Perhaps there are some parallels in the recognition and development of imaging findings in schizophrenia and ME & FND.
With first-onset of psychosis the psychiatrist looks for evidence to suggest an "organic cause", eg a brain tumour. A simple example is the idea that while auditory hallucinations would be expected near 100% in psychosis, visual hallucinations were less common and suggested the psychosis might be secondary — The association between visual hallucinations and secondary psychosis: a systematic review and meta-analysis (2023, Cognitive Neuropsychiatry)
But for many years most of the time patients either didn't get neuroimaging because the clinical exam showed nothing focal to warrant it or got something fairly basic like a non-contrast CT head to look for something like an obvious tumour or raised intracranial pressure. Usually nothing was found and essentially the studies would be reported as normal. This reduced the incentive to do neuroimaging in these patients because the pickup rate was so very low. When MRI started becoming clinically available there was significant resource constraint and patients whose CTs were nearly always normal anyway were not prioritised compared to something like MS which did show things. Now MRI is much more available as a clinical routine and its capabilities are expanding. It's only in the last few years that the field of psychoradiology has started. (This term was to differentiate it from neuroradiology though I suspect ultimately the Venn diagram will overlap much more as we learn more.)
So, finding nothing -> don't look hard -> finding nothing (and repeat)
Then some people do decide to look a bit harder and start to find things or there's a serendipitous observation, which leads to:
finding something -> look harder -> finding something more and more often (and repeat).
For FND in particular, but probably applying in some measure to ME, there has been / continues to be the added issue that the aetiologic hypothesis resulted in a specifically mandated do not look with imaging and other clinical tests.
With first-onset of psychosis the psychiatrist looks for evidence to suggest an "organic cause", eg a brain tumour. A simple example is the idea that while auditory hallucinations would be expected near 100% in psychosis, visual hallucinations were less common and suggested the psychosis might be secondary — The association between visual hallucinations and secondary psychosis: a systematic review and meta-analysis (2023, Cognitive Neuropsychiatry)
But for many years most of the time patients either didn't get neuroimaging because the clinical exam showed nothing focal to warrant it or got something fairly basic like a non-contrast CT head to look for something like an obvious tumour or raised intracranial pressure. Usually nothing was found and essentially the studies would be reported as normal. This reduced the incentive to do neuroimaging in these patients because the pickup rate was so very low. When MRI started becoming clinically available there was significant resource constraint and patients whose CTs were nearly always normal anyway were not prioritised compared to something like MS which did show things. Now MRI is much more available as a clinical routine and its capabilities are expanding. It's only in the last few years that the field of psychoradiology has started. (This term was to differentiate it from neuroradiology though I suspect ultimately the Venn diagram will overlap much more as we learn more.)
So, finding nothing -> don't look hard -> finding nothing (and repeat)
Then some people do decide to look a bit harder and start to find things or there's a serendipitous observation, which leads to:
finding something -> look harder -> finding something more and more often (and repeat).
For FND in particular, but probably applying in some measure to ME, there has been / continues to be the added issue that the aetiologic hypothesis resulted in a specifically mandated do not look with imaging and other clinical tests.