Therapeutic Treatment of Acquired Hearing Loss Presentation (2016)
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Transcript of Therapeutic Treatment of Acquired Hearing Loss Presentation (2016)
Therapeutic Prevention of Acquired Hearing LossMelanie McQueen, B.S. and Annelise Gerardi, B.H.S.The University of Texas at AustinSchool of Communication Sciences of Disorders
Overview● Introduction to Oxidative Stress● Role of Oxidative Stress in Acquired
Hearing Loss● Antioxidant Prevention of
Noise-Induced Hearing Loss
Acquired Hearing Loss● Oxidative Stress (free radical
formation)● Types of hearing loss driven by
oxidative stress: ○ Noise-Induced Hearing Loss (NIHL) ○ Drug-Induced Hearing Loss○ Age-Induced Hearing Loss
● NIHL is the most responsive to therapeutic treatment
What Causes NIHL?● Mechanical damage● Ischemia● Oxidative stress
○ Free radical formation in Organ of Corti = death of hair cells
Strategies for Reducing NIHL● Reduce the sound level at the source● Reduce time of exposure to the source● Design better hearing protection
devices● Decrease oxidative stress that induces
cell death in the inner ear through drugs or dietary supplements
Article One: Post-exposure treatment attenuates noise-induced hearing lossNeuroscience (2005)D. Yamashita, H.Y. Jiang, C. Le Prell, J. Schacht, and J. Miller
Background● Free radical formation can occur up to
10 days after noise exposure● Can antioxidant intervention during this
period reduce NIHL?● Can antioxidant intervention during this
period reduce NIHL?
Subjects● 42 male guinea pigs● Divided into 7 groups:Group 1 Group 2 Group 3 Group 4 Group 5 Group 6 Group 7
Control Saline injected on Day 1 (3 days before noise exposure)
Salicylate + trolox injected Days 1 to 14
Salicylate + trolox injected 1 hour after noise exposure until Day 14
Salicylate + trolox injected 1 day after noise exposure until Day 14
Salicylate + trolox injected 3 days after noise exposure until Day 14
Salicylate + trolox injected 5 days after noise exposure until Day 14
*Trolox = 50mg/kg, twice daily*Salicylate = 75 mg/kg, twice daily
Method● Animals in all groups were subjected to
noise on Day 4.● Stimulus = One-octave band noise
centered at 4 kHz @ 120 dB SPL for 5 hours
Outcome Measures● ABR Thresholds:
○ ABR thresholds at 4, 8, and 16 kHz were measured 7 days before treatment and 10 days after noise exposure
● Histological Examinations:○ Left ears processed for histological
hair cell counts○ Right ears processed for
immunohistochemical staining
Results● Reduction in NIHL threshold shift was
directly related to onset of preventative drug treatment
● Effectiveness of treatment decreased with time after noise exposure
Discussion● NIHL and sensory cell death can be
attenuated up to 3 days after noise exposure using a combination of antioxidants (salicylate + trolox)
● Pretreatment was most effective● In general, free radical formation was
reduced in cochlear cells by antioxidant therapy.
Implications● NIHL is a major cause of acquired
hearing loss in the world● Complete elimination of mechanical
cochlear damage and avoidance of acute accidental noise is impractical
● Therefore, could antioxidant treatment within a time window of noise exposure reduce NIHL in humans?
Article Two: Increased vitamin plasma levels in Swedish military personnel treated with nutrients prior to automatic weapon training Noise Health (2011)C. Le Prell, C. Johnson, A. Lindblad, A ̊. Skjo ̈nsberg, M. Ulfendahl, K. Guire, G. Green, M. Campbell, and J Miller
Background● The previous study demonstrated the
effectiveness of combined antioxidants in the prevention of NIHL in guinea pigs
● Can antioxidant treatment translate to the prevention of NIHL in humans?
Subjects● 31 subjects:
○ 10 Swedish military officers○ 21 Swedish military academy trainees
● Advertisements posted on base to encourage people to participate
● Exclusion factors: ○ Gastrointenstinal disturbances, neurological
disturbances, hematological disorders, and auditory/vestibular issues
● Requirements: ○ Symmetrical normal hearing, Type A tymps,
ipsilateral reflexes, and threshold asymmetry at </ 15 dB at all frequencies
Treatment● Micronutrient treatment combination
of beta carotene, vitamin C, vitamin E, and magnesium in the form of a pill
● Dosage was 6 pills a day (3 at a time, twice daily)
Study Design ● Double blind study● Randomized - Subjects
received nutrient or placebo condition for “Arm 1”
○ Each “arm” consisted of a single weapons training class
○ For “Arm 2,” there was a washout period before switching to other pill
Outcome Measures● Questionnaire
○ Self-reporting Hearing and Tinnitus survey
● Otoscopy● Tympanometry● Reflex Testing at 1 kHz @ 100 dB HL● Pure Tone Audiometry● DPOAE’s
Outcome Measures● Noise Exposure levels:
○ 40 shots fired from automatic machine gun in a bunker for over 1 minute while standard hearing protection was worn
● Blood Sampling and Analysis: ○ Collected from 9/10 of the officers○ Levels for vitamin C, vitamin E, beta
carotene and magnesium were measured
○ Taken one day before testing and 2 hours after exposure
Results:● Adverse effects:
○ One subject reported queziness within one day of study. 2 reported feeling ill during or after treatment
● Plasma levels: ○ Post treatment, levels increased for all except
magnesium
○ No reliable change in plasma levels when placebo was consumed first
● Pre 1 Test Outcomes: ○ Minimal differences seen between soldiers and
officers relating to age or effect
● Pre 2 Test Outcomes: ○ No effects on baseline measures
Results● Audiometry:
○ No effect on baseline thresholds thus no opportunity to measure protection against TTS as a function of treatment
● Tinnitus: ○ Reported sporadically, but not
significant
● Treatment group showed a 4-12 dB smaller TTS than placebo group for within subject comparisons
Measured Antioxidant Levels Before and 2 Hours Post Exposure for Placebo and Non Placebo Groups
Black = Pre Gray = Post
Discussion● No consistency in results
● No reliable noise-induced threshold shift was measured for either the placebo or non-placebo group
○ Does not support use of a preventative drug for human hearing protection
● However, elevated plasma levels were found in the blood of participants, which could be helpful for future studies
Discussion● Ear protection was good for avoiding
NIHL in humans...○ However, it created a lack of noise
induced changes, so it could not be determined if nutrients have beneficial effects in relation to hearing loss
● Need to design better studies in order to obtain successful human trials
Sources:Yamashita D; Jiang HY; Le Prell CG; Schacht J; Miller
JM, Neuroscience [Neuroscience], ISSN: 0306-4522, 2005; Vol. 134 (2), pp. 633-42; Publisher: Elsevier Science; PMID: 15961244, Database: MEDLINE
Le Prell CG; Johnson AC; Lindblad AC; Skjönsberg A; Ulfendahl M; Guire K; Green GE; Campbell KC; Miller JM, Noise & Health [Noise Health], ISSN: 1463-1741, 2011 Nov-Dec; Vol. 13 (55), pp. 432-43; Publisher: Medknow Publications Pvt. Ltd; PMID: 22122960, Database: MEDLINE