QUANTITATIVE EVALUATION OF SPASTICITY OF POST-STROKE PATIENTS IN THE CHRONIC PHASE

M. Okawada^1,2,3, K. Tanamachi^1,2, W. Kuwahara^1,2, M. Kawakami¹, F. Kaneko^2,1

¹Keio University School of Medicine, Department of Rehabilitation Medicine, Tokyo, Japan, ²Tokyo Metropolitan University, Department of Physical Therapy, Faculty of Health Sciences Graduate School of Health Sciences, Tokyo, Japan, ³Kanagawa University of Human Services, Graduate Course of Health and Social Work, Yokosuka, Japan

Background: Spasticity is defined as impairment of motor function characterized by an angular velocity-dependent increase in muscle tone that inhibits movement in hemiplegic patients after stroke. Clinically, muscle tone is evaluated using the Modified Ashworth Scale (MAS). However, since MAS manually grades resistance during constant-velocity passive motion, velocity-dependent changes remain undetected. Additionally, the measurements are sorted on a categorical scale of six; hence,detailed differences cannot be detected. We aimed to develop an evaluation method to overcome these shortcomings.

Purpose: Wedevelopeda device for passive dorsiflexion of the wrist joint by a motor (extension device) and attempted to quantitatively evaluate spasticity by acquiring a surface electromyogram (sEMG).Subsequently, we verified whether this method could detect velocity-dependent changes in muscle tone.

Methods: The subjects werepost-strokepatients with severehemiparesisin the chronic phase. Subjects had severe upper-limb motor deficits, including spasticity. Using our extension device for evaluation, first,the wrist joint of the subjects was passively moved from the initial wrist position of 45 deg of palmar flexion to 60 deg of dorsiflexion at angular velocities of 90, 135, and 180 deg/sec.At that time, the sEMG of the flexor carpi radialis and flexor digitorum profundus (FDP) were acquired. The sEMG was processed with a 5-500 Hz bandpass filter, and the root mean square (RMS) was calculated with a window width of 0.3sec. In the RMS of each muscle, the integrated value per sec from the start to the end of dorsiflexion was calculated. The wrist and finger flexors were given the scores of 0, 1, 1+, 2, 3, or 4 on the MAS. To analyze the MAS scores, the scores of 1+, 2, 3, and 4 were transformed to 2, 3, 4, and 5, respectively (transformed scores: 0, 1, 2, 3, 4, and 5).

Results: In each subject, the correlation coefficient between the RMS of FDP and the angular velocity (90, 130, 180deg/sec) showed strongly positive values. In all subjects, the slope of the RMS of FDP and the angular velocity for each subject showed a strong positive correlation with the MAS of fingers. In addition, there was a significant positive correlation between the MAS of the finger and the RMS of FDP at an angular velocity of 180 deg/sec; however, no significant correlation was observed at angular velocities of 90 and 135 deg/sec.

Conclusions: The RMS of FDP increased in an angular velocity-dependent manner.Our results suggest that the angular velocity-dependent characteristics can be clarified by evaluating at least up to 180 deg/sec in multiple stages. This study also confirmed the feasibility of quantitative evaluation of spasticity.

Implications: Spasticity is a factor that inhibits movement in post-stroke patients, and its evaluation plays an important role in determining the therapeutic options and prognosis. To date, there has been no method to assess angular velocity-dependent wrist spasticity quantitatively. The method used in this study may help examine detailed changes in spasticity in the future.

Funding acknowledgements: This study was supported by AMED (Grant Number JP18he0402255) and JSPS KAKENHI (Grant Number JP19H01088).

Keywords:
Stroke
Spasticity
Upper-limb

Topics:
Neurology: stroke
Neurology

Did this work require ethics approval? Yes

Institution: Keio University

Committee: Certified Review Board of Keio

Ethics number: N20180010-4