LAS VEGAS, NV At PAINWeek 2012, Francis Nahm, MD, of Seoul National University, Seoul, South Korea, and colleagues presented two cases studies where lumbar sympathetic block with botulinum toxin type B provided prolonged sympathetic pain blocking in patients with complex regional pain syndrome.

While lumbar sympathetic block is effective for sympathetic mediated pain the lower extremities, its effects are short-lived. To prolong the effects of lumbar sympathetic block, sympathetic destruction by radiofrequency or with alcohol or phenol has been used. Sympathetic destruction has very little high quality evidence for neuropathic pain, and, at best, the effects of chemical sympathectomy are temporary.

Botulinum toxin inhibits the release of acetylcholine at the cholinergic nerve terminals. Since the pre-ganglionic sympathetic nerves are cholinergic, botulinum toxin can be used for sympathetic blocks. Further, botulinum toxin inhibits the secretion of pain mediators and can block neuro-inflammatory chain reactions. Botulinum toxin type B has greater affinity to the sympathetic nerve than type A. Botulinum toxic, when compared with sympathetic destruction for neuropathic pain, has no tissue damage, and a reversible and prolonged effect.

Dr. Nahm and colleagues reported on two males treated with botulinum toxin type B, one for right ankle and foot pain that had lasted three months, and one for left ankle and foot pain that had lasted seven months. Both had previously received lumbar sympathic blocks with local anesthetics, but the effects lasted for only a few hours. After the two patients received lumbar spinal block with botulinum toxin type B, they experienced prolonged sympathetic tissue blocking, one for at least one month and the other for at least two months. Dr. Nahm noted that neither patient had tissue destruction or serious complications.