- Overview of functional neurological disorder
- Prevalence and characteristics of chronic fatigue
- Understanding chronic pain in FND
- Interplay between fatigue, pain, and neurological symptoms
- Implications for diagnosis and treatment strategies
Functional neurological disorder (FND) is a condition characterised by neurological symptoms that are not explained by structural disease, but rather arise from a disruption in the normal functioning of the nervous system. Individuals with FND can experience a wide range of physical, sensory, and cognitive symptoms, including seizures, paralysis, movement disorders, and speech difficulties. These symptoms are real and can be severely disabling, yet often fluctuate in severity and presentation over time.
A key component of FND is that the symptoms are not intentionally produced, and they are not due to degenerative or inflammatory neurological conditions. Instead, FND is understood as a disorder of brain network integration, particularly involving areas responsible for attention, emotion, and motor control. Functional changes in areas such as the prefrontal cortex and limbic system have been implicated through neuroimaging studies, which support an emerging understanding of FND as a network-based brain disorder.
FND often co-occurs with other conditions, including chronic fatigue and pain, which can compound the disabling nature of the disorder. These symptoms are not merely secondary, but frequently central to the patient’s overall experience of illness. Chronic fatigue, in particular, can significantly impair daily functioning and is not alleviated by rest, while pain can appear in various forms, from generalised body discomfort to specific regional pains. The complex overlap of neurological symptoms with chronic fatigue and pain necessitates a holistic and multidisciplinary approach to symptom management.
Although the cause of FND is multifactorial, risk factors may include psychological stress, trauma, physical injury, medical illness, or a combination of these elements. However, not all patients report such triggers, and the presence of such factors is not necessary for diagnosis. This underlines the importance of careful clinical assessment and patient-centred dialogue, both to establish the diagnosis and to begin effective management.
The diagnosis of FND is now approached through the identification of positive clinical signs that are inconsistent or incongruous with recognised neurological diseases. These include Hoover’s sign for functional weakness or entrainment tests for functional tremors. By using such signs, clinicians can diagnose FND based on what is observed during examination, rather than simply excluding other conditions. This paradigm shift helps reinforce the legitimacy of the disorder and promotes earlier entry into appropriate care pathways.
Understanding FND as a functional disorder rather than a psychosomatic or malingering condition has important implications. It reduces stigma and encourages timely, evidence-based treatment approaches focused on rehabilitation, education, and psychological therapies where appropriate. An emphasis on collaborative care, involving neurologists, psychologists, physiotherapists, and occupational therapists, can lead to improved outcomes and reduce the burden of symptoms like chronic fatigue and pain.
Prevalence and characteristics of chronic fatigue
Chronic fatigue is a common and often debilitating symptom reported by individuals with FND. Studies estimate that up to 70–80% of patients with FND experience persistent fatigue that significantly impacts their daily functioning. Unlike normal tiredness, chronic fatigue in this population is described as overwhelming and disproportionate to exertion, frequently not relieved by rest or sleep. This pervasive sense of physical and mental exhaustion can interfere with work, social activities, and self-care, contributing to a diminished quality of life.
Patients often describe a type of fatigue that is not just physical but also cognitive, with a profound sense of mental fog, difficulty concentrating, and impaired memory. These characteristics overlap with symptoms observed in other fatigue-related disorders, such as chronic fatigue syndrome or fibromyalgia, making differential diagnosis a clinical challenge. However, in FND, the fatigue is intricately linked to the broader constellation of functional neurological symptoms, including dissociative episodes, motor dysfunction, and sensory changes.
Chronic fatigue in FND typically lacks a clear medical explanation based on routine laboratory or imaging tests, which can lead to patient frustration and delay in receiving effective symptom management. It may fluctuate unpredictably in intensity and duration, with many patients reporting good and bad days. These fluctuations can reinforce a cycle of activity avoidance and deconditioning, ultimately perpetuating the fatigue.
Psychological and psychosocial factors often play a role in the experience and perpetuation of chronic fatigue in FND. Depression, anxiety, sleep disturbances, and past trauma have all been associated with increased fatigue severity. However, it is essential to view fatigue not as a symptom secondary to psychological distress, but as a central and primary experience for many individuals with FND. Recognition of this perspective by healthcare professionals is vital in legitimising the patient’s experience and initiating a comprehensive and empathetic approach to care.
Effective management of chronic fatigue in FND requires a multidisciplinary approach. Education about the nature of the symptom, gradual re-engagement in daily activities through physiotherapy, cognitive behavioural therapy, and strategies to improve sleep hygiene are commonly employed. Therapeutic interventions should be tailored to the individual’s needs, acknowledging the fluctuating nature of the symptom and reinforcing self-management techniques. Integrating fatigue management into overall FND care is crucial for improving functioning and long-term outcomes.
Understanding chronic pain in FND
Chronic pain in functional neurological disorder (FND) is a multifaceted and often misunderstood aspect of the condition. It may present as localised pain, such as limb pain or headaches, or as widespread pain resembling that seen in fibromyalgia. Patients frequently describe their pain as burning, aching, or stabbing, and it may occur in conjunction with non-painful sensory disturbances, such as numbness or tingling. These sensations often do not correspond to typical anatomical nerve distributions, which can make evaluating and treating the pain more complex.
The mechanisms behind pain in FND are not yet fully understood, but current evidence suggests that altered central pain processing plays a significant role. Neuroimaging studies have identified functional abnormalities in brain areas involved in pain perception and regulation, including the insula, anterior cingulate cortex, and prefrontal cortex. These regions are also implicated in the processing of emotion and attention, underlining the importance of a biopsychosocial framework for interpreting symptoms.
A significant feature of pain in FND is its variability. Patients may report fluctuating intensity and localisation, sometimes following or preceding episodes of other neurological symptoms. For example, limb weakness or non-epileptic seizures may coincide with or aggravate ongoing pain. The unpredictability of the pain further adds to the overall burden of living with FND, often leading to social withdrawal, sleep disruption, and increased anxiety about symptom recurrence or worsening.
Pain can be amplified by factors such as stress, fatigue, and emotional distress, reflecting the interconnectedness between physical and psychological states in FND. The presence of chronic fatigue can exacerbate the experience of pain and reduce individuals’ ability to engage in daily activities or undertake physical rehabilitation. Similarly, untreated pain can hinder recovery from motor and sensory symptoms. This dynamic interplay highlights the need for integrated symptom management across multiple domains.
Traditional pharmacological treatments for chronic pain often yield limited benefits in FND. Therefore, non-pharmacological strategies tend to form the backbone of effective care. Physiotherapy focused on restoring function rather than relieving pain, psychological therapies such as cognitive behavioural therapy, and approaches like mindfulness and graded motor imagery are commonly employed. These interventions aim to modulate central pain processing and improve coping strategies, with the goal of enhancing overall function rather than eliminating symptoms entirely.
Communication about pain in FND should be handled with empathy and validation. Patients often feel disbelieved or misunderstood due to the absence of identifiable pathology on scans or tests. Validating the experience of pain, while providing education on its functional origin, can strengthen the therapeutic alliance and foster better outcomes. Clear explanations that differentiate between “not organic” and “not real” are crucial, helping patients understand that their pain is legitimate and treatable within the context of functional brain changes.
Given the persistent and distressing nature of chronic pain in FND, a comprehensive and individualised management plan is essential. This must consider the interaction between pain, chronic fatigue, emotional wellbeing, and neurological symptoms. Addressing pain within a broader symptom management strategy ensures a more holistic and patient-centred approach, increasing the likelihood of functional recovery and better quality of life.
Interplay between fatigue, pain, and neurological symptoms
The relationship between chronic fatigue, pain, and the neurological symptoms of FND is intricate and reciprocal, creating a complex clinical picture that often challenges both patients and healthcare providers. These symptoms rarely exist in isolation and instead interact dynamically, with each influencing the intensity and perception of the others. For instance, the presence of severe fatigue can amplify the perception of pain, while persistent pain may contribute to the development or exacerbation of fatigue and other functional symptoms such as weakness, gait instability, or dissociation.
This interplay is rooted in shared neurobiological pathways involving central sensitisation, abnormal attention mechanisms, and disrupted emotional regulation. Neuroimaging studies have shown that individuals with FND, particularly those with concurrent chronic fatigue and pain, tend to exhibit altered activity in brain networks associated with interoception, threat detection, and executive control. These include the insular cortex, amygdala, and prefrontal cortex—regions that are also integral to how the brain interprets and responds to internal sensations, emotional stress, and external stimuli. As such, dysregulation in these networks may manifest across multiple symptom domains, intensifying both fatigue and pain within the FND spectrum.
Functionally, the cycle begins when a patient experiences one primary symptom—such as fatigue or pain—that hinders their activity level. This reduction in activity can lead to physical deconditioning, disturbed sleep, and higher emotional stress, which subsequently worsen fatigue and pain. Moreover, cognitive and attentional biases commonly observed in FND may lead patients to hyper-focus on bodily sensations, interpreting them as threatening or catastrophic. This heightens stress responses and perpetuates symptoms. For example, a minor ache may be perceived as severe pain due to increased vigilance, fuelling further physical and psychological distress.
These interconnected symptoms often lead to significant disruption in daily life, with many individuals facing difficulties maintaining employment, relationships, or daily responsibilities. Fluctuating symptom severity and the unpredictability of when fatigue or pain will strike contribute to a sense of loss of control, further exacerbating anxiety, helplessness, and even depressive symptoms. In turn, these emotional responses can heighten neurological symptoms, closing a reinforcing loop that sustains functional impairment.
Symptom management strategies must account for this multidirectional interaction. Addressing only one domain—such as pain relief through pharmacotherapy—without considering fatigue, psychological status, and functional movement patterns may limit treatment success. Instead, multidisciplinary interventions that integrate physiotherapy, psychological support, and education—notably about the interconnected nature of symptoms—are better suited to break the cycle. Importantly, therapies should aim to improve resilience, emotional regulation, and overall function, rather than simply reduce symptoms in isolation.
Understanding the synergy between chronic fatigue, pain, and neurological manifestations in FND also facilitates improved communication between patients and clinicians. When healthcare professionals articulate this interrelationship clearly, validating the lived experience of the patient while offering a coherent explanation of their symptoms, trust is established and engagement in treatment plans increases. This approach is a fundamental aspect of patient-centred care in FND, empowering individuals through knowledge and participation in their recovery journey.
Implications for diagnosis and treatment strategies
Effective diagnosis and treatment strategies for functional neurological disorder (FND), particularly when complicated by chronic fatigue and pain, rely on a nuanced understanding of symptom presentation and individual experience. A growing consensus emphasises the need for a positive diagnosis based on recognised clinical features, rather than a process of exclusion. Clinicians are encouraged to identify functional signs during examination, communicate the diagnosis clearly and empathetically, and engage the patient as an active participant in their treatment plan. Establishing trust from the outset lays the foundation for meaningful engagement in rehabilitation and symptom management.
Once a diagnosis is confirmed, the treatment approach should be holistic and multidisciplinary, reflecting the complexity of FND and its associated symptoms. Because chronic fatigue and pain are core elements of the condition for many patients, addressing them directly is crucial. Physiotherapy forms the cornerstone of rehabilitation, with a shift from traditional strength-focused models to goal-directed functional retraining. This typically involves graded activity, pacing strategies, and techniques to normalise movement patterns, all adapted to the fluctuating nature of fatigue and pain.
Psychological interventions also play a significant role in the management of FND. Cognitive behavioural therapy (CBT) has shown promise in improving physical function, reducing distress, and helping patients to reframe unhelpful thoughts about their symptoms. For those with significant anxiety, depression, or trauma histories, additional therapeutic modalities such as mindfulness-based cognitive therapy or trauma-focused interventions may be warranted. Education about the condition—in particular, the role of the brain in generating real physical symptoms without structural damage—is often a turning point in patient understanding and motivation for recovery.
In terms of managing chronic fatigue, treatment plans must recognise its persistent and non-restorative nature. Patients benefit from energy conservation techniques, sleep hygiene education, and activity scheduling that builds endurance without exacerbating symptoms. Health professionals should support a balanced approach to activity and rest, discouraging the boom-and-bust cycle that often perpetuates fatigue and deconditioning. Symptom management for pain may include elements of graded exposure and desensitisation techniques, with careful attention to the patient’s experience and low reliance on medication, which often offers limited benefit in functional pain syndromes.
Interdisciplinary team collaboration enhances the effectiveness of all therapeutic interventions. Coordinated care involving neurologists, physiotherapists, psychologists, occupational therapists, and specialist nurses allows for tailored strategies that address the interplay between motor symptoms, chronic fatigue, pain, psychological wellbeing, and social functioning. Regular team discussions and shared goal setting ensure that care remains aligned with the patient’s needs and priorities, fostering engagement and resilience.
Communication with patients throughout the diagnostic and treatment processes is a key determinant of success. It is essential to validate the individual’s symptoms, explain the functional basis of their presentation without implying psychological causation, and maintain a hopeful yet realistic outlook. Empowering patients with knowledge about the reversibility of neural plasticity-driven conditions like FND helps shift the narrative from one of chronic illness to one of rehabilitation and improvement. When chronic fatigue and pain are acknowledged as integral components of the disorder rather than secondary concerns, the patient feels heard and respected, which can in itself improve outcomes.
Innovative models of care are emerging, including specialist outpatient programmes and integrated FND clinics offering co-located services. These models enable continuity, enhance therapeutic alliance, and reduce fragmentation of care—a common barrier reported by patients. Telehealth solutions are also being increasingly utilised, expanding access to specialist support and allowing for regular follow-up, particularly valuable for managing chronic symptoms that fluctuate or re-emerge over time.
Ultimately, the success of any treatment strategy for FND with chronic fatigue and pain depends on its flexibility, the commitment of the care team, and the degree to which it encompasses the complex interplay of physical, psychological, and social factors. A commitment to person-centred care, underpinned by empathy, education, and evidence-based interventions, offers the best prognosis for reducing symptom severity and enhancing quality of life.
