Botulinum toxin type B in the spastic arm: a randomized, double-blind, placebo-controlled, preliminary study

Area of Science:

• Neurology
• Rehabilitation Medicine
• Pharmacology

Background:

• Upper limb spasticity is a common and disabling consequence of stroke or traumatic brain injury.
• Overactivity in elbow flexor muscles significantly impairs functional recovery and quality of life.
• Botulinum neurotoxins are established treatments for focal spasticity, but optimal dosing for upper limb involvement requires further investigation.

Purpose of the Study:

• To evaluate the efficacy and safety of two distinct doses of botulinum toxin type B (rimabotulinumtoxinB, BoNT/B) for treating spasticity in upper limb muscles.
• To compare the effects of 10,000U and 15,000U of BoNT/B against a placebo in patients with post-stroke or TBI-related hemiparesis.

Main Methods:

• A randomized, double-blind, placebo-controlled trial was conducted at a tertiary care center.
• Twenty-four adult hemiparetic patients with disabling elbow flexor overactivity received either 10,000U BoNT/B, 15,000U BoNT/B, or placebo, injected into spastic upper limb muscles.
• Outcomes assessed at 1 month included active elbow extension, upper limb function (Modified Frenchay Scale), subjective self-assessment of pain and stiffness, and spasticity measures (Tardieu, Ashworth).

Main Results:

• Both BoNT/B doses significantly improved active elbow extension compared to placebo (P=.028).
• The higher dose (15,000U) demonstrated significant improvements in subject-perceived stiffness (P=.005) and a composite measure of pain, stiffness, and function (P=.017), with effects lasting 3 months.
• No adverse events were reported for either BoNT/B dose. No significant change in overall upper limb function (MFS) was observed, though a trend suggested benefit in patients with lower baseline MFS scores.

Conclusions:

• RimabotulinumtoxinB, at doses up to 15,000U, is a safe and effective treatment for spastic upper limb muscles, particularly improving active elbow extension and reducing perceived stiffness.
• The higher dose of BoNT/B offers sustained improvements in subjective symptoms of stiffness and function.
• Further research may explore optimal dosing strategies and patient selection for maximizing functional gains in upper limb spasticity management.