Earlier this year, Dr Elisha Josef and colleagues at Murdoch Children’s Research Institute in Melbourne, Australia published results from their ME Research UK-funded study looking at brain functional connectivity, cognitive symptoms and fatigue in adolescents with ME/CFS.
Also interested in this area of research is another Australian group, from a bit further up the coast in Queensland, which has recently published a paper investigating brainstem connectivity in adults with ME/CFS.
Functional connectivity describes the links that exist between different regions of the brain, and which allow information to be processed. Activity occurring in two regions of the brain at the same time suggests a connection between those regions – either in the form of a direct pathway, or a more indirect cause-and-effect.
The previous study in adolescents found that their functional connectivity – measured using magnetic resonance imaging (MRI) – was reduced following a period of mental exertion, and this was mirrored by a decrease in their performance on a number of tests of cognitive function. However, brain functional connectivity decreased by a similar amount in a healthy control group.
In the more recent study – conducted by Dr Leighton Barnden and colleagues at Menzies Health Institute – the researchers assessed various regions of the brainstem in 45 people with ME/CFS and 27 healthy control subjects. Functional MRI was used to measure connectivity at rest, and while the participants were performing a series of tests of attention and concentration.
In these cases, deficits in intra-brainstem connectivity were found in the ME/CFS group compared with the healthy control group, but only while they were performing the cognitive tests. Specifically, connectivity was reduced between the medulla (responsible for autonomic function) and midbrain (motor function, and auditory and visual processing) within the brainstem, and between the brainstem and other parts of the brain.
The authors conclude that deficits in brainstem connectivity may help explain some of the autonomic changes in ME/CFS, as well as impairments in attention, memory, cognitive function and other symptoms.
Why do these results differ from those of Dr Josef’s group. The most obvious answer is that the studies were looking at different patient groups. While the earlier study was in adolescents, the more recent study appears to have been in a group of adult subjects – their ages are not reported, but some of their characteristics and the fact they provided their own informed consent suggests they were adults.
In addition, the two studies were looking at different – although overlapping – regions of the brain, and there were also a number of other methodological differences between them.
Abnormalities in the brainstem of people with ME/CFS have been reported as far back as 1995, so it is good to see research continuing in this area, and we look forward to reading more from this group.