14-and-6 Hz positive bursts in childhood encephalopathies.

14-and-6 Hz positive bursts, a benign epileptiform variant, have also been described in comatose children with liver disease, chiefly Reyes syndrome. To determine the incidence of this pattern in children in stupor or coma, 154 portable EEGs in 111 children with mental status changes were reviewed. Seven children showed 14-and-6 Hz bursts in the setting of moderate to marked background slowing. They were similar to positive bursts seen in normals in location, duration, morphology, frequency and repetition rate. They differed in being readily activated by stimulation. The etiology was toxic/metabolic in 4 cases, primary cerebral insult in 2 cases and a combination of the two in 1 case. Amongst an age-matched control population, 5 of 75 showed 14-and-6 Hz positive bursts in stage I or II sleep. There were no statistically significant differences in incidence rates between the 2 groups. 14-and-6 Hz positive bursts may occur in diverse encephalopathies of childhood, not just Reyes syndrome. The similar incidence rate, morphology and topography to normals suggest that the presence of these wave forms in encephalopathies represents persistence of a normal EEG feature rather than an expression of some underlying pathophysiological process.