Journal of Rehabilitation Medicine 51-4inkOmslag | Page 73

J Rehabil Med 2019; 51: 307–311 SHORT COMMUNICATION SPASTIC CO-CONTRACTION, RATHER THAN SPASTICITY, IS ASSOCIATED WITH IMPAIRED ACTIVE FUNCTION IN ADULTS WITH ACQUIRED BRAIN INJURY: A PILOT STUDY Alexandre CHALARD, PT, MS 1,2 , David AMARANTINI, PhD 1 , Joseph TISSEYRE, MS 1 , Philippe MARQUE, MD, PhD 1,3 , Jessica TALLET, PhD 1 and David GASQ, MD, PhD 1,4 From the 1 ToNIC, Toulouse NeuroImaging Center, Université de Toulouse, Inserm, UPS, 2 Ipsen Innovation, Les Ulis, 3 Department of Physical Medicine and Rehabilitation and 4 Department of Functional Physiological Explorations, University Hospital of Toulouse, Hôpital de Rangueil, Toulouse, France Objective: To elucidate the adverse consequences of spasticity and spastic co-contraction of elbow flex- ors on motor impairment and upper limb functional limitation. Design: A pilot case-controlled prospective observa- tional study. Subjects: Ten brain-injured adults, and 10 healthy controls. Methods: The co-contraction index was computed from electromyographic recordings of elbow flexors during sub-maximal (25% Maximal Voluntary Cont- raction) isometric elbow extension. Spasticity was assessed with the Tardieu scale, upper limb limita- tion using a goniometer during active elbow exten- sion, motor selectivity with the Fugl-Meyer Assess- ment for the upper limb, and motor function with the Action Research Arm Test. Results: Greater co-contraction occurred in patients with brain injury compared with controls. In cont- rast to spasticity, strong associations were found between the co-contraction index, the limitation of active elbow extension, the Fugl-Meyer Assessment, and the Action Research Arm Test. Conclusion: This pilot study suggests that spastic co-contraction rather than spasticity is an important factor in altered upper limb motricity in subjects with brain injury, leading to abnormal restricting arm movement patterns in subjects with more seve- re motor impairment. Practical applications directly concern the pre- and post-therapeutic evaluation of treatments aimed at improving motor skills in sub- jects with brain injury. Key words: brain injury; hemiplegia; muscle hypertonia; up- per extremity. Accepted Jan 29, 2019; Epub ahead of print Feb 15, 2019 J Rehabil Med 2019; 51: 307–311 Correspondence address: David Gasq, Toulouse NeuroImaging Cen- ter, CHU Purpan, Pavillon Baudot, place du Dr Baylac 31024 Toulouse, France. E-mail: [email protected] M uscle overactivity, including spasticity and spas- tic co-contraction in particular, describes invo- luntary motor unit recruitment, which occurs in spastic LAY ABSTRACT Spasticity and spastic co-contraction are expressions of muscle overactivity that occur in spastic paresis syn- drome after a brain injury. The objective of the pre- sent pilot study was to improve our understanding of the respective adverse consequences of spasticity and spastic co-contraction on motor disability. In contrary to spasticity, spastic co-contraction is strongly associa- ted with motor impairment in subjects with brain injury. Therapies should be directed toward reducing spastic co-contraction in order to improve motor function. paresis syndrome after a brain injury, such as stroke or traumatic brain injury (1). Spasticity is defined as an increase in velocity-dependent stretch reflexes, and is clinically manifested by excessive responses to mus- cle stretch (2). Spasticity is used as a convenient way to assess muscle overactivity during passive and fast muscular stretch. Spastic co-contraction, as assessed by electromyography using the muscle co-contraction index (3), refers to increased antagonist muscle recru- itment triggered by the volitional command of agonist muscles in the absence of a phasic stretch (1). It has been well established that spasticity and spastic co- contraction have different underlying physiological mechanisms (1), but their consequences on motor function remain to be confirmed and elucidated. It has been suggested that spastic co-contraction may contri- bute to limitations in active movement (4). However, to date, the impact of this disabling form of muscle overactivity on motor function in brain-injured adults has been only sparsely and indirectly studied (5). In addition, most treatments aimed at improving upper limb function, such as rehabilitation or botulinum toxin, focus on spasticity as the primary outcome in clinical practice (6). The aim of the present pilot study was therefore to elucidate the adverse consequences of spasticity and spastic co-contraction of elbow flexors on upper limb motor impairment and disability. The results of this study may have direct application in improving the evaluation and implementation of treatments aimed at improving motor function in subjects with brain injury. This is an open access article under the CC BY-NC license. www.medicaljournals.se/jrm Journal Compilation © 2019 Foundation of Rehabilitation Information. ISSN 1650-1977 doi: 10.2340/16501977-2528