I donīt particularly hope I have this after all these years!
But it was certainly an interesting link with a lot of information:

http://jnnp.bmj.com/content/76/3/307.full

HOW CERTAIN CAN WE BE THAT A SYMPTOM IS FUNCTIONAL?

īSeveral recent studies have shown that patients whose symptoms are considered neurologically unexplained after appropriate assessment rarely turn out to be diagnosed with a somatic neurological disorder later. However, it should be born in mind that these studies were carried out at specialist centres, and that the risk of a misdiagnosis of disorders characterised by functional symptoms may be higher in less well investigated patients. Stone et al found that a neurological explanation had been found in one of 42 patients with functional weakness or sensory loss after a mean of 12.5 years of follow up.52 Crimlisk et al found that only three of 64 patients with functional weakness had developed an identifiable somatic disorder explaining the weakness 6 years after the initial assessment (two out of these three patients were misdiagnosed because they had disorders with variable symptoms).5,53 Couprie et al found an unexpected somatic explanation in four of 56 patients with a functional neurological problem after 1.5–9.5 years.54ī........


īThat does not mean that neurologists should rush into calling a symptom functional. There are also risks of overdiagnosing functional problems.63,64 In particular, patients with atypical or rare organic disease presentations may not receive appropriate treatment or be denied financial help for incapacity from the government.65 Once a clinician has diagnosed a problem as functional, patients are less likely to be taken seriously by colleagues or to receive palliative or curative treatment.66ī............