Several lines of evidence come together to provide some confidence that the diagnosis of FND can be made, at least in sufficiently experienced hands, in a way that is helpful to patients.

• There is a reasonable body of evidence to support the discriminatory value of the positive physical signs we have on an individual basis. Some studies looking at combinations of signs, for example in FND seizures provide further support
• When neurologists diagnose FND, the diagnosis remains stable over time. Misdiagnosis rates are no worse than for other neurological or psychiatric disorders¹
• These clinical features have been present over time (for example in books from the 19^th century) and over the world (for example as assessed by neurologists in rural Tanzania)
• The clinical signs identify a group of patients that respond positively to clinical treatments directed  towards those problems in the setting of a randomised control trial.

Clinicians will not always get it right, just as they will sometimes misdiagnose faints as epilepsy, FND as multiple sclerosis or spinal disease as motor neurone disease. Each time that happens is a tragedy for that individual but that shouldn’t mean that no doctor should make diagnoses.

References:

1. Stone J, Smyth R, Carson A, et al. Systematic review of misdiagnosis of conversion symptoms and ‘hysteria’. BMJ 2005; 331: 989.