Adult-Onset Myoclonus in a Large Urban Inpatient Setting: A Retrospective Cohort Study

Myoclonus is a hyperkinetic movement with various attributable etiologies, semiologies, and treatment outcomes. To our knowledge, few studies investigated adult-onset myoclonus in an inpatient setting.

We retrospectively reviewed charts of adult inpatients with myoclonus at New York Presbyterian Brooklyn Methodist Hospital between 2011 and 2021. Data was analyzed with descriptive statistical methods to elucidate etiology-specific demographics and outcomes.

279 individuals, 56.63% female, were included in our study, aging at 70.61 + 15.76 years. More than 50% were not initially diagnosed with myoclonus by the admitting medical team, and more than 50% had 2 or more ascribable etiologies. Symptomatic myoclonus - mostly of toxic-metabolic or hypoxic-ischemic etiology - accounted for most cases. Hypoxic-ischemic etiologies had shorter durations prior to presentation and were also most resistant to treatment. Renal-associated myoclonus was most associated with asterixis, whereas stimulus-sensitive myoclonus was strongly associated with hypoxic-ischemic etiology. Mortality in-hospital was strongly associated with hypoxic-ischemic etiology and least associated with neurodegenerative and idiopathic etiologies. Treatment response rate diminished in patients who were tried on a second or third anti-seizure drug compared to those trialed on one.

Myoclonus remains an underdiagnosed hyperkinetic movement disorder with various ascribable etiologies of varying demographic characteristics and treatment outcomes.