Neuropathic pain

Overview

What is Neuropathic Pain?

Neuropathic pain is pain caused by damaged nerves or other nervous system problems.

When a part of the body is injured, nerve cells in the area send a signal through the spinal cord to the brain. The brain translates this signal into the sensation of pain.

Normally, when the injury heals, the signal stops and the pain goes away. When a person has nerve damage, the signals can continue to cause pain for months or years.

Sometimes people have neuropathic pain without a clear reason.

Causes

Medical conditions that can cause neuropathic pain include:

• Nerve damage from diabetes (diabetic neuropathy)
• Infection (shingles, HIV)
• Stroke
• Amputation can cause a form of neuropathic pain called phantom limb pain. People with phantom limb pain feel pain in a part of the body that is no longer there.
• Nerve damage from a past injury
• Nerve damage from surgery
• Alcoholism
• Multiple sclerosis
• Cancer
• Chemotherapy

Sometimes people have neuropathic pain without a clear reason.

Symptoms

Neuropathic pain usually feels burning, shooting, tingling, sharp, or stabbing. The pain may be there all the time or it may come and go. It is often worse at night and when resting.

Some people may also have increased sensitivity to pain (hyperalgesia) or feel pain from actions which do not normally cause pain (allodynia) such as gentle touches.

Complications

People with severe neuropathic pain can have difficulty carrying out daily activities such as working, socialising and preparing food.

Some people may find it hard to get to sleep or may wake from sleep because of pain. This leads to changes in sleep patterns and fatigue. Neuropathic pain is a source of emotional distress that can cause depression and anxiety.

Established Treatments

Treatment of neuropathic pain is unique to each person; there is no single medicine that works for all cases. Sometimes doctors use a combination of techniques to treat neuropathic pain. The goal is to control the pain and minimize its effect on a person’s life.

Pain Medicines for Neuropathic Pain

Pregabalin and gabapentin are medicines designed to treat neuropathic pain. Doctors also use medicines that were created for other conditions like depression and epilepsy. Anti-seizure medicines (valproate, carbamazepine) help to control nerve signals and antidepressants (amitriptyline, duloxetine) act on parts of the brain that process pain.

Painkillers such as paracetamol, NSAIDs (ibuprofen, naproxen) and opioids (tramadol, codeine, morphine, oxycodone) can also be helpful.

Pain Other Treatments

• Physical therapy
• Relaxation/meditation techniques
• Cognitive behavioural therapy (CBD)
• Acupuncture
• Occupational therapy
• Injection of numbing or pain relieving medicines
• Devices that affect nerve signals
• Surgery

Your doctor can provide more information about treatment of neuropathic pain.

Treatment with Medical Cannabis

Medical Cannabis and Treatment of Neuropathic Pain

The cannabis plant contains many compounds which affect the human body in different ways. Cannabinoids THC (Δ9-tetrahydrocannabinol) and CBD (cannabidiol) are the most abundant active compounds. THC is responsible for the intoxicating effects of cannabis.

The endocannabinoid system is part of the pain signalling process. It is thought that cannabis can suppress pain by interacting with the endocannabinoid system, specifically the CB1 receptor. Another receptor which could possibly be involved at the spinal level is the glycine receptor (GlyRs)

Currently published studies have conflicting results and are limited by small sample size and short duration. Long term effects of cannabis usage and interactions with other medicines are not yet fully understood. Further large scale trials of longer duration are needed before any conclusions can be drawn on the use of cannabis-based medicines in neuropathic pain.

• A double-blind, randomized, placebo-controlled, parallel group study of THC/CBD spray in peripheral neuropathic pain treatment
  This study compared efficacy of THC/CBD with a placebo for treatment of peripheral neuropathic pain. It was a double-blind trial which means neither patients nor staff knew which treatment was administered. Patients continued using their existing pain relief medicines.
  
  246 patients with peripheral neuropathic pain and allodynia were divided into two groups and given either the THC/CBD spray or a placebo for 15 weeks. They recorded their pain severity on a numeric scale.
  
  Results found that the THC/CBD group had a statistically significant improvement in pain compared to the placebo group. Measures of sleep quality also showed a positive change in the THC/CBD group.
  
  The most common treatment-related side effects in the THC/CBD group were dizziness, nausea, fatigue and changes in sense of taste. The serious adverse events that occurred were not considered to be treatment-related.
  
  
• Sativex successfully treats neuropathic pain characterised by allodynia: a randomised, double-blind, placebo-controlled clinical trial
  This double-blind study also compared the effect of THC/CBD on peripheral neuropathic pain with a placebo. Patients continued using their existing pain relief medicines.
  
  125 patients with peripheral neuropathic pain and allodynia were divided into two groups and treated with either the THC/CBD spray or a placebo for five weeks. Pain severity was recorded on a numeric scale.
  
  Results found that the reduction in pain was greater in the group receiving THC/CBD than in the placebo group. Sleep quality and allodynia also improved in the THC/CBD group.
  
  Gastrointestinal side effects (nausea, vomiting diarrhoea, constipation) were more common in the THC/CBD group. One severe psychiatric adverse effect occurred in each group (with THC/CBD, emotional stress associated with paranoid thinking and confusion in the placebo group). Six further mild-to-moderate psychiatric side effects occurred in the THC/CBD group compared to three in the placebo group, mainly mood related. One patient on THC/CBD had transient mucosal ulcerations.
  
  
• A double-blind, randomized, placebo-controlled, parallel-group study of THC/CBD oromucosal spray in combination with the existing treatment regimen, in the relief of central neuropathic pain in patients with multiple sclerosis
  This double-blind study compared a THC/CBD spray with a placebo for treating central neuropathic pain. Patients continued using their existing pain relief medicines.
  
  339 people with neuropathic pain from multiple sclerosis that was not adequately controlled with existing medication were divided into two groups and given either a placebo or the THC/CBD spray for 14 weeks. Pain severity was recorded on a numeric scale.
  
  Results found that by the last week, 50% of patients taking THC/CBD had at least a 30% improvement in pain compared to 45% of patients on placebo. This was not deemed statistically significant.
  
  The most common adverse effects in the THC/CBD group were dizziness,
  fatigue, somnolence, vertigo, and nausea. One patient taking THC/CBD experienced serious disorientation.
  
  
• Comparison of analgesic effects and patient tolerability of nabilone and dihydrocodeine for chronic neuropathic pain: randomised, crossover, double blind study
  Nabilone is a man-made compound similar to THC. This double-blind study compared the effect of nabilone on neuropathic pain with the weak opioid painkiller dihydrocodeine. Patients continued using their existing pain relief medicines.
  
  96 patients with neuropathic pain were given the first treatment for six weeks, followed by a two week washout period. They then received the second treatment for six weeks. Pain severity was recorded a numeric scale.
  
  Results concluded that dihydrocodeine was a better treatment for chronic neuropathic pain than nabilone. More patients had clinically significant pain relief from dihydrocodeine, although a small number of patients responded well to nabilone.
  
  Side effects in both groups were mild. Nabilone caused nausea more frequently than dihydrocodeine while dihydrocodeine was associated with more tiredness and nightmares. Neither drug caused major adverse events.

References available at end of page.

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Related Advocacy Groups

There are several organizations in Australia which provide information and support to people with neuropathic pain and their families. Below are links to their websites:

Australian Pain Management Association

Pain Australia

Chronic Pain Australia