The cause of neuropathic pain is not well founded yet due to the lack of research in this specific area, and because sometimes the patiens exhibit either short term or long term pain, which makes it very hard for tracking causes.

What is known is that it happens when a nerve is injured, and the amount of stress put upon it is what determines the length, resistance, and continuity of the pain itself.

The National Pain Foundation cites allodynia (when someone feels pain when exposed to things that do not usually cause pain), burning pain, stabbing pain, extreme pain, prickling/numbness, and even loss of feeling due to the lack of transmission from the nerve to the brain.

The treatment is difficult because nerve pain is not treated with the same medicines as muscular pain. In fact, they treat this illness with medicines usually reserved for herpes, shingles, seizures and even depression. This is the case because these specific medicines reach those very delicate nerve endings that regular pain medication only reaches in the gross motor of our bodies. This type of application of medications is known as "off-label use"

Included is a link that can help you understand this condition. As a sufferer of fibromyalgia myself I know quite well how hard these people have it.