How do you differentiate between functional neurologic disorder from other underlying movement disorders?  

Functional movement disorder (FMD), like most movement disorders, is a clinical rule-in diagnosis based on specific diagnostic criteria and clinical features of the patient's presentation. The examination and the phenomenology of the exhibited movements are key to diagnosing FMD. Variability, distra...

I have also found video reviews to be extremely helpful. Sometimes this can give an idea about distractibility, suggestibility, and variability as discussed above. It can also provide insight into the patient's emotional state during abnormal movement episodes.

I would also recommend the use of videotaping the movements as well as collateral information from witnesses (Thenganatt and Jankovic, PMID 25243097).

I like the use of functional MOVEMENT disorder here instead of functional NEUROLOGIC disorder. Movement is a non-specific term, but neurologic implies the problem is indeed neurological. We do know that patient confusion about the true nature of a conversion disorder diagnosis brings a poor prognosi...