Muscle sodium content in patients with ME/CFS
A German team of researchers used magnetic resonance imaging (MRI) to measure levels of sodium in the tissues of the legs of people with ME/CFS and healthy people. Too much sodium can lead to muscle weakness. Too little can trigger spasms and cramping.
“This study provides evidence that sodium content of lower leg muscles is higher in ME/CFS than in healthy controls at rest and after exercise. Furthermore, our findings indicate an inverse correlation between mean muscle sodium content and handgrip strength. Thus, sodium overload may play a role in the pathophysiology of ME/CFS and may allow for potential treatment targeting.
This study demonstrates the feasibility of monitoring changes in muscle sodium content in ME/CFS and healthy subjects after exercise using 23Na-MRI.”
More information:
Muscle sodium content in patients with Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome, by Elisabeth Petter, Carmen Scheibenbogen, Peter Linz, Christian Stehning, Klaus Wirth, Titus Kuehne, Marcus Kelm in Journal of Translational Medicine Vol 20, #1, p 580 December 9, 2022
Research abstract:
Background: Muscle fatigue and pain are key symptoms of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). Although the pathophysiology is not yet fully understood, there is ample evidence for hypoperfusion which may result in electrolyte imbalance and sodium overload in muscles.
Therefore, the aim of this study was to assess levels of sodium content in muscles of patients with ME/CFS and to compare these to healthy controls.
Methods: Six female patients with ME/CFS and six age, BMI and sex matched controls underwent 23Na-MRI of the left lower leg using a clinical 3T MR scanner before and after 3 min of plantar flexion exercise. Sodium reference phantoms with solutions of 10, 20, 30 and 40 mmol/L NaCl were used for quantification.
Muscle sodium content over 40 min was measured using a dedicated plugin in the open-source DICOM viewer Horos. Handgrip strength was measured and correlated with sodium content.
Results: Baseline tissue sodium content was higher in all 5 lower leg muscle compartments in ME/CFS compared to controls. Within the anterior extensor muscle compartment, the highest difference in baseline muscle sodium content between ME/CFS and controls was found (mean p/m SD; 12.20 p/m 1.66 mM in ME/CFS versus 9.38 p/m 0.71 mM in controls, p=0.0034).
Directly after exercise, tissue sodium content increased in gastrocnemius and triceps surae muscles with + 30% in ME/CFS (p=0.0005) and + 24% in controls (p=0.0007) in the medial gastrocnemius muscle but not in the extensor muscles which were not exercised. Compared to baseline, the increase of sodium content in medial gastrocnemius muscle was stronger in ME/CFS than in controls with + 30% versus + 17% to baseline at 12 min (p=0.0326) and + 29% versus + 16% to baseline at 15 min (p=0.0265). Patients had reduced average handgrip strength which was associated with increased average muscle tissue sodium content (p=0.0319, R2=0.3832).
Conclusion: Muscle sodium content before and after exercise was higher in ME/CFS than in healthy controls. Furthermore, our findings indicate an inverse correlation between muscle sodium content and handgrip strength. These findings provide evidence that sodium overload may play a role in the pathophysiology of ME/CFS and may allow for potential therapeutic targeting.
Dr Katrina Pearce comments on the MEA website:
- People with ME/CFS are often advised to increase their sodium/salt intake to help with orthostatic intolerance, however, findings in this study would not be due to this as the differences are too large and excess sodium is excreted by the kidneys. Therefore, a lower dietary intake would not change the results.
- In conclusion, there are some very clear significant findings in this study on a very small sample size, however, more investigation is needed to explain these results, especially if potential treatments targeting the high sodium muscle content are to be considered.
