Myoclonus and startle syndromes

Abstract

The term “myoclonus” is used to identify brief and jerky involuntary movements, originating from brief active contractions of muscles (positive myoclonus) or brief interruptions of ongoing electromyographic activities (negative myoclonus). Myoclonic movements can have variable clinical manifestations, which make it difficult for practicing neurologists to develop an organized framework for the diagnosis and treatment of the underlying disorder. This chapter is structured as if physicians encounter patients who primarily present with myoclonus. A step-by-step approach is described starting from the phenomenology identification, followed by a classification, a diagnostic approach, examples of selected myoclonic syndromes, investigations, and concludes with a concise review of therapeutic options for myoclonus. Video clips are provided to illustrate salient clinical features associated with common myoclonic disorders. Tables are included as a summary of each section, which emphasize important useful clinical points for physicians. A recommended reading list is intended for readers who would like to expand their knowledge on certain topics.