Table 2: Overview of study parameters of tDCS studies.

Main author and year Instrument Stimulation (anodal) Sample Time (minutes) Intensity (mA) Session (active + sham) Improvement (perception or distress) Sustained effect
Randomized clinical trials
Shekhawat, et al., 2013 [63] CGI, VAS LTPC 25 10, 15, and 20 with each current 1 and 2 6 Drop of 0.2 to 0.9 mean points on VAS overnight relief
Forogh, et al., 2015 [64] THI, VAS, CGI LTPC 22 20 2 5 No improvement none
Pal, et al., 2015 [65] THI, STSS, HADS, VAS, CGI prefrontal cortex 42 20 2 5 No improvement none
Shekhawat, et al., 2015 [58] MML, VAS LTPC 10 20 2 4 Drop of 1.2 point on VAS. No change in MML transient
Shekhawat, et al., 2013 [63] TFI, MML, TCHQ, TSNS, HADS, THQ, HHI, CGI, VAS LTPC (followed by hearing aids for 6 months) 40 20 2 5 No improvement none
Teismann, et al., 2014 [15] THI, VAS, THQ, TQ LAC (plus tailor made notched music training) 34 30 2 5 Drop only on THQ, but not on THI or VAS 5 to 31 days
Randomized crossover clinical trials
Vanneste, et al., 2011 [32] VAS RDLPFC 12 20 1.5 2 Drop of perception (41.67% on VAS) and distress (43.20% on VAS) 18 to 62 hours (mean = 24h)
Garin, et al., 2011 [66] VAS LTPC 20 20 1 3 Significant drop of VAS score < 1 hour
Faber, et al., 2012 [67] VAS, HADS RDLPFC 15 20 1.5 6 Significant drop of VAS score. No changes in HADS scores not mentioned

Legend: AC: Auditory Cortex; CGI: Clinical Global Improvement; DLPFC: Dorsolateral Prefrontal Cortex; HADS: Hospital Anxiety and Depression Scale; HHI: Hearing Handicap Inventory; LTPC: Left Temporoparietal Cortex; MML: Minimal Masking Level; RDLPFC: Right Dorsolateral Prefrontal Cortex; STSS: Subjective Tinnitus Severity Scale; TCHQ: Tinnitus Case History Questionnaire; TFI: Tinnitus Functional Index; THI: Tinnitus Handicap Inventory; THQ: Tinnitus Handicap Questionnaire; TPC: Temporoparietal Cortex; TSNS: Tinnitus Severity Numeric Scale; and VAS: Visual Analogue Scale.