Whole-body tremulousness: isolated generalized polymyoclonus.
BACKGROUND
Acquired generalized repetitive myoclonus may be mistaken for tremor. Distinguishing myoclonus has etiologic and therapeutic implications.


OBJECTIVE
To describe isolated generalized polymyoclonus and the outcomes of etiologic evaluations at the time of diagnosis.


METHODS
Computer search of the Mayo Movement Neurophysiology Laboratory database and medical records linkage system.


METHODS
Department of Neurology, Mayo Clinic.


METHODS
Nineteen adults with generalized repetitive myoclonus confirmed using surface electromyography (burst duration <50 milliseconds), and other neurologic features minimal or absent.


METHODS
Treatment of myoclonus and underlying causes.


METHODS
Clinical presentation and underlying etiologies.


RESULTS
We identified 19 patients with isolated generalized polymyoclonus resembling whole-body tremor. Onset was most often subacute (12 patients), mean symptom duration was 1.8 years, and mean age at onset was 55 years. Referral diagnoses or patient complaints were tremor, tremulousness, or shaking in all but 5 patients. All the patients had repetitive myoclonus of all limbs, impairing gait in 14 patients. Surface electromyography confirmed nonperiodic muscle burst durations of less than 50 milliseconds, typical of myoclonus. Clinical and serologic screening for cancer and autoimmunity revealed metastatic breast cancer in 2 patients (1 positive for ganglionic acetylcholine receptor antibody) and antibody profiles implicating neurologic autoimmunity in 3 patients (CRMP-5 IgG or neuronal voltage-gated potassium channel antibodies). Medications known to occasionally trigger myoclonus (opioids, selective serotonin reuptake inhibitors, and a serotonin-norepinephrine reuptake inhibitor) were being taken by 7 patients. Myoclonus resolved after discontinuation of selective serotonin reuptake inhibitor therapy in 1 patient; drug discontinuation was declined and follow-up was inadequate in the other 6.


CONCLUSIONS
Isolated whole-body tremulousness should raise the suspicion of generalized polymyoclonus, confirmed using routine surface electromyography. Recognition is important because the differential diagnosis includes autoimmunity and drug-induced myoclonus.
McKeon
Andrew
A
Department of Neurology, Gonda 8 South, Mayo Clinic, 200 First St SW, Rochester, MN 55902, USA. mckeon.andrew@mayo.edu
Pittock
Sean J
SJ
Glass
Graham A
GA
Josephs
Keith A
KA
Bower
James H
JH
Lennon
Vanda A
VA
Ahlskog
J Eric
JE
D000328:Adult; D000368:Aged; D000588:Amines / Q000627:therapeutic use; D000927:Anticonvulsants / Q000627:therapeutic use; D015551:Autoimmunity / Q000502:physiology; D001943:Breast Neoplasms / Q000150:complications / Q000601:surgery; D002998:Clonazepam / Q000627:therapeutic use; D003509:Cyclohexanecarboxylic Acids / Q000627:therapeutic use; D003937:Diagnosis, Differential; D004576:Electromyography; D018691:Excitatory Amino Acid Antagonists / Q000627:therapeutic use; D005260:Female; D000077206:Gabapentin; D020233:Gait Disorders, Neurologic / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009207:Myoclonus / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D017367:Selective Serotonin Reuptake Inhibitors / Q000009:adverse effects; D014202:Tremor / Q000175:diagnosis / Q000503:physiopathology*; D005680:gamma-Aminobutyric Acid / Q000627:therapeutic use
D000588:Amines; D000927:Anticonvulsants; D002998:Clonazepam; D003509:Cyclohexanecarboxylic Acids; D018691:Excitatory Amino Acid Antagonists; D000077206:Gabapentin; D017367:Selective Serotonin Reuptake Inhibitors; D005680:gamma-Aminobutyric Acid