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. 2021 Oct 24;11(11):1394. doi: 10.3390/brainsci11111394

Table 6.

Parameters assessed by the included studies. (a) Studies reporting on intracochlear electrical stimulation. (b) Studies reporting on extracochlear electrical stimulation.

(a) Studies Reporting on Intracochlear Electrical Stimulation
Authors, Year Stimulation Type (CI) AC/DC Parameter(s) Tested Value Tested Parameter Comparison in Terms of Tinnitus Reduction p-Value
Arts et al., 2015 [82] CI AC C sham stimulation, −10, 20, 50, 80% DR 50% > sham stimulation 0.033
80% > sham stimulation 0.014
E Basal (x1, x3), central (x1, x3), apical (x1, x3), pitch-matched (x1, x3) Apical > pitch-matched 0.042
Central > pitch-matched 0.043
A Random, sine wave, fixed No comparison performed NA
Arts et al., 2016 [51] CI AC C 2.5–12.1 nC Low > high NI
E 1–all No comparison performed NA
P (+), (−) first charge-balanced No comparison performed NA
PR 200–5000 pps/channel High > low NI
Pulse width 60–88 μs No comparison performed NA
Dependency of environmental sounds Independent, dependent Not statistically different >0.05
Chang et al., 2012 [83] CI AC C Soft, medium, loud Loud > soft 0.027
High rate: medium > soft 0.043
High rate: medium > loud 0.008
E Apical, middle, basal Not statistically different NI
PR 100–200, 5000 pps Not statistically different NI
Dauman et al., 1993 [57] CI AC C 0.1–1.7 mA No comparison performed NA
E Apical, middle, basal No comparison performed NA
PR 80, 125, 250 Hz No comparison performed NA
Kloostra et al., 2020 [72] CI AC C Near-threshold (T level), moderate (C level) Moderate > near-threshold <0.001
E Basal, apical
Single electrode, full array		 Not statistically different
Not statistically different		 0.712
NI
PR 720, 1200, 2400 Hz Not statistically different 0.493
Olze et al., 2018 [64] CI AC A Square wave No comparison performed NA
PR 62 Hz No comparison performed NA
Punte et al., 2013 [65] CI AC E 1, 2, 3, 4 most basal electrodes, all All > most basal electrodes 0.042
Rothholtz et al., 2019 [71] CI AC C 0–120 μA No comparison performed NA
E E1–E16 60 pps at most apical, high rates close to tinnitus matched pitch NST
PR 40–10000 Hz
Rubinstein et al., 2003 [71] CI AC C 300 μA–1.5 mA No comparison performed NA
PR 4800 pps No comparison performed NA
Pulse duration 25, 50, 80 μs/phase No comparison performed NA
E tinnitus pitch-matched Not comparison performed NA
Zeng et al., 2011 [70] CI AC C subthreshold, 0–10 loudness scale 1–6 > 7–10 NST
E Apical, basal 4 most apical > 4 most basal NST
PR 20–100, 5000 Hz 20–100 Hz > 5000 Hz NST
(b) Studies Reporting on Extracochlear Electrical Stimulation
Authors, Year Stimulation Type (RW, PM, OW) AC/DC Parameter(s) Tested Value Tested Parameter Comparison in Terms of Tinnitus Reduction p -Value
Péan et al., 2010 [79] OW AC C NI No comparison performed NA
P (+), (−) first charge-balanced (+) > (−) NST
PR NI No comparison performed NA
Pulse shape Square pulse, capacitive discharge Square pulse followed by a capacitive discharge NST
Daneshi et al., 2005 [56] PM AC C 60–500 μA No comparison performed NA
PR 50–600 Hz No comparison performed NA
Di Nardo et al., 2009 [58] PM DC+ C 0–500 μA No comparison performed NA
PR 50–1600 Hz 50, 100 Hz > 200–1600 Hz NST
Graham et al., 1977 [74] PM AC C 1–100 μA No comparison performed NA
PR 1–10000 Hz No comparison performed NA
Ito et al., 1994 [87] PM NI NI NI No comparison performed NA
Konopka et al., 2001 [60] PM DC+ C 20–600 mA No statistically different NI
PR 60–10000 Hz No statistically different NI
Konopka et al., 2008 [59] PM AC C 0.15–1.15 mA No comparison performed NA
PR Tinnitus pitch-matched No comparison performed NA
Mahmoudian et al., 2013 [62] PM AC C 60–500 μA No statistical difference between RI and NRI 0.61
PR 1 Hz No comparison performed NA
Frequency
modulation		 50 Hz No comparison performed NA
Mahmoudian et al., 2015 [61] PM AC C 50–500 μA No statistical difference
between RI and NRI		 >0.05
PR 1 Hz No comparison performed NA
Frequency
modulation		 50 Hz No comparison performed NA
Matsushima et al., 1994 [85] PM AC A Sinusoidal, 1 kHz No comparison performed NA
C 0–70 μA No comparison performed NA
PR 10 kHz No comparison performed NA
Matsushima et al., 1996a [63] PM AC A Sinusoidal, 100 Hz No comparison performed NA
C 0–300 μA No comparison performed NA
PR 10 kHz No comparison performed NA
Matsushima et al., 1996b [55] PM AC A Sinusoidal No comparison performed NA
C 200 μA No comparison performed NA
PR 10 kHz No comparison performed NA
Okusa et al., 1993 [86] PM AC C 0–100 μA No comparison performed NA
PR 50, 100, 200, 400 Hz 50 > 100 >200 > 400 Hz NST
Rothera et al., 1986 [66] PM AC, DC C 0–100 μA AC suprathreshold, DC (+) subthreshold NST
DC P (+)/(−) (+) > (−) NST
AC PR 30–3000 Hz No comparison performed NA
Watanabe et al., 1997 [68] PM AC C 5–160 μA No comparison performed NA
PR 400 Hz No comparison performed NA
Carlson et al., 2020 [84] PM AC C NI NA NA
E
P
PR
Aran et al., 1981 [77] RW, PM AC, DC Tinnitus side Ipsilateral, contralateral Ipsilateral > contralateral NST
AC, DC E RM, PM RW > PM NST
AC PR Low (<100 Hz), high (>200 Hz) High > low NST
AC C 5–300 μA No comparison performed NA
RW AC, DC P (+)/(−) (+) > (−) NST
Cazals et al., 1978 [75] RW, PM AC, DC C 20–300 μA No comparison performed NA
AC, DC E RW, PM RW > PM NST
AC, DC P (+)/(−) (+) > (−) NST
AC PR >50–200 Hz No comparison performed NA
Cazals et al., 1984 [78] RW DC+ C 2, 5V No comparison performed NA
Hazell et al., 1993 [76] RW AC A Square, ramp, sinusoid Sinusoid > (ramp, square) NST
C 0–300 μA >+6 μA for hearing threshold NST
PR 10–200 Hz (20–50 Hz) < 100 Hz NST
House et al., 1984 [73] PM AC A Carrier wave dependent of sound No comparison performed NA
RW (control) AC PR 60, 1600 Hz No comparison performed NA
Portmann et al., 1979 [80] RW, PM AC, DC C 0–500 μA No comparison performed NA
E RW, PM RW > PM NST
P (+)/(−) (+) > (−) NST
PR 50–6400 Hz No comparison performed NA
Portmann et al., 1983 [81] RW, PM DC+ C 1–5V No comparison performed NA
E RW, PM RW > PM NST
Rubinstein et al., 2003 [67] RW AC C 300 μA–1.5 mA No comparison performed NA
PR 4800 pps No comparison performed NA
Pulse duration 25, 50, 80 μs/phase No comparison performed NA
Wenzel et al., 2015 [69] RW AC C 0–3 mA No comparison performed NA
PR 0–100 Hz No comparison performed NA
Pulse duration 50 μs–8 ms No comparison performed NA

A: amplitude modulation; AC: alternative current; C: current level; CI: cochlear implant; DC: direct current; E: electrode location; NA: not applicable; NI: no information; NRI: non-residual inhibition group; NST: no statistical test performed; OW: oval window; P: polarity; PM: promontory; PR: pulse rate; RI: residual inhibition group; RW: round window. The p-value is the result of a statistical comparison test between the tinnitus questionnaire scores used for specific parameter values. Significant p-values are in bold.