Nerve pain (also known as neuropathic pain) is difficult to diagnose and measure. Patients often describe the pain as “burning” or like “electric shocks.” Others may report itching, numbness, or a pins and needles sensation.
The source of neuropathic pain is not always easy to locate. It could be coming from muscles, joints, spinal cord injury, or a neurologic disease such as multiple sclerosis, Parkinson disease, or Lou Gehrig disease. Loss of blood supply to the nerves from diabetes or as a side effect of chemotherapy for cancer can also cause neuropathic pain.
For some time now, neuroscientists have been working on finding easy and simple ways to identify and quantify neuropathic pain. So far, they have come up with several screening tools in the form of questionnaires.
These include the Leeds Assessment of Neuropathic Symptoms (LANSS), the Neuropathic Pain Questionnaire (NPQ), the Neuropathic Pain Scale (NPS), the Douleur Neuropathique en 4 Questions, DN4, ID-Pain, and painDETECT.
Each one measures type of sensations experienced by patients. Most are self-administered (the patient fills out the form). A few are clinician-administered (the examiner asks the questions and completes the form).
The questionnaires are not designed to measure frequency, intensity, or duration of the symptoms. Only the Neuropathic Pain Scale (NPS) attempts to measure quality of pain. The rest are just screening tools but represent a step in the right direction for at least recognizing what’s going on in the patient’s body. They provide a piece of the diagnostic puzzle but the information gained must be used in context of the whole patient.
As useful as these screening tools are in clinical practice, there are some drawbacks. For one thing, they were designed to assess just one area of pain. Many patients come to the physician or pain clinic because of pain in several areas of the body. There are often cases of widespread pain (throughout the head, neck, body, and limbs).
Sometimes the questionnaires fail to identify someone who (when tested by the physician) is found to have a true neuropathic problem. Neuropathic pain questionnaires don’t cover all possible pain types — just the most commonly reported descriptors. So some people will fall through the cracks if the survey doesn’t include questions about the specific type of pain experienced by that person.
The questionnaires do not help point to the underlying cause or true etiology of the problem. That requires additional testing, lab work, and X-rays or other imaging studies. Electrophysiologic tests such as EMGs (electromyograpies of the muscles) or nerve conduction tests may also be needed.
But from the studies done so far, the screening questionnaires are simple and easy to use and do help identify neuropathic pain. That is an important first step because it can be very difficult to sort out pain types and pain patterns without a starting point like this.
In summary, having a tool that can screen specifically for neuropathic pain is a break through in pain diagnosis. The information gathered from studies using these tools has shown that neuropathic pain is linked to specific pathophysiologic mechanisms.
That means it may someday be possible to develop “designer drugs” to help with pain management. Such drug treatment targets the exact cell receptor or nerve fibers that can turn off (or prevent) the pain or blocks the nerve pathways causing the pain. Now that we have valid and reliable screening tools for neuropathic pain, future studies to develop assessment tools to measure treatment effects are also needed.