Functional neurologic disorder
Functional neurologic disorder or functional neurological disorder (FND) is a condition in which patients experience neurological symptoms such as weakness, movement disorders, sensory symptoms, and blackouts. As a functional disorder, there is by definition no known disease process affecting the structure of the body, yet the person experiences symptoms relating to their body function. Symptoms of functional neurological disorders are clinically recognisable, but are not categorically associated with a definable organic disease. The intended contrast is with an organic brain syndrome, where a pathology (disease process) can be identified which affects the body's physiology. Subsets of functional neurological disorders include functional neurological symptom disorder (FNsD), conversion disorder, functional movement disorder, and functional seizures. The diagnosis is made based on positive signs and symptoms in the history and examination during consultation of a neurologist (see below). "FND is the second most common diagnosis in neurology clinics after headaches," and has become more prevalent among adolescents and older adults in the wake of the COVID pandemic and lockdowns. Physiotherapy is particularly helpful for patients with motor symptoms (weakness, gait disorders, movement disorders) and tailored cognitive behavioural therapy has the best evidence in patients with dissociative (non-epileptic) attacks. Signs and symptoms There are a great number of symptoms experienced by those with a functional neurological disorder. While these symptoms are very real, their origin is complex, since it can be associated with severe psychological trauma (conversion disorder), and idiopathic neurological dysfunction. The core symptoms are those of motor or sensory dysfunction or episodes of altered awareness: Limb weakness or paralysis Blackouts (also called dissociative or non-epileptic seizures/attacks) – these may look like epileptic seizures or faints Movement disorders including tremors, dystonia (spasms), myoclonus (jerky movements) Visual symptoms including loss of vision or double vision Speech symptoms including dysphonia (whispering speech), slurred or stuttering speech Sensory disturbance including hemisensory syndrome (altered sensation down one side of the body) Dizziness and balance problems Associated conditions Epidemiological studies and meta-analysis have shown higher rates of depression and anxiety in patients with FND compared to the general population, but rates are similar to patients with other neurological disorders such as epilepsy or Parkinson's disease. This is often the case because of years of misdiagnosis and accusations of malingering. Causes A systematic review found that stressful life events and childhood neglect were significantly more common in patients with FND than the general population, although many patients (around 70%) report no stressors. Converging evidence from several studies using different techniques and paradigms has now demonstrated distinctive brain activation patterns associated with functional deficits, unlike those seen in actors simulating similar deficits. The new findings advance current understanding of the mechanisms involved in this disease, and offer the possibility of identifying markers of the condition and patients' prognosis. FND has been reported as a rare occurrence in the period following general anesthesia. Diagnosis A diagnosis of a functional neurological disorder is dependent on positive features from the history and examination. Positive features of functional weakness on examination include Hoover's sign,