Isolated transient myoclonus in the elderly: an under-recognized condition?

ABSTRACT

BACKGROUND: Cases of transient myoclonus without other neurological manifestations in the elderly have very rarely been reported. OBJECTIVE: To report clinical features of elderly people with isolated transient myoclonus. METHODS: Clinical and laboratory features of 11 consecutive patients with isolated transient myoclonus (six men and five women; mean age, 75 years) were reviewed. Transient myoclonus was defined as an acute onset of tremulous myoclonus with/without asterixis in adults without other neurological symptoms. RESULTS: Preceding infections were recorded in five patients (pneumonia, two; upper respiratory tract infection, two; and septic arthritis of the shoulder, one). Myoclonus predominantly affected the head and/or neck (n=10) and upper extremities (n=11), compared with the trunk (n=2) and lower extremities (n=6). Asterixis was observed in six patients. Laboratory testing, neuroimaging, and electroencephalograms revealed no specific abnormalities. With or without treatment using benzodiazepines, myoclonus in all patients resolved completely within 1-4 days, although five had recurrence 2-19 months after their first episodes. Among these five patients, the accompanying asterixis patterns (presence or not) in four were different in the first and subsequent episodes. CONCLUSIONS: Isolated transient myoclonus with or without asterixis may be more common than generally believed, and it could be a clinical entity or disease spectrum. Transient myoclonus is a benign condition in the elderly, but can be under-reported or misdiagnosed. Therefore, it is important to recognize that the elderly may have this syndrome.