DIFFERENCES IN GAIT PATTERNS BETWEEN PATIENTS WITH SWEDD AND NORMAL SUBJECTS

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DIFFERENCES IN GAIT PATTERNS BETWEEN PATIENTS WITH SWEDD AND NORMAL SUBJECTS

DO-YOUNG KWON

Department of Neurology, Korea University College of Medicine Ansan Hospital, Ansan City, Republic of Korea

YU-RI KWON

BK21 Plus Research Institute of Biomedical Engineering Konkuk University, Chungju, Republic of Korea YOON-HYEOK CHOI, JIN-YOUNG HA and SANG-HYUK KIM

School of Biomedical Engineering Konkuk University, Chungju, Republic of Korea

GWANG-MOON EOM School of Biomedical Engineering Konkuk University, Chungju, Republic of Korea BK21 Plus Research Institute of Biomedical Engineering

Konkuk University, Republic of Korea JI-WON KIM*

School of Biomedical Engineering Konkuk University, Chungju, Republic of Korea BK21 Plus Research Institute of Biomedical Engineering

Konkuk University, Republic of Korea kjw802@kku.ac.kr

Received 17 June 2020 Accepted 28 June 2020 Published 7 September 2020

Whether gait assessment can distinguish patients with scans without evidence of dopaminergic deficit (SWEDD) from normal individuals remains unclear. In the present study, the gait patterns in SWEDD patients and normal individuals were investigated. 10 patients with SWEDD and 10 healthy normal subjects were recruited. A GaitRite linear walkway was used to quantitatively assess level walking. Eight spatiotemporal variables were selected for

*Corresponding author.

This is an Open Access article published by World Scientific Publishing Company. It is distributed under the terms of the Creative Commons Attribution 4.0 (CC BY) License which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Vol. 20, No. 9 (2020) 2040022 (9 pages) °c The Author(s)

DOI:10.1142/S0219519420400229

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comparison between two groups. For statistical analysis, independent sample t-tests were performed to compare between normal individuals and SWEDD patients. Compared with normal individuals, SWEDD patients exhibited a shorter step length (p<0:001). In addition, SWEDD patients showed a wider distribution of heel-to-heel (HH) base of support compared with normal individuals (p<0:000). SWEDD patients had a tendency to deteriorated gait speed (p¼0:072) and double-limb support cycle (p¼0:088). These results indicate that SWEDD patients adopted a walking strategy that utilized increased step length and width to compensate for deteriorated dynamic balance. These results indicate that quantitative gait assessment could be useful for more accurate diagnosis of SWEDD patients. In addition, understanding clinical features of SWEDD patients might contribute to efficient interventions. Keywords: SWEDD; normal subject; gait; step length and HH base of support.

1. Introduction

Scans without evidence of dopaminergic deficit (SWEDD) is the neurological condition in patients clinically having Parkinsonism who showed normal dopami-nergic functional imaging.1,2SWEDD patients are considered to have a

heteroge-neous movement disorder with various underlying conditions3–5and their clinical

manifestations are similar to Parkinson’s disease (PD).6 In addition, it has been

reported that SWEDD patients have different prognoses compared with PD patients.6Thus, understanding the clinical characteristics of SWEDD patients is

important for the correct assessment and appropriate interventions.

To date, literature regarding the clinical characteristics of SWEDD patients is lim-ited. Recently, the clinical features of SWEDD patients were quantitatively charac-terized by comparison with PD patients. Kwonet al.evaluated bradykinesia of the upper limb and found that SWEDD patients had better speed, amplitude, and regularity than PD patients.7In an objective assessment of handwriting, sentence length and letter

height were significantly smaller in PD patients compared with SWEDD patients.8

Based on these findings, SWEDD patients appear to have less deteriorated motor symptoms than PD patients. Whether SWEDD patients can be distinguished from normal subjects remains unclear. In the objective assessment of bradykinesia, SWEDD patients exhibited less speed, amplitude, and regularity than normal subjects during finger tapping task.7 Conversely, in a handwriting assessment

study, SWEDD patients were not compared with normal subjects.8Compared to

normal subjects, quantitative clinical features of PD are well known; however, the clinical features of SWEDD patients have not been extensively studied. Therefore, early differentiation of SWEDD patients from normal subjects is important for better understanding of these patients.

In the present study, gait characteristics of SWEDD patients were investigated. Abnormal gait is a representative clinical feature of patients with a movement disorder such as PD. In many studies, PD patients showed gait patterns with shorter stride length,9,10slower stride velocity,10and increased double-limb support

period11 compared with normal subjects. Recently, Kwon et al. investigated gait

characteristics of SWEDD patients and found SWEDD patients walked with faster

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gait speed, longer step length, and shorter double-limb support period compared with PD patients12; however, SWEDD patients were not compared with normal

subjects. Whether gait assessment can distinguish SWEDD patients from normal subjects remains unclear. Therefore, differences in gait patterns between SWEDD patients and age-matched healthy individuals were investigated in the present study.

2. Materials and Methods 2.1. Subjects

The present study included 10 patients with SWEDD and 10 healthy normal subjects and all participants provided written informed consent. All participants could walk independently without assistive devices. The SWEDD patients were recruited from KOREA hospital in Ansan city, Korea. The SWEDD patients had Parkinsonism but with normal dopamine transporter (DAT) imaging and normal brain MRI. The nor-mal subjects were recruited from elderly communities in Ansan city. Patients with a history of stroke and/or taking medications that affect walking were excluded. Table1 shows subject characteristics. No significant differences were observed in height, weight, and age (p>0:05) between the study participants indicating the controls were appropriately recruited to control for the effect of subject characteristics.

2.2. Experiments and analysis

Participants performed gait assessment using a GaitRite walkway system (66 cm 427 cm, CIR Systems Inc. Clifton, NJ, USA) which can provide spatiotemporal variables (Fig.1). The system is a portable walkway embedded with many pressure sensors and has been validated as a reliable quantitative gait assessment tool.13,14

Prior to the main experiment, the participants warmed up (e.g., stretching and practiced walking on the walkway several times to become familiar with the ex-perimental environment. Participants were also asked to walk barefoot straight along the walkway at a preferred natural pace as if walking down the street.

Table 1. Subject information and clinical characteristics. SWEDD patients (n¼10) Controls (n¼10)

Variables Mean (SD) Mean (SD) P-value

Age (years) 68.2 (9:51) 70.1 (4:11) 0.417 Height (cm) 151.8 (4:80) 153.9 (4:15) 0.148 Weight (kg) 58.1 (10:8) 62.2 (8:94) 0.203 BMI (kg/m2) 25.15 (3:87) 26.24 (3:24) 0.341

UPDRS (scores) 21.3 (12:7)

H&Y Stage (stage) 1.60 (0:68)

Notes: BMI, body mass index; UPDRS, Unified Parkinson’s Disease Rating Scale; H&Y, Hoehn and Yahr.

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Each participant completed three walking trials and the average was used for subsequent analysis.

Eight spatiotemporal variables were selected among the variables provided by GaitRite software for comparison between SWEDD patients and control subjects. For spatial gait variables, step length, heel-to-heel (HH) base of support, and foot progression angle were selected. Figure 2shows the schematic definition of spatial variables. Step length was defined as distance between heel center and opposite heel center. HH base of support was defined as vertical distance between line of pro-gression and heel center of opposite foot. Finally, propro-gression angle was calculated as the angle between the progression line and midline of foot. For temporal vari-ables, stance of cycle, double-limb support of cycle, swing of cycle, and single limb support of cycle were used in the present study.12

Fig. 2. Schematic definition of spatial variables. Fig. 1. Experimental walkway for gait assessment.

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For statistical analysis, independent sample t-tests were evaluated using SPSS 16.0 (SPSS Inc., Chicago, IL, USA) to compare SWEDD patients with normal subjects. Ap-value<0:05 was considered statistically significant.

3. Results

Table 2 shows the results for the comparison of normal subjects and SWEDD patients. Although the study participants had similar height, a significant difference was observed in step length (p<0:01).

Specifically, SWEDD patients exhibited a shorter step length compared with normal subjects as shown in Fig.3(a). In addition, HH base of support in SWEDD patients was significantly longer than in normal subjects (p<0:001) as shown in Fig.3(b); thus, SWEDD patients walked with a longer base width compared with normal subjects. Although a significant difference was not observed, SWEDD patients tended to walk more slowly with longer double-limb support stance

(a) Step length (b) HH base support

Fig. 3. Significant difference in spatial gait variables between SWEDD and control subjects (**p<0:01, ***p<0:001).

Table 2. Gait patterns in SWEDD patients and controls.

SWEDD patients Controls Significance

Variables Mean (SD) Mean (SD) (p-value)

Stride velocity (cm/s) 84.3 (21:1) 95.3 (16:2) 0.072 Step length (cm) 46.3 (8:0) 53.0 (4:7) 0.003

HH base of support (cm) 11.45 (2:53) 6.39 (2:61) 0.000

Foot progression angle (deg) 6.6 (6:5) 6.5 (3:8) 0.964 Stance of cycle (%) 64.39 (1:84) 63.84 (1:83) 0.345 Double-limb support of cycle (%) 29.2 (3:3) 27.5 (3:0) 0.088 Swing of cycle (%) 35.6 (1:9) 36.2 (1:8) 0.341 Single-limb support of cycle (%) 35.6 (1:9) 36.2 (1:9) 0.340 Notes: SWEDD, scans without evidence of dopaminergic deficit; SD, standard deviation; HH, heel-to-heel.

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compared with normal subjects (p<0:10) as shown in Fig.4. In contrast, no sig-nificant differences were found in foot progression angle, stance of cycle, or swing cycle (p>0:1).

4. Discussion

In the present study, whether SWEDD patients exhibit gait abnormalities com-pared to normal subjects was investigated. Several gait functions were deteriorated in SWEDD patients compared with control subjects. Specifically, SWEDD patients exhibited gait pattern with a shorter step length compared with control subjects. In addition, SWEDD patients adopted an increased HH base of support gait strategy compared to normal controls. Furthermore, SWEDD patients tended to walk more slowly with a long double-limb support gait cycle compared with controls.

Patients with movement disorder PD or SWEDD typically exhibit gait dys-function. Quantitative gait assessment is useful to identify abnormal gait. For example, PD patients showed abnormal gait patterns, i.e., shorter stride length,9,10

reduced speed,10 and increased double-limb support.11 Furthermore, PD patients

exhibit more abnormal gait patterns compared with SWEDD patients.12In a

pre-vious study, gait assessment was shown useful for differentiating SWEDD from PD.12 However, SWEDD patients may have normal as well as abnormal gait

functions. Distinguishing abnormal from normal gait characteristics early is im-portant for effective therapy and interventions in SWEDD patients. The present study has demonstrated that SWEDD patients have abnormal gait characteristics that can be distinguished from normal individuals gait characteristics.

SWEDD patients showed gait pattern with a shorter step length compared with normal subjects although they were similar in age, height, and weight. This indi-cates that SWEDD patients used a more conservative gait strategy to maintain dynamic balance by taking shorter steps. In a previous study, SWEDD patients exhibited shorter step length compared with PD patients.12However, in the present

(a) Strid velocity (b) Double limb support of cycle Fig. 4. Comparison of gait speed and double-limb support period in SWEDD patients and control subjects.

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study, the step length was not normal in the SWEDD patients. These results indicate that step length could be a useful gait variable for differentiating SWEDD from healthy individuals as well as from PD.

In addition, a significant difference was observed in HH base of support between the study groups (p<0:000). This indicates the center of mass (COM) in SWEDD patients moved in a more lateral direction during level walking compared to normal controls. A wider HH base of support has been shown to indicate reduced dynamic balance ability during level walking.15A wider distribution of HH base of support

values accompanied decreased dynamic balance during gait and was associated with reduced gait speed.16,17In the present study, gait speed of SWEDD patients was

slower than in control subjects although a significant difference was not observed (p¼0:072). SWEDD patients may adopt a gait strategy with reduced gait speed for compensation of deteriorated dynamic balance ability. Based on this result, HH base of support could also be an important indicator for distinguishing SWEDD patients from normal subjects. However, whether this variable differs between SWEDD patients and PD patients should be investigated in further studies.

Double-limb support cycle tended to be longer for SWEDD patients compared to controls, although a significant difference was not observed (p¼0:088). Reportedly, double-limb support stance has been assessed as a stability factor during gait.18The

results from the present study showed that SWEDD patients might make longer the double-limb support cycle to stabilize their deteriorated dynamic balance. In a previous study, SWEDD patients exhibited a decreased double-limb support cycle compared with PD patients.12Double-limb support may also be a helpful diagnostic

indicator for distinguishing SWEDD patients from normal subjects and PD patients if further investigation is performed with more subjects.

SWEDD patients could not be differentiated from controls in other gait vari-ables. Specifically, SWEDD patients had normal progression angle. PD patients also showed normal progression angle in a previous study.12 Furthermore, SWEDD

patients exhibited normal stance and swing phase indicating SWEDD patients have normal ratio between stance and swing phase, contrary to PD patients.12

Recently, gyro sensors and accelerometers have been used for the assessment of gait. For example, Kimet al.have investigated upper acceleration patterns during level walking.19In particular, the wearable sensors provide quantitative gait

pat-terns in various conditions such as stairs or slopes. Therefore, further studies with a larger study cohort should be performed.

In the present study, SWEDD patients were differentiated from normal indivi-duals by assessing level walking. SWEDD patients had normal as well as abnormal gait characteristics. The present study had a limitation due to the small number of subjects; however, specific gait variables might aid in understanding clinical features of SWEDD patients. Based on the results and current literature, gait assessment could be an important tool for distinguishing SWEDD, PD, and normal subjects and may help clinicians to accurately diagnose patients with a movement disorder.

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5. Conclusions

In the present study, SWEDD patients exhibited gait pattern with shorter step length, a wider distribution of base of support due to deteriorated dynamic balance, and tended to show deteriorated gait speed and double-limb support cycle. The results can contribute to earlier distinction of SWEDD patients from normal subjects, and the understanding of gait patterns in SWEDD patients which can aid in choosing effective therapies for this clinical population.

Acknowledgments

This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education and Ministry of Science (2018R1C1B6008083 and 2019R1C1C1008209). Do-Young Kwon and Yu-Ri Kwon contributed equally to this study.

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Figure

Table 1. Subject information and clinical characteristics.

Table 1.

Subject information and clinical characteristics. p.3
Fig. 2. Schematic definition of spatial variables.
Fig. 2. Schematic definition of spatial variables. p.4
Fig. 1. Experimental walkway for gait assessment.
Fig. 1. Experimental walkway for gait assessment. p.4
Fig. 3. Significant difference in spatial gait variables between SWEDD and control subjects (** p &lt; 0:01, ***p &lt; 0:001).
Fig. 3. Significant difference in spatial gait variables between SWEDD and control subjects (** p &lt; 0:01, ***p &lt; 0:001). p.5
Table 2 shows the results for the comparison of normal subjects and SWEDD patients. Although the study participants had similar height, a significant difference was observed in step length ( p &lt; 0:01).

Table 2

shows the results for the comparison of normal subjects and SWEDD patients. Although the study participants had similar height, a significant difference was observed in step length ( p &lt; 0:01). p.5
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