implant

40. 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

41. 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

42. 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

43. 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

44. Answer • E

45. References • 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. • NYC department of education website: http://schools.nyc.gov/Offices/Health/HearingVisionScreening/default.htm. Accessed February 13. 2011 • 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 • Sanford, B and Weber, P. Treatment of hearing impairment in children. www.UpToDate.com. Access 16 Feb 2011. • Sanford B and Weber P. Etiology of hearing impairment in children. www.UpToDate.com. Access 7 Feb 2011 • Adcock, L and Freysdottir, D. Screening the newborn for hearing loss. www.uptodate.com Access 6 Feb 2011. • Recommendations for Preventitive Pediatric Health Care. AAP.org. Access 13 Feb 2011. • Gifford, KA et al. Hearing Loss in Children. Peds in Review 2009;30: 207-215.