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Functional Terms Defined


What’s in a label?

Diagnostic labeling is causing a significant amount of confusion amongst patients and doctors alike.  One doctor may use the term Functional Neurological Disorder or Functional Movement Disorder, but then another may use Conversion Disorder.

The inability of the medical community to agree to a specific definition and label for functional symptoms leaves many patients confused about their diagnosis and struggling to find where they fit. These various labels individually have different meanings, which contributes to the confusion. The many different theories and beliefs about functional symptoms are the major contributing factor why the various medical specialties are reluctant to agree on a label. However, all the above terms are theoretically referring to the same set of symptoms.

Functional added to DSM-5

Functional Neurological Symptoms Disorder was added as an inclusion term to Conversion Disorder in the DSM-5, which published in May of 2013. The term was once used in the 19th and early 20th centuries to refer to disorders like migraine and Tourette’s syndrome, and it was not the only change to Conversion Disorder in the DSM-5.

The need to identify a psychological stressor was one change to the criteria. Doctors have a habit of connecting functional symptoms to any recent or old stress without relevant evidence.  It is questionable how one can ever be sure that a psychological stressor is ever relevant or is converting into a physical symptom?  Many patients found after a psychological evaluation that they did not have a connection. Yet, they had functional symptoms. Therefore, a need emerged for the updated changes in the new edition of the classification manual.

FND Hope’s observation is that Psychologists most often use Conversion Disorder where Functional Neurological Disorder is a term used more commonly amongst those more familiar with FND. FND is starting to be picked up by general neurologists.

As an organization, we take a strong stance for using the term Functional Neurological Disorder. We do not choose this term to alienate those with a known psychological connection or Conversion Disorder experience, but because it is a general term that more accurately describes what all patients with like symptoms are experiencing. “The term functional, despite drawbacks, is not used here as a synonym for psychogenic, but instead as a way of describing a group of disorders in which there is a functional rather than structural disturbance in nervous system functioning and where a biopsychosocial model is critical in understanding their nature.”¹

Functional Terms and Labels Defined

  • • Psychogenic Suggests psychological causation.
    • Conversion Disorder Diagnostic term in the DSM: The term ‘Conversion Disorder’ is a term referring to patients that are converting mental stress into physical symptoms.
    • Somatisation Symptom Disorder is used to refer to symptoms that are either very distressing or result in significant disruption of functioning, as well as excessive and disproportionate thoughts, feelings and behaviors regarding those symptoms. The patient should be persistently symptomatic for at least 6 months. Distressing symptoms need not be medically unexplained anymore. Somatic Symptoms Disorder is different from the heading Somatic Symptoms Disorder and Related Illness.
    • Medically Unexplained Symptoms Suggests that a medical explanation might one day be apparent and could refer to many medical symptoms that are not thought to be psychogenic, but still are not of a known cause.
    • Functional Broad term suggesting a functional rather than a structural deficit, which could apply to several neurological disorders not regarded as psychogenic, but where structural pathology is absent, eg, migraine.
    • Hysteria Historical term that carries substantial stigma in society and implies a link between symptoms and the uterus.
    • Non-Organic Defines the condition by what it is not; the term organic is itself not well defined.
    • Hoover Sign Is a clinical sign used to differentiate between unilateral organic and functional leg weakness.
    • Protocol Is a term used for clinical trials.
    • Somatoform Was a diagnostic code which has now been replaced with Somatic Symptoms Disorder. A group of psychiatrists has publicly acknowledged that the guidelines for Somatoform Disorder actually failed to meet current standards to qualify as a true mental health disorder.

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