How is nonconvulsive status epilepticus (NCSE) differentiated from nonepileptic encephalopathy as the cause of EEG triphasic waves?

Updated: Sep 24, 2018
  • Author: Kalyani Korabathina, MD; Chief Editor: Tarakad S Ramachandran, MBBS, MBA, MPH, FAAN, FACP, FAHA, FRCP, FRCPC, FRS, LRCP, MRCP, MRCS  more...
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Often, TWs are interpreted as generalized periodic patterns, slow spike-wave complexes, or rhythmic sharp waves. This is significant because such patterns are usually associated with nonconvulsive status epilepticus (NCSE). However, some studies have also suggested an association with nonepileptic encephalopathies (ie, anoxic, toxic, metabolic). One study reported the incidence of NCSE in patients with anoxic brain injury to be as high as 8%. [5]

This raises the possibility of overinterpretation of some EEG patterns as NCSE. This notion of variable interpretation of generalized periodic epileptiform discharges was further examined in one study that compared general neurologist and electroencephalographer interpretations of an EEG sample depicting a generalized periodic pattern. Indeed, variability exists in the interpretation of generalized periodic epileptiform discharges in that more than 50% of general neurologists did not consider the possibility of NCSE. [6] This is important because NCSE is treatable.

A limited number of studies have attempted to differentiate between patterns of nonepileptic encephalopathy from those of NCSE by considering the morphology of the waveforms and their response to external stimulation. [7] In addition, the clinical response to benzodiazepines should also be part of diagnostic evaluation. [8]

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