Occupational Noise Induced Hearing Loss

Transcription

1 Occupational Noise Induced Hearing Loss M Baxter FRACS SISA Adelaide June 2014

2 ENT in Personal Injury Claims EAR Hearing Loss -main, Dizziness Nose Injuries ->cosmesis,breathing: Loss of sense of smell: secondary sinusitis Throat -Laryngeal Injuries, Voice Disorders Face Facial paralysis Dr Malcolm Baxter, FRACS

3 Occupational Noise Induced Hearing Occupational Noise Induced Hearing Loss Loss Dr Malcolm Baxter, FRACS

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7 Some Definitions Auro-,oto- pertaining to the ear auroscope,otoscope,auricular,otic Tympano- of the middle ear -tympanotomy,tympanoplasty Myringo- of the tympanic membranemyringitis,myringotomy,myringoplasty Mastoid-of the mastoid cells -mastoidectomy, mastoiditis Ossiculo- of the ossicles ossiculoplasty Labyrinth-of the peripheral inner ear balance system(labyrinth)- Labyrinthitis, labyrinthectomy Dr Malcolm Baxter, FRACS

8 Measuring Sound The Decibel db Defined by Sound pressure Measured environmentally with a Sound Pressure Meter Dr Malcolm Baxter, FRACS

9 Hearing Loss Sensorineural, Conductive & Mixed Both can be Congenital or Aquired Dr Malcolm Baxter, FRACS

10 Some Causes of SNHL (Sensorineural Hearing Loss) Congenital - Inherited/familial SNHL, Cochlear dysplasias/aplasias Trauma -head injury, (+/- Fractured base of skull. Noise damage (NIHL, Acoustic Trauma) Toxic - Ototoxicity Inflammatory Suppurative labyrinthitis, mumps, meningitis Neoplastic - Acoustic Neuroma Menieres Disease Dr Malcolm Baxter, FRACS

11 Excessive Noise and the Inner Ear Hair Cells can be damaged by a number of noxious agents-eg Infection, Toxins and drugs, Noise. Noise must be of sufficient intensity and duration High Frequency sounds (hair cells) generally affected first Dr Malcolm Baxter, FRACS

12 What is Excessive Noise? 85dB generally considered the critical level-ie noises above this will damage the hair cells However it will generally take several hours of continuous noise at this level to cause damage However as the Intensity rises the unsafe time rapidly decreases eg 110 db may take 15 mins Concept of NOISE DOSE Dr Malcolm Baxter, FRACS

13 Noise Damage to Hearing Noise Induced Hearing Loss( NIHL) continued or repeated noise exposure over the unsafe level for a period of time -often years Acoustic Trauma Sudden severe episode often just once or several close together Dr Malcolm Baxter, FRACS

14 TESTING HEARING Whisper test Tuning Fork Tests- Weber, Rinne Audiometry AirBone Tympanometry Speech Audiometry Otoacoustic Emissions Evoked Response Audiometry CERA (Cortical) ABR (Brain Stem) ElectroCochleography (ECochG) Dr Malcolm Baxter, FRACS

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21 Assessing the Claimant for Occupational NIHL Agent -> IME (ENT Specialist) Examination History Examination Audiogram Is all consistent with NIHL? If Yes -Conversion Audio Threshold levels -> PLH ->WPI Dr Malcolm Baxter, FRACS

22 Doubtful or Inconclusive Audiometric Results Frank Malingering Patient understanding or poor cooperation Disparity with Previous audiograms Consider CERA (Cortical Evoked Response Audiometry)

23 CERA (Cortical Evoked Response Audiometry) An Objective test-does not depend on patient responding to a sound When a sound is heard in the cochlea an electrical signal is generated which passes upwards through the brain stem to the cortex-the most developed part of the brain where it is perceived as sound-this signal may be picked up by an electrode on the skull surface.

24 CERA (continued): A person being tested is presented with a series of clicks in the ear at various frequencies and increasing volume which, when heard, produce surface signals which may be recorded and magnified by a computer. Thus the true threshold of hearing can be detected without patient co-operation. This test can be regarded as definitive for compensation purposes.

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26 AMA Guides to Evaluation of Permanent Impairment AMA 2 Vic (W/C Pre 1992) AMA 4 AMA 5 AMA 6 NT (W/C), Vic (W/C, CTP) NSW (CTP), Tas (W/C, CTP), Qld (W/C) NSW (W/C), ACT (W/C, CTP), SA (W/C, CTP), WA (W/C, CTP), QLD (W/C common law. CTP) NT (CTP) These have tables of percentage hearing loss Dr Malcolm Baxter, FRACS

27 Dr Malcolm Baxter, FRACS BUT In the majority of Aust jurisdictions (? All except NT) the Hearing Loss tables in the Guides are NOT used to calculate Percentage Loss of Hearing (PLH) Instead use the tables in Improved Procedure for Determining Percentage Loss of Hearing published by the National Acoustic Laboratories in 1988 May also be directed to use Guidelines published by the Hearing Committee of the Australian Society of Otolaryngology Head & Neck Surgery in concert with the tables

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30 Calculate PLH from the Tables The losses at Frequencies 2, 3 and 4 khz are those at which NIHL is believed to occur BUT if the worker has been exposed to noise for > 30 years the lower frequencies are also believed to be affected use 1.5,occassionally 1kHz NIHL believed NEVER to exceed 70dB Dr Malcolm Baxter, FRACS

31 Deduct for Non Compensable factors Notably PRESBYCUSIS Some jurisdictions apportion ie deduct a proportion for work outside the jurisdiction Dr Malcolm Baxter, FRACS

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34 Compensable Level In most jurisdictions the net PLH figure (after deductions for Presbycusis and Apportionment) must equal or exceed a certain % for a successful claim Eg in Victoria must have 10% PLH to get compensation Dr Malcolm Baxter, FRACS

35 Conversion to WPI The net compensable figure may be converted to a WPI figure from the appropriate table, Dr Malcolm Baxter, FRACS

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37 AMA 6 Newest and Latest So far only NT CTP mandates this. Method of calculation radically different from Current Australian practice using NAL tables So far NT does not mention use of NAL tables like all other Australian Jurisdictions so have to use the straight AMA6 Method Allows loading for Tinnitus Dr Malcolm Baxter, FRACS

38 Tinnitus Usually arises from damaged hair cells Unilateral or bilateral or all over Very common in Australian Population NIHL and other causes including spontaneous Dr Malcolm Baxter, FRACS

39 Tinnitus cont. Severity does not necessarily reflect severity of HL. Occasionally may be present with no HL. No specific treatment-masking, Tinnitus Retraining Some jurisdictions allow loading eg Comcare up to 5%, Victoria Nil Dr Malcolm Baxter, FRACS

40 Hearing Aids There is no operation or medication for NIHL (or other SNHL unless profound when Cochlear Implants may be considered- NIHL NEVER gives HL of this severity) Hearing Aids are the only treatment There is no magic formula for when Hg Aids should be prescribed. Should be considered in a claim if the person is having significant communication problems Dr Malcolm Baxter, FRACS

41 THANK YOU Questions?

42 HEARING LOSS CLAIMS Presentation to SISA 20 June 2014 Tracey Kerrigan

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44 Introduction Hearing loss claims technical and difficult Section 113(2) a legal fiction Whole of the loss is deemed to occur immediately before notice Whole of the loss deemed to occur in the employment of last employer

45 Introduction cont Onus of Proof Section 31(2) and Section 113(2) rests on last noisy employer Must show you have not contributed to worker s hearing loss Section 31(4) exception for workers who have retired on account of age or ill-health more than 2 years ago

46 Investigation and determination of claim Has the worker left your employment or is he a current employee? Do you bear the onus of proof? Can you show that you did not expose the worker to noise? Is there a pre-employment audiogram? Has the loss increased and is the audiogram relevant? What is the level of noise exposure and what does noise mean? Was hearing protection in force/in use?

47 Determination/Investigation cont Are you the last employer? Is the claim within time? Date of claim for calculating entitlement?

48 Practical tips Do you investigate or can you get the other side to do the work? Is an IME necessary? What audiograms are in existence? Hearing loss questionnaire? Lump sum check for prior payments. Can you reject outright or accept for medical expenses? Evidence of exposure and hearing protection.

49 Practical tips cont. Differing WPI assessments. What to do? Can you negotiate the section 43 entitlement? Hearing aids can you shop around? What is your liability? Can you finalise the liability? Prior assessments not paid is there a reduction under Clause 9.15 of the WorkCover Guides to Evaluation of Permanent Impairment