Demographics of patients with FND vary, depending on presenting neurological symptoms and disorder subtype. Existing data indicate a correlation between FND and younger age, female sex, physical disability,7 and a history of abuse or trauma.3,8 A challenge in concretely ascertaining the prevalence of FND is that conditions such as fibromyalgia, chronic pelvic pain, globus hystericus, and nonepileptic seizures can also be characterized as medically unexplained functional disorders, even within the network of neurology care.4
Misdiagnosis and bias are not uncommon
Ambiguity in classifying and evaluating FND can affect physicians’ perceptions, assessment, and care of patients with suggestive presenting symptoms. A major early challenge in diagnosing FND is the inconsistency of characterizing terminology (pseudoneurological, somatic, dissociative, conversion, psychogenic, hysterical, factitious, functional, medically unexplained9,10) and definitions in the literature. Neurological symptoms of unidentifiable organic cause can greatly diminish quality of life4; FND is a scientifically and clinically useful diagnosis for many combinations of nonrandomly co-occurring symptoms and clinical signs.
The pitfall of misdiagnosis. Remain cautious about making a diagnosis of FND by exclusion, which might yield an incorrect or false-negative finding because of an atypical presentation. It is important to avoid misdiagnosis by prematurely closing the differential diagnosis; instead, keep in mind that a medically unexplained diagnosis might be better explained by conducting a robust social and medical history and obtaining additional or collateral data, or both, along with appropriate consultation.4,9
Misdiagnosis can lead to a circuitous and costly work-up, with the potential to increase the patient’s distress. You can reduce this burden with early recognition of FND and centralized management of multidisciplinary care, which are more likely to lead to an accurate and timely diagnosis—paramount to empowering patients with access to the correct information and meaningful support needed to enhance treatment and self-care.9
Bias, haste, and dismissal are unproductive. Even with a clear definition of FND, it is not uncommon for a physician to rapidly assess a patient’s clinical signs, make a diagnosis of “unknown etiology,” or openly question the veracity of complaints. Furthermore, be aware of inadvertently characterizing FND using the prefix “pseudo” or the term “hysterical,” which can be psychologically discomforting for many patients, who legitimately experience inexplicable symptoms. Such pejoratives can lead to stigmatizing and misleading assessments and treatment paths4—courses of action that can cause early and, possibly, irreparable harm to the patient–physician relationship and increase the patient’s inclination to go “doctor-shopping,” with associated loss of continuity of care.
Why is it difficult to diagnose FND?
The latest (5th) edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) describes conversion, somatoform disorder, and FND synonymously.DSM-5 diagnostic criteria for conversion disorderare11:
- a specified type of symptom or deficit of altered voluntary motor or sensory function (eg, weakness, difficulty swallowing, slurred speech, seizures)
- clinical evidence of the incompatibility of the symptom or deficit and any recognized neurological or medical disorder
- incapability of better explaining the symptom or deficit as another medical or mental disorder.
- The symptom or deficit causes distress or impairment that (1) is clinically significant in occupational, social, or other important areas of function or (2) warrants medical evaluation.
The overarching feature of these criteria is the inconsistency of symptoms with recognized neurological, physiological, or psychiatric conditions. Although identification of psychological factors can help clarify and provide a treatment direction, such identification is not essential for making a diagnosis of FND. Malingering does not need to be refuted as part of establishing the diagnosis.12
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