Neurological symptoms – such as pain and cognitive difficulties, are central to ME/CFS, however little is known about the exact mechanisms that cause them.
Previous research has considered specific signals in the brain – blood oxygenation level-dependent (BOLD) signals, in people with multiple sclerosis (MS), and those with traumatic brain injuries – conditions which also have neurological symptoms.
Results from these studies have shown that:
- In healthy people, completing ongoing cognitive tasks causes BOLD signals to decrease – this decrease is known as “BOLD adaptation”.
- In those with MS, and those with traumatic brain injuries, BOLD signals increased.
Although the mechanisms of BOLD adaptation are unclear, it is believed to improve the energy efficiency of the information processing performed by networks of nerve cells.
Based on this – and the links between ME/CFS and disrupted energy metabolism, a team of researchers including Dr Zack Shan – who is currently working on a research project funded by ME Research UK, have published the results of a study that aimed to investigate whether people with ME/CFS would also demonstrate an absence of BOLD adaptation.
The researchers used functional magnetic resonance imaging (fMRI) scans to look at how BOLD signals differed during cognitive tasks between people with ME/CFS and healthy controls.
The study had a “relatively large” sample size – 34 people with ME/CFS (27 women), and 34 healthy controls (27 women), and used a consistent process for ME/CFS diagnosis – a consensus diagnosis by two clinicians (who were members of the research team) using the Canadian Consensus Criteria for ME/CFS.
Results were complex, but indicated that following the cognitive tasks:
- BOLD signals for people with ME/CFS remained similar (although slightly increased) – showing no sign of BOLD adaptation.
- For healthy controls, BOLD signals decreased – indicating BOLD adaptation.
The authors suggest that the absence of BOLD adaptation in people with ME/CFS may represent a potential neurophysiological mechanism for the disease.
ME Research UK adds that more research is needed to understand BOLD adaptation – or the absence of it, in people with ME/CFS, and how the diversity of ME/CFS may impact the findings – such as the severity of disease, length of diagnosis, delay to diagnosis, and age of symptom onset. It may also be important to consider the impact of participant characteristics such as sex – including the number of hormonal events, and ethnicity.
