The language to describe functional neurological symptoms has changed, especially in the last 100 years, but the problem itself dates from antiquity. Recent work has demonstrated that patients with this group of conditions form a significant minority of neurologists’ caseload and that they do badly on the whole,1 which highlights the need for effective treatments. However, decent therapies require good knowledge of mechanism of the illness and this is currently not the case. Although tests, such as Hoover's sign and the entrainment test have helped us to make positive diagnoses of conversion, there are few other reasons to believe that all patients falling under the rubric of ‘functional neurological symptoms’ are suffering from the same illness. The only things they have in common are that they lack the features of currently accepted ‘organic’ disease, that disability has arisen as a result of a presumed problem with higher mental function, whatever that may be, and that the categories are fairly stable over time.2 …