Not too long ago, many doctors approached chronic pain as something that is “all in the head.”

If you had pain without a discernible cause in the body, if there wasn’t all-singing, all-dancing inflammation, a doctor might say, ‘It’s probably in your head.’ And women are more likely to suffer from chronic pain, so you might have been labelled a hysterical woman, who should go see her therapist. When we cannot see pain, we arrogantly assume the body is not dysfunctional, rather than maybe we just don’t have the tools with the right sensitivity to detect the dysfunction.

But, as science has advanced, so has the determination of the cause of pain, most notably that chronic pain is real and it does have a biological cause. The debate remains as to how much the nervous system versus the brain itself is involved as that cause and how cell systems contribute to this.

“There’s a lot of abnormality in the body still that we as neuroscientists haven’t fully clocked on to yet, so we tend to blame the nervous system. [We think] the brain is going wrong. I’m not saying the brain isn’t important, but maybe it is going wrong because there’s still a lot of low-grade inflammation and connective tissue cells sitting there constantly yelling at the nerves, ‘I’m not happy, I’m not happy.’”

- Dr Franziska Denk, a senior lecturer at King’s College London

A recent area of interest, as scientists work to determine the causes or chronic pain, is the glia. These are various types of cell that are linked to or support the nerves or neurones, the cells that actually transmit impulses from the body to the brain or the spinal cord, and back again. And, with many conditions, including chronic pain and neurodegenerative illnesses, research typically has focused on the neurones and what their role in disease might be. But for a number of years, a contingent of scientists have proposed this pathology may not be in the nerves, but in the glial cells associated with the system as a whole.

Types of glia exist in a number of areas in the body, performing a variety of support functions — cells of the central nervous system, dealing with waste, supporting and insulating axons, conducting impulses from the cell body, even playing a role in immunity. And, according to Prof Alexei Verkhratsky, a professor of neurophysiology at the University of Manchester in the UK, “as long as these glial cells are doing everything fine, there’s no disease whatsoever. They are taking care, they are restoring homeostasis, they are restoring whatever mini-trauma, they are fighting pathogens.” So what if these glia are also responsible for what has been described as the “silent epidemic” of chronic pain?

In the United States as many as one in five people has chronic pain. In the UK, that number is about one in seven with moderately or severely disabling chronic pain. Glia could be the reason why people who have suffered trauma or an accident continue to feel pain long after their injuries have healed. This is the textbook example of a case of pain that once had a biological function – to indicate an injury – which has become a pathology in itself.

Because glia regulate the activity of neurones in myriad complex ways, it is very difficult to target their effects on chronic pain. Dealing with one form of glial communication may leave others unaffected, or not. This contributes to the difficulty scientists have had in finding drugs to treat the condition of chronic pain as well as other neurological disorders.

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