Botulinum Toxin for Peripheral Neuropathic Pain

Botulinum toxin Type A can relief peripheral neuropathic pain.

What is Botulinum toxin?

High doses of botulinum toxin are known to cause paralysis of muscles. The toxin is a protein and is produced by a bacterium called Clostridium Botulinum. Botulinum toxin was first introduced in medical practice in the 1970s to treat squint and other eye disorders. Since then it has found uses in other areas of medicine and more recently in the treatment of peripheral neuropathic pain. Only very small doses, enough to weaken but not paralyse muscles, are used medically.

What is the evidence that Botulinum toxin can help peripheral neuropathic pain?

The neuropathic pain special interest group (NeuPSIG) at the international association for the study of pain (IASP) has recommended Botulinum toxin A as third line treatment for peripheral neuropathic pain.1 Since then a multicentre trial (BOTNEP) demonstrated a clinically important pain relieving effect in 152 patients after two administrations of Botulinum toxin A2.

How is Botulinum Toxin used for peripheral neuropathic pain?

Botulinum toxin A is not licensed for this indication and needs to be approved by a panel at the Walton Centre for every patient before this can be offered.

Only patients who have failed first line and second line treatments (anti-epileptics and antidepressants) are offered this treatment after careful discussion of the risk and benefits.

Two treatments of Botulinum toxin are initially tried in moderate to severe peripheral neuropathic pain after an assessment in the Walton Centre specialist neuropathic pain or facial pain clinic.

If the area to be injected is very sensitive a local anaesthetic cream will be applied up to 1 hour before the injections.

Outcomes will be collected after each injection in the form of a pain score from 0 to 10 and a global impression of change score.

If there is significant pain relief we will offer ongoing repeat injections initially after 12 weeks, and then within two weeks of the return of pain.

How does Botulinum toxin help to treat peripheral neuropathic pain?

How Botulinum toxin helps with neuropathic pain is not yet fully understood. It is thought that Botulinum toxin may reduce the transmission of pain messages to the spinal cord and brain. This may then have a knock-on effect on the central pain processing systems that causes hypersensitivity and amplification of pain.

What do you need to do before you can be considered for this treatment?

• You need to have tried at least two different drug treatments for neuropathic pain before you are considered for botulinum toxin injections.

• You need to have completed a pain diary for one month prior to the start of this treatment.

What does the treatment involve?

The treatment involves 5 to 40 injections of Botulinum toxin into the painful area which will be mapped for hypersensitivity to light touch or pinprick. The area will then be divided into 2 x 2 cm squares and 1 to 2 injections performed into the skin of each square. These injections are repeated twelve weeks after the first course of treatment.

Are there any side effects?

In the clinical trials Botulinum toxin was well-tolerated. The commonest side effects were pain on the injection site. Muscular weakness like drooping of the eyelid or corner of the lip can be experienced after facial injections. No serious irreversible side effects have ever been reported in trials of Botulinum toxin in neuropathic pain. The injections themselves can be very painful but are usually well tolerated after local anaesthetic cream treatment.

You cannot have botulinum toxin injections if you are pregnant, or any risk you may be pregnant. This is because the effects upon the unborn child are unknown.

YOU MUST INFORM US BEFORE HAVING THE INJECTIONS IF YOU THINK YOU ARE PREGNANT

What to do after treatment?

It will be necessary to stay for a short while after treatment until comfortable. A detailed pain diary will need to be completed to record the average daily pain and frequency of pain attacks occurring post injections.

Who might benefit from Botulinum toxin for neuropathic pain?

Only patient with peripheral neuropathic pain who did not respond or did not tolerate nerve pain medication are offered botulinum toxin injections. There are alternatives like strong morphine based pain killers that need to be trialled and demonstrate a good effect at a low dose before continued permanently. Any area outside the face might benefit from high dose capsaicin patches which will be discussed. Electric stimulation of the peripheral nerve or spinal cord might be an alternative. If there is no significant benefit from the injections, they will be stopped after 24 weeks.