Primary progressive myoclonus of aging

Abstract

Myoclonus in older individuals usually occurs in the context of associated neurologic features which allow the diagnosis of the underlying disorder. We encountered 7 patients with a newly recognized myoclonus syndrome; we use the term primary progressive myoclonus of aging (PPMA) for this syndrome. Our purpose was to characterize the clinical and electrophysiological properties of this syndrome. Our database was searched for the presence of "myoclonus" in the physical examination. Medical records and laboratory data were retrospectively reviewed, including electrophysiology data. We applied our criteria for PPMA: (1) asymmetric symptomatic action myoclonus, (2) >/=65 years of age, (3) cortical myoclonus physiology, (4) no dementia, (5) no associated features of defined neurodegenerative disorders, and (6) no secondary cause found. Seven patients fulfilled criteria. Age at presentation ranged from 70 to 87 years. Mean duration from myoclonus onset to last follow-up was 2.9 years. Electrophysiology showed positive-negative back-averaged transients, consistent with cortical myoclonus. No patient demonstrated dementia. Brain imaging in all cases was unremarkable. PPMA is a unique syndrome with characteristic findings that differentiate it from dementias and defined neurodegenerative syndromes. It is important to distinguish primary PPMA from other syndromes seen in older individuals to avoid diagnostic confusion. Some cases showed a response to levetiracetam.