Evaluation of Myoclonus

Last updated: April 8, 2026, 1:27 PM Pacific Time (PDT)

Symptom-first framework for new or worsening myoclonus. Start by separating epileptic or cortical myoclonus, toxic-metabolic causes, post-hypoxic states, medication effects, infectious or autoimmune encephalitis, and spinal or brainstem patterns before narrowing to chronic syndromic causes.

All Immediate stabilization Cortical / epileptic Toxic / metabolic Structural / inflammatory Back to Main Page

Interactive diagnostic assistant

Activate the assistant to re-rank likely myoclonus causes from partial clinical data.
Presentation
Phenotype clues
Neuro red flags
Toxic / metabolic clues
Context

Likely diagnoses from entered data

Recommended next labs, imaging, and diagnostics

Flowchart

First pass
Myoclonus is a phenomenology problem before it is a diagnosis
Clarify whether the movement is actually myoclonus, then decide whether it is cortical/epileptic, toxic-metabolic, post-hypoxic, structural, spinal, or part of a chronic syndrome.
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Immediate stabilization
Treat seizures, airway issues, and toxic-metabolic emergencies first
Myoclonus plus obtundation, ongoing seizure concern, severe metabolic derangement, or post-arrest state should move ahead of pattern refinement.
Cortical / epileptic
Stimulus-sensitive
Cortical / epileptic myoclonus
Often multifocal, stimulus-sensitive, and tied to encephalopathy or epilepsy.
Post-arrest
Post-hypoxic myoclonus
Early post-anoxic myoclonus and chronic Lance-Adams syndrome live here.
Toxic / metabolic
Diffuse encephalopathy
Uremic / hepatic / electrolyte / medication-related
The most common inpatient bucket when myoclonus is new and diffuse.
Withdrawal / intoxication
Substance-related or serotonin-toxic pattern
Medication review matters early.
Structural / inflammatory
Fever + AMS
Infectious or autoimmune encephalitis
Myoclonus can accompany inflammatory CNS disease.
Focal / segmental
Brainstem, spinal, or focal structural pattern
Segmental or spinal myoclonus points away from diffuse metabolic disease.
Chronic syndromic
Longstanding / recurrent
Chronic syndrome or neurodegenerative context
Consider epilepsy syndromes, degenerative disease, essential myoclonus, and rarer inherited/metabolic causes.

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