NIHL Part 2

Requirements for a diagnosis of NIHL R1 High frequency impairment (single HTL 10dB > at 3,4 or 6 than at 1 or 2) R2 Noise emission level accumulative to 100dB (A) NIL for sufficient number of years at 85dB (A). Impact noise R3 Identifiable high frequency notch or bulge in 3 – 6kHz range 10dB or more

Modifying factors Compatibility with age and exposure Borderline cases – probability tests Complications – conductivity, asymmetry Asymmetry – if noise was unilateral Better HF ear shows NIHL – yes One does and other borderline – probably yes Not much difference and only 1 ear shows NIHL – borderline Only worse – unlikely

Additional Risk Factors - introduce impurities in dx Other employment noise Medical conditions of the ear including surgery Head injury Ototoxicity Diabetes and peripheral vascular disease Uncontrolled hypertension ??? Social exposure Family history Firearms/Exposives Untoward acoustic events Other causation of unknown origin

Asymmetry – supportive or not?

Supportive of NIHL or not?

Supportive Very early NIHL R1 and R3 both minimally met

Supportive of NIHL or not?

Not supportive/borderline Left is supportive Right is NOT supportive. Why not? Not much difference in the HF and one ear has a significant notch or bulge and the other has little or no trace. Does not currently support but might indicate developing NIHL REVIEW 12/12

Supportive of NIHL or not?

Supportive R1 and R2 both met Worth investigation if more noise on left side at work

Supportive of NIHL or not?

Supportive Asymmetrical hearing impairment. Apply “Appendix A, note 11” R1 and R3 supported in the better high frequency ear Probability “more likely than not”

Supportive of NIHL or not?

Not supportive Asymmetrical hearing impairment. Apply “Appendix A, note 11” Only the worse ear shows NIHL. Only a possibility not a probability of NIHL. Possibility is <50%. Therefore on balance of probability not NIHL.

Asymmetry All prior examples assume symmetrical exposure to noise Apparent explanation should be considered: Firearms exposure Acoustic shock to one side Noise biases towards one side Other employees have same finding Asymmetrical NIHL IS supported if there is an “apparent explanation”

Screening outcome codes HSE Categorisation Scheme Category Action 1. ACCEPTABLE HEARING ABILITY Hearing within normal limits None 2.MILD HEARING IMPAIRMENT May indicate developing NIHL Warning 3. POOR HEARING Suggests significant NIHL Referral 4. RAPID HEARING LOSS Reduction in hearing level of 30 dB or more, within 3 years or less. Referral

HSE Screening criteria Not a sensitive criteria to recognise NIHL especially in early critical stages Not sensitive to small year on year changes – critical identifier of NIHL risk (30db vs 10dB) Reliant on entire Auditory pathway Bone Conduction Audiology is required to identify NIHL BC establishes cochlear and retrocochlear conditions Therefore BC testing is a definitive assessment for NIHL providing criteria for dx are met

Published on line (new) Noise Induced Hearing Loss – An Examination of the Methods of Assessment in a Cross-sectional Study of 87 Industrial Workers Clinical Otolaryngology November 2017

Abstract Objectives The surveillance of noise-induced hearing loss (NIHL) according to the Health & Safety Executive (HSE) differs from the medico-legal criteria used to assess NIHL. Our study compares the two systems and proposes a novel method of simplifying the medico-legal criteria and applying it to ascertain noise-induced hearing loss. Design The anonymised audiograms of a group of 87 industrial workers from a single site were analysed with both methods.

Results The comparison showed approximately one-third of the workers assessed in this study had their noise-induced hearing loss underestimated by the HSE criteria. The majority of these individuals were over 40 years of age. Conclusions The HSE criteria for noise-induced hearing loss needs review and re-alignment with the medico-legal criteria to address the discrepancy between the two systems. This article is protected by copyright. All rights reserved

IDC Diagnostics Categories (IDC 1-5) Normal versus age Predominantly medical Mild NIHL notch/bulge 10 – 30dB when extrapolated Significant NIHL notch/bulge > 30dB Deterioration – notch/bulge increases by 10dB or more. Requires experienced consideration of audiogram over time

Questions? Thank you!

NIHL Quiz 4 audiograms plus answer sheet Which diagnosis A- D fits which audiogram 1-4 Which ears supports NIHL (R1 and R3) Which require urgent medical referral (yes or no) Mark yourself out of 12