1. The causes of OS are symptomatic or organic; the causes of EME can be genetic, metabolic, or entirely unknown. OS causes tonic spasms and partial seizures. EME causes myoclonic and partial seizures. The EEG of OS contains periodic S-B and is irrespective of waking and sleeping, while EME may have S-B only during sleep. OS commonly transitions to West syndrome. EME transition to West syndrome is transient, if there is any transition at all. The EEG course of S-B in OS is that they turn into hypsarrhythmia in 3–6 months. The EME S-B course is long lasting.4,5 However, the distinction between these two conditions may be difficult because brief spasms are difficult to distinguish from myoclonus. The distinction between S-B and hypsarrhythmia with extreme fragmentation in sleep also is difficult in many cases because in OS, the S-B evolves into the more continuous asynchronous spike- and slow-wave activity of hypsarrhythmia.3
Source: Epileptic Encephalopathy, Atlas of Pediatric EEG
Citation: Laoprasert P. Atlas of Pediatric EEG; 2011 Available at: Accessed: October 29, 2017
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