What is Neuropathic Pain?

Neuropathic pain is a type of pain that is caused by damage to the nervous system following an injury or illness and affects approximately 1% of the population.

It is often sharper and more intense than other types of pain and does not typically respond well to standard analgesic pharmacotherapy. Instead, management techniques for neuropathic pain frequently involve neurostimulation therapy to address the changes to the nerves directly.

Characteristics

From a clinical perspective, neuropathic pain is a multidimensional condition that can vary considerably with respect to intensity, location and time. Neuropathic pain typically presents as a sharp, intense pain that is sometimes described as shooting through the body. However, other patients describe a pain with different characteristics, such as a burning or heavy sensation, or numbness in a region of the body.

Neuropathic pain is often associated with a chronic pain disorder that will not resolve spontaneously, and can have a significant impact on the quality of life of the patient. The management of the condition can also prove to be difficult, particular when it does not respond adequately to standard pharmacological analgesics.

Types: Stimulus-evoked and Stimulus-independent

There are two main types of neuropathic pain, known as stimulus-evoked and stimulus-independent.

Stimulus-evoked pain is aggravated by movement or being touched in certain areas of the body. Stimulus-independent pain is not affected by such movements or touch, but may vary in intensity and be constant or intermittent.  

Mechanism

Neuropathic pain presents as a result of injury or illness that interferes with the nerves that are usually involved in the transmission of pain signals. This damage occurs when the nerves are compressed, entrapped, sectioned, bruised or stretched.

In a healthy person, the nociceptive pain pathway provides useful information of noxious stimuli in specific parts of the body, such as extreme cold or heat, in order to allow the body to react and protect itself from harm. This information is carried from the nociceptors at the site of the stimuli to the brain via nerves in the nervous system.

When damage to the nerves that are involved in the signaling of pain pathways are activated, the signals can be permanently or intermittently activated, even in the absence of noxious stimuli.

There are various circumstances that may cause damage to the nerves and lead to the presentation of neuropathic pain. These include:

• Alcoholism
• Autoimmunity
• Back pain
• Cancer
• Diabetes
• Exposure to toxins
• HIV
• Infections
• Nutritional imbalance
• Post-therapeutic neuralgia
• Surgery
• Trigeminal neuralgia

Management

Unlike nociceptive pain, neuropathic pain does not usually respond well to standard analgesic medication, such as paracetamol, aspirin or ibuprofen. This is likely due differences in the mechanism of pain and, instead neuropathic pain can often be managed more effectively with neurostimulation.

Neurostimulation therapy involves microelectrodes to deliver mild electrical impulses to the epidural space in the central nervous system of the body. The aim of the treatment is to restore normal sensation and reduce the impact of neuropathic pain on the quality of life of patients.

The results of neurostimulation therapy are highly variable, but the success rates are much higher with neuropathic pain that other types and it is most useful for patients that have pain that is unresponsive to other management techniques.

References

• http://www.grunenthal.com/grt-web/Grunenthal_Group/Patients/Definition_of_Pain/Pathogenesis/Neuropathic/en_EN/265300345.jsp;jsessionid=C9CC5C6F8FE6CC258E9F052A50DB5309.drp1
• http://www.ajmc.com/journals/supplement/2006/2006-06-vol12-n9suppl/jun06-2326ps256-s262/