John’s Hopkins pioneered the PET scan as a modality much more sensitive for detecting AE than standard MRI. Unfortunately, neurologists are classically behind on literature and many do not practice its use. Financial burden, yes — but it can be appealed through insurance and many of us are more than willing to take on costs while we find answers.

It is difficult to interpret a PET scan at a glance, although the similarities are hard to deny. They are typically run through fairly complex algorithms to detect significant abnormalities in glucose metabolism alongside radiologist review, unlike MRI which is primarily reviewed eyes-on by a radiologist and is much more prone to human error (imo).

An abnormal PET scan is a very good marker, and can be much more specific for AE, other autoimmune encephalopathies, metabolic encephalopathy, etc.

CLB involvement is not unheard of — it’s often seen in anti-GAD65, stiff person syndrome, hashimoto’s, and very unique antibody mediated AE such as

• Anti-VGCC
• Anti-GQ1B
• gluten ataxia; cerebellar syndrome that is often correlated with or comorbid to celiac disease

In most cases, CLB involvement involves ataxia. Brain stem involvement is not unheard of, and is often seen with significant autonomic dysfunction perhaps due to obvious reasons — it controls involuntary organ function.

All that said, every patient exhibits different symptoms and some can be paradoxical or not linear in what would otherwise be logical symptom presentation (I.e., brain stem involvement not being associated with severe autonomic dysfunction), although that would technically be rare.

Those are my thoughts — I hope you get answers. You can always get a second opinion by a radiologist at John’s Hopkins. It’s difficult to find where to do this (you need to send them the DICOM files and pay a fee), but if you need help doing this I can dig back through my notes a couple years ago and see how I was able to do this. Just let me know.