Here’s an overview of a 2018 Research Study which received grant funding from the IETF:
Principal Investigator: Vibhash Sharma, MD
University of Kansas Medical Center
Although essential tremor (ET) is the most common tremor disorder, its diagnosis can be challenging, and misdiagnosis of ET is not uncommon. The most common movement disorder confused with essential tremor is tremor predominant Parkinson’s disease (PD). Dopamine transporter (DaT) scan is the only available diagnostic tool utilized in the differentiation of ET from PD. However, due to its expense and limited availability it is important to develop a relatively inexpensive tool that can easily and efficiently be utilized in clinical settings to aid in the accurate diagnosis of ET. With growing evidence of gait abnormalities in ET, studying quantitative gait measures may potentially aid in differentiating ET and PD. In this pilot study, we aim to quantitatively analyze gait and balance in the clinical setting using wireless sensors to determine if the gait abnormalities are present in early ET, and whether comparing various aspects of gait and balance can help to differentiate between ET and PD.
The study will include patients who have received a DaTscan as part of their clinical care, to help confirm a diagnosis of either ET or PD. The DaTscan results will be considered the “gold standard” diagnosis, which will be compared to the results of the gait and balance assessments to determine if these assessments can similarly differentiate the patients as either ET or PD.
The study will be conducted in the Parkinson’s Disease and Movement Disorder Center at the University of Kansas Medical Center.
Summary Update for A Pilot Study for Quantitative Assessment of Gait in Essential Tremor Using Wireless Sensors
Principal Investigator: Vibhash Sharma, MD
University of Kansas Medical Center (KU)
July 2019 Update
The comparison of essential tremor (ET) to healthy controls has been completed but work is still being done on the comparison between ET and Parkinson’s disease (PD) and the comparison of outcomes with DaTscans.
We have performed gait assessments for 53 patients with essential tremor and 31 age matched healthy controls. The data obtained for essential tremor patients and healthy controls has been analyzed. We found that ET patients have impairment in multiple gait parameters (stride length, lower cadence, reduced gait speed and increased double support percent) when compared to normative values. When compared to age matched healthy controls, we again found significant impairment in multiple gait parameters including gait speed, stride length, increased double support percent, toe out angle and reduced lower limb swing. Interestingly, we also observed reduced right arm swing in patients when compared to healthy controls, which was also noted in ET patients with negative DaTscan. We presented our results at the KU Research Day and will be presenting again in September 2019 at the International Congress of Parkinson’s Disease and Movement Disorder (MDS) meeting to be held in Nice, France. As part of a separate initiative, during the last year, we have performed gait assessment for more than 1,200 PD patients from which we will extract a subset for the comparison with ET patients.
Work continues on the study and results are anticipated by the end of 2019.
Final Report on “A Pilot Study for Quantitative Assessment of Gait in Essential Tremor Using Wireless Sensors.”
Principal Investigator: Vibhash Sharma, MD
University of Kansas Medical Center
January 28, 2020
The pilot study for gait analysis in patients with Parkinson disease (PD), essential tremor (ET) and healthy controls has been completed. Gait analyses were performed during clinic visits. The time taken to perform gait analysis was between 3 to 10 minutes per person.
The Parkinson disease group was very large and diverse, therefore for comparison with the essential tremor group, we identified Parkinson disease patients who were diagnosed in the last five years. Additionally, we also identified ET patients who had normal DaTscan and PD patients who had abnormal DaTscan from our database. We created different groups from the dataset (Table 1).
Table 1
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Gait measures obtained during gait analysis were analyzed and comparisons between the various groups were done using ANOVA. Pertinent variables amongst different groups (All ET, PD and HC) are summarized in table 2 (below). Comparisons between various groups are summarized below:
- ET (n=71, mean age 68.1 years) vs Healthy Controls (n=31, age 63.9 years)
Patients with ET were found to have significantly reduced gait speed and stride length compared to healthy controls. There was also a significant increase in double support time and increased toe out angles compared to healthy controls, suggesting impaired dynamic balance. Additionally, ET patients showed an increase in turn duration and reduced turn velocity. When compared to normative data provided by Mobility Lab/APDM, ET patients also showed reduced cadence.
PD less than or equal to 5 years of diagnosis (n=68, 66.4 years) vs Healthy Controls (n=31, 63.9 years)
Patients with PD showed significantly reduced gait speed, stride length, turn velocity and arm range of motion compared to healthy controls. PD patients also showed significant increase in duration of turn and number of steps during turn when compared to healthy controls. Cadence was reduced when compared to normative values, but when compared to healthy controls this difference was not statistically significant.
PD less than or equal to 5 years of diagnosis (n=68, 66.4 years) vs ET group (n=71, mean age 68.1 years)
On comparing all PD patients with the overall ET group, no significant difference was seen across multiple gait measures including gait speed, gait cycle duration, stride length, double support time, or cadence. ET patients were found to have an increase in double support time compared to PD and arm range of motion was reduced in PD compared to ET, however only reduction in left arm range of motion in PD patients compared to ET was statistically significant.
To further assess gait parameters between PD and ET, gait measures obtained from patients with PD diagnosed in the last 5 years with abnormal DaTscan were compared with ET patients who had a normal DaTscan.
PD less than or equal to 5 years of diagnosis + Abnormal DaT scan (n=16, 69.1 years) vs ET + Normal
DaTscan (n= 14, 64.1 years).
On comparing gait measures no significant difference was noted among different gait measures including cadence, gait speed, stride length, or gait cycle duration. Again, ET patients showed increased double support time and toe out angle when compared to PD, but these changes were not statistically significant.
As several of our patients with PD were on dopaminergic medications at the time of gait analysis which can affect gait measures, we identified PD patients who were 1) OFF of levodopa at the time of gait analysis or 2) newly diagnosed PD patients not on dopaminergic medications. We compared gait measures in this group of PD patients (n=22) with healthy controls and ET.
PD diagnosed < 5 years (with no medications) (n=22, 61.5 years) vs Healthy controls (n=31, 63.9 years)
PD patients had significantly lower gait speed and stride length. Cadence was reduced in PD patients, but the difference was not statistically significant. There was significant reduction in upper limb arm velocity and range of motion in PD compared to controls. Additionally, lower limb foot strike angle was significantly lower in PD patients. The duration of turn was significantly higher in PD patients and turn velocity was significantly reduced. The number of steps during a turn was higher in PD, but this difference was not statically significant.
PD diagnosed < 5 years (with no medications) (n=22, 61.5 years) vs ET patients (n = 71, 68.1 years)
Both PD and ET showed similar cadence, gait speed, gait cycle duration and stride length. ET patients had significantly increased double support time and increased duration for anticipatory postural adjustment. PD patients showed reduced arm swing velocity on left (p>0.05) and reduced arm range of motion bilaterally (p<0.05). There was no significant difference in turn duration, turn velocity and number of steps in turn (p>0.05).
PD diagnosed < 5 years (with no medications) (n=22, 61.5 years) vs ET patients with negative DaTscan (n = 15, 69.1 years)
Both PD and ET showed similar cadence, gait speed, and gait cycle duration. ET patients had significantly reduced stride length as compared to PD. This result is likely due to parkinsonian features in ET patients in this group due to which DaT scan was obtained. We did not see this difference in stride length in other comparisons.
ET patients had significantly increased double support time (p<0.05) and increased toe out angle but not statistically significant. PD patients showed reduced arm swing velocity and reduced arm range of motion bilaterally (however p>0.05).
There was no significant difference in turn duration, turn velocity and number of steps in turn (p>0.05).
Based on the above findings, gait assessments using wireless sensors in the clinic could help to differentiate gait measures between ET and healthy controls and PD and healthy controls. The analysis was quick to perform in the clinic and can be utilized to track gait with disease progression. However, it seems that the gait in early PD and ET is similarly affected and it may be difficult to differentiate PD and ET by gait assessment using wireless sensors in the clinic. Interestingly we found that ET patient had increased double support time across different comparison which suggest dynamic balance is more impaired in ET as compared to early PD. Future studies are needed to support our findings.
Table 2: Comparison of gait measures between different groups.
| Gait measure (mean) | Normative value | ET (n=71) | PD (n=68) | HC (n=31) | p value | |
| iSAW Parameters | ||||||
| Gait – Lower limb speed mean (m/s) | L | 1.23 | 0.88 | 0.90 | 1.05 | ET vs HC: 0.000 PD vs HC: 0.000 PD vs ET: >0.05 |
| R | 0.86 | 0.88 | 1.01 | ET vs HC: 0.000 PD vs HC: 0.000 PD vs ET: >0.05 | ||
| Gait – Lower limb double support (%GCT) | L | 18.97 | 24.42 | 23.19 | 21.14 | ET vs HC: 0.001 PD vs HC: 0.052 PD vs ET: >0.05 |
| R | 24.59 | 23.58 | 21.59 | ET vs HC: 0.001 PD vs HC: 0.061 PD vs ET: >0.05 | ||
| Gait – lower limb cadence (steps/min) | L | 113.63 | 102.22 | 103.50 | 105.23 | >0.05 |
| R | 102.21 | 103.24 | 104.83 | >0.05 | ||
| Gait – lower limb stride length (m) | L | 1.3 | 1.037 | 1.046 | 1.20 | ET vs HC: 0.000 PD vs HC: 0.000 PD vs ET: >0.05 |
| R | 1.009 | 1.013 | 1.15 | ET vs HC: 0.000 PD vs HC: 0.000 PD vs ET: >0.05 | ||
| Gait – lower limb toe out angle (degrees) | L | 8.54 | 11.12 | 9.81 | 5.98 | ET vs HC: 0.007 PD vs HC: 0.068 PD vs ET: >0.05 |
| R | 14.77 | 13.02 | 10.0 | ET vs HC: 0.015 PD vs HC: 0.225 PD vs ET: >0.05 | ||
| Upper limb arm velocity(degree/sec) | L | 180.96 | 165.43 | 151.11 | 184.09 | ET vs HC: 0.657 PD vs HC:0.095 PD vs ET: >0.05 |
| R | 148.37 | 153.74 | 185.94 | ET vs HC: 0.197 PD vs HC: 0.349 PD vs ET: >0.05 | ||
| Upper limb range of motion (degrees) | L | 43.7 | 37.78 | 28.00 | 41.99 | ET vs HC: 0.743 PD vs HC: 0.001 PD vs ET: 0.002 |
| R | 29.43 | 25.10 | 46.79 | ET vs HC: 0.000 PD vs HC: 0.000 PD vs ET: >0.05 | ||
| Turns- Duration (Sec) | 2.1 | 2.44 | 2.48 | 2.1 | ET vs HC: 0.014 PD vs HC: 0.005 PD vs ET: >0.05 | |
| Steps in turn (n) | 3.7 | 3.81 | 3.91 | 3.4 | ET vs HC: 0.169 PD vs HC: 0.051 PD vs ET: >0.05 | |
| Turn velocity | 156.40 | 147.99 | 180.07 | ET vs HC: 0.004 PD vs HC: 0.000 PD vs ET: >0.05 | ||