Botulinum toxin A injections in phantom pain patients are not a useful treatment option – a case series

Objective: To assess the therapeutic effects and tolerability of botulinum toxin A (BtA) injections in 11 patients with chronic phantom pain after amputation.

Background: The management of phantom pain is a great therapeutic challenge. Although many patients experience pain control by standard treatments, a sizeable proportion still suffers from phantom pain interfering with the activities of daily living. In 2003, the use of botulinum toxin A was reported in a small series of phantom pain patients.

We here present our therapeutic experiences with BtA in upper and lower limb amputees including patients with traumatic avulsions of the brachial plexus.

Methods: 11 patients with phantom pain after limb amputation were offered BtA injections. In all patients previous treatments with analgesics and/or non-pharmacological treatments were insufficient or not tolerated. All patients were injected with 100 MU BtA (Allergan®) (6–8 injection sites around the trigger points of phantom pain). If treatment failed to improve pain at 100MU, patients were offered another injection with 200 MU.

Treatment outcome was evaluated by direct clinical assessment including pain assessment by VAS self-rating 3–4 days, 2 weeks and 4 weeks after injection.

Results: Injection of BtA with a 27G needle caused acute, but transient increase of pain for minutes to 2–3 hours. Five patients reported acute changes in the phantom representation like swelling or melting of the phantom after injection.

In only one patient phantom pain (VAS 6–10) of his left lower limb was almost completely abolished by the BtA injection. Pain recurred after 8 months. A second injection did not show any clinical effects.

In all other patients (7 lower limb amputees, 2 arm amputees and one “hemi“-amputee with brachial plexus avulsion) injections were well tolerated However none of these patients reported any symptomatic benefit. Two patients were accepted follow-up injections with 200 MU BtA three month after the first injection even without any benefit.

Conclusion: Botulinum toxin A injections are apparently not a useful treatment option in phantom pain refractory to standard medical or surgical treatments. Only one of eleven patients responded with a marked pain reduction for 8 months. However, the lack of efficacy upon reinjection in this patient might be explained by a placebo effect of the first injection.

Based on our results further trials of BtA in amputees should only focus on the treatment of involuntary stump movement