Uses of Botulinum toxin in Parkinson’s disease

You most likely know that Botulinum toxin (more commonly referred to as Botox®, among other brand names) is used for cosmetic purposes to decrease wrinkles. Prior to being used in this way, Botulinum toxin was used for medical purposes to control abnormal movements. In the right hands, it can be a very effective measure to control a variety of problems related to PD.

What is botulinum toxin?

Botulinum toxin is a substance produced by the bacteria Clostridium botulinum. Botulism is caused by the harmful effects of this toxin. If the toxin enters the bloodstream, it can spread throughout the body, causing widespread muscle weakness. In its full-blown form, botulism can cause difficulty with swallowing and breathing by causing weakness of the muscles that control these functions.

The good news is that decades ago, scientists learned how to isolate the toxin and harness its power for medical use, and it can be safely injected into particular muscles in order to decrease unwanted movements of those muscles.

How does Botox work?

Usually, a message gets transmitted from the nerve to the muscle by release of the chemical acetylcholine from the nerve endings. When Botulinum toxin is injected into a muscle, it gets taken up by the nerve endings that interface with the muscle, and interferes with the release of acetylcholine, thereby stopping communication between the nerve and the muscle. When this communication is decreased, the muscle is weakened and certain Parkinson’s symptoms are lessened.

Conditions treated using botulinum toxin in Parkinson’s disease

1. Dystonia – Dystonia refers to an involuntary twisting of a body part, which can be painful and can interfere with a person’s desired movement. In PD, dystonia can be a motor symptom due to the disease, appearing first thing in the morning before taking medication or as a dose of medication is wearing off. Alternatively, dystonia can be a side effect of Levodopa. A common dystonia in young onset PD involves toe curling or foot inversion (turning in).  This dystonia often occurs only in particular circumstances such as while walking or running. Other dystonias involve frequent and persistent eye closure, known as blepharospasm, or neck turning, known as cervical dystonia. These can be associated with PD, but may also accompany other forms of parkinsonism such as Multiple System Atrophy or Progressive Supranuclear Palsy. Botulinum toxin injections, targeting the particular muscles that are moving excessively, can be effective in all these scenarios.
2. Tremor – Although Botulinum toxin is not commonly used for this purpose, there are case reports in the literature showing its effective use for the control of tremor.
3. Drooling – Likely due to the decreased swallowing rate of patients with PD, sialorrhea, or drooling, can be a feature of the disease. Drooling is not only an annoyance, but can result in significant embarrassment and social isolation.  Botulinum toxin injections into the salivary glands can decrease production of saliva and thereby decrease drooling.
4. Urinary incontinence – This can be caused by a small, contracted bladder. Botulinum toxin injections into the bladder can relax the bladder thereby allowing for more normal urination. A known side effect of this treatment however, is urinary tract infection, so make sure you are aware of all the risks and benefits before starting the treatment. In addition, there are causes of urinary problems in PD that are not amenable to Botulinum toxin treatment, so you will need to discuss your particular situation with a urologist.

Botulinum toxin is used in various other medical settings such as dystonia that is not related to Parkinson’s disease, migraine, and limb spasticity or stiffness after stroke.

Different types of Botulinum toxin

There are eight different botulinum toxin species that occur in nature. There are only two however, that are produced commercially – Botulinum toxin A and B.

The commercially available products are:

1. Botox® – Botulinum toxin A
2. Dysport®  – Botulinum toxin A
3. Xeomin®  – Botulinum toxin A which is produced free of complexing proteins
4. Myobloc®  – Botulinum toxin B

Each of the above agents are FDA approved for a slightly different list of clinical indications.

What does Botulinum toxin treatment for Parkinson’s look like?

The effects of Botulinum toxin take hold about 3-10 days after the injections and last approximately three to four months, so the treatments typically need to be repeated on a regular basis. Although this means routine injections, it also means that Botulinum toxin injections do not have any permanent side effects. Some side effects may still occur with Botulinum toxin injections and the doctor who performs the procedure will review these with you. An advantage of using Botulinum toxin for the treatment of the conditions noted above, is that the toxin typically only impacts the areas into which it is injected, as opposed to oral medications which have a more widespread effect, and therefore more potential for side effects.

Side effects of using Botox

In general, side effects of Botulinum toxin can be due to over-weakening of the injected muscle, which, if done on leg and foot muscles, for example, could interfere with walking.

Uncommonly, Botulinum toxin can diffuse to neighboring muscles and cause more widespread side effects. For example, injections of neck muscles could result in toxin diffusing locally to muscles used for swallowing and cause difficulty swallowing. Even less common, are side effects due to travel of the toxin to more distant parts of the body via the bloodstream. For example, injections of any body part could theoretically result in difficulty swallowing or breathing if the toxin travels to these muscles. This is very rare however and Botulinum toxin injections are typically very safe. The full risk profile for your particular situation however, needs to be discussed with the physician performing the injections.

There are typically no limitations after the injections and you can return immediately to your normal activities.

Although dermatologists often use Botulinum toxin for cosmetic purposes, only a neurologist is qualified to determine whether the injections can help with certain PD symptoms. If you are interested to investigate whether Botulinum toxin injections may help you, discuss this with your neurologist. If he/she feels that they may be helpful, but does not perform them, he/she can refer you to a neurologist who does.

Tips and takeaways

• Botulinum toxin injections can help in the management of certain features of Parkinson’s disease.
• If you think you have a symptom that can be treated with Botulinum toxin (dystonia, drooling, urinary incontinence), discuss it with your neurologist.
• There may be a role for Botulinum toxin injections in control of tremor, but this is less commonly done.