All in the mind?

Functional weakness is a common and disabling problem, but along with other functional symptoms this topic receives less attention than it should in medical school teaching and textbooks. Functional weakness is weakness that is not explained by disease. It is also known as psychogenic or non-organic weakness, or conversion disorder-motor subtype according to DSM-IV, the widely used US psychiatric diagnostic system. Alternatively, according to the World Health Organization’s (WHO) coding system, ICD-10, it is known as dissociative motor disorder.

For theoretical and practical reasons we prefer the term “functional weakness” to “neurological weakness not explained by disease.” For most patients it avoids connotations that the patient is “making it up” or that it is “all in the mind,” which is common with alternative terms such as psychogenic, somatoform, psychosomatic, or hysteria.1 Terms such as non-organic, medically unexplained, or unexplained by disease are problematic because they define the problem by something