Functional Neurological Disorder (FND) is a common and complex condition affecting the nervous system. It involves problems with how the nervous system functions rather than structural damage to the brain or nerves. FND is frequently observed in neurological clinics, accounting for 6% to 16% of new outpatient visits. FND is recognized as a genuine neurological condition, dispelling historical misconceptions that it is “all in the head” or feigned.
Understanding Functional Neurological Disorder
Functional Neurological Disorder is best understood as a “software” problem within the brain, where the “hardware”—the brain’s physical structure—remains intact. Unlike conditions such as multiple sclerosis or Parkinson’s disease, which involve identifiable structural damage, FND involves disruptions in how brain networks communicate and process signals. This disruption leads to a range of physical, sensory, and cognitive symptoms. Historically, FND was often misunderstood and labeled with terms like “conversion disorder” or “hysteria,” which contributed to stigma. Current understanding affirms its neurological basis; symptoms are not intentionally produced and are outside conscious control. Research using functional neuroimaging has shown altered connectivity between different brain regions in individuals with FND, particularly increased activity in the limbic system, which is involved in emotion regulation and stress response.
Recognizing the Diverse Symptoms
Individuals with FND can experience a wide array of symptoms that affect various parts of the body and nervous system. These symptoms can fluctuate in severity and may appear suddenly. They are often influenced by attention, sometimes worsening when focused upon and improving with distraction.
Motor symptoms are frequently observed, including functional weakness or paralysis in limbs, where muscle power may return to normal when triggered involuntarily. Functional movement disorders, such as tremors, dystonia, tics, and gait disturbances, are also common. These movements can mimic other neurological conditions but arise from a different underlying mechanism.
Sensory symptoms can involve functional numbness, tingling, or loss of sensation, sometimes with distinct boundaries that do not follow typical nerve patterns. Individuals may experience pain, including chronic migraine, or changes in vision like blurred vision, double vision, tunnel vision, or temporary blindness. Hearing disturbances, like ringing in the ears or heightened sensitivity to sound, can occur.
Seizure-like episodes, known as functional neurological seizures (FNS) or dissociative seizures, are a symptom. These episodes resemble epileptic seizures but are not caused by abnormal electrical activity in the brain. FNS can manifest with thrashing movements, unresponsiveness, eye closure, side-to-side head movements, or pelvic thrusts, and may last many minutes. Unlike epileptic seizures, prolonged post-event confusion is less common, and individuals may retain some awareness during the episode.
Other symptoms include functional speech difficulties, such as slurred speech, stuttering, or aphonia. Cognitive symptoms like “brain fog,” memory issues, difficulty concentrating, word-finding difficulties, and problems with multitasking are reported. Persistent fatigue is a common co-occurring symptom, often impacting quality of life. Dissociative symptoms, characterized by feelings of being disconnected from one’s body, thoughts, or surroundings, can be part of the FND experience.
Diagnosis and Contributing Factors
The diagnosis of FND is primarily made through a thorough neurological examination and observation of specific positive clinical signs, rather than solely by excluding other conditions. These “rule-in” signs indicate that the nervous system’s basic wiring is intact, but its function is disrupted. For instance, Hoover’s sign is a test for functional leg weakness: when a person struggles to lift one leg, the examiner may feel a normal, involuntary downward push from the “weak” leg when the person attempts to lift the other leg. Similarly, the tremor entrainment test assesses functional tremor by observing if the tremor changes rhythm or temporarily disappears when the unaffected limb performs a rhythmic movement.
While there is no single cause for FND, it is considered a multifactorial condition that often develops from a combination of factors. These factors are categorized as predisposing, precipitating, and perpetuating.
Predisposing factors can include a genetic vulnerability, a history of other physical illnesses like migraine, or certain personality traits such as a tendency to be “always on the go” or difficulty “letting go” of abnormal patterns.
Precipitating factors are specific events that may trigger the onset of symptoms, such as physical injury, acute illness, infections, or periods of intense stress. For example, a limb injury might precede functional weakness, or a panic attack could trigger functional seizures.
Perpetuating factors are elements that contribute to the persistence of symptoms once they have started. These can be internal, like unhelpful beliefs about the illness or difficulty managing emotions, or external, such as avoidance behaviors that inadvertently reinforce symptoms, or a lack of attention to psychological health. While psychological stressors and a history of childhood adversity can be risk factors, they are not present in all individuals with FND.
Pathways to Management
The management of FND typically involves a multidisciplinary approach, tailoring treatments to the individual’s specific symptoms and needs. This collaborative effort includes neurologists, physiotherapists, occupational therapists, and psychological therapists. Patient education and strong communication between the patient and healthcare providers are important, helping individuals understand their condition and actively participate in their recovery.
Physiotherapy plays a significant role, especially for motor symptoms like weakness, tremor, and gait issues. Therapists use techniques like retraining movement patterns, often by diverting attention from the affected limb to encourage more automatic, normal movements. This can involve task-specific exercises, visualization, and mirror therapy, which helps correct distorted perceptions of movement. Graded exercise programs are implemented to improve strength, endurance, and manage fatigue and pain.
Occupational therapy focuses on helping individuals manage daily activities and improve their independence. Occupational therapists work on strategies for pacing activities, managing fatigue and pain, and addressing cognitive challenges like memory and concentration. They assist with sensory modulation and integrating relaxation techniques into daily routines to manage stress and anxiety.
Psychological therapies, particularly Cognitive Behavioral Therapy (CBT) and Acceptance and Commitment Therapy (ACT), are used. CBT helps individuals identify and modify unhelpful thoughts, beliefs, and behaviors related to their symptoms, including avoidance behaviors, and teaches coping mechanisms like distraction and relaxation. ACT focuses on increasing psychological flexibility by encouraging acceptance of symptoms and committing to actions aligned with personal values, even in the presence of distress.
Speech and language therapy is beneficial for individuals experiencing functional speech difficulties, such as dysphonia or stuttering, and swallowing problems. Therapists work on retraining speech patterns and improving muscle tension or breathing that may interfere with normal vocalization. While there is no specific medication to cure FND symptoms directly, medications may be prescribed to manage co-occurring conditions like chronic pain, anxiety, or depression. For instance, certain antidepressants can be helpful for neuropathic pain or sleep disturbances, but anti-seizure medications are not effective for functional seizures and may even worsen symptoms.