Diagnostic approach and treatment options for myoclonus

Myoclonus is a hyperkinetic movement disorder characterized by sudden, brief involuntary movements that are shock-like and/or jerky. Positive myoclonus is generated by abrupt muscular contractions, which occur synchronously in the affected body part, while negative myoclonus, also referred to as asterixis, results from a brief interruption or silencing of muscle activity leading to a sudden movement due to loss of muscle tone. Myoclonus manifests across a highly heterogeneous group of neurologic and systemic disorders. Due to its varied clinical presentations and multiple etiologies, diagnosing and managing myoclonus in clinical practice remains challenging. The authors retrieved publications that focus on myoclonus as a movement disorder from various electronic databases. The included articles contained discussion on clinical or electrophysiologic findings of myoclonus and its classification. This review outlines a practical diagnostic guide for clinicians that includes consideration of the newly developed 2025 International Association of Parkinsonism and Related Disorders (IAPRD) Axis classification system. This consensus-based framework organizes the diagnostic process into clinical features (Axis 1 A), clinical neurophysiology (Axis 1B), and etiology (Axis II). By systematically evaluating historical data, physical examination findings, and ancillary tests, clinicians can successfully arrive at a clinical syndrome which helps guide investigations to determine the underlying etiology. Neurophysiological assessments are important in determining the specific neuroanatomic generator (cortical, cortical-subcortical, subcortical, brainstem, spinal, propriospinal, peripheral). Categorizing myoclonus by its physiological subtype ultimately dictates the most effective symptomatic treatments. While resource-limited settings may necessitate a primarily clinical approach, employing this step-by-step localization aids in avoiding unnecessary testing and ensures optimal patient care.