Diagnostics
faculty of kinesiology and rehabilitation sciences at the University of Leuven, is one of those researchers. Eschewing the idea of an autoimmune cause completely, she believes the key to understanding fibromyalgia lies in the spine, or more specifically the cerebrospinal fluid (CSF) that circulates around the brain and spinal cord. The lynchpin of her theory is based on the existence of Tarlov cysts – fluid-filled sacs found on the nerve roots of the spine. “Tarlov cysts are an under-recognised condition because most doctors believe they are clinical findings that have no importance and do not cause any symptoms,” she says. “But we have found that almost all of the patients who have Tarlov cysts, have chronic pain.” The occurrence of the cysts, Hulens explains, is due to increased cerebrospinal pressure, which she posits to cause irritation to the nerves and even cause nerve damage. To support the theory, she and seven other researchers conducted a study that put 197 patients diagnosed with fibromyalgia, CFS or both conditions, under an MRI scanner looking for Tarlov cysts. The prevalence was 39% among the cohort, but Hulens says even those who did not have them showed other signs of increased cerebrospinal pressure. “A lot of the patients had dilated nerve root sheaths, but they didn’t look like cysts yet,” she explains.
“[Fibromyalgia has] always been linked to viruses or autoimmune disease, but everybody gets different viruses and everybody has IgGs against them. I don’t think that’s a cause.”
Dr Mieke Hulens, University of Leuven
An accompanying element of Hulens’ theory is that the reason symptoms often cross over with fibromyalgia and CFS patients is that the two diseases share a common pathophysiology – increased cerebrospinal pressure. In another study, published at the start of this year, she sought to explain this link by connecting small fibre neuropathy, thought to be a potential cause of pain and abnormal skin sensations present in both fibromyalgia and CFS patients, with the pathological impact of Tarlov cysts. In the small retrospective study, she and her fellow researchers used intraepidermal nerve fibre density (IENFD) data from 17 patients, all of which had Tarlov cysts. They found that 82% of patients had an IENFD value below 5%, which is an indication of small fibre neuropathy. CSF pressure, her paper contends, initiates formation of the cysts, but also damages axons and neurons inside nerve root sheaths and dorsal root ganglia (DRG) – a cluster of neurons in a dorsal root of a spinal nerve. This is not the first time that DRG has been implicated in the pathophysiology of fibromyalgia, and Hulens believes it could explain the small fibre neuropathy. Another part of her theory
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is grounded in the upright, mostly standing position human beings tend to be in day-to-day. She contends that hydrostatic pressure in the CSF is the highest in the lowest nerve roots, which is why Tarlov cysts tend to be more prominent in the sacral nerve roots and may explain why those suffering with fibromyalgia and CFS often report bowel and bladder issues along with their widespread pain.
An autoimmune cause?
For Hulens part, the answer to whether fibromyalgia has an autoimmune cause is an unequivocal no. “It’s always been linked to viruses or autoimmune disease, but everybody gets different viruses and everybody has IgGs against them. I don’t think that’s a cause,” she says.
The root cause, she believes, is likely a hereditary predisposition in the genes that leads to increased CSF pressure. She points to research from 2004 led by University of Cincinnati psychiatry and behavioural neuroscience professor Lesley Arnold that found the family members of patients with fibromyalgia were eight times more likely to have the disease than those of patients with rheumatoid arthritis. “It’s a bit like increased blood pressure,” she adds. “That’s hereditary too, but increased blood pressure is very easy to measure, so there have been very large epidemiological studies showing that even moderate increases in blood pressure are harmful.” In contrast, Hulens says there is a belief that only very high cerebrospinal pressure is harmful because little is known about the effects of moderate increases. “Those [moderate increases] are the patients with fibromyalgia and CFS,” she believes. Although it is anecdotal, in her role as a physical medicine and rehabilitation physician, Hulens says many of her patients get symptom relief through a redcution in sitting, and using a reclining chair when they do, to reduce the amount of CSF pressure, which elevates in traditional seated positions where the feet make contact with the floor. Beyond that, she says treatments that lower CSF pressure range from drugs with “significant side effects” and “disappointing” therapeutic benefit, to extreme methods like installing a shunt or conducting a lumbar puncture, both of which carry risks – especially shunting, which can result in CSF leakage.
Discussions about the element of risk in procedures indicated from both sides of the fibromyalgia research spectrum: autoimmune and neurological, help to bring the discussion back to patient care. Those that suffer from the disease, says Svensson, are speaking up for themselves, as she observed in a meeting about potential treatments. “The patient representatives were very vocal in the discussion, saying ‘let us decide if it’s worth taking the risk, because we don’t have a life today,’” she recounts. “That left me so touched and motivated to continue this work.”
Practical Patient Care /
www.practical-patient-care.com
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