Download Myoclonus

Myoclonus
-Definition: Quick, shock-like involuntary simple muscle jerks
Classification
-Regular vs. irregular
-Positive (muscle contraction) vs. negative (muscle tone lapse, ie asterixis).
-Spontaneous vs. action-induced vs. sensory-induced
-Focal vs. generalized vs. multifocal/segmental
-Pathology could be in cortex (seizure, cortical) vs. brainstem (palatal, exaggerated startle) vs. spinal
-------------------------------------------------------------------------------------------------------------------------------------ETIOLOGY
? Physiologic  ? epileptic  ? secondary causes  If everything else negative, called “Essential myoclonus”
1) Epileptic causes
-Progressive myoclonic epilepsy type 1 (myoclonic epilepsy with ataxia)
-Primary myoclonic epilepsy
-MERFF, other mitochondrial disorders
-Angelman Syndrome
-Lafora Disease
-DRPLA
2) Secondary causes (not in order of prevalence):
-Dementias: AD, CJD, FTLD-TDP, LBD
-Storage disorders: Lafora body disease, Tay Sachs, Batten’s Disease, DRPLA, etc
-Basal ganglia problems: PD (orthostatic myoclonus), dopa-dyskinesia, MSA, HD, CBD, PSP, dystonia, SCA
2/14/19/24.
-Viral encephelopathies: HSV, subacute sclerosing panencephelitis, AIDS-dementia complex, Whipple’s.
-Metabolic encephalopathy/endocrine: Liver, renal, hyponatremia, hypoglycemia, hyperglycemia,
hyperthyroid, Biotin deficiency, Hashimoto’s encephalopathy.
-Autoimmune: Opsoclonus-myoclonus (infectious, toxin, or paraneoplastic causes), celiac disease, NMDA .
-Toxic/drugs: Excessive pepto-bismol, heavy metals, methylbromide, DDT, TCAs, opioids, lithium, SSRIs
(serotonin syndrome), anticonvulsants (particularly gabapentin), antibiotics, calcium channel blockers,
amantadine, levodopa.
-Physical/focal CNS damage: Tumors, angiomas, encephalitis, post-hypoxic action-induced myoclonus (Lance
Adams Syndrome), trauma, heat stroke, electric shock, decompression injury, Friedrich’s ataxia, ataxiatelangiectasia.
-Exaggerated Startle Syndromes: Hyperekplexia (symptomatic or hereditary; lack habituation)
-Spinal Myoclonus: Rhythmic, spontaneous, persistent, continues in sleep. 2/2 trauma, tumor, disc herniation,
infection. (May also get nonrhythmic symmetric flexion of various parts of body called propriospinal myclonus,
though this form is most often/almost always psychogenic).
-Palatal myoclonus/tremor: Two DIFFERENT types: Essential palatal tremor(ear click) vs. Symptomatic palatal
tremor (2/2 cerebellar dysfunction). Etiology is broad. Nothing really helps. At least SOME of the patients are
psychogenic, perhaps many of them.
-Essential Myoclonus: Familial, isolated, like essential tremor.
-Psychogenic myoclonus: Testing is definitive and helpful.
3) DDx:
-Tics (myoclonus has no urge, interferes with voluntary motor activity, cannot be suppressed)
-Chorea, tremor, peripheral disorder (hemifacial spasm, fasciculation, myokymia), ballismus, ataxia, EPC.
Treatment:
-Try to treat underlying problem.
-Consider EMG if concerned for psychogenic, or EEG if concerned for seizures.
Symptomatic relief:
-First line: Klonopin 3-20mg/day is best. Also could try Depakote 1000-2000mg/day, keppra 1000-3000mg/day
-Second line: Primidone 500-750mg/day, PB 60-180mg/day, Zonisamide 100-600mg/day. Usually necessary to
combine agents.
-AVOID gabapentin, phenytoin, carbamezapine, lamictal.