by Simon McGrath
A new study, from Julia Newton’s group in Newcastle, UK, has found evidence that reduced blood flow to the brain is associated with muscle abnormalities in CFS patients.
Earlier work by the same group had found that with many CFS patients, muscles don’t regulate acid levels properly after exercise. Another study, by Ben Natelson, had shown reduced blood flow to the brain of most in a sample of CFS patients. This new study looked at both muscle acidity regulation and blood flow to the brain in the same people with CFS. They found a strong correlation between the two, both at rest and in response to a challenge.
This is tantalising stuff: there is a marked link between factors that potentially underlie physical fatigue (i.e. flawed acid regulation in muscles) and factors potentially affecting mental fatigue (reduced blood flow to the brain, which has been linked to reduced poor cognitive performance). Unfortunately the study is relatively small and they didn’t have the funding to include a control group, so at this stage the findings are tentative.
Links between muscle acidity and brain blood flow at rest
Measurements of brain blood flow and muscle pH were taken for all patients when resting and when challenged. The data from the measurements at rest showed that higher pH (less acid and less ideal) correlated with lower brain blood flow (again, less blood flow is less ideal). The correlation coefficient was 0.67 (on a scale of 0-1.0), which is very high by the standards of CFS research.
Links between muscle acidity and brain blood flow in response to challenge
Many people with ME/CFS find that their problems are provoked when they do something rather than when they are at rest. Using an exercise challenge has proved helpful in revealing abnormalities in CFS patients before, such as the Lights’ gene expression work and the Pacific Labs study of Post-Exertional Malaise.
Professor Newton’s group used a similar approach here, with patients repeatedly exercising a calf muscle while muscle pH was measured using Magnetic Resonance Spectroscopy. Compared with expected results (based on previous studies with healthy controls), the muscle pH didn’t recover fully.
Brain blood flow challenge
The ‘challenge’ to brain blood flow was a little different, using something called the ‘Valsalva Manoeuvre’. Here, the patient covers their nose and mouth and tries to exhale hard briefly, before releasing their breath – it’s the same trick you would use to clear blocked ears. This simple procedure triggers a surprisingly complex but predictable series of changes in blood pressure and heart rate as the body brings things back to equilibrium by, for example, contracting blood vessels to raise blood pressure.
Using the Valsalva Manoeuvre as the challenge, researchers measured brain blood flow and found that in CFS patients the final part of the brain blood vessels’ response to the Valsalva Manoeuvre was delayed. What’s more, this delayed response was strongly correlated with poor recovery of muscle pH after exercise (r=0.65, 0-1 scale).
So: both at rest and in response to a challenge, there was a strong correlation between brain blood flow and muscle pH. And in both cases the worse outcome for muscle (higher muscle pH) correlated with the worse outcome for brain blood flow (lower flow/delayed response to challenge).
The previous findings of reduced brain blood flow and muscle dysfunction are interesting, but the new result indicating a strong relationship between the two makes it an area of real promise.
Of course, this is a small study and possibly a similar strong correlation exists in healthy people (albeit at more normal levels of pH/blood flow). What’s needed to advance this area is replication of the findings in studies including matched healthy controls – and Julia Newton is hoping to get funding for just such a study.
Simon McGrath has a biochemistry degree from Oxford University. He later worked for Oxfam, a UK charity. After having ME/CFS for nearly 20 years, he takes a very keen interest in the latest research.