Botox for chronic pain and CRPS

An interesting study suggests that Botox prolongs the benefit of lumbar sympathetic blocks in patients with CRPS. But Botox is no newcomer to the treatment of chronic pain.

Botox for chronic pain

Botulinum Toxin (or Botox) is a purified protein produced from the highly potent and infectious toxin Clostridium Botulinum. This is the same toxin that causes botulism, a potentially fatal form of food poisoning. However, there are numerous varieties of Botox, each producing a different action on the body. The Botox used in pain medicine is a temporary muscle-relaxant. It works by binding to the junction between nerves and muscles, blocking nerves that cause muscle contraction, reducing muscular hyperactivity and easing pain.

In addition to CRPS, conditions treated with Botox include:

• neuropathic pain;
• myofascial pain syndrome;
• arthritis;
• chronic pelvic pain;
• chronic spinal pain;
• migraine; and
• headache.

It usually takes two to four weeks before patients obtain optimum relief. Although the beneficial effect is only temporary – usually lasting two or three months – occasionally, the benefit lasts much longer.

What are sympathetic nerve blocks?

Sympathetic nerve blocks are a routine weapon in the pain medicine arsenal. They involve the injection of local anaesthetic and, very often, another drug – typically, a steroid – to prolong its beneficial but short-term effect.

For people suffering from CRPS, the injection site depends on where the location of the CRPS:

• the sympathetic nerves in the lower back (a lumbar sympathetic block) for lower limbs; or
• the sympathetic nerves of the neck (a stellate ganglion block) for upper limbs.

A pain medicine specialist performs the procedure under x-ray or ultrasound guidance, ensuring precise delivery.

The target is the sympathetic nervous system (SNS) in both cases. The SNS encompasses a series of nerves radiating from the spine to control involuntary functions such as sweating and blood flow. It’s believed that dysfunction of the SNS following trauma may play a significant role in developing and maintaining CRPS.

However, as with so many procedures, there’s no guarantee that a nerve block will produce any benefit at all.

Botox for chronic pain: The study

A study at Seoul National University Hospital in South Korea now seem to have proved the hypothesis “that botulinum toxin would prolong the duration of a lumbar sympathetic block” in patients with CRPS in a lower limb.

Researchers randomly assigned forty eight patients to one of two groups; one group receiving Botox, the other (the control group) a local anaesthetic. As an objective measure, the researchers recorded the temperature of both soles on the patient’s feet before administering the block and again at intervals of one and three months. Also, using a visual analogue scale (VAS), they recorded reported pain intensity. On a VAS, patients are asked to score their pain between zero and ten, where zero is no pain, and ten is the worst pain imaginable.

After one month, on average, the Botox group recorded a higher temperature increase in the blocked foot than the control group – a finding maintained at three months. Crucially, however, the reduction in reported pain intensity was even more significant than the temperature increase among the Botox group at both one and three months, with that reduction in pain lasting longer.