For patient after patient seeking to cure chronic back pain, the experience is years of frustration. Whether they strive to treat their aching muscles, bones and ligaments through physical therapy, massage or rounds of surgery, relief is often elusive – if the pain has not been made even worse. Now a new working hypothesis explains why: persistent back pain with no obvious mechanical source does not always result from tissue damage. Instead, that pain is generated by the central nervous system (CNS) and lives within the brain itself.
I caught my first whiff of this news about eight years ago, when I was starting the research for a book about the back-pain industry. My interest was both personal and professional: I'd been dealing with a cranky lower back and hip for a couple of decades, and things were only getting worse. Over the years, I had tried most of what is called 'conservative treatment' such as physical therapy and injections. To date, it had been a deeply unsatisfying journey.
Like most people, I was convinced that the problem was structural: something had gone wrong with my skeleton, and a surgeon could make it right. When a neuroscientist I was interviewing riffed on the classic lyric from My Fair Lady, intoning: 'The reign of pain is mostly in the brain,' I was not amused. I assumed that he meant that my pain was, somehow, not real. It was real, I assured him, pointing to the precise location, which was a full yard south of my cranium.
Like practically everyone I knew with back pain, I wanted to have a spinal MRI, the imaging test that employs a 10-ft-wide donut-shaped magnet and radio waves to look at bones and soft tissues inside the body. When the radiologist's note identified 'degenerative disc disease', a couple of herniated discs, and several bone spurs, I got the idea that my spine was on the verge of disintegrating, and needed the immediate attention of a spine surgeon, whom I hoped could shore up what was left of it.
Months would pass before I understood that multiple studies, dating back to the early 1990s, evaluating the usefulness of spinal imaging, had shown that people who did not have even a hint of lower-back pain exhibited the same nasty artefacts as those who were incapacitated. Imaging could help rule out certain conditions, including spinal tumours, infection, fractures and a condition called cauda equina syndrome, in which case the patient loses control of the bowel or bladder, but those diagnoses were very rare. In general, the correlation between symptoms and imaging was poor, and yet tens of thousands of spinal MRIs were ordered every year in the United States, the United Kingdom and Australia.
Very often, the next stop was surgery. For certain conditions, such as a recently herniated disc that is pressing on a spinal nerve root, resulting in leg pain or numbness coupled with progressive weakness, or foot drop, a nerve decompression can relieve the pain. The problem is that all surgeries carry risks, and substantial time and effort is required for rehabilitation. After a year, studies show, the outcomes of patients who opt for surgery and those who don't are approximately the same.
More invasive surgeries carry greater risks. Lumbar spinal fusion – surgery meant to permanently anchor two or more vertebrae together, eliminating any movement between them – is recognised as particularly hazardous. Even when the vertebral bones fuse properly, patients often do not get relief from the pain that sent them to the operating room. Beyond that, fusion surgery often results in 'adjacent segment deterioration', requiring a revision procedure.