Neuropathic pain, often referred to as neuralgia, is a complex condition that occurs in 10% of adults over the age of 30. The causes of this pain are as complex and mysterious as the treatment plans, but a new finding in neuropathic pain may simplify both diagnosis and treatment.
A brief overview of the condition is necessary before jumping straight into the research. Neuropathic pain, as a condition, is named based on its location. These include:
- Central neuropathic pain (CNP): This pain occurs as a result of damage or injury to the nerves in the brain or spinal cord, the two parts of the body that make up the central nervous system.
- Peripheral neuropathic pain (PNP): Nerves that feed into the brain and the spinal cord, such as those that run through the arms and the legs, make up the peripheral nervous system. Peripheral neuropathic pain involves nerves in this system.
- Mixed neuropathic pain (MNP): As the name would suggest, this type of neuropathic pain involves the nerves of both the central and peripheral nervous system.
Symptoms of neuropathic pain are not limited to simple pain. A person with this condition might also feel buzzing, tingling, or cold sensations in the involved area. Patients may not be able to differentiate between hot and cold. Pain may be intermittent and sharp or steady and dull.
Typically a diagnosis is made by taking a thorough patient history and conducting a physical exam. A nerve conduction study and additional blood work may be ordered to test for underlying conditions.
Cause of neuropathic pain
The primary cause of neuropathic pain is damage to the nervous systems, but this damage can occur due to several factors.
- Diabetes: This is a primary cause of neuropathic pain. Continued exposure to high blood sugar levels leads to nerve damage, which can lead to peripheral diabetic neuropathy.
- Amputation: Phantom limb pain is a type of neuropathic pain.
- Shingles (herpes zoster infection)
- Cancer and/or chemotherapy drugs
- Multiple sclerosis
- Facial nerve damage
- Conditions that affect the back, hips, and legs (such as sciatica and spinal stenosis)
Treatment of neuropathic pain is difficult and often unsuccessful. Many patients reach for either prescription or over-the-counter pain medications and anti-inflammatory drugs, but this does not fix the underlying cause of pain.
The best way to address neuropathic pain is to find the source and fix the damage if possible. Diabetic patients may not be able to cure their diabetes, but keeping better control over blood sugar levels may be able to stop the damage from worsening. Back conditions like spinal stenosis (narrowing of the spinal column) may be addressed through surgery.
If a neuropathic condition cannot be reversed, there are a number of medications prescribed. Tricyclic antidepressants have been successful for diabetic neuropathy, but not for phantom limb pain or pain related to cancer. Other prescription treatments include serotonin-norepinephrine reuptake inhibitors and calcium channel alpha-2-delta ligands. Both of these are also good options for diabetic and post-herpetic neuropathy.
New findings from research on neuropathic pain
Many of the currently available treatments are only minimally effective, and they may not be recommended for long-term, chronic use (i.e. opioids). The best way to treat neuropathic pain would be to avoid it altogether, and researchers at the University of California, Davis have found a key mechanism that triggers neuropathic pain. Endoplasmic reticulum stress (ER stress) is a key process that causes neuropathic pain, and this discovery could lead to new treatments to prevent pain in high-risk populations (such as those with diabetes or limb amputation).
The endoplasmic reticulum is an organelle located in cells. Its primary job is to transport proteins through the cell. Endoplasmic reticulum stress seems to be a response to the actions of soluble epoxide hydrolase, an enzyme which helps to break down a naturally-occurring analgesic lipid. Blocking this action seemed to protect the cells from endoplasmic reticulum stress.
The effects of this action were particularly profound for patients with diabetes, up to 70% of whom will develop neuropathic pain during the course of the disease.
Co-author of the article published July 6 in the journal Proceedings of the National Academy of Sciences Bruce Hammock, distinguished professor at the UC Davis department of entomology and nematology and the UC Davis Comprehensive Cancer Center, believe this discovery is key to unlocking effective treatments. He notes:
“This is a fundamental discovery that opens new ways to control chronic pain. We can now specifically search for agents to control ER stress and its downstream pathways. This search is already underway in a number of laboratories working on cancer and other diseases.”
Armed with this research, scientists can now focus their studies on neuropathic pain from other causes to see if ER stress is also present in those patients. This could lead to a new class of medicines that aim to limit or reverse the signs of endoplasmic reticulum stress.
Neuropathic pain is a complex condition that involves many complex processes in the body. While current treatments may not work for everyone, and they may not be long-lasting, this new finding offers a glimmer of hope for those who suffer from this debilitating chronic condition.
If you or a loved one suffer from neuropathic pain, talk to your doctor about what this research could mean for you.