Functional Neurological Disorders Flashcards
DYSFUNCTION/PAIN
What is FND
a personexperiences abnormal functionin a system that can be demonstrated to becapable of normal function.
Definition and characteristics
- there is a change in neurological functioning, significantly influenced by attention,
- These disorders do not require psychological stressors for diagnosis, as outlined in DSM-V, challenging previous beliefs about their etiology.
- Distinctive FND’s include weakness, tremor, dystonia, gait disorder, jerks, tic-like behaviours, paroxysmal non-epileptic seizures (PNES)
- The psychiatric and physical features are not so distinct
Epidemiology
- Incidence rates range from 4-12 cases per 100,000 people annually, with a prevalence of 50 per 100,000.
- FNDs can occur at any age but are most common between 37-50 years, with a higher prevalence in females (61–87%).
- Sometimes patients are diagnosed with stroke however it’s actually a FND e.g paralysis occuring in one side of a patient is misdiagnosed- this is why careful examination is important!
Risk Factors:
Include physical (minor traumas can be triggers for FND), genetic/epigenetic factors, social environmental influences (higher education levels associated with FND), psychiatric diseases, and the presence of other neurological disorders (e.g Parkinson’s disease, headaches, epilepsy- functional seizures that overlap).
Functional Motor Disorders (FMD)
- Excess Movement: Encompasses dystonia, tremor, jerks, tic-like behaviors.
- Poverty of Movement: Includes symptoms like weakness and slowness. It refers to reduced movements, functional paralysis).
- Gait and Balance Disorders: (Persistent FMDs)
other types of FND:
- Functional Cognitive Disorders (brain fog, memory problems)
- Sensory Disorders
- Paroxysmal Non-Epileptic Seizures (PNES)
FMD’s are not only characterised by motor disorders but also…
non-motor symptoms and other FND’s are also prevalent → anxiety, fatigue, pain, sensory symptoms
FMD topography:
the most common disorders are weakness (lower limb), tremor (upper limb) and dystonia (upper limb). FMD’s can be isolated (54.1%) or combined (45.9%) → e.g functional weakness with tremor or with dystonia
Can FMD be associated with other neurological diseases?
- e.g migraines, cerebrovascular disease, PD, polineuropathy
-Polineuropathy is a medical term referring to a condition that involves damage or disease affecting peripheral nerves (neuropathy) in roughly the same areas on both sides of the body), hyperkinetic movement disorder symptom (MDS), epilepsy, multiple sclerosis and others → comorbid neurological disorders- The functional disorders often occur after the first neurological disorders
Diagnosis
- Relies on a comprehensive clinical history and examination, with support from electrophysiological testing.
- Key diagnostic criteria include positive signs of inconsistency and incongruency across symptoms.
- Inconsistency of a diagnosis can present as variability of symptoms over time → paroxysmal FND, functional slowness in one side etc.
- Early diagnosis of FMD’s is vital as lack of FMD diagnosis led to high disability
- FMD’s have specific phenomenological features which support their diagnosis e.g hoover’s sign, drift without pronation, parkinsonism, excess movement, dystonia, tics, axial manifestations, balance issues.
Functional weakness
Characterized by symptoms that do not align with neurological patterns, identifiable through signs like Hoover’s sign and normal motor evoked potentials (MEP). Hoover’s sign is when contralateral hip flexion induces hip extension on the weak side of the patient. Abduction finger sign- mirror synchronisa, where the weak hand shows movement when the other hand is maximally contracted.
Functional tremor
- Notable for its variability and responsiveness to distraction, with diagnostic manoeuvres that can demonstrate changes in tremor characteristics.
- Tremor gets worse when there’s increased attention to it and decreased distraction in FMD’s. This is different in parkinson’s disease where tremor increases with distraction such as mental tasks.
- Main types of distraction for functional tremor: Arithmetic calculation, side to side tongue movements, finger tapping, postural adjustments
- Entrainment is the synchronisation of the tremor frequency to the frequency of the contralateral repetitive movement such as finger tapping.
- Electrophysiology is used to demonstrate these + signs → This moves towards a more lab supported criteria for the diagnosis of tremor!
- The tremor stops during performance (frequency and amplitude decreases on the graph, entrainment or suppression during finger tapping, tremor increases with loading), this is then used to validate the diagnosis.
Functional dystonia
- Presents often as fixed dystonia, with a lack of overflow movements and can include paroxysmal dystonia. It can be modulated by distraction. Presents with torsional movements and painful postures. Functional dystonia do not respond to botox treatments.
- Dystonias can be fixed, paroxysmal or mobile functional → functional dystonia, idiopathic dystonia, functional weakness, functional facial spasm/disorders.
- Different functional dystonias can include: stiff person syndrome.
- Functional dystonia can also include diagnosis of motor disorders with fixed postures e.g functional dystonia of the tongue which led to tremor- easy to miss these structural causes.
- Paroxysmal dystonias can result from things like insulinoma
CRPS-I:
- This type of dystonia overlaps between functional movement disorders and peripherally induced movement disorders
- Challenges include minor trauma history, vasomotor changes, oedema, pain, fixed posture of the fingers in CRPS1-dystonia. As opposed to idiopathic upper limb dystonia where there is no trauma before onset, mobile dystonia, overflow and is action induced.
Functional Gait Disorder:
- Exhibits unique patterns such as knee buckling, walking on ice, and scissoring gait.
- Caveats to this diagnosis is that bizzare gait does not always mean functional movement disorder as huntingtons disease patients can also develop dystonia
