Does botulinum toxin treatment improve upper limb active function?

Background: Spasticity following lesions of the central nervous system such as stroke is a major cause of impairment and disability, especially when it affects the upper limb, and can be focally relieved by intramuscular injections of botulinum toxin (BT). Functional improvements of the affected upper limb after a BT focal treatment remain controversial.

Objective: We aimed to assess the functional effects of BT treatment on upper-limb spasticity in the literature, identify flaws and deficiencies in proving these effects and propose leads for future trials.

Methods: We searched the MEDLINE and Cochrane databases for trials, reviews and meta-analyses assessing the effect of BT injection in upper-limb spasticity. This was a non-systematic narrative review, and the selection of articles was based on the authors' expertise. The review focused on stroke-related spasticity and disability.

Results: Patients' therapeutic targets involved use of the disability assessment scale (DAS) or goal attainment scale (GAS). Impairments and passive function goals prevailed for active function and participation and were more frequently achieved for the former than the latter. Meta-analyses showed no to mild effect sizes for improvement in upper-limb function but failed to show higher and/or better use of the paretic upper limb in activities of daily living after BT injection.

Conclusion: BT injections for impairment and passive function are related to improved kinematic parameters; however, the relation between relief of spasticity and improved upper-limb activity has not been established. Possible explanations for the lack of functional effect in studies are first, disability is mainly due to muscle weakness rather than spasticity, so patients with the best underlying motricity may benefit the most from BT injections; second, assessment methods may not be adapted to screen eligible patients; third, most studies' endpoints were at 4 to 12 weeks after a single injection, but repeated treatment sessions might be needed to observe functional outcome on the upper limbs; and finally, the association of rehabilitation programs or non-pharmacological treatments may enhance the functional effects of BT injections.