To the patient and the doctor it often looks as if you have had a stroke or have symptoms of multiple sclerosis. However, unlike these conditions, with functional weakness there is no permanent damage to the nervous system which means that it can get better or even go away completely.
The diagnosis should usually be made by a consultant neurologist so that other neurological causes can be excluded. The diagnosis should be made on the basis of positive features in the history and the examination (such as Hoover's sign). It is dangerous to make the diagnosis simply because tests are normal. Neurologists get the diagnosis wrong around 5% of the time (which is the same for many other conditions)
Many patients with functional weakness suffer from not being believed by doctors or other people. Although psychological factors can be important they are not exclusively so and the problem is not 'made up' or 'imagined'. Patients with functional weakness are as disabled and distressed by their symptoms as patients with multiple sclerosis.
Functional weakness may also be described as 'dissociative motor disorder' and less helpfully as 'conversion disorder'
Treatment involves understanding and believing the diagnosis and gradually restoring nervous system function with graded exercise,learning how to manage symptoms of fatigue and pain when present and treatment of associated symptoms of worry or low mood if present. Hypnosis may also be useful.