Paroxysmal Dyskinesias
Paroxysmal movement disorders are a group of highly heterogeneous conditions presenting with attacks of involuntary hyperkinetic movements — commonly dystonia, chorea, or ataxia — without loss of consciousness. First described in 1940, these disorders demonstrate considerable genetic and clinical heterogeneity, challenging the principle of one phenotype representing a single etiology. Traditionally divided into paroxysmal dyskinesias (dystonia/chorea) and episodic ataxias based on phenomenology, advances in genetics have revealed substantial pleiotropy: a single gene variation can present with many phenotypes, and different genetic variations can produce similar phenotypes.
Bottom Line
- Three main types: Paroxysmal kinesigenic dyskinesia (PKD, most common, triggered by sudden movement), paroxysmal nonkinesigenic dyskinesia (PNKD, triggered by alcohol/coffee/stress), and paroxysmal exercise-induced dyskinesia (PED, triggered by sustained exercise)
- Genetic testing is increasingly important: Diagnostic yield of 35–50% with next-generation sequencing panels; results guide specific treatment and genetic counseling
- PRRT2 mutations cause 65% of PKD and respond excellently to low-dose carbamazepine/phenytoin
- SLC2A1 (GLUT1 deficiency) causes 20% of PED and responds to ketogenic diet/triheptanoin
- Antiseizure medications are mainstay for PKD and many paroxysmal disorders; generally ineffective for PNKD (use benzodiazepines and trigger avoidance instead)
- Always rule out secondary causes: MS/NMO, autoimmune encephalitis (LGI1, NMDAR, CASPR2), vascular disorders (Moyamoya), metabolic abnormalities, functional disorders
Classification and Clinical Presentation
Paroxysmal Kinesigenic Dyskinesia (PKD)
PKD is the most common paroxysmal movement disorder. It presents with chorea-dystonia triggered by sudden voluntary movements, commonly standing up or transitioning from walking to running.
- Age of onset: 1–20 years
- Attack duration: <1 minute (typically seconds)
- Frequency: ≥1 per day
- Phenomenology: Usually highly asymmetric or unilateral attacks of dystonia, chorea, or both; a preceding sensory aura has been reported
- Treatment: Excellent response to low-dose antiseizure medications (carbamazepine, phenytoin)
- Genetics: PRRT2 mutations account for up to 65% of cases (autosomal dominant, incomplete penetrance)
Paroxysmal Nonkinesigenic Dyskinesia (PNKD)
PNKD is rarer and more variable than PKD, with onset in infancy or early childhood and a tendency for remission in adulthood.
- Duration: Up to 4 hours
- Frequency: Variable (daily to only a few times per year)
- Triggers: Coffee, alcohol, emotional stress, exhaustion
- Phenomenology: Dystonia, chorea, or both; may include dysarthria, dysphagia, inability to move, and pain; normal exam between attacks
- Treatment: Benzodiazepines may help; trigger avoidance is primary strategy; antiseizure drugs are generally NOT effective
- Genetics: PNKD gene mutations account for ~70% of cases (autosomal dominant, near-complete penetrance)
Paroxysmal Exercise-Induced Dyskinesia (PED)
PED presents from childhood to adulthood with dystonia and/or chorea primarily affecting the lower extremities, triggered by at least a few minutes of sustained exercise.
- Duration: 5–30 minutes
- Distribution: Predominantly lower extremities
- Associated features: Developmental delay and epilepsy may coexist; multiple family members may be affected
- Treatment: Depends on underlying genetic defect; trigger avoidance; acetazolamide or benzodiazepines may help empirically
- Key genetic cause: SLC2A1 (GLUT1 deficiency) accounts for ~20% — responds to ketogenic diet or triheptanoin
Other Paroxysmal Presentations
| Presentation | Key Features | Associated Gene |
|---|---|---|
| Paroxysmal nocturnal dyskinesia | Hyperkinetic movements during N2/REM sleep, more frequent during morning awakenings; non-epileptiform on EEG | ADCY5 (most common); rarely PRRT2 |
| Alternating hemiplegia of childhood | Onset <18 months; paroxysmal hemiplegia with alternating laterality; rostrocaudal gradient; aborts with sleep | ATP1A3 |
| Benign paroxysmal torticollis | Recurrent head/neck posturing, irritability, nausea, vomiting; onset <3 months, resolves by age 4; migraine association | — |
| Shuddering attacks | Head and shoulder shuddering; onset within first year, resolves by age 4 | — |
Episodic Ataxias
Episodic ataxias (EAs) are rare paroxysmal movement disorders presenting with attacks of cerebellar dysfunction, including truncal ataxia, incoordination, and ocular motor abnormalities. Nine types are recognized in the OMIM catalog.
| Type | Gene | Duration | Key Features | Treatment |
|---|---|---|---|---|
| EA1 | KCNA1 | Seconds to minutes | Brief attacks with interictal myokymia; onset <20 years; may include tinnitus, cramps, deafness; can progress to chronic ataxia | Antiseizure meds; may respond to acetazolamide |
| EA2 | CACNA1A | Minutes to hours/days | Most common EA; interictal nystagmus; may present with hemiplegic migraine, epileptic encephalopathy; can progress to chronic ataxia | Acetazolamide (excellent response); 4-aminopyridine; levetiracetam; flunarizine |
| EA3 | — | Minutes | Brief attacks with myokymia and tinnitus | Acetazolamide |
| EA5 | CACNB4 | Hours | Resembles EA2; onset in adulthood; may include epilepsy | Acetazolamide |
| EA6 | SLC1A3 | Hours | Resembles EA2; nystagmus, migraine with alternating hemiplegia; can progress to chronic ataxia | Acetazolamide |
| EA8 | UBR4 | Minutes to hours | Overlaps EA1 and EA2; myokymia, tinnitus, intention tremor | Poor response to acetazolamide; may respond to clonazepam |
| EA9 | FGF14 | Seconds to days | Late-onset cerebellar ataxia, vertigo, nystagmus, tremor; fever may trigger in children | Acetazolamide, benzodiazepines |
Genetics
Genetic testing is increasingly central to the diagnosis and treatment of paroxysmal movement disorders. The overall diagnostic yield with next-generation sequencing is 35–50%.
| Gene | Inheritance | Primary Phenotype | Other Phenotypes | Treatment Implications |
|---|---|---|---|---|
| PRRT2 | AD | PKD (65% of cases) | Benign familial infantile seizures, hemiplegic migraine, episodic ataxia | Low-dose carbamazepine/phenytoin (excellent response) |
| PNKD (MR1) | AD | PNKD (70% of cases) | Migraines outside of attacks | Benzodiazepines; trigger avoidance |
| SLC2A1 | AD (most), AR (rare) | PED (20% of cases) | Seizures, intellectual disability, spastic paraparesis, choreoathetosis | Ketogenic diet; triheptanoin (normalizes brain energy metabolism) |
| ADCY5 | AD | PNKD + nocturnal dyskinesia | Axial hypotonia, chorea, dystonia, facial myokymia | Caffeine; GPi DBS |
| ATP1A3 | AD | PNKD, alternating hemiplegia of childhood | Rapid-onset dystonia-parkinsonism, CAPOS syndrome, episodic ataxia | Flunarizine, benzodiazepines |
| CACNA1A | AD | EA2 | Hemiplegic migraine type 1, epileptic encephalopathy, SCA6 (CAG expansion) | Acetazolamide; 4-aminopyridine |
| PDHA1 | X-linked | PED + PNKD | Developmental delay, seizures | Thiamine; ketogenic diet |
| ECHS1 | AR | PED | Leigh-disease-like phenotype | Mitochondrial cocktail |
| GCH1 | AD | PED (rare) | Dopa-responsive dystonia (DRD) | Levodopa (excellent response) |
| KCNA1 | AD | EA1 | Progressive ataxia, epileptic encephalopathy, PKD | Antiseizure medications; acetazolamide |
Approach to Genetic Testing
- Traditional single-gene testing (PRRT2 first for PKD, then SLC2A1) may miss diagnoses due to genetic pleiotropy
- Next-generation sequencing gene panels are now preferred (diagnostic yield 35–50%)
- Consider microarray in children with intellectual disability or epilepsy (detects copy-number variants missed by NGS/WES)
- Gene panels offer better coverage and reduce incidental findings compared with whole-exome sequencing
- Genetic counseling is critical in this rapidly evolving field
Pathophysiology
Paroxysmal movement disorders arise from dysfunction in synaptic neurotransmission within the basal ganglia and cerebellum. The underlying mechanisms include:
- Ion channels: ATP1A3, CACNA1A, SCN8A, CACNB4 — affect calcium, sodium, and potassium channels controlling neuronal excitability
- Solute carriers: SLC2A1 — impaired glucose transport across the blood-brain barrier
- Synaptic vesicle fusion: PRRT2, PNKD, TBC1D24 — disrupt synaptic transmission
- Postsynaptic signaling: ADCY5 — aberrant cAMP production in striatum
- Energy metabolism: ECHS1, PDHX, HIBCH — mitochondrial enzyme deficiencies
- Neurotransmitter synthesis: GCH1 — impaired dopamine synthesis
Secondary Causes
| Category | Conditions | Key Clues | Treatment |
|---|---|---|---|
| Immune-mediated | MS, NMO, ADEM | Onset in adulthood; other neurologic deficits; associated myelitis; brief painful tonic spasms (more common with NMO) | Carbamazepine/oxcarbazepine for spasms; treat underlying disease |
| Autoimmune encephalitis | Anti-LGI1 (faciobrachial dystonic seizures), anti-NMDAR (dystonic posturing), anti-CASPR2, Hashimoto | LGI1: brief (<3 sec) face+arm seizures + hyponatremia + bradycardia; may precede limbic encephalitis | Corticosteroids, IVIg, plasma exchange |
| Systemic autoimmune | SLE, antiphospholipid syndrome, Behçet disease | Adulthood onset, systemic involvement | Carbamazepine; treat underlying condition |
| Vascular | Contralateral ICA stenosis (limb-shaking TIA), Moyamoya disease | Limb-shaking paroxysms; exercise-induced symptoms with Moyamoya | Revascularization surgery, secondary prevention |
| Metabolic | Hypo/hyperglycemia, hypocalcemia, thyroid disorders | Association with meals; seizures, confusion, tremor may coexist | Correct underlying abnormality |
| Traumatic | Central and peripheral trauma | Younger patients; unilateral finger/wrist/ankle flexion-extension paroxysms | Carbamazepine, clonazepam, botulinum toxin |
| Functional | Functional paroxysmal movement disorders | Acute onset, variable/inconsistent phenomenology, suggestibility, distractibility, entrainment | Cognitive behavioral therapy |
Treatment
Treatment Approach by Phenotype
- PKD: Low-dose antiseizure medications are highly effective (carbamazepine, phenytoin, lamotrigine); expect excellent response, especially with PRRT2 mutations
- PNKD: Antiseizure drugs generally NOT effective; benzodiazepines may help; focus on trigger avoidance (caffeine, alcohol, stress); GPi DBS for rare refractory cases
- PED: Treatment guided by genetics: ketogenic diet for SLC2A1/GLUT1 deficiency; levodopa for GCH1; thiamine for PDHA1; mitochondrial supplements for ECHS1; empiric acetazolamide or benzodiazepines
- ADCY5-related dyskinesia: Caffeine reduces frequency and severity of paroxysms; GPi DBS may be beneficial
- Episodic ataxias: Acetazolamide is first-line for EA1, EA2, EA3, EA5, EA6 (degree of response varies); 4-aminopyridine for EA2 (RCT evidence); EA8 responds poorly to acetazolamide (try clonazepam)
Treatment Summary by Genetic Etiology
| Gene/Defect | First-Line Treatment | Alternative |
|---|---|---|
| PRRT2 (PKD) | Carbamazepine/phenytoin (low dose) | Lamotrigine |
| PNKD/MR1 | Trigger avoidance | Benzodiazepines |
| SLC2A1 (GLUT1) | Ketogenic diet | Triheptanoin, modified Atkins diet |
| ADCY5 | Caffeine | GPi DBS |
| ATP1A3 | Flunarizine | Benzodiazepines |
| PDHA1 | Thiamine | Ketogenic diet |
| ECHS1 | Mitochondrial cocktail | Benzodiazepines |
| GCH1 | Levodopa | — |
| CACNA1A (EA2) | Acetazolamide | 4-aminopyridine, flunarizine |
| KCNA1 (EA1) | Antiseizure medications | Acetazolamide |
| SCN2A (gain-of-function) | Sodium channel blockers | — |
| GNAO1 | GPi DBS | — |
Paroxysmal Movement Disorders and Epilepsy
There is a significant and underappreciated overlap between paroxysmal movement disorders and epilepsy:
- Shared genes: PRRT2 (benign familial infantile seizures), SLC2A1 (absence/myoclonic epilepsy), KCNMA1, SCN8A, DEPDC5, CHRNA4
- Shared triggers: Sudden movement, stress, sleep deprivation
- Shared treatment response: Both respond to antiseizure medications that modulate ion channels
- Both epilepsy and paroxysmal movement disorders can occur in the same individual or family — infantile convulsions were reported in 9 of 11 families with PKD
- A framework of channelopathies (KCNMA1, SCN8A), transportopathies (SLC2A1), and synaptopathies (PRRT2, PNKD) has been proposed
- The concept of “basal ganglia epilepsy” — ion dysfunction manifesting as paroxysmal movements — has been proposed but remains debated
When to Suspect a Secondary Cause
Onset in adulthood, presence of additional neurologic deficits, abnormal interictal examination, acute onset with rapid progression, painful tonic spasms (think MS/NMO), faciobrachial dystonic seizures (think LGI1), or association with meals (think metabolic disorder) should prompt investigation for secondary etiologies including brain MRI, vascular imaging, autoimmune panels, metabolic workup, and genetic testing.
Primary source: Continuum (Minneap Minn) 2025;31(4):1152–1181 — Paroxysmal Movement Disorders