1. S-89.3480 Acoustics Seminar 18.2.2015 Petteri Hyvärinen
Tinnitus
S Acoustics Seminar
Petteri Hyvärinen

2. Outline Basic understanding of tinnitus How can tinnitus be studied?
What it (probably) is and isn’t
How can tinnitus be studied?
Principles of clinical trials
Some examples

3. Tinnitus basics

4. Tinnitus Tinnitus — from latin word tinnire (to ring)
Tinnitus is the perception of sound in the absence of a corresponding external acoustic stimulus1
Almost any kind of sound
Indistinct & w/o meaning (vs. hallucinations)
1Langguth et al. Lancet Neurol. 2013;12:920–930

5. Tinnitus ~10–15% of the population affected 1–2% invalidated
Risk factors
Hearing impairment
Age
Male

6. Tinnitus Cause unknown, theories exist
Earlier: thought to originate from cochlea
Now: pathology of the central nervous system (CNS)
Hearing loss can lead to tinnitus
Maladaptive plasticity
Compare to phantom pain

7. Tinnitus --- CNS
Schaette Hearing Research

8. Tinnitus --- CNS Where in the auditory pathway? What changes?
Not possible to pinpoint
Although changes due to tinnitus can be observed, proving causality is quite challenging
What changes?
Reorganization of neural maps
Increased synchrony
Not only auditory!
Attention, anxiety, depression, stress, etc…

9. Tinnitus --- CNS

10. Tinnitus Still too straightforward …
There’s tinnitus and then there’s tinnitus
Objective tinnitus
The sound can be heard by another person
Blood vessels
Somatosensory tinnitus
Modulated by neck tension, head position, jaw
~20%–70% of tinnitus cases, depending on who you ask
Other forms of subjective tinnitus
What “tinnitus” usually refers to

11. Diagnosing tinnitus Three components of tinnitus
Auditory features (pitch, loudness, location, masking, …)
Emotional features (distress)
Attentional features (awareness, cognitive load)

12. Diagnosing tinnitus No objective measures
Instead, subjective questionnaires and scales
Tinnitus Handicap Inventory (THI)
Tinnitus Questionnaire (TQ)
Tinnitus Handicap Questionnaire (THQ)
Tinnitus Functional Index (TFI)
Visual analogue scales (VAS) …
Treatment effect measured by comparing these at different timepoints

13. Diagnosing tinnitus in the future …
Neuroimaging
(f)MRI
Structural changes
EEG / MEG
Evoked responses
Oscillatory activity
Functional connectivity
Require big datasets TINNET
Collaboration on heterogeneity of tinnitus
Aim: objective measures for tinnitus

14. Diagnosing tinnitus Big challenge: it’s never just the sound
How to disentangle all possible confounding factors?
Different components of tinnitus don’t correlate
Louder not necessarily more irritating
So what should you measure?

15. Tinnitus treatments Many approaches
Counselling, CBT
Hearing aids
Sound therapy
Pharmacotherapy
Brain stimulation
Many treatments aim at management of tinnitus
Not necessarily abolishing tinnitus
Stress reaction   tinnitus distress

16. Tinnitus treatments Exapmle: Sound therapy Just masking
Loud enough to mask tinnitus
Unnoticeable, relaxing
Bedside sound generators
Combined with CBT
Tinnitus retraining therapy (TRT)
Individualized
Tailor-made notched music therapy (TMNMT)
Promoting plasticity
Lateral inhibition

17. Tinnitus treatments Poor evidence Placebo effect
Heterogeneity of tinnitus
Trial design flawed
Placebo effect
Remarkable
No physiological explanation
Why did it work?
Does it matter?

18. Tinnitus recap A very diverse condition It’s not in the ear
Many problems because all forms treated as same
It’s not in the ear
Hearing loss can lead to tinnitus
There are treatments
None of them work 100%
They might not be what you’d expect

19. Designing experiments

20. Experiment design How would you design an experiment?
“My tinnitus went away after I started wearing this healing crystal bracelet”
You want to sell these bracelets to tinnitus patients  show that wearing one cures tinnitus

21. Clinical trials (in tinnitus)
Key aspects in clinical trials (of tinnitus)1
Trial type (RCT, N, power calc.)
Control condition* and blinding
Trial duration
Study population*
Outcome measures*
Statistical sig. vs. clinical relevance
Trial reporting
Ethical aspects
1Landgrebe et al J Psychosom Res. 73:112–121

22. The scientific method Make hypotheses Derive predictions
Make experiments based on predictions
Analysis and conclusions

23. Experiment design RCT = randomized controlled trial
Gold standard of clinical studies
Control groups
Blinding
So why doesn’t everyone just do RCTs?
You need a hypothesis
You need a lot of subjects
Specificity vs. generality: statistical power

24. Example of a study (tDCS)
transcranial direct current stimulation (tDCS)
Brain stimulation method
Used successfully for depression
Promising method for tinnitus
neuroConn DC-STIMULATOR PLUS

25. tDCS study Two electrode montages:
LTA left temporal anode  targeting AC
Bifrontal  targeting frontal areas
Similar results for LTA and bifrontal in earlier studies
However, targeting of stimulation is different
So is it just a sham effect?
Does tDCS work differently than what expected?

26. tDCS study Double-blind sham-controlled trial
Comparing two electrode montages
LTA vs. bifrontal
2 mA current, 20 min daily for 10 days
Pre-treatment vs. 4 weeks after first treatment (18 days)

27. tDCS study Pre- and post-treatment measures: THI and mini-TQ
Beck Depression Inventory
Beck Anxiety Inventory
VASs: loudness, irritability, overall effect on life
MEG measurements
High-freq audiometry
Tinnitus pitch matching & masking levels

28. tDCS study Trial started in beginning of 2014
Now ~30 subjects have completed
Preliminary results
Subjects with low THI scores don’t improve
Difference between pre and post treatment for sham vs. active
LTA vs. bifrontal not so clear
Aim is to increase N by 15–20 subjects
Takes time

29. Questions?

30. Questions

31. Questions How to measure changes in tinnitus?
Do auditory hallucinations and tinnitus differ? How?
How does an RCT help you support causality of treatment  improvement?