HEARING & HEARING LOSS Dr I Butler 2015
DISCLOSURE Sponsorship to attend local and international workshops Cochlear (Southern ENT) Med el
TOPICS Anatomy Classification of hearing loss Congenital hearing loss Hearing screening Evaluation of hearing Tinnitus Sudden hearing loss Acoustic trauma Surgery and implantable devices
BASIC ANATOMY & PHYSIOLOGY
HEARING LOSS Disabling hearing impairment: (WHO) Permanent, unaided puretone average >30dB in the better ear Basic classification of degree of hearing loss
Conductive hearing loss middle ear infections, trauma Hearing loss mixed sensorineural hearing loss genetic ototoxic medication Perceptual/central processing disorder infections
HEARING LOSS Incidence 3-6:1000 live births +6000 babies born each year in SA with disabling hearing impairment Acquired hearing loss during childhood Prevalence of 1,9% (19:1000) at age 15y Hearing loss in the elderly Mild hearing loss 2x risk of dementia Moderate hearing loss 3x risk of dementia Severe hearing loss 5x risk of dementia
THE IMPORTANCE OF EARLY DIAGNOSIS OF HEARING LOSS Central role of hearing in cognitive development Neuroplasticity Neurons that fire together, wire together (Donald Hebb) Synaptic pruning Re-distribution of sensory association areas Limited window of opportunity CNS development School readiness Learning Ability Emotional Development Behavioural Development Hearing Cognitive Development Receptive Language Expressive Language Yoshinaga-Itano et al(2001), Marschark & Wauters(2008)
THE IMPORTANCE OF EARLY DIAGNOSIS OF HEARING LOSS Proven benefits of early intervention: Infants who are identified with hearing loss and receive the appropriate intervention before the age of one year develop communication skills on a par with their normal hearing peers. Economic benefit to society Proven negative effect of late/no intervention: Proven negative impact on future vocational and socio-economic outcomes References: Yoshinaga-Itano Swanepoel
HEARING SCREENING WHY? Early diagnosis leads to early intervention Universal vs Targeted screening Targeted screening will miss 50% of cases Available resources
HEARING SCREENING How? Otoacoustic emissions (OAE) Tests auditory pathway up to cochlear outer hair cells Automated Auditory Brainstem Response (aabr) Tests auditory pathway up to brainstem level
HEARING SCREENING When? 90% of SA children currently have no access to hearing screening services International guidelines Screen ALL newborn infants by 1 month of age Local guidelines (HPCSA position statement 2007) Depends on context Hospital» Screen by 1 month Clinic» Screen by 14 weeks (one of first 3 immunization visits)
EVALUATION OF HEARING Clinical Tuning fork tests Rattle test Audiology Pure tone audiometry Speech discrimination Tympanometry Stapedius reflex Paediatric audiometry (PEDO) visual-reinforced play free-field or ear specific Brainstem evoked response audiometry (BERA) Cortical response telemetry
TINNITUS Definition Classification Tinnitus Pulsatile Non-pulsatile Clinical picture Pulsatile Non-pulsatile Management Unilateral Bilateral Unilateral Bilateral Consider middle ear/skull base tumour Consider raised intracranial pressure Consider retrocochlear pathology Consider cochlear damage
THE TIP OF THE ICEBERG
GLOMUS JUGULARE
GLOMUS JUGULARE
SUDDEN SENSORINEURAL HEARING LOSS Definition More than 30dB loss, within 3 days, over 3 adjacent frequencies Characteristics Usually unilateral Fullness in the affected ear Tinnitus (70%) Balance disturbance (40%) Higher frequencies affected the most HL may vary from mild to severe No gender predilection 20-40% have viral prodrome
SUDDEN SENSORINEURAL HEARING LOSS Evaluation: H&N exam Otoscopy Tuning fork tests Audiometry Tympanometry, PTA, speech discrimination Blood Neutrophil-lymphocyte ratio Platelet-lymphocyte ratio Auto-immune & inflammatory markers
SUDDEN SENSORINEURAL HEARING LOSS Management: Oral steroids Start with 1mg/kg/day for 5-7 days and then taper over a further 2 weeks Intra-tympanic steroids Unproven: Hyperbaric oxygen therapy Carbogen Pentoxifylline Anti-viral agents Dextran Diuretics Heparin Histamine
ACOUSTIC TRAUMA Explosive noise or prolonged exposure to excessive noise AKA: Noise induced hearing loss (NIHL) Damage is a function of: Intensity of the sound Duration Frequency spectrum Individual susceptibility/predisposition (for eg. genetic factors, renal impairment, medication)
ACOUSTIC TRAUMA Pathogenesis: Pressure wave Tympanic membrane rupture Ossicular dislocation Oval/round window rupture Basilar membrane rupture Fracture of hair cells/stereocilia Metabolic exhaustion Temporary threshold shift or permanent threshold shift
ACOUSTIC TRAUMA Prolonged exposure Industrial standard 85dB for 8 hours Typically shows up first at 4KHz Indoors: bilateral symmetrical loss Tinnitus prevention
OCCUPATIONAL NOISE INDUCED HEARING LOSS Always a sensorineural hearing loss Almost always bilateral High-frequency losses rarely exceed 75 db, and low-frequency losses rarely exceed 40 db. Hearing loss does not progress after noise exposure is discontinued. As hearing loss progresses, the rate of hearing loss decreases. Loss is always greater at the frequencies 3000-6000 Hz than at 500-2000 Hz. Loss is usually greatest at 4000 Hz. The 4000-Hz notch is often preserved even in advanced stages. In stable exposure conditions, losses at 3000, 4000, and 6000 Hz usually reach a maximum level in 10-15 years. Dobie RA. A method for allocation of hearing handicap. Otolaryngol Head Neck Surg. Nov 1990;103(5 (Pt 1)):733-9.
SURGERY
OTOSCLEROSIS
OTOSCLEROSIS Pre-op Post-op
BONE CONDUCTION BAHA (Cochlear corp) Available from the early 1970s Percutaneous abutment Osseo-integrated implant Bilateral stimulation from a single implant Bone conduction thresholds better than 45dB in EITHER ear Simple surgery BUT percutaneous abutment results in high skin infection rate (50%) and loss of implant in 17%.
BAHA attract /BAHA 4 Large magnetic disc is attached to the abutment instead. Changes the system from percutaneous to transcutaneous. Disadvantages: Sound attenuation Pressure on skin People have a low acceptance of the percutaneous abutment AND the high complication rate
PONTO SYSTEM (OTICON)
VIBRANT SOUNDBRIDGE (MED EL) Transcutaneous system Floating mass transducer (FMT) Developed initially for SNHL and intact ossicular chain Later modified for mixed/conductive HL
VIBRANT SOUNDBRIDGE (MED EL) Criteria for SNHL: AC within the shaded area Criteria for mixed/conductive HL: BC within the shaded area
BONEBRIDGE (MED EL) Transcutaneous system Similar audiological criteria and gain compared to percutaneous systems FMT is relatively large and you need to carefully plan its position.
COCHLEAR IMPLANTS
AUDITORY BRAINSTEM IMPLANTS
AUDITORY MIDBRAIN IMPLANTS