Journal of Neurology Research, ISSN 1923-2845 print, 1923-2853 online, Open Access
Article copyright, the authors; Journal compilation copyright, J Neurol Res and Elmer Press Inc
Journal website https://www.neurores.org

Review

Volume 13, Number 1, September 2023, pages 12-32

Functional Neurological Disorder: Historical Trends and Urgent Directions

Figures

Figure 1.
Figure 1. Common functional neurological disorder (FND) presentations and specialists involved in their care. Multiple symptoms grouped together depict the complex FND presentations encountered by various physicians simultaneously. Neurologists and primary care physicians (PCPs) evaluate most symptoms.
Figure 2.
Figure 2. The umbrella of functional disorder (FD), containing functional neurological disorder (FND) and other extra-neurological functional diagnosis.
Figure 3.
Figure 3. Electronic healthcare record screenshot demonstrating functional neurological disorder (FND) sub-diagnostic categories.
Figure 4.
Figure 4. Common triggers and risk factors for pediatric and adult functional neurological disorder (FND) that characterize the biopsychosocial model: emotional antecedents, work problems, accidents, family difficulties [30], change in relationship, housing, employment status [31-33], and witnessing functional or organic movement disorders [34].
Figure 5.
Figure 5. Frequently used cognitive behavioral therapy (CBT) techniques, demonstrating a greater influence in cognitive and behavioral processes, with unclear impact on the sensorimotor (somatic) system, and less impact in the biological (stress physiology) and emotional domains of the nervous system.
Figure 6.
Figure 6. The integrative functional neurological disorder (FND) pathophysiological model representing dysfunctional processes in the cognitive neo-cortex, the limbic system, the autonomic nervous system (ANS), and the sensorimotor (somatic) processes.

Tables

Table 1. Factors Concerning FND and FD Classification and Management
 
FND: functional neurological disorder; FD: functional disorder; PCP: primary care physician.
1. FND patients present to multiple specialties.
2. A large umbrella of FD is increasingly recognized.
3. Shared dysfunctional structures, pathways, risk factors and pathophysiological mechanisms underly various FD.
4. Patients with FND commonly have psychological and functional physical symptoms.
5. FND’s reductionist healthcare record classification may overlook the shared pathophysiology across subtypes.
6. There are no generally available management protocols to guide the specialists who evaluate functional symptoms, including PCP, to help them target the common pathophysiological processes and provide individualized FND treatment based on phenotype.

 

Table 2. Considerations Regarding FND Epidemiology and Socioeconomic Burden
 
FND: functional neurological disorder.
1. FND incidence is increasing in both children and adults.
2. The childhood-adulthood continuum permeates risk factors and psychological well-being.
3. FND patients frequently have psychological comorbidities that influence clinical outcome.
4. FND carries significant mortality, social, and financial impacts.
5. FND patients frequently change healthcare providers.
6. FND has gained media platform interest over the past decade, although insufficient considering its considerable incidence.
7. The significance of the childhood-adulthood functional continuum has not been systematically integrated into adult early assessment and management protocols.
8. Lacking are standardized psychological assessments to use with a suspected or confirmed FND patient.
9. Globally agreed and adopted FND prevention tools do not exist.
10. Deficient are social educational campaigns discussing risk factors, mechanisms of disease production, and prevention.

 

Table 3. Findings From FND Treatment Studies
 
FND: functional neurological disorder; RCTs: randomized controlled trials; CBT: cognitive behavioral therapy; PT: physical therapy.
1. FND is still characterized by suboptimal outcomes despite the utilization of PT, CBT, and multidisciplinary care.
2. Physical, psychiatric, psychological, psychophysiological assessment and care, somatization management, education, and continued follow-up, characterizing multidisciplinary programs, appear to be valuable.
3. CBT possesses fewer interventions in the emotional, autonomic, sensorimotor (somatic), and unconscious nervous system networks.
4. PT, multimodal and multidisciplinary care mainly utilize CBT principles, as opposed to techniques from other psychotherapeutic schools.
5. Other psychotherapeutic modalities have not been thoroughly evaluated through RCTs.
6. Multimodal and multidisciplinary care are difficult to access and involve multiple care providers, complicating the physician-patient relationship.
7. Head-to-head trials comparing the outcomes between various psychotherapies and clinical studies combining skills from various psychotherapies have not been performed.
8. Easy to adopt management protocols that could be universally utilized are lacking.
9. The ideal psychotherapy duration and delivery method has not been sufficiently determined by clinical trials.
10. Well-validated outcome measures considering FND-specific characteristics and pathophysiology are lacking.
11. Therapeutic modalities have not been thoroughly scrutinized against FND pathophysiology.

 

Table 4. Summary of FND Pathophysiological Theories With Supporting Dysfunctional Networks Demonstrating Near-Constant Impairment of Multiple Processes Within Four Major Functional Areas: Limbic System, Neo-Cortex, ANS, and Somatic (Sensorimotor)
 
Pathophysiological theoriesAssociated dysfunctional areas, networks, and processes
Various networks are simultaneously dysfunctional. ANS: autonomic nervous system; FND: functional neurological disorder.
Psychological [116]Neo-cortex and sensorimotor networks: Hypo-activation of cortical and subcortical motor pathways. Limbic system: Abnormal emotional regulation. ANS: Hyperarousal. Sensorimotor: Stereotyped motor behaviors.
Neurobiological [153]Limbic and sensorimotor: Altered conductivity between the amygdala and motor areas. ANS: Lower heart rate variability, hyperarousal.
Childhood trauma, cognitive and learning theories [151]Neo-cortex: Increased self-focused attention, impaired voluntary attention. ANS: Abnormal functioning of the hypothalamic-pituitary-adrenal (HPA) axis. Sensorimotor and limbic connectivity: somatosensory experiences linked to affective states.
Defense mechanisms [152]Neo-cortex: Increased vigilant attention. Limbic: Inhibited emotional processing. ANS linked to impaired cognition (neo-cortex): Dissociative response to autonomic arousal.
Hypnosis [154]Neo-cortex and sensorimotor: Increased connectivity between the motor cortex and the precuneus. Neo-cortex: Increased hypnotic suggestibility.
(Epi)genetic [151]Neo-cortex: Affected left hippocampal volume, increased dissociation. Limbic: Reduced emotional responsiveness. ANS: Inability to shut down stress responses.

 

Table 5. Examples of Pathophysiologically Oriented, Intuitive Interventions, and Their Management Impact, Performed During Clinical Interview and Physical Examination
 
Physical examination featurePathophysiological process assessed by the physicianPhysiological functionPhysician’s intuitive intervention and management impact
ANS: autonomic nervous system; FND: functional neurological disorder.
Patient demonstrates apprehension about FND recoveryEmotional appraisalCognition influences emotional responses“What past events have shaped this emotional response?” Increases patient’s awareness about emotional appraisal.
Emotional retrievalRecollection of emotionally charged memories“Tell me about other moments when you have felt that way.” Biographical assessment, practices emotional retrieval, allows the exploration of further networks as stated below.
Patient becomes restless and fidgetySensorimotor-affective couplingPhysical sensations linked to emotional states“As you recall those memories and emotions, what are you noticing in your body?” Creates awareness about the link between sensations and emotions, practices interoception, allows exploration of further networks.
InteroceptionNoticing internal sensations
Patient’s movements continue, tapping the right leg, rubbing the hands together. There is mild facial flushing and sweating.Autonomic activationActivation of the ANS“I notice that your energy level and movements have increased, are you sensing that too?” Practices interoception, brings awareness to emotional-motor connections, involuntary motor activation linked to emotions and memories, creates opportunity for autonomic self-assessment and regulation.
Limbic-motor couplingLinking emotions to motor functions
Involuntary activation of motor pathwaysSurvival responses to protect against adverse, stressful situations
The patient states “I am feeling strange right now”Defense mechanismsReduce uncomfortable internal experiences.“Tell me more about this strange feeling? How does it feel? Where is it? What is it telling you?” Practices interoception, explores defense mechanisms, making sense of the patient’s experience, uniting mind-body.