Objective
To study the incidence and prevalence of diagnosed myoclonus in Olmsted County, Minnesota.
Little is known about the frequency and distribution of myoclonus in the general population.
Design
Descriptive study with case ascertainment through a records-linkage system.
Patients and Methods
We used a medical records-linkage system to identify all subjects whose records contained
documentation of myoclonus or of diseases known to exhibit myoclonus. The records
of all potential patients were reviewed by a neurologist, and only patients with pathologic
and persistent myoclonus were included. Population denominators were derived from
census data.
Results
The average annual incidence rate of pathologic and persistent myoclonus for 1976
through 1990 was 1.3 cases per 100,000 person – years. The rate increased with advancing
age and was consistently higher in men. Symptomatic myoclonus was the most common
type, followed by epileptic and essential myoclonus; dementing diseases were the most
common cause of symptomatic myoclonus. The lifetime prevalence of myoclonus, as of
January 1, 1990, was 8.6 cases per 100,000 population, and the prevalence increased
with advancing age.
Conclusion
Although our figures are probably under-estimated, they are the first attempt, to
our knowledge, to measure myoclonus morbidity in the general population. We found
clinical features and age and sex distributions different from those previously described
in clinical series.
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Article Info
Footnotes
This study was supported in part by the Myoclonus Research Foundation and by the Rochester Epidemiology Project (National Institutes of Health grant AR30582 ).
Identification
Copyright
© 1999 Mayo Foundation for Medical Education and Research. Published by Elsevier Inc. All rights reserved.
