Post-stroke spasticity: follow-up and functional implications of chronic long-term treatment with botulinum toxin

Background: Around 40% of stroke survivor develop spasticity. Plantar flexors (PF) muscles are often affected, with severe functional impairment. The treatment of choice is botulinum toxin type A (BoNT-A) combined with adjuvant treatments. The temporary pharmacological effect implies periodic reassessment and reinjection. These long-term chronic programs require monitoring the functional impact of each cycle and the clinical evolution in relation to aging and repeated interventions. Aim: Evaluating changes of functional level in patients with post-stroke spasticity treated with BoNT-A by assessing the long-term maintenance of the therapeutic efficacy. Design: Retrospective longitudinal observational study. Setting: Outpatients. Population: Chronic stroke survivors undergoing BoNT-A treatment and subsequent intensive rehabilitation (10 sessions in a day-hospital regime). Methods: Medical records of the enrolled patients were consulted. The primary endpoint was the change in PF spasticity by at least 1 point on the Modified Ashworth Scale (MAS) at each cycle. Secondary endpoints were the assessment of possible trends in gait parameters (Six Minute Walking Test [6MWT]; Timed Up and Go [TUG], and 10 Meters Walking Test [10mWT]) pre- and post-injection and at each cycle. Results: Thirty-six patients were enrolled. A reduction of at least one MAS point for PF was recorded after each cycle in all subjects. A time-dependent reduction in the proportion of patients reporting an improvement higher than the minimal clinically important difference (MCID) in 6MWT and 10mWT was observed. In the case of TUG, this data kept stable at all cycles. A one-point increase in the basal functional ambulation classification (FAC) score resulted in a reduction in the probability of having a TUG improvement greater than the MCID. The opposite correlation was found for 6MWT and 10mWT. Conclusions: With the proposed treatment, the clinical significance TUG improvement remains constant throughout repeated cycles and the proportion of patients with improvement in 6MWT and 10mWT tends to decline over time. The predictive value of basal FAC on the functional variables expected improvement may provide a potential treatment targeting tool. Clinical rehabilitation impact: These results may deliver prognostic indication allowing an optimized integration of different post-BoNT-A rehabilitation approaches, agreeing with current evidence. Adequate monitoring and treatment protocols are crucial for the stability of functional level and may prevent excessive fluctuations.