Have doctors found the key to diagnosing long COVID?

In their case report, US doctors say a brain PET scan could be key to confirming the common condition

Brain PET scans could be a useful screening test for post-acute COVID-19, according to US doctors in a case report of a patient who had persistent symptoms for nine months. 

Transverse view of PET. Non-specific scattered areas of low-level hypometabolism are present at the bilateral frontal, left precuneus, occipital and parietal regions. Notably, the gyrus rectus is spared. Source: BMJ Case Reports.
PET scan