Intramuscular botulinum toxin in complex regional pain syndrome: case series and literature review.

Background: Pain associated with Complex Regional Pain Syndrome (CRPS) is frequently excruciating and intractable. The use of botulinum toxin for relief of CRPS-associated pain has not been well described.

Objectives: To assess whether intramuscular botulinum toxin injections cause relief of pain caused by CRPS, and to assess the risks of this treatment.

Study Design: Retrospective chart review.

Setting: Outpatient clinic.

Methods: 37 patients with spasm/dystonia in the neck and/or upper limb girdle muscles.

Intervention: EMG-guided injection of Botulinum Toxin - A (BtxA), 10-20 units per muscle. Total dose used was 100 units in each patient. Local pain score was measured on an 11-point Likert scale, 4 weeks after BtxA injections.

Results: Mean pain score decreased by 43% (8.2 ± 0.8 to 4.5 ± 1.1, P < 0.001). 97% patients had significant pain relief. One patient had transient neck drop after the injections.

Limitations: This is a retrospective study, it lacks a control group and hence the placebo effect cannot be eliminated. This study does not provide information on the efficacy of this treatment after 4 weeks.

Conclusions: Intramuscular injection of botulinum toxin in the upper limb girdle muscles was beneficial for short term relief of pain caused by CRPS. The incidence of complications was low (2.7%).