Myoclonus epilepsy with ragged-red fibers
Jun. 10, 2021
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This article includes discussion of benign infantile seizures and benign familial and nonfamilial infantile seizures. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.
Benign familial and nonfamilial infantile seizures occur in the first year or 2 of life and universally remit without developmental sequelae. There are several distinct forms that overlap in presentation but are distinguishable by several clinical, neurophysiologic, and genetic factors that will be reviewed here.
• Benign familial infantile seizures and benign nonfamilial infantile seizures are distinct syndromes with overlapping clinical presentations.
• Family history, genetic studies, and at times seizure semiology and EEG can be used to distinguish these syndromes from each other, though these are often unreliable.
• The syndromes are characterized by seizure onset in the first year of life, remission by 2 years of life, and the absence of neurodevelopmental sequelae.
• Rarer subtypes have been described that are associated with choreoathetosis, familial hemiplegic migraine, or other distinct features.
In 1963 Fukuyama described cases of epilepsy occurring in the first 2 years of life which were characterized by focal seizures, absence of etiologic factors, and benign outcome (18). Later, Watanabe and colleagues reported on the localization and semiology of these seizures. Specifically, they described partial epilepsy of infancy with complex partial seizures and benign partial epilepsy with secondarily generalized seizures in infancy (57; 58; 56). Other groups documented prognosis (46), and presence or absence of familial occurrence (53; 54; 55).
Since the description of the original syndromes (familial and nonfamilial) and their categorization in the 1989 Classification of Epilepsies and Epileptic Syndromes of the International League Against Epilepsy (ILAE), other rarer related syndromes have emerged. These include benign familial infantile seizures with choreoathetosis (48) or paroxysmal dyskinesia (16), benign familial neonatal-infantile seizures (25; 24; 61), benign familial infantile seizures with familial hemiplegic migraine (49; 51; 36), benign infantile seizures with mild gastroenteritis (09), and benign infantile focal seizures with midline spikes and wave during sleep (17).
The terminology of these syndromes has evolved slightly over time. Vigevano and colleagues focused their attention on cases that exhibited a family history of convulsions with benign outcome during infancy and autosomal dominant inheritance, suggesting the term "benign infantile familial convulsions” (53; 54; 55). In 2001, the ILAE Task Force on Classification and Terminology stated that the term "seizure" should be used preferentially over the term "convulsion" (15), a stance that has been supported by Berg and colleagues (01). Thereafter the syndromes were referred to as “benign familial infantile seizures” and “benign nonfamilial infantile seizures” (15), which are distinct syndromes with some overlapping features (32; 07). In the 2010 report of the ILAE Commission on Classification and Terminology (01), “benign infantile epilepsy” and “benign familial infantile epilepsy” have been identified and classified among the electroclinical syndromes of infancy.
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