[Treatment of phantom pain with botulinum-toxin A. A pilot study]

Therapy of phantom pain following amputation is still difficult, since pathophysiological mechanisms are not clarified. Botulinum-toxin A never has been used for this issue. We report four successfully treated cases with chronic phantom pain longer than 3 years.

We injected 100 IU botulinum-toxin A (4x25 IU in 0,5 ml preservative-free saline 0.9%) in four muscle-triggerpoints of the amputation stump of each patient. All triggerpoints were painful to compression before injection, all patients reported referred sensations in the phantom-foot from at least one of them. Controls were performed by questioning and pain-diaries after 1,2 and 5 weeks.

In all cases phantom pain was reduced about 60-80%. The three patients, who had pain attacks, reported a dramatically reduction of the number of attacks (about 90%). In two of them duration of attacks shortened from 120 to 5-10 min and a reduction of pain intensity from VAS 9 to VAS 1 and VAS 9 to VAS 2 was reported. Disorder of sleep disappeared in both affected patients within 2-3 weeks. Three patients,who could move the phantom foot (mental), had a subjective weakness a few days after botulinum-toxin A injection; in one case although injection was performed in the muscles of the femur!

This is the first report of the use of botulinum-toxin A in the treatment of phantom pain. The contribution of the muscles in the cause of phantom pain is unclear and may be local, as a trigger of spinal reflexes or by modulation of "cortical reorganisation" after amputation. Botulinum-toxin A could work analgesic by the relaxation of the stump muscles or by modulation of neuronal transmitters, for example substance P, with an indirect influence of the CNS.