The association between causes and electrophysiology in myoclonus: When and why electrophysiology?

Abstract

Objective: We aimed to identify the possible causes of myoclonus and related electrophysiological features in a cohort of young patients. Patients and Methods: We performed a retrospective analysis of all clinical and electrophysiological recordings of patients who had myoclonus and were under 60 years between 2005 and 2018. The clinical data included age at examination, gender, age at onset, and main neurological or systemic findings, underlying cause and electrophysiological features constituted surface electromyogram, long-loop reflexes, electroencephalography, and somatosensory-evoked potentials. Results: In the study period, we identified 155 patients with myoclonus. Myoclonus was most commonly related with epilepsy and movement disorders. Myoclonus with epilepsy was the leading cause between 10 and 30 years, whereas myoclonus with movement disorders was more common after 30 years. In our country, SSPE was an important cause of myoclonus under the 20 years of age. We identified cortico-subcortical subtype followed by cortical, cortical reflex, subcortical-basal ganglia, subcortical-brainstem and propriospinal subtypes, and correlated these subtypes with relevant disorders. Conclusion: The electrophysiological classification provides anatomical subtyping, which is favorable in diagnosing certain cases such as brainstem and propriospinal myoclonus. Certain characteristics such as reflex nature of myoclonus and accompanying features narrow the list of differentials and help in making the diagnosis.

Keywords

• cause
• electrophysiology
• long-loop reflex
• myoclonus