Subcutaneous Botulinum Toxin for Cutaneous Allodynia - Enriched Responder Trial

Not Applicable

Terminated

Brief Summary: 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: Patients with post-herpetic neuralgia, complex regional pain syndrome, and 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.

Recruitment & Eligibility

Inclusion Criteria

Moderate to severe pain (greater than 2/10) of duration more than 6 months despite previous therapy, excluding botox injection
The patient exhibits at least 80% pain relief following injection of local anesthetic subcutaneously into scar as assessed by change in NRS
Patient reports more than 3 weeks of greater than 50% pain relief from previous botox injection
The patient reports the presence of hyperalgesia, allodynia, dysesthesia, or hypoesthesia surrounding the scar in the absence of the botox injection
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
Any ongoing disability claim
Currently being treated for any severe psychiatric disorder, including anxiety or depression
History of any adverse reaction to botulinum toxin
History of botulism
Untreated infection
Coagulopathy
(Females) - positive pregnancy test
Surgery in the last 6 months

Arm && Interventions

Group	Intervention	Description
Placebo then Botox	Saline	Injection 1: Saline- Subcutaneous injection of saline into scar tissue Injection 2: Botulinum Toxin Type A- Patients receive a subcutaneous injection of Botulinum Toxin Type A into the scar tissue
Botox then Placebo	Saline	Injection 1: Botulinum Toxin Type A- Patients receive a subcutaneous injection of Botulinum Toxin Type A into the scar tissue Injection 2: Saline- Subcutaneous injection of saline into scar tissue
Placebo then Botox	Botulinum Toxin Type A	Injection 1: Saline- Subcutaneous injection of saline into scar tissue Injection 2: Botulinum Toxin Type A- Patients receive a subcutaneous injection of Botulinum Toxin Type A into the scar tissue
Botox then Placebo	Botulinum Toxin Type A	Injection 1: Botulinum Toxin Type A- Patients receive a subcutaneous injection of Botulinum Toxin Type A into the scar tissue Injection 2: Saline- Subcutaneous injection of saline into scar tissue

Primary Outcome Measures

Name	Time	Method
Time to Analgesic Failure	Duration of trial (2-20 months, depending on how long pain relief lasts)	Participants completed the Pain Numeric Rating Scale everyday after the injections. Outcome measure represents the number of days before pain returned to baseline levels.

Secondary Outcome Measures

Name	Time	Method
NRS Score Three Weeks After Injection	3 weeks after injection	Pain scores were measured at baseline, 3 weeks after placebo, and 3 weeks after botox. Scores range from 0 (no pain) to 10 (severe, disabling pain).
Improvement in Psychosocial Function as Assessed by Outcomes as Dictated by the IMMPACT Guidelines	Duration of trial (2-20 months, depending on how long pain relief lasts)	The Beck Depression Inventory was used to assess psychosocial function. Scores were measured at baseline, their final questionnaire following the first injection visit, and their final questionnaire following their second injection visit. Scores range from 0-63, with lower scores representing less severe depression symptoms and higher scores representing more severe depression symptoms.