Intended for healthcare professionals

Student Education

All in the mind?

BMJ 2012; 344 doi: https://doi.org/10.1136/sbmj.d7768 (Published 27 January 2012) Cite this as: BMJ 2012;344:d7768
  1. Joanna Perthen, final year medical student1,
  2. Jon Stone, consultant neurologist and honorary senior lecturer in clinical neurosciences2
  1. 1Newcastle University
  2. 2Edinburgh University Western General Hospital

The diagnosis, management, and challenges of functional weakness

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.

Terminology

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 that it is not. Terms such as conversion disorder and dissociative disorder imply unproved aetiological or poorly characterised processes. In contrast, functional weakness is an aetiologically neutral term, referring to the mechanism of symptoms rather than their cause, and suggests a clear aim for treatment, namely the return of normal function.

Epidemiology

Functional weakness is a common presentation globally within neurology, general medical wards, and emergency departments. Around one in three new neurology outpatients in the United Kingdom2 and Europe3 have symptoms poorly explained by disease. One in six have a primary diagnosis that is functional or “non-organic,” such as functional weakness or non-epileptic attacks.2 The incidence of functional weakness (at least five per 100 000) and frequency of disability is similar to multiple sclerosis.4 Although it can be a transient phenomenon, more typically it is associated with other …

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