Bradykinesia
- This refers to a decrease in movement velocity.
- A reduction in amplitude is known as hypokinesia.
- When correctly used, akinesia means a complete lack of movement or an inability to initiate movement.
Rigidity
- This is described as an enhanced static or postural reflex, characterised by either a "lead pipe" or "cogwheel" quality (which has tremor superimposed on it).
- It is typically asymmetric.
Chorea
- This is an involuntary, continuous, irregular hyperkinetic disorder where movements or movement fragments occur with variable rate and direction, unpredictably and randomly.
- All body parts can be involved, and symptoms usually worsen during voluntary actions.
- Individuals might produce semivolitional movements to disguise the choreic movements or incorporate them into seemingly purposeful actions, such as touching the face (parakinesias).
Ballism
- This involves involuntary, high-amplitude, flinging movements, typically originating proximally.
- These movements can be brief or continuous and may occur with chorea.
- If chorea affects one side of the body (hemiballism, often due to a Subthalamic Nucleus (STN) lesion), it may become milder and evolve into chorea over time.
Athetosis
- These are slow, writhing, continuous, involuntary movements (not sustained postures like dystonia).
- Athetosis often accompanies basal ganglia disorders, producing chorea or dystonia.
Akathisia
- This refers to an uncomfortable sensation of inner restlessness or the voluntary activity performed to relieve that restlessness.
- It often manifests as an inability to remain seated, crossing and uncrossing the legs, or pacing.
- Causes include neuroleptic medication, but it can be difficult to distinguish from tics and restless legs syndrome (RLS).
Dystonia
- This is a group of disorders characterised by involuntary muscle contractions (which can be sustained or spasmodic) leading to abnormal body movements or postures.
Dyskinesia
- This describes any disordered (non-voluntary) and involuntary, non-suppressible movement, including chorea/athetosis/ballism (and to a lesser degree, dystonia).
- The limbs, neck, and face are most frequently affected, though axial symptoms can also occur.
- Facial dyskinesia may appear wry or overemotional, with common features like head bobbing, clenching, lip smacking, and tongue protrusion.
- Limb movements can be proximal or distal, and of either high or low amplitude, appearing as tapping, whirling, or writhing.
- Dyskinesia syndromes include abdominal (belly dancers') dyskinesia, levodopa-induced dyskinesia, tardive dyskinesia, and paroxysmal dyskinesias.
Tremor
- This is an involuntary rhythmic oscillation of a body part around a set point.
- Tremors can be regular or irregular, unilateral or bilateral, symmetrical or asymmetrical, and present in one or several body regions.
- The frequency and amplitude of a tremor are heavily dependent on its underlying cause.
Myoclonus
- This is a sudden, arrhythmic, involuntary movement that is "shock-like" in its rapidity.
- When multiple, these movements do not blend into one another, which differentiates them from chorea.
- True myoclonus results from brief synchronous firing of agonist and antagonist muscles. Positive myoclonus involves muscle (cortex) contraction (e.g., hypnic jerks, a sudden body-wide contraction that occurs as a person drifts between sleep and wakefulness).
- Myoclonus is most often a symptom within a collection rather than a primary pathology.
- Symptomatic myoclonus can be a feature of cortical, basal ganglionic, or cerebellar degeneration (such as Creutzfeldt-Jakob disease or PD); hepatic, renal, endocrine, and other metabolic derangements; myoclonic epilepsies; and periodic leg movements of sleep, among others.
Ataxia
- This involves clumsy or poorly organised movements due to deficits in the cerebellar, vestibular, or proprioceptive pathways. It can affect speech, manual dexterity, or gait.
- Patients often feel as if they are drunk.
- Poor ataxia is not associated with deficits in strength or motor planning.
- Movements are poorly aimed at timely actions, and patients have difficulty properly estimating the distance needed to reach a target or terminate an action at the correct moment.
Clonus
- This is a rhythmic movement resulting from a hyperactive stretch reflex.
Asterixis
- This is an example of negative myoclonus, characterised by a sudden and involuntary relaxation of a dorsiflexed hand or other body part.
- The Electromyography (EMG) pattern of negative myoclonus is distinctive, showing aperioidic electrophysiologic silence in the antagonist muscle group.
Tic
- These are brief movements (motor tics) often preceded by a feeling of discomfort that builds until the tic occurs, followed by a temporary feeling of relief.
- These "premonitory urges" can be a feeling of itching or tension in the affected body part (sensory tic).
- A key characteristic of tics is their semivoluntary (suppressible) nature, though they typically rebound with increased frequency and severity after conscious suppression.
- They are purposefully executed but performed out of a feeling of need. Tics can be clonic (brief), dystonic (sustained), or phonic (vocal).
- Simple tics are isolated actions like throat clearing or winking, while complex tics involve speech or coordinated actions, sometimes including obscene gestures (copropraxia) or vocalizations (coprolalia).
Stereotypies
- These are repetitive movements or vocalizations that mimic a purposeful action but are performed outside that action's normal context.
- They are involuntary or semivoluntary (e.g., hand-wringing in Rett syndrome).
- Stereotypies should be differentiated from compulsions (epilepsy) and perseverative/repetitive behavior (e.g., ADHD, OCD).
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