Background
- Rapid, brief, shock-like movements involving muscle or group of muscles
- If sudden muscle contractions = 'positive myoclonus'
- If brief loss of muscular tone = 'negative myoclonus' (e.g. asterixis)
- ¼ drug related
- 10% functional
- Cortical myoclonus = hands/feet/face
- Brainstem = stimulus (noise) → braintem reflexes
Types
Cortical
- Post hypoxia
- 1° generalised
- Juvenile myoclonic epilepsy)
Subcortical
- Essential myoclonus
- Reticular reflex myoclonus
- Opsoclonus-myoclonus syndrome
- Hyperekplexia
Spinal
Peripheral
- Incl. hemifacial spasm
Functional
Common so hints for organic include:
- Consistent findings
- Slow onset
- Distraction ≠ improved symptoms
- Response to anit-epileptic meds
Clinical
Symptoms
- Age of onset, duration, FHx
- Spont onset or with action
- Ryhthmiticity
- Precipitating (drugs)
- Stimuli, particularly sound triggers (brain stem), touch
Signs
- Region involved:
- Central [generalized] in brain stem or
- Peripheral [cortical cause]
- Look for action (rather than passive) myoclonus
Differential Dx
- Dystonia
- MS
- Parkinson's disease
- CJD
- Serotonin syndrome
- Huntington disease
- Subacute sclerosing panencephalitis
- Alzheimer's
- Gaucher disease
Investigations
- Baseline bloods / tox
- EMG and EEG
- MRI (brain if clinical "central" cord if "peripheral")
Management
- Call neurology for advice
- If cortical: Valproate or levetiracetam
- If cortical: Avoid phenytoin, carbamazepam (may worsen)
- if spinal: Use levetiracetam
- Botulinum only for use by neurologist