Table 2. Summary of Clinical Studies of Transcranial Stimulation in ET, by Year of Publication.
| Study | Method of Stimulation | Target Location | Method of Assessment | Outcome |
|---|---|---|---|---|
| Gironell et al.41 (n = 10 ET) | Single session repetitive cerebellar TMS, 1 Hz, 70 mm butterfly coil, 100% maximal output, 30 trains of 10 seconds each | 2 cm caudal to inion | Tremor Rating Scale (TRS), accelerometry | Improved TRS and accelerometry ratings at 5 minutes but returned to baseline by 60 minutes |
| Hellriegel et al.46 (n = 20 total, 10 ET) | Single session of 40 seconds of continuous theta burst stimulation: 50 Hz, figure of 8 coil, 80% active motor threshold vs. 30% AMT (control intervention) | Primary motor cortex | TRS, accelerometry, MEPs | Improved accelerometry 45 minutes after cTBS, not TRS clinical scores; also real cTBS did not reduce MEP in ET subjects but did in HC |
| Popa et al.42 (n = 22 total, 11 ET) | Five sessions of repetitive cerebellar TMS 1 Hz, figure of 8 coil, daily×5 days, 90% resting motor threshold, 900 pulses over 15 min, to each cerebellar hemisphere | Cerebellar lobule VIII (neuronavigated) | TRS | TRS total improved by 23% at day 29 |
| Gironell et al.48 (n = 10 ET) | Transcranial direct current stimulation (tDCS): 2 cathodal electrodes (25 cm2), 2 mA×20 minutes, 10 consecutive sessions | Both cerebellar hemispheres, 3 cm lateral to the inion | TRS, accelerometry, disability rating scale | No change at day 1, day 10 or day 40 in either TRS or accelerometry |
| Bologna et al.47 (n = 27 total, 16 ET) | Single session cerebellar continuous theta burst stimulation: 50 Hz stimulation repeated 5 Hz over 40 seconds at 80% of active motor threshold, figure 8 coil | 3 cm lateral and 1 cm below the inion | Cortical excitability, tremor frequency, tremor amplitude | Cerebellar cTBS reduced MEPs in HC but not ET cohort Intervention had no effect on TRS, tremor frequency or smoothness of reaching movements |
| Badran et al.44 (n = 10 ET) | 15 daily sessions of 1 Hz rTMS to pre-SMA, butterfly coil for 20 minutes each; sham-controlled | Halfway between Fz and FCz | TRS | 23% reduction in TRS vs 18% reduction in sham-TMS |
| Helvaci Yilmaz et al.49 (n = 6 ET) | 10 daily weekday sessions of anodal tDCS to the dorsolateral prefrontal areas and inion at 2 mA for 20 minutes + 5 more tDCS sessions as above, delivered every other day after 30 days from initial intervention | Prefrontal areas (Fz and C4) | TETRAS motor and ADL rating scales | Statistically significant difference in TETRAS-motor 20% and TETRAS-ADL 17% at 50 days compared to pre-intervention baseline |
Abbreviations: tDCS, Transcranial Direct Current Stimulation; TETRAS, The Essential Tremor Rating Assessment Scale; TRS, Tremor Rating Scale (Fahn Tolosa Marin).