This is one of the most unusual pieces of research around long covid. In truth, it may answer a number of complex questions.
In long COVID patients a strong negative relationship was detected between midbrain volume and “breathing difficulty.” Our study demonstrated an abnormal brainstem volume in both ME/CFS and long COVID consistent with the overlapping symptoms.
Thapaliya, Kiran, et al. "Brainstem volume changes in myalgic encephalomyelitis/chronic fatigue syndrome and long COVID patients." Frontiers in Neuroscience 17 (2023): 1125208.
Brainstem volume increases in Long Covid