SLR - March 2016 - Melissa Hurwitz

Title: Ultrasound-Guided Nerve Block with Botulinum Toxin Type A for Intractable Neuropathic Pain

Reference: Moon YE, Choi JH, Park HJ, Park JH, Kim JH. Ultrasound-Guided Nerve Block with Botulinum Toxin Type A for Intractable Neuropathic Pain. Toxins (Basel). 2016 Jan 8; 8(1).

Scientific Literature Review

Reviewed By: Melissa Hurwitz, DPM
Residency Program: Mount Sinai Hospital NY, NY

Podiatric Relevance: Neuropathic pain has been defined as “pain initiated or caused by a primary lesion or dysfunction in the nervous system” by the International Association for the Study of Pain. Patients with chronic intractable neuropathic pain are often prescribed many different types of medications, from opioids and topical agents to anticonvulsants and antidepressants in attempts at providing adjuvant analgesia. The complexity of neuropathic pain makes treatment by various drugs difficult due to undesired side effects experienced at the adequate doses of these medications. Diabetic patients are a huge part of many podiatric practices that are requesting relief of neuropathic pain which they experience despite being on medication regimens prescribed by pain specialists. This article exposes a new possible alternative modality for local relief of intractable neuropathic pain by way of treating the affected nerves themselves. This form of treatment not only gives the patient more options but also could potentially provide the podiatric physician with a new tool to directly treat such neuropathic foot pain in an office setting before referring the patient out for treatment.

Methods: The authors of this study thus report two patients successfully treated with ultrasound-guided nerve block using BoNT-A for intractable post herpetic neuralgia  and painful diabetic neuropathy. The first case discusses a 63 year-old female with a very sharp and burning pain on a whole left arm (from shoulder to all fingers, C5-8 dermatome) which she had been experiencing from post herpetic neuralgia diagnosed by a dermatologist. Despite being on high doses of neurontin and a fentanyl patch the patient continued to report 8/10 pain. In this patient, a US guided brachial plexus nerve block was attempted using 10 mL of 0.4 percent lidocaine followed by an injection of 10 mL of 0.1 percent bupivacaine with 50 Botox units (BOTOX®, Allergan Inc., Irvine, CA, USA) was administered around the brachial plexus.

The second case was with a 74-year-old man who suffered from a five-year history of severe left diabetic leg pain with a burning and tingling sensation from left knee to all toes (VAS 10/10). Despite being on a regimen consisting of Pregabalin 225 mg/day, acetaminophen plus tramadol 500 plus 60 mg/day, and nortriptyline 10 mg/day, his pain was still severe (VAS 9/10). For this patient, an ultrasound-guided lumbar plexus block (LPB) with 10 mL of 0.4 percent lidocaine was performed, followed by a block to the same region using with 0.1 percent bupivacaine 10 mL and 50 Botox units.

Results: The first patient described who received the Brachial plexus block w/ lidocaine reported her intial VAS score to drop from 8/10 to 3-4/10 for only three days. The second injection for this patient using Botox subsequently reduced this patient’s VAS score from a 8/10 to 2-3/10, and at the five-month follow-up, her pain was well controlled (VAS 3/10) and she was satisfied with BoNT-A treatment.

The second patient who received the ultrasound-guided lumbar plexus block (LPB) with 10 mL of 0.4% lidocaine reportedly decreased his VAS from 9/10 to 4/10 for seven days. After the second block with 0.1 percent bupivacaine 10 mL and 50 Botox units, the patient reported a decreased VAS of 9/10 to 2/10. At four months follow-up observation, the patient's pain was well controlled (VAS 2/10).

Conclusions: While botulism toxin Type A has recently been known for an analgesic effect in various chronic pain conditions, there is no data currently available of using the medication as a nerve block for post herpetic neuralgia and painful diabetic neuropathy. In these cases, BoNT-A for BPB and LPB alleviated pain effectively on intractable post herpetic neuralgia and painful diabetic neuropathy patients especially who showed side effects and were reluctant to conventional treatment. Until now, there has not been any study that has demonstrated the use of BoNT-A for nerve blocks for relief of painful diabetic neuropathy.  While there have been several studies that have attempted to provide a method of intradermal botox injections over multiple sites, some patients dropped out of the study due to intolerable pain by multiple injections. In this study, nerve blocks using BoNT-A did not require additional pain control prior to injection. Thus, ultrasound-guided nerve block with BoNT-A may be a useful and alternative treatment modality for chronic intractable neuropathic pain conditions including painful diabetic neuropathy. This new innovative method of treatment could be particularly helpful to those patients that do not respond well to conventional therapy. More studies including long-term follow-up, double-blind investigations, and a comparison of different dosage and injection techniques are needed in the future.

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