# Medical Devices for Tremor Suppression: Current Status and Future Directions
## 7 Tremor Suppression Devices: Place in Therapy
\begin{table}
\begin{tabular}{c c c c c} \hline
**Type of Device** & **Study Participants (_n_)** & **Efficacy** & **Risks** & **Refs** \\ \hline \hline \multicolumn{5}{c}{**Electrical Stimulation Systems: Transcutaneous Electrical Nerve Stimulators**} \\ \hline \multirow{5}{*}{Cala ONE \(\ddagger\)} & \multirow{5}{*}{ET (77)} & \(\bullet\) & Improved upper limb & \multirow{5}{*}{\(\bullet\)} & \multirow{5}{*}{\(\bullet\)} \\  & & TETRAS tremor scores & & \\  & & (\(p\) = 0.017) & & \\ \cline{1-1}  & & \(\bullet\) & Improved subject-rated & & \\ \cline{1-1}  & & BF-ADL scores (\(p\) = 0.001) & & \\ \hline \multirow{5}{*}{Cala Trio \(\ast\)} & \multirow{5}{*}{ET (205)} & \(\bullet\) & Improved upper limb & \multirow{5}{*}{\(\bullet\)} \\  & & TETRAS tremor scores & & \\ \cline{1-1}  & & (\(p\) \(<\) 0.0001) & & \\ \cline{1-1}  & & \(\bullet\) & Improved subject-rated & & \\ \cline{1-1}  & & BF-ADL scores (\(p\) \(<\) 0.0001) & & \\ \hline \multicolumn{5}{c}{**Electrical Stimulation Systems: Functional Electrical Stimulators**} \\ \hline MOTIMOVE & ET (3); PD tremor (4) & 67\% tremor suppression & & [79] \\ \cline{1-1} \cline{2-5}  & & \(\bullet\) & 52\% tremor suppression & [81] \\ \cline{1-1} \cline{2-5}  & & \(\bullet\) & Reduced UPDRS score & & \\ \cline{1-1}  & & (\(p\) = 0.001) & & \\ \hline \multicolumn{5}{c}{**Wearable Orthoses: Active Orthoses**} \\ \hline \multirow{5}{*}{WOTAS exoskeleton} & ET (7); MS tremor (1); Posttraumatic tremor (1); Mixed tremor (1) & & \\ \cline{1-1}  & Pneumatic actuator-based orthosis & ET (5) \(\lx@sectionsign\); PD tremor (5) \(\lx@sectionsign\) & 98.1\% tremor suppression [95] & [93; 94; 95] \\ \cline{1-1} \cline{2-5}  & PMLM-based orthosis & PD tremor (5) \(\lx@sectionsign\) & 97.6\% tremor suppression & [96] \\ \cline{1-1} \cline{2-5}  & Voluntary-driven & ET (1) \(\lx@sectionsign\) & 99.8\% tremor suppression & Not reported [97] \\ \cline{1-1} \cline{2-5}  & elbow orthosis & & & \\ \cline{1-1} \cline{2-5}  & MMS-based WTSG & Not reported & Not reported & [98] \\ \cline{1-1} \cline{2-5}  & Myoelectric-controlled & & & [99; 100; 101; 102] \\ \cline{1-1} \cline{2-5}  & orthosis & ET (2); Healthy (4) & Not reported & [103; 102] \\ \cline{1-1} \cline{2-5}  & Myoelectric-controlled & & & \\ \cline{1-1} \cline{2-5}  & orthosis (ver. 2) & Healthy (1) & 50–80\% tremor suppression [104] & [104; 105] \\ \cline{1-1} \cline{2-5}  & BSN-based orthosis & Healthy (6) \(\lx@sectionsign\) & 77\% tremor suppression & [105] \\ \hline \multicolumn{5}{c}{**Wearable Orthoses: Semi-Active Orthoses**} \\ \hline Double viscous beam & \multirow{2}{*}{Not reported} & Not reported & & [107] \\ \cline{1-1} \cline{2-5}  & orthosis & & & \\ \cline{1-1} \cline{2-5}  & MR damper-based & & & [108; 109; 110; 111] \\ \cline{1-1} \cline{2-5}  & orthosis & & & \\ \cline{1-1} \cline{2-5}  & SETS system & Not reported & Not reported & [112] \\ \cline{1-1} \cline{2-5}  & Electromagnetic & & & \\ \cline{1-1} \cline{2-5}  & brake-based orthosis & Healthy (3) \(\lx@sectionsign\) & 88\% tremor suppression & [113] \\ \cline{1-1} \cline{2-5}  & Pneumatic hand cuff & ET (1) & 30\% tremor suppression & [114] \\ \hline \end{tabular}
\end{table} 
Table 1: Summary of the tremor suppression devices and study results. ET is associated with a staggering cost of direct medical expenses, indirect productivity and income losses, nonmedical expenses, and disability benefits. The unemployment rate increases to about 88% in patients whose ET progresses from mild to severe [147], leading to forced early retirements. Collectively, patients with mild ET have a 1.83-year average loss of employment, corresponding to a $280 billion in income loss [147]. In patients with moderate to severe tremors, the average loss of employment is 6.5 years [147]. ET and PD tremors likely increase the economic burden more than currently estimated due to their progressive natures and the underreported cases. The development of a medical device for tremor suppression is an under-researched area.