Objective: To determine the effectiveness of a biomechanical glove in the setting of essential tremor (ET) using both Kinematic and clinical evaluation.
Background: Essential tremor (ET) is the most common movement disorder amongst adults, affecting approximately 1% of the population. Treatment options exist for ET , but they are limited in their effectiveness. A glove-based tremor dampener has been recently developed as a potential solution with its effectiveness currently unknown. This study aims to evaluate the effectiveness of this device.
Methods: Patients 18 Years and older with diagnosed ET were recruited by their treating neurologist for this ethics-approved study. The participants completed a series of tasks, static and dynamic, taken from the Fahn-Tolosa-Marin (FTM) scale. These tasks were performed under three conditions: a baseline assessment with no glove, an assessment with a weight-matched (sham) glove, an assessment with the true device. Outcomes were collected by clinical assessment using the FTM scale, and kinematic analysis via a multi-sensor kinematic unit. Descriptive statistical analysis was conducted.
Results: Preliminary data from 10 patients is presented here. By kinematic analysis, a decrease in the tremor amplitude of acceleration greater than 20% from baseline was defined as a significant improvement. For static tasks, 6/10 patients improved with the true glove, while 5/10 improved with the sham. For dynamic tasks, 8/10 improved with the true glove, while 7/10 improved with the sham. This was calculated comparing the patient's three worst tasks. By the FTM scale, those patients that had improved by kinematic analysis had a 0.81-point score clinical improvement across all static tasks with the real glove. and a 0.30-point improvement with the sham. There was a 0.57-point improvement in dynamic tasks with the real glove, and a 0.39-point improvement with the sham.
Conclusions: Clinical and kinematic data demonstrating the effect of a glove-based tremor dampener for ET has been presented in this study. This preliminary analysis may demonstrate a greater tremor reduction using the true glove when compared to the sham, but larger sample sizes are required to validate these findings. This study is in progress and more patients are being recruited. This data will be critical in informing further development of this device and similar assistive technology for ET.
Prevalence and Impact
- Essential tremor (ET) is the most common movement disorder amongst adults, affecting ~1% of the general population, with the prevalence increasing with age [1 , 2].
- ET characterized by high frequency, low amplitude, kinetic and postural tremors . These tremors, by clinical definition, affect the arms bilaterally, although they can also affect the head, voice, face and legs .
- ET has been shown to impact several domains of affected patient's quality of life, both physical and psychosocial .
- Many patients cannot maintain their occupation due to their tremor, and patients may resort to using alcohol to control their tremors [1,6].
Treatment and Management of ET and Limitations
- Treatment options are limited in their effectiveness and not all patients may benefit from them.
- Current management: medical therapy and, in refractory cases, surgical intervention .
- First line drugs, propranolol and primidone and only around half of patients respond, and tremor reduction is only up to 60% .
- When drugs are ineffective or intolerable due to side effects, surgical options are considered [3, 6]. Surgical intervention with deep brain stimulation has been to dramatically reduce symptoms , but several patients may not be eligible due to the inherent risks of surgery and postoperative complications.
- Other therapeutic options exist for those patients who are both refractory to medication and ineligible for surgery, including focused ultrasound thalamotomy and targeted botulinum toxin injections, but these are limited in their availability and efficacy [4,7,8].
Glove-Based Dampener and Aim of Study
- A recently developed glove-based tremor dampener is a potential solution . The device has been developed specifically to resist tremors in patients with ET and Parkinson's disease.
- This study Aims to do so in the ET patient population, using clinical, kinematic, and subjective measures.
Kinematic data was collected from 10 patients with essential tremor. Patients performed a set of tasks, classified as static or dynamic.
(1) Resting on a table (2) Arms outstretched (OS)
with shoulders protracted at 90O. hands pronated
(3) Arms OS with shoulders protracted at 90O . hands neutral
(4) Pen hovering over an X on a paper (5) Holding an empty cup
and a full cup (355 ml of liquid) at (a) Position 3 (b) Cup brought towards mouth and angle and held at angle of maximal tremor.
Dynamic Tasks (based off FTM)
(1) Spiral 1 (2) Spiral 2 (3) writing a sentence (4) Line A* (5) Line B* (6) Line c* (7) Finger-to-Nose (FtN) testing*
*Used solely for FTM score analysis due to limitations in kinematic analysis
The circuit of tasks were performed three times: (1) with no glove-based dampener (2) with a weight-matched sham glove (550g) (3) with the glove-based tremor dampener on their dominant arm (i.e true glove) (pictured in text). The dampener utilizes a ball joint damper surrounded by a non-Newtonian fluid, along with a tuned mass damper. FTM scores for each task were recorded by a single-rater. Kinematic data from the dominated hand, forearm, wrist, elbow, and shoulder were collected using a multisensory kinematic unit consisting of goniometers, torsiometers, and an accelerometer via DataLINK. Root-mean squared (RMS) accelerometry power is the metric for kinematic severity used here. Data was analyzed using MATLAB.
N.B. Error bars demonstrate intrinsic variability in our population rather than "true" error.
Fig. 1: Percent Change in Accel. RMS Power (right), FTM Score Change for Improved Patients (left)
Clinically significant improvement was defined as a percent reduction in tremor of 20% (dashed line) when averaging the patient's three worst tasks at baseline (tasks with the highest baseline RMS power). The number of patients who responded per this definition, with their average associated FTM score improvements, is presented in the grid below.
Fig. 2: Average RMS of Acceleration Per Task Across Patients
This is shown for baseline, sham, and dampener trials. The average RMS of acceleration for the dampener is lower than the baseline and sham for 7/9 static tasks and 3/3 dynamic tasks..
Fig. 3: Average FTM score change per task (above)
FTM data is displayed as point change from baseline for the sham and the dampener. The FTM score was lower (improved) in the dampener than the baseline and sham for 6/9 static tasks and 6/6 dynamic tasks.
Fig. 4: Bandpower analysis (left)
Welch's power special density (PSD) of the accelerometry
data was generated (presented here as % contribution of
each 1 Hz interval to the total bandpower, from 2-15 Hz).
Data was bandpass filtered between 1.5 and 19.5 Hz with
a 0.5 Hz slope. PSD for patients who responded and those
who didn't is presented separately for sample tasks.
Maximal bandpower range was determined
(static responders= 4-5 Hz, static non-responders= 4-5 Hz; dynamic responders= 6-7 Hz, dynamic nonresponders= 4-5 Hz)
1.This preliminary analysis may demonstrate a greater tremor reduction using the dampener when compared to the sham, but larger sample sizes are required to determine statistical significance
2.Trend that dampener improves tremor over the sham, both
3. Patients who respond to the dampener for dynamic tasks may have higher frequency tremor, which could assist in identification of patients who may derive benefit, based on the tasks they find challenging
Limitations and future Directions
1. More study participants to be recruited to add to our sample size to strengthen conclusions
2. Interrater reliability of FTM scoring to be conducted
3. Further analysis to assess the reasons why some improvement was seen with the sham – there is likely a contribution of weight in reducing tremor, as seen in previous research
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