Effects of benzodiazepines on triphasic waves - Implications for nonconvulsive status epilepticus

Nonconvulsive. status epilepticus (NCSE) is often diagnosed based on abolit ion of rhythmic sharp waves by benzodiazepines. It is possible that sharp w aves resulting from metabolic (nonepileptic) encephalopathies may also resp ond to benzodiazepines and are potentially misdiagnosed as NCSE. The author s hypothesized that triphasic waves (TW) resulting from metabolic encephalo pathy are abolished by benzodiazepines. They retrospectively identified pat ients with TW resulting from metabolic encephalopathy who had EEG recording s before, during, and after benzodiazepine administration. Benzodiazepines were given either because of the possibility of NCSE or for a medically ind icated purpose. All patients were diagnosed definitively with a metabolic c ause of encephalopathy and not NCSE. Ten patients (mean age, 59 years) met the criteria and were reviewed. TW resolved persistently in four patients a nd intermittently in six patients. Background activity slowed in five patie nts and was attenuated in five patients. Unresponsive patients did not arou se and three of five drowsy patients became less responsive. Rhythmic sharp waves resulting from metabolic encephalopathy are abolished by benzodiazep ines, similar to NCSE, but without improvement in mental status. This sugge sts that definitive electrographic diagnosis of primary NCSE should not be based entirely on abolition of sharp waves by benzodiazepines. This also im plies that gamma -aminobutyric acid neurotransmission is important in the e xpression of TW.