Objective:

In this report, we aimed to investigate clinical and electrophysiological features of patients with late-onset myoclonus.

Background: Myoclonus is characterized by sudden, brief and irregular jerks and may develop secondary to various genetic, neurodegenerative or systemic causes. New-onset myoclonus in the elderly is mainly related to dementia or systemic diseases.

Methods: We retrospectively assessed the medical records of patients who were referred to the electromyography laboratory. From these records, we included all patients who had onset after the age of 60 years and myoclonus confirmed by polymyography. Demographic and clinical features were retrieved from the medical records. In all patients, surface electromyography during rest, arms outstretched, and goal-directed movement, BR, ASR, SSS, and LLR were done.

Results: There were 67 patients (31 male, 46.2%) who fulfilled the inclusion criteria. Mean age was 69.5 ± 7.7 years. Types of myoclonus were spinal segmental myoclonus (n=1), orthostatic myoclonus (n=7), polyminimyoclonus (n=12), multifocal cortical myoclonus (n=13) and probable cortico-subcortical myoclonus involving upper extremities (n=34). The latter three displayed reflex sensitivity. Segmental spinal myoclonus was associated with paraneoplastic disorder. Orthostatic myoclonus was almost always associated with a neurodegenerative disorder (dementia, PSP, CBD and PD). Four patients were diagnosed with probable CJD. Seven patients did not have specific diagnoses. BR was abnormal in five patients. Startle reflexes showed abnormality related to coexistent neurodegenerative disorder, not type of myoclonus.

Conclusions: Myoclonus in our cohort was mostly associated with parkinsonism and dementia. The reason of low frequency of systemic disorder was less referral from other departments. Although myoclonus was disabling for patients with orthostatic myoclonus and segmental spinal myoclonus, it was barely visible in other patients. Some patients were not classified into a specific parkinsonism syndrome, however, they had some degree of parkinsonism hindering the diagnosis of primary myoclonus of aging.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/myoclonus-in-the-elderly-retrospective-analysis-of-clinical-and-electrophysiological-characteristics-of-patients-referred-to-an-electrophysiology-laboratory/