Generalized periodic discharges with triphasic morphology

Generalized periodic discharges (GPDs) are electroencephalographic (EEG) waveforms that can be seen in a wide array of encephalopathies. By definition, they are repeated and generalized waveforms with relatively uniform morphology and duration, with a quantifiable interdischarge interval between consecutive waveforms, and recurrence of the waveform at nearly regular intervals (Fig. 1) [1]. There are different theories for their etiology and pathophysiology. Early work suggested that GPDs were due to widespread cortical destruction with relative sparing of white Generalized periodic discharges (GPDs) with triphasic morphology are an electroencephalographic (EEG) pattern traditionally associated with encephalopathy and coma, although they have been observed in a wide array of neurological disorders. The clinical significance of these waveforms and their relationship to seizures and prognosis has been debated, and differentiation between interictal patterns, patterns associated with seizures, and patterns representing nonconvulsive status epilepticus can at times be a challenge. The most established literature suggests that GPDs, including those with triphasic morphology, are associated with the development of electrographic seizures, but that in the absence of clinical information, distinguishing waveforms based on morphology alone may not be clinically useful. Recent work has advocated for a more proactive approach in evaluating GPDs with triphasic morphology. Further studies of nonsedating antiseizure drugs in patients with GPDs with triphasic morphology that incorporate continuous EEG monitoring will be useful in tailoring therapy to optimize long-term clinical outcomes and recovery.