Functional neurologic disorders and related disorders

Victor W Mark MD (Dr. Mark of the University of Alabama at Birmingham has no relevant financial relationships to disclose.)
Originally released April 18, 2001; last updated January 13, 2020; expires January 13, 2023

This article includes discussion of psychogenic neurologic disorders, combat neurosis, conversion disorder, functional cognitive disorder, functional movement disorder, functional neurologic disorder, functional neurologic symptom disorder, hysteria, medically unexplained disorder, pseudoseizure, psychogenic neurologic disorder, psychogenic nonepileptic seizure, and shell shock. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.


This topic reviews functional neurologic disorder, Munchausen syndrome, Munchausen syndrome by proxy, and Ganser syndrome. These neurobehavioral disorders are related by their (1) resemblance to other, more familiar neurologic disorders; (2) lack of well-established biomarkers (eg, structural lesions on brain imaging studies, seizure waveforms on EEGs); and (3) aggravation of symptoms with the patient's or caregiver's attention to the disorder. However, the features and causes for these disorders are very different among themselves and are reviewed.

Key points


• Functional neurologic disorders are commonly encountered in general neurologic practices and, hence, knowing their manifestations and treatment is crucial for clinical care.


• The disturbance is involuntary, and yet at the same time it can be intermittently improved by the patient, depending on the patient's reducing attention to the deficits.


• Although it can be improved intermittently by the patient, the disturbance is generally disabling unless expert professional care intervenes.


• There is no consistent association between functional neurologic disorders and either posttraumatic emotional stress or sexual abuse.


• Functional neurologic disorder responds best to empathetic concern by the clinician; demonstration that the disorder lacks a structural or permanent etiology; explanation that it can be improved with distraction; and guided attempts to reduce triggers of onset. Cognitive behavioral therapy, combined with physical therapy when warranted, is emerging as an efficacious intervention.


• Although most forms of functional neurologic disorder are relatively benign, Munchausen syndrome by proxy (the intentional false reporting of illness by caregivers of dependent individuals) demands rapid intervention.

Historical note and terminology

"Hysteria" was the original term for fluctuating and disabling neurologic disorders in alert sufferers, which were attributed from classical times to a "wandering uterus" in women (Zimmer 2004). Offray de La Mettrie, for example, published in 1738 an account of episodic catalepsy (waxy immobility of the limbs) in a woman that he attributed to hysteria arising from amenorrhea (Walusinski 2012). Eighteenth century treatments for hysteria were radical and untested, including bloodletting, beatings, diet, fresh air, and writing (Meek 2013).

Broca's 1861 seminal and replicated discovery that aphasia emanates from focal lesion in the brain as found on autopsy inspired subsequent neuroscientists to trace other neurobehavioral disorders to their respective specific brain regions. Broca's contemporary neuroscientist Briquet related functional neurologic disorders of both women and men also to cerebral disease, but in contrast to aphasia, these disorders did not leave visible lesions at autopsy (Crommelinck 2014). Nonetheless, Briquet relocalized functional neurologic disorders from the uterus to the brain. Reynolds published in 1869 a prescient overview of functional behavioral disorders of motor control and sensation that appeared to be based on an ideological fixation and were amenable to compassionate behavioral retraining (Reynolds 1869). In 1888 Blocq comprehensively described a case series of the acute inability to stand and walk despite full motor control of the legs while the patients were supine, which he termed “astasia-abasia,” a term that continues today (Okun and Koehler 2007). Although he doubted that the disturbance had a purely psychologic etiology, his pathophysiologic hypothesis—that marked emotional distress can aggravate cerebral inhibition over spinal walking mechanisms—is remarkably similar to current pathophysiologic hypotheses for functional disturbances. Late in his career, Charcot opined that functional disorders emanated from focal disturbances of the nervous system, but which could not be identified on autopsy. He, therefore, postulated that functional neurologic disorder may emerge from a “dynamic” lesion, for which extant neurologic examination techniques could not identify (Goetz 2016).

At the turn of the 19th century, Freud (who trained as a neurologist under Charcot) hypothesized that an unconscious and involuntary cognitive process called “conversion” caused functional neurologic disorders (Breuer and Freud 1895; Freud 1899). In this model, emotionally conflicting memories of young life abuse or other upsetting personal experiences are involuntarily repressed and “converted” to severe somatic involuntary disturbances. Although no experimental evidence for this process was adduced for this nonfalsifiable model, this concept became firmly established and continues today in contemporary medical care (Carson et al 2016). Commonly, functional neurologic disorder is called “conversion disorder,” including in present-day medical diagnostic classifications for clinical billing.

A surge of interest in functional neurologic disorders came with World War I, when European soldiers returned from combat with a variety of fluctuating neurologic deficits without traumatic brain injury (Jones et al 2007; Linden and Jones 2013). These postcombat disorders were considered to be neurologic, even though their precise etiologies were unclear. However, the neurologic interest in the causes, physiological basis, and treatment of functional disorders became overshadowed, for the most part, by the successful outcomes of the psychoanalysis that was developed by Freud (Crommelinck 2014). Over the course of the 20th century, the lack of rigorous empirical evidence for unconscious repression led to a return of interest to the neurophysiological basis of functional disorders, beginning in the 1960s, and continues to the present.

A wide variety of synonyms for these disorders have been used up to the present, which hampers understanding. These terms include hysteria, conversion disorder, medically unexplained disorder, shell shock, combat neurosis, psychogenic neurologic disorder, and pseudoseizure. Edwards and Bhatia emphatically recommended the term “functional neurologic disorder” on the grounds that patients find this less objectionable than rival terms (Stone et al 2002b; Edwards and Bhatia 2012), which helps to emphasize the reversibility of the disorder (Reuber et al 2005; Stone et al 2005). PubMed shows a continual adoption of this term over others over the past decade.

"Somatization disorder" or "Briquet syndrome" is a variant of functional disorder in which diverse bodily complaints (eg, fatigue, insomnia, irritable bowel) occur without resembling specific neurologic disorders and without objective physiologic evidence (Khouzam and Field 1999; Stone et al 2005). "Malingering" is the fully aware simulation of a medical disorder (frequently neurologic) for personal gain, particularly for money, material goods, or improved access to specific privileges (eg, transfer from jail). "Factitious disorder" is the willful simulation of a medical disorder without clear financial or opportunistic gain (Bauer and Boegner 1996). Instead, sufferers have a need for an enhanced feeling of control or attention. "Munchausen syndrome" is a variant of factitious disorder (often with diverse complaints), in which the patient undergoes frequent clinic or hospital evaluation, sometimes resulting in invasive, even injurious, testing or treatment. The term was coined by Asher (Asher 1951), who thought that the wide meanderings of afflicted patients from clinic to clinic and their elaborate health histories resembled the fantastic travels regaled by a fictitious character depicted by Raspe in 1785, Baron Munchausen (Pankratz 1986). (This individual was likely inspired by the real Baron Münchhausen; consequently, German spellings of this disorder also appear.) "Munchausen syndrome by proxy" refers to a caregiver's bearing false evidence of medical illness in another individual who is incompetent to represent himself (a child, in most cases described thus far) (Meadow 1977). Ganser syndrome involves the inconsistent confabulation of knowledge of facts (Ganser 1898).

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