Leveraging a neurotoxin
Botulinum toxin is among the most effective pharmacologic agents accessible to neurologists, but it is also one few resident physicians experience using. Derived from the lethal bacterium, Clostridium botulinum, this neurotoxin can cause flaccid paralysis and death among newborns or these poisonous effects can be tactically harnessed for good. In this week’s BrainWaves episode, Dr. Anh-Thu Vu discusses the therapeutic uses of this bacterial product.
The toxin’s active component is a core protein with a heavy chain that binds to the neuron, and a light chain that cleaves SNARE proteins preventing release of vesicles that contain neurotransmitters. When used therapeutically in our movement disorders clinic, it is administered as intramuscular injections, and the targets and amount used depend on what is being treated. With only 1-10 units used on facial muscles (for disorders like blepharospasm), and 50 or more units on larger muscle groups like the trapezius (for some cases of spasmodic torticollis). Benefits start to take effect over a week and typically last 3-5 months.
What conditions are amenable to botulinum toxin treatment?
- Focal or Segmental Dystonias (e.g., cervical dystonia, “writer’s cramp”)
- Hemifacial spasm
- Spastic bladder
- Chronic Migraine
It can also help improve quality of life in stroke patients with spasticity, but not necessarily improve function of the affected limb. It can reduce sialorrhea in patients with parkinsonism and ALS, but caution must be exercised to avoid dysphagia. In particularly violent neck tics, it can be helpful in reducing the sensory urge to perform the tic.
For more information on the benefits of botulinum toxin, the toxin serotypes, and the process of chemodenervation, check out the podcast and hear what Dr. Vu has to say.
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Emory Movement Disorders Fellowship Director, Dr. Stewart Factor, and Dr. Hyder Jinnah in their expertise in the area of dystonia.