Subcutaneous Botulinum Toxin for Cutaneous Allodynia

Study Overview
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Brief Summary
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Superficial injection of Botulinum toxin has been advocated for cosmetic purposes but has also been reported to be helpful for some pain conditions. The investigators have observed prolonged profound analgesia following subcutaneous superficial injection of Botulinum Toxin Type A (BTA) in patients with certain types of neuropathic pain. The investigators propose to study if addition of BTA extends pain relief compared to placebo when injected subcutaneously into areas of cutaneous allodynia (the property that a normally non-noxious stimulus is perceived as painful).

Detailed Description
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Post-surgical neuromatous pain patients have marked cutaneous allodynia. Touching their skin with normally non-painful stimuli results in pain. Injected local anesthetics are often effective in providing temporary relief. In the course of clinical practice the investigators have observed that a number of patients with cutaneous allodynia have had marked persistent benefit from subcutaneous injection of Botulinum toxin Type A. Rather than killing targeted neurons, Botulinum toxin type A inhibits release of acetylcholine from cholinergic nerve terminals in a prolonged but ultimately reversible manner. Neuropathic pain and its hallmark allodynia are classically difficult to treat. Standard treatment with tricyclic antidepressants, anti-epileptic drugs, opiates and spinal cord stimulation is frequently disappointing leaving patients with refractory pain. Surgical or percutaneous ablation of involved nerves has fallen out of favor among many due to disappointing results. A pilot study is needed to assess the efficacy of superficially injected Botulinum Toxin type A for treatment of cutaneous allodynia and spontaneous pain among patients with neuropathic pain.

Official Title
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Subcutaneous Botulinum Toxin for Cutaneous Allodynia

Conditions
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Pain

Intervention / Treatment
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* Drug: Botulinum Toxin A
* Drug: Placebo - Saline


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria:- Moderate to severe pain (greater than 4/10) of duration more than 6 months despite previous therapy. The patient exhibits at least 80% pain relief following injection of local anesthetic subcutaneously into scar as assessed by change in NRS The patient reports the presence of hyperalgesia, allodynia, dysesthesia, or hypoesthesia surrounding the scar Age 18-100 Ability to read, write, and converse in English, provide informed consent, and follow study procedures Exclusion Criteria: Any neuromuscular disorder such as myasthenia gravis, eaton lambert, muscular dystrophy Any ongoing legal action related to their pain Allergy to local anesthetics A current or history of any severe psychiatric disorder History of any adverse reaction to botulinum toxin History of botulism Untreated infection Coagulopathy Females - positive pregnancy test Surgery within the past 6 months at the site of the painful scar

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Placebo then Botox<br> | Drug: Placebo - Saline<br>* Subcutaneous Saline injection given at site of scar neuroma<br>|
| Experimental: Botox then Placebo<br> | Drug: Botulinum Toxin A<br>* Subcutaneous injection of Botulinum Toxin Type A into the patient's scar tissue<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Time Until Analgesic Failure | Participants made daily NRS reports via Palm Pilot, and failure was defined as (Pre-injection baseline NRS) - (Mean NRS for any 3 preceding days) ≤ 0; or 9 months | Each participant was assessed for up to 224 days per intervention (injection) or until they returned to NRS baseline | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| NRS Score Three Weeks After Injection | The NRS scores range from 0-100, where 0 indicated no pain and 100 indicated the worst pain. | Three weeks after injection |