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Sympathetic Blockade with Botulinum Toxin - A Promising New Treatment for Reflex Sympathetic Dystrophy

Reflex sympathetic dystrophy (RSD), also known as complex regional pain syndrome (CRPS) Type I, is a complex, chronic, pain syndrome that can affect any part of the body, however, it occurs most frequently in the extremities - hands, feet, arms, legs, shoulders or knees. It has been recognized by many clinicians as a distinct clinical condition for over 100 years and has been known by various names including algodystrophy, Sudeck's atrophy, causalgia, and sympathetically maintained pain.

Reflex sympathetic dystrophy is characterized by:

Severe, chronic, pain - often described as stinging or burning
Sensory abnormalities - allodynia (extreme sensitivity to touch)
Motor changes such as tremor or stiffness
Edema (tissue swelling) and hyperhydrosis (excessive sweating)
Progressive changes to skin, hair, nails, muscle, and bone
Increasing dysfunction of the affected limb
Sympathetic nerve block injections have long been used for the treatment of RSD, however, pain relief is achieved for only a short period of time for many patients. Surgical or chemical sympathectomy is also a widely used treatment for RSD but, in general, also has not been found to provide effective, long-term pain relief for many people who suffer with RSD. Clearly, there is an urgent need to develop more effective, long-lasting pain relief treatment options for patients with RSD.

In an article published in 2009 in the Annals of Neurology (Volume 65; pp. 348-351), investigators from the Stanford University School of Medicine in Stanford, California, reported on the results of a pilot, randomized, controlled study in which they evaluated the efficacy of sympathetic nerve block injections with botulinum toxin type A (BTA) for the treatment of RSD.

Because this was intended to be a pilot (preliminary) study, only 9 patients were recruited for inclusion in the trial. Seven (7) of these 9 patients eventually completed the trial and served as the basis for the data-set analysis of the study. All 7 patients had sympathetically-maintained pain of the lower extremity cause by CRPS type I (RSD). All of these patients had previously failed to achieve adequate pain relief with analgesic medications that are often prescribed for patients with RSD (such as anticonvulsants and tricyclic antidepressants).

At the initation of the study protocol, all patients received a standard lumbar sympathetic nerve block injection of 0.5% bupivacaine (a local anesthetic). If, after 30 days of receiving a standard lumbar sympathetic block, the intensity of pain had returned to "baseline" levels (same level of pain as before receiving the standard injection of 0.5% bupivacaine), the patients received a second lumbar sympathetic block injection of 0.5% bupivacaine plus 75 units of botulinum toxin type A. (BTA). The preliminary end-point measured by the study was the time to return to baseline pain intensity, which was then considered as "analgesic failure". Patients were required to keep daily records of pain intensity using a visual analog pain intensity scale, starting at 7-days before the first injection and continuing daily for 30 days, thereafter.

The results of this pilot study demonstrated that the duration of pain relief was extended significantly when botulinum toxin type A (BTA) was added to the standard 0.5% bupivacaine lumbar sympathetic block. The mean time of pain relief with the standard sympathetic block of 5% bupivacaine alone was less than 10 days. In contrast, the addition of BTA to the standard sympathetic block extended the mean time of pain relief to 71 days (10 weeks). The only adverse event recorded among the patients who received the BTA-supplemented sympathetic block injection was nausea and vomiting in one patient which resolved spontaneously after 2 days.

In conclusion, this pilot study offers preliminary evidence that lumbar sympathetic blockade with a combination of a local anesthetic (0.5% bupivacaine) and botulinum toxin type A (BTA) may be a reasonable treatment option for the management of sympthetically-maintained pain in patients with CRPS type I who have failed to respond to other treatments. The authors noted, however, that since only a small number of patient were included in this pilot study, nevertheless, the promising results obtained warrant further evaluation of BTA-supplemented sympathetic blockade in a larger cohort of patients with RSD.