Functional effects of botulinum toxin type-A treatment and subsequent stretching of spastic calf muscles: a study in patients with hereditary spastic paraplegia

Abstract

Objective: Although calf muscle spasticity is often treated with botulinum toxin type-A, the effects on balance and gait are ambiguous. Hereditary spastic paraplegia is characterized by progressive spasticity and relatively mild muscle weakness of the lower limbs. It is therefore a good model to evaluate the functional effects of botulinum toxin type-A.

Design: Explorative pre-post intervention study.

Subjects: Fifteen subjects with pure hereditary spastic paraplegia.

Methods: Patients with symptomatic calf muscle spasticity and preserved calf muscle strength received botulinum toxin type-A injections in each triceps surae (Dysport®, 500-750 MU) followed by daily stretching exercises (18 weeks). Before intervention (T0), and 4 (T1) and 18 (T2) weeks thereafter, gait, balance, motor selectivity, calf muscle tone and strength were tested.

Results: Mean comfortable gait velocity increased from T0 (0.90 m/s (standard deviation (SD) 0.18)) to T1 (0.98 m/s (SD 0.20)), which effect persisted at T2, whereas balance and other functional measures remained unchanged. Calf muscle tone declined from T0 (median 2; range 1-2) to T1 (median 0; range 0-1), which effect partially persisted at T2 (median 1; range 0-2). Calf muscle strength did not change.

Conclusion: Botulinum toxin type-A treatment and subsequent muscle stretching of the calves improved comfortable gait velocity and reduced muscle tone in patients with hereditary spastic paraplegia, while preserving muscle strength. Balance remained unaffected.