Table 1
Distinguishing features of myoclonus and other movement disorders.
| MYOCLONUS | TICS | DYSTONIA | TREMOR | CHOREA | |
|---|---|---|---|---|---|
| Duration/Cadence of movements | Very brief, shock-like | Brief | Sustained, longer duration | Sustained, longer duration | Could be brief |
| Onset | Abrupt | Brief | Gradual | Gradual | Rapid |
| Reflex/Trigger | Frequent | Premonitory urge | May be kinesigenic | Rest, postural, or action | No |
| Termination | Abrupt | Abrupt | Progressive | Progressive | Progressive |
| Suppressibility | No | Temporary | No | Temporary | No |
| Pattern | Simple | Simple/complex | Multiplanar complex | Sinusoidal, may be rhythmic | Flows from one body part to another |
| Neurophysiological testing | Back-averaging EEG potentials preceding EMG | Organization of the movement | May be useful for treatment | EMG/NCS can distinguish action tremor from myoclonus | Unhelpful |
Figure 1
CONSORT (Consolidated Standards of Reporting Trials) flowchart detailing study sample size and exclusion criteria.
Figure 2
Bar graph detailing number of cases per identified etiology for myoclonus. The total number of charts reviewed was 279 individuals. Almost half of studied cases had one probable etiology, whereas the remainder had 2 or more probable etiologies.
Table 2
Sample of final diagnoses encountered per class of etiology.
| ETIOLOGY | DIAGNOSES |
|---|---|
| Toxic-metabolic | Hepatic encephalopathy Hyponatremia Hyperglycemic non-ketotic state Diabetic ketoacidosis |
| Hypoxic-ischemic | Anoxic Brain Injury Hypoxic-Ischemic Encephalopathy Lance-Adams Myoclonus Cerebrovascular Disease (Post-Stroke) Intraparenchymal hemorrhage |
| Infectious | Urinary tract infection Septic encephalopathy COVID-19 pneumonia Creutzfeldt-Jakub Disease Cryptococcosis |
| Renal | Uremic encephalopathy Dialysis disequilibrium syndrome |
| Epileptic | Juvenile-onset myoclonic epilepsy Symptomatic myoclonic epilepsy Myoclonic status epilepticus |
| Neurodegenerative | Parkinson’s Disease Multiple System Atrophy Dementia with Lewy Bodies Alzheimer’s Disease |
| Iatrogenic | Gabapentin-induced myoclonus Budesonide/formoterol toxicity Bupropion toxicity Quetiapine toxicity Phenytoin-induced myoclonus Tramadol-induced myoclonus Opiate/narcotic withdrawal Alcohol withdrawal |
| Psychogenic | Psychogenic non-epileptic spells (PNES) Functional myoclonus-like movement disorder |
| Autoimmune/Paraneoplastic | NMDA Encephalitis GAD-65 Antibody-Associated Encephalitis Progressive Encephalopathy w/Rigidity, Myoclonus |
| Spinal | Cervical spinal stenosis Transverse myelitis |
| Neoplastic | Cerebral meningioma Intracranial metastases T-cell lymphoma |