Question

1. what do the terms "double-blind" and "controlled" mean in the title of botulinum toxin type A in MS-related tremor?

2. why did the treatment work to reduce tremor(trembling?

3. why was muscle weakness a side effect of the treatment?

4. what other ways is botulinum toxin used medically?

Answer 1

1) A double-blind study is one in which neither the participants nor the experimenters know who is receiving a particular treatment. This procedure is utilized to prevent bias in research results. Double-blind studies are particularly useful for preventing bias due to demand characteristics or the placebo effect.

Controlled study is an experiment or clinical trial in which two groups are used for comparison purpose. In a controlled exposure study, one group of participants is exposed to a substance (e.g.a drug or a pollutant) while those in the "control" group are not.

2) Normally, your nerves send electrical messages to your muscles so they will move when you want them to. These messages travel from the nerves to the muscles via a chemical called acetylcholine. But if you have MS, the disease damages the nerves and throws those signals out of sync. It makes your muscles tense up and move when you don’t want them to.

• Botulinum toxin type A works by blocking the release of acetylcholine from nerve endings. Acetylcholine is a neurotransmitter required by muscles for muscular contraction. By eliminating the ability of a muscle to contract, it relaxes, thereby decreasing spasticity and tone.
• The blockade of acetylcholine does not occur immediately. Most patients do not begin to see the effect of a botulinum toxin injection for a few days, and it may take a few weeks for the maximum benefit to become apparent.
• Additionally, the benefit of botulinum toxin injections is not permanent; after a few months (typically three), the effect of the injections is no longer seen, and the injections need to be repeated.

3) Local weakness of the injected muscle represents the expected pharmacological action of botulinum toxin. However, weakness of nearby muscles may also occur due to spread of toxin.Long term inhibition of acetylcholine release at the neuromuscular junction of striated muscles, thus resulting in chemical denervation and muscle weakness or paralysis.

4) Other uses:

• Treatment of urinary incontinence due to detrusor overactivity associated with a neurologic condition [e.g., spinal cord injury (SCI), multiple sclerosis (MS)] in adults who have an inadequate response to or are intolerant of an anticholinergic medication.
• Prophylaxis of headaches in adult patients with chronic migraine (≥15 days per month with headache lasting 4 hours a day or longer).
• Treatment of upper limb spasticity in adult patients.
• Treatment of cervical dystonia in adult patients, to reduce the severity of abnormal head position and neck pain.  
• Treatment of severe axillary hyperhidrosis that is inadequately managed by topical agents in adult patients.
• Treatment of blepharospasm associated with dystonia in patients ≥12 years of age.
• Treatment of strabismus in patients ≥12 years of age