Functional neurologic disorder

Functional neurologic disorder (FND), also known as functional neurological disorder, is a condition where patients experience neurological symptoms like weakness, movement disorders, sensory symptoms, and blackouts. Despite these symptoms, there is no identifiable disease process affecting the body's structure. Symptoms are clinically recognisable but are not associated with a definable organic disease.

Signs and Symptoms

Patients with FND exhibit a range of symptoms related to motor or sensory dysfunction or episodes of altered awareness, which include:

• Limb weakness or paralysis
• Blackouts or dissociative seizures resembling epileptic seizures
• Movement disorders such as tremors, dystonia, and myoclonus
• Visual symptoms like loss of vision or double vision
• Speech symptoms including dysphonia, slurred, or stuttering speech
• Sensory disturbances such as hemisensory syndrome
• Dizziness and balance problems

Epidemiological studies note higher rates of depression and anxiety in FND patients compared to the general population, similar to other neurological disorders like epilepsy or Parkinson's disease.

Causes

Stressful life events and childhood neglect are more common in FND patients. Studies show distinct brain activation patterns in FND patients, differing from those simulating deficits. FND has also been noted as a rare occurrence post-general anaesthesia.

Diagnosis

Diagnosis relies on positive features from the patient's history and examination. Key diagnostic tools include:

• Hoover's sign: Weakness of hip extension that normalises with contralateral hip flexion.
• Entrainment and distractibility in tremors: If the tremor aligns with rhythmical movements of another limb, it indicates a functional tremor.
• Functional dystonia: Often presents with an inverted ankle posture or clenched fist.
• Dissociative seizures: Characterised by prolonged unresponsiveness and dissociation prior to the attack.

FND does not appear on blood tests or structural brain imaging, and it can occur alongside other neurological diseases. The diagnosis is also supported by the ICD-11, which lists it as "Dissociative neurological symptom disorder," and the DSM-5, which details criteria for functional neurological symptoms.

Differential Diagnoses

Multiple sclerosis shares overlapping symptoms with FND, leading to potential misdiagnosis.

Treatment

Effective treatment requires a firm diagnosis and often involves a multi-disciplinary approach. Treatment options include:

• Physiotherapy and Occupational Therapy: Especially beneficial for motor symptoms.
• Medications: Sleeping tablets, painkillers, anti-epileptic medications, and antidepressants may be used, particularly if depression is co-morbid.

Physiotherapy is noted to be particularly effective for motor symptoms, with studies indicating positive outcomes. However, access to treatment can be challenging, with limited expertise and possible dismissal by healthcare professionals. Advances in diagnostic criteria and increasing evidence are improving understanding and treatment approaches.

History

FND has historically been misunderstood, with early beliefs attributing it to a neurological disorder affecting both sexes. Over time, the term "conversion disorder" was used but fell out of favour due to its negative connotations and the stigma attached. Misdiagnosis with conditions like tumours or epilepsy has occurred, leading to significant patient suffering.

During the COVID-19 pandemic, an increase in functional tic-like behaviours among adolescents was noted, believed to be influenced by social media content regarding Tourette Syndrome. FND remains a stigmatised condition, with ongoing debate about its causes and appropriate treatment approaches.

---

Self-assessment MCQs (single best answer)

Which of the following is NOT a symptom associated with Functional Neurologic Disorder (FND)?

What is the main characteristic of Functional Neurologic Disorder (FND)?

Which diagnostic tool is used to identify weakness of hip extension that normalises with contralateral hip flexion in FND?

Why might patients with FND experience difficulties in accessing treatment?

Which of the following treatments is noted to be particularly beneficial for motor symptoms in FND patients?

What term did the ICD-11 use to classify FND?

Which historical term for FND fell out of favour due to its negative connotations and stigma?

What is a common comorbid condition seen in patients with FND?

Which of the following is an example of a sensory disturbance seen in FND?

What significant event in recent history led to an increase in functional tic-like behaviours among adolescents?