THE RELATIONSHIP BETWEEN CLINICAL AND MUSCLES SYNERGIES OUTCOME MEASURES OF THE UPPER LIMB MOTOR RECOVERY AFTER STROKE: A LONGITUDINAL STUDY

G. Pregnolato¹, L. Maistrello¹, D. Rimini², T. Lencioni³, I. Carpinella³, M. Ferrarin³, J. Jonsdottir³, A. Turolla^4,5

¹IRCCS San Camillo Hospital, Laboratory of Rehabilitation Technologies, Venice, Italy, ²Salford Care Organisation, Medical Physics Department—Clinical Engineering, Salford, United Kingdom, ³IRCCS Fondazione Don Carlo Gnocchi, Milan, Italy, ⁴Alma Mater Studiorum Università di Bologna, Department of Biomedical and Neuromotor Sciences – DIBINEM, Bologna, Italy, ⁵IRCCS Policlinico Sant’Orsola-Malpighi, Division of Occupational Medicine, Bologna, Italy

Background: In motor neuroscience, a central issue is to explain how the Central Nervous System (CNS) controls and coordinates voluntary movements. The muscle synergies model is based on the hypothesis that the CNS solved the problem by combining pre-organised low-level units, called motor models. Non-negative matrix factorization (NMF) algorithm decomposes electromyography signals (sEMG) acquired during subjects’ motor performance to extract muscle synergies. To date, the changes of muscle synergies after stroke and the relationships between clinical outcomes and muscles synergies parameters are still debated.

Purpose: The aim of the study is to investigate any relationship between clinical outcomes and muscle synergies parameters in stroke survivors who underwent to a specific upper limb motor training.

Methods: We enrolled 55 patients with diagnosis of first stroke, residual upper limb motor movements and no severe cognitive impairment. All patients concluded 20 sessions of a technological-based training for upper limb motor recovery. All patients were clinically assessed before (T0) and after (T1) the treatment and they underwent to a sEMG acquisition of 16 upper limb muscles during the execution of 7 exercises in virtual reality environment (i.e., VRRS system, Khymeia Group, Italy), both with unaffected and affected limb. For muscle synergies extraction, we used NMF algorithm to decompose the sEMG signals. The muscles synergies parameters are the following: number of modules of the unaffected limb and affected limb, number of shared modules and the similarity index, considered as the median of scalar products among modules of both limbs. We analysed clinical outcomes and muscle synergies parameters with descriptive analysis, correlation analysis and linear regression models. The level of statistical significance was imposed at 0.05.

Results: After treatment, results showed a significant improvement for all clinical variables (e.g., Fugl Meyer Upper Extremity p<0.001) and a significant difference for similarity index (p=0.044) but no differences in number of modules. Correlation analysis showed a positive correlation between the similarity index the Fugl-Meyer Upper Extremity score, and the linear regression models confirmed that the similarity index was dependent on the level of upper limb motor function (β= 0,002; P =0.0003). After data stratification based on the recovery phase (i.e., sub-acute, no.=36, or chronic phase, no.=19), only the patients in a sub-acute phase showed a significance improvement for the similarity index (p=0.009).

Conclusions: In our study, results confirmed that the use of technological device in upper limb treatment enhanced motor recovery after a stroke. Moreover, muscle synergies parameters showed that the affected limb was more similar to unaffected limb after the training. Finally, we confirmed that clinical outcomes and muscles synergies provided the same information about motor improvements, and no change in the number of modules was observed.

Implications: Our study confirmed the efficacy to employ technological devices, in particular robotic device and Virtual Reality, in motor rehabilitation after stroke. Moreover, results showed that the similarity of motor recruitment improved, specifically in sub-acute phase. Finally, the implication of muscle synergies on neurorehabilitation field, may provide a tailored rehabilitation training based on the mechanisms which underpin the movements in stroke survivors.

Funding acknowledgements: The study was funded by the Italian Ministry of Health (Grant Agreement No. RF-2019-12371486).

Keywords:
Muscle Synergies
Upper Limb Motor Impairment
Stroke Rehabilitation

Topics:
Neurology: stroke
Disability & rehabilitation
Research methodology, knowledge translation & implementation science

Did this work require ethics approval? Yes

Institution: IRCCS San Camillo Hospital, Venice, Italy

Committee: Ethics Committee of Venice and IRCCS San Camillo Hospital

Ethics number: CE protocol no. 2015.14