Objective: To describe various forms of myoclonus in admitted patients in a 10-year period.

Background: Myoclonus consists of brief, shock-like involuntary movements. It may occur from increased (positive) or inhibition of muscle contraction (negative myoclonus)¹. Causes include normal physiological movements, epilepsy, medications, neurodegenerative diseases, and infection^2-4. Studies attempted to characterize its features and etiologies in inpatient and outpatient settings^2-5. We herein describe myoclonus characteristics in an inpatient setting of a large urban hospital over 10 years.

Method: We performed a chart review of admitted adult patients from 2010 to 2021 at New York Presbyterian Brooklyn Methodist Hospital. All ICD-10-CM codes relating to myoclonus were included. Exclusionary criteria included pediatric cases, outpatient visits, and lack of myoclonus documentation.  Collected data included age, gender, semiology, and etiology of myoclonus, diagnostics, and treatments. We provide a preliminary summary of this data.

Results: Using our search criteria, we identified 600 subjects. Of the initial 90 reviewed, 15 pediatric, 15 without myoclonus, and 12 ambulatory cases were excluded. Of 48, average age of myoclonus onset was 69 years. 60% were female, 42% White, 42% Black, 10% Hispanic/Latino, and 4% Asian. Etiologies included: 35% toxic-metabolic; 33% hypoxic/ischemic; 17% infectious; 17% neurodegenerative; 13% epileptic; 13% iatrogenic; 8% physiologic; and 7% autoimmune encephalitis. 46 had treatments targeting underlying cause; 28 also had symptomatic treatment with antiepileptics, most commonly levetiracetam. All subjects responded to treatment except 1 with Parkinson’s Disease and 3 with anoxic encephalopathy.

Conclusion: We provide a comprehensive description of admitted patients with myoclonus in a large urban setting.  Myoclonus was found in a mostly older population with equal distribution between whites and blacks. Our cohort was overwhelmingly female, differing from past studies showing higher rates of myoclonus in males⁴. Metabolic derangements and anoxia were the most common etiologies unlike in previous large cohorts in whom dementia was the common cause⁴. Only four did not improve, suggesting that treating the underlying disease and/or adding symptomatic medications alleviated myoclonus. Our large decade-spanning database and comprehensive records are strengths. Limitations include inter-assessor variability and possible selection bias.

References: 1. Caviness, J. 2019. Myoclonus. Continuum Movement Disorders, 25(4):1055-80.
2. Zutt R, Elting J, van der Hoeven J, Lange F, Tijssen M. 2017. Myoclonus subtypes in tertiary referral center. Cortical myoclonus and functional jerks are common. Clinical Neurophysiology, 128(1):253-9.
3. Bhidayasiri R, Saksornchai K, Kaewwilai L, Phanthumchinda K. 2011. A census of movement disorders at a Thai university hospital. Journal of the Neurological Sciences, 301(1-2):31-4.
4. Caviness J, Alving L, Maraganore D, Black R, Mcdonnell S, Rocca W. 1999. The incidence and prevalence of myoclonus in Olmsted County, Minnesota. Mayo Clinic Proceedings, 74(6):565-9.
5. Caviness J. 2001. Epidemiology of myoclonus. Advances in Neurology, 89:19-22.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/myoclonus-in-a-large-urban-center-10-year-experience/