Overview
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Myoclonus Management in CBS (NCT06218921) is a Phase 2 clinical trial evaluating the efficacy of a combination therapy approach for treating myoclonus in patients with Corticobasal Syndrome (CBS)[^1].
Trial Details
...Overview
Mermaid diagram (expand to render)
Myoclonus Management in CBS (NCT06218921) is a Phase 2 clinical trial evaluating the efficacy of a combination therapy approach for treating myoclonus in patients with Corticobasal Syndrome (CBS)[^1].
Trial Details
| Field | Value |
|-------|-------|
| NCT ID | NCT06218921 |
| Status | Recruiting |
| Phase | Phase 2 |
| Intervention | Drug: Combination therapy (clonazepam + levetiracetam) |
| Enrollment | 50 participants |
| Duration | 16 weeks |
Scientific Rationale
Myoclonus occurs in approximately 30-50% of CBS patients and significantly impacts functional ability. The myoclonus in CBS is typically:
- Cortical in origin: Linked to underlying tau pathology
- Action-induced: Triggered by voluntary movements
- Stimulus-sensitive: Triggered by touch, sound, or sudden movements
- Focal or multifocal: Often asymmetric
Treatment of myoclonus in CBS presents unique challenges:
- Limited response to standard therapies
- Need for therapies that address both myoclonus and underlying tauopathy
- Drug interactions with other CBS medications
- Cognitive side effects from many antimyoclonic agents
Study Objectives
Primary Endpoints
Change in Myoclonus Rating Scale (MRS)
Functional impact assessmentSecondary Endpoints
- Cognitive safety assessments (MMSE, MoCA)
- Sleep quality (PSQI)
- Caregiver burden (ZBI)
Treatment Approach
The trial evaluates a sequential treatment approach:
Phase 1: Clonazepam Optimization
- Low-dose clonazepam (0.25-1.5 mg/day)
- Addresses cortical myoclonus via GABAergic mechanisms
- Monitor for sedation and cognitive effects
Phase 2: Levetiracetam Addition
- Add-on levetiracetam for partial responders
- Different mechanism of action
- Lower risk of cognitive impairment
Phase 3: Combination Therapy
- Optimized combination for optimal responders
- Goal: maximize efficacy with minimal side effects
Mechanism of Action
Clonazepam
- GABA-A receptor positive allosteric modulator
- Enhances inhibitory neurotransmission
- Reduces cortical excitability
- Particularly effective for action myoclonus
Levetiracetam
- Binds to synaptic vesicle protein SV2A
- Modulates neurotransmitter release
- Reduces cortical myoclonus through distinct mechanisms
- Minimal cognitive side effect profile
Relevance to CBS
This trial addresses a significant unmet need in CBS care:
Symptom-specific focus: Direct targeting of myoclonus, not just underlying disease
Practical approach: Uses available medications with known safety profiles
Personalized medicine: Sequential escalation allows individualized treatment
Quality of life focus: Measures functional outcomes and caregiver burdenInclusion Criteria
- Diagnosis of probable or possible CBS
- Clinically significant myoclonus (MRS score ≥3)
- Age 45-85 years
- Stable medications for ≥4 weeks
Expected Outcomes
- Evidence-based treatment algorithm for CBS myoclonus
- Optimal dosing recommendations
- Safety profile in CBS population
- Functional improvement metrics
Clinical Presentation of Myoclonus in CBS
Characteristics of Cortical Myoclonus
Myoclonus in corticobasal syndrome exhibits distinct features that distinguish it from other myoclonic disorders:
Electrophysiological Findings:
- Cortical reflex myoclonus: Giant somatosensory evoked potentials (SEP)
- Positive myoclonus: Jerk-locked back-averaging reveals cortical origin
- Enlarged cortical potentials: N20-P37amplitude > 10 μV
- Stimulus sensitivity: Abnormal sensory gating
Anatomical Substrate:
- Cortical pathology in primary sensorimotor cortex
- Supplementary motor area involvement
- Dysfunction of corticothalamic pathways
- Loss of inhibitory interneurons
Differential Diagnosis:| Feature | Cortical Myoclonus | Subcortical Myoclonus | Reticular Myoclonus |
|---------|-------------------|---------------------|---------------------|---------------------|
| Distribution | Focal/multifocal | Generalized | Axial | Generalized |
| Trigger | Voluntary movement | Startle | Sensory input |
| EEG | Abnormal | Normal | Normal |
| Response to clonazepam | Good | Variable | Good |
Myoclonus Impact on Function
Myoclonus significantly affects daily activities:
- Eating: Spills food due to sudden jerks
- Writing: Pen dropped due to hand myoclonus
- Walking: Stumbling from leg jerks
- Dressing: Difficulty with buttons due to finger myoclonus
- Speaking: Speech interruption from axial jerks
Pharmacological Management
First-Line Treatments
Clonazepam:
- Dosing: 0.25-1.5 mg/day in divided doses
- Mechanism: GABA-A receptor allosteric modulation
- Efficacy: 50-70% response rate in cortical myoclonus
- Onset: 2-4 weeks for maximal effect
- Titration: Start 0.25 mg, increase weekly
Levetiracetam:
- Dosing: 500-3000 mg/day
- Mechanism: SV2A binding, reduces glutamate release
- Efficacy: 40-60% response rate
- Advantages: Minimal sedation, few drug interactions
Adjunctive Treatments
Piracetam:
- Dosing: 2400-9600 mg/day
- Mechanism: AMPA receptor modulation
- Use: Add-on to clonazepam or levetiracetam
Valproic Acid:
- Dosing: 500-2000 mg/day
- Mechanism: GABA elevation, sodium channel blockade
- Caution: Liver function monitoring required
Treatments with Limited Efficacy
Benzodiazepines (beyond clonazepam):
- Diazepam: Limited efficacy, significant sedation
- Lorazepam: Shorter duration, similar profile
Antiepileptics (ineffective):
- Phenytoin: May worsen myoclonus
- Carbamazepine: Usually ineffective
Non-Pharmacological Approaches
Environmental Modifications
Seating:
- Padded armrests for arm support
- Stable chairs with lateral support
- Tray tables for eating stability
Writing Aids:
- Weighted pens (20-30g)
- Ergonomic grips
- Tablet-based input methods
Assistive Devices
- Utensil adaptations: Weighted cutlery
- Self-feeding devices: Robotic arm supports
- Communication: Speech-generating devices for severe cases
Physical Therapy
Goals:
- Maintain range of motion
- Strengthen proximal muscles
- Teach compensation strategies
Techniques:
- Gentle stretching before activities
- Proprioceptive neuromuscular facilitation
- Functional task practice
Outcome Measures in Detail
Myoclonus Rating Scale (MRS)
The primary outcome measure, the MRS, evaluates:
Section A: Myoclonus Distribution (0-32 points):
- Facial: 0-4
- Neck: 0-4
- Right/Left arm: 0-8 each
- Right/Left leg: 0-4 each
Section B: Myoclonus Intensity (0-16 points):
- Stimulus-sensitive: 0-4
- Action myoclonus: 0-4
- Myoclonus at rest: 0-4
- Spontaneous myoclonus: 0-4
Section C: Functional Impact (0-52 points):
- self-care: 0-16
- Mobility: 0-12
- Communication: 0-12
- Domestic activities: 0-12
Interpretation:
- 0-10: Mild myoclonus
- 11-30: Moderate
- 31-50: Severe
- 51-100: Very severe
Functional Independence Measure (FIM)
The FIM assesses:
- Self-care: 35 points maximum
- Sph continence: 8 points
- Mobility: 30 points
- Communication: 14 points
- Social cognition: 21 points
- Total: 126 points maximum
Safety Assessments
MMSE (Mini-Mental State Examination):
- 30-point scale
- <24 indicates cognitive impairment
- Monitor for medication-induced worsening
MoCA (Montreal Cognitive Assessment):
- 30-point scale
- More sensitive to mild impairment
- Specific attention subtests
PSQI (Pittsburgh Sleep Quality Index):
- 21-point scale
- >5 indicates poor sleep
- Benzodiazepines may improve or worsen
ZBI (Zarit Burden Interview):
- 22 items, 0-88 scale
- >20 indicates significant burden
- Caregiver wellbeing essential
Study Design Details
Randomization
- 1:1 allocation to intervention groups
- Block randomization (size 4)
- Stratified by baseline myoclonus severity
Blinding
- Single-blind design (outcomes assessor)
- Participant blinding not possible due to intervention nature
Schedule
| Visit | Timing | Assessments |
|-------|--------|--------------|
| V1 | Week 0 | Baseline all |
| V2 | Week 2 | Safety, MRS |
| V3 | Week 4 | Primary efficacy |
| V4 | Week 8 | Safety, MRS |
| V5 | Week 12 | All outcomes |
| V6 | Week 16 | Final assessment |
Biomarker Correlation
Neuroimaging Correlates
The trial includes MRI correlates:
- Cortical thickness: Reduced in proportion to myoclonus severity
- FDG-PET hypometabolism: Correlates with myoclonus distribution
- DaTscan: Documents dopaminergic deficit
Electrophysiological Studies
- Giant SEPs: Baseline abnormality predicts treatment response
- Long-latency reflexes: Abnormal in cortical myoclonus
- EMG mapping: Identifies muscle involvement patterns
Cost-Effectiveness Analysis
Healthcare Resource Utilization
The trial will collect:
- Medication costs
- Emergency visits
- Caregiver time
- Assistive device costs
Quality of Life
Utilities:
- EQ-5D-5L collected at each visit
- Will generate QALY estimates
- Compare intervention vs. standard care
Regulatory Considerations
Orphan Drug Status
Corticobasal syndrome is:
- Designated as orphan disease in US and EU
- Specific therapies receive orphan drug incentives
- This trial may support future FDA submissions
Future Drug Development
Results may inform:
- Pivotal trial designs for CBS myoclonus
- Regulatory endpoints selection
- Combination therapy approaches
References
[^1]: ClinicalTrials.gov. [Myoclonus Management in CBS - NCT06218921](https://clinicaltrials.gov/study/NCT06218921). Accessed March 2026.
See Also
- [Corticobasal Syndrome](/diseases/corticobasal-syndrome)
- [CBS/PSP Clinical Trials Guide](/therapeutics/cbs-psp-clinical-trials-guide)](/clinical-trials)
- [Myoclonus in CBS/PSP](/therapeutics/myoclonus-cbs-psp)](/therapeutics)
- [Symptom Management in CBS](/therapeutics/cbs-symptom-management)
Pathway Diagram
The following diagram shows the key molecular relationships involving Myoclonus Management in CBS (NCT06218921) discovered through SciDEX knowledge graph analysis:
Mermaid diagram (expand to render)