Researchers at Johns Hopkins University published a retrospective study in which they examined the PET scans of patients who had been definitively diagnosed with autoimmune encephalitis over a ten-year period. They compared patients with anti-NMDA receptor encephalitis with other subgroups. They found those with anti-NMDAr AE consistently showed abnormalities in the form of hypometabolism (lower metabolism) in a part of the brain called the occipital lobe. The authors recalled that formerly some of the first published cases of anti-NMDAr AE included reports of PET scan abnormalities that included occipital hypometabolism, along with other notable observations.
However they mentioned there has been some uncertainty of the specificity and practicality of using PET in autoimmune encephalitis, as there can be wide variations found in patients in the same subgroup (including anti-NMDA). In addition, all hospitals do not utilize PET scans in the diagnostic workup for AE. Despite these challenges, they stated this type of diagnostic testing may be a useful biomarker for the diagnosis and monitoring of patients.
The full paper has recently been made available online and can be viewed here. Many thanks to Dr. John Probasco and the group at Johns Hopkins who conducted this study.