Burst Patterns Occurring during Drowsiness in Clinical EEGs

ABSTRACT.

There is an extensive range of EEG patterns associated with drowsiness. The occurrence of burst patterns with a sharp configuration or containing sharp transients was evaluated in 700 consecutive clinical EEGs of adults and children. All recordings included 16 channels of EEG and two channels of eye movements. Recordings included mostly bipolar but also referential montages. Patterns were classified by consensus and regarded as normal variants or of uncertain significance. The main reasons for referral were epilepsy or psychiatric disorders. One or more of 16 different patterns were found in 39% of all subjects. Vertex sharp waves were the most common (n = 178) and were initially asymmetrical in 17 cases. Hypnagogic paroxysmal spike-wave bursts were seen in 21/165 children. Sharp transients were also prominent in generalized sharp bursts (n = 21), frontocentral sharp bursts (n = 3), temporal or vertex sharp waves with alpha (n = 6), and beta bursts (n = 11). Some drowsiness patterns containing spikes included benign sporadic sleep spikes (n = 13), 6/sec spike and wave (n = 2), and 14 and 6/sec positive spikes (n = 10). Arch-shaped series of waves included the midline theta rhythm (n = 19), rhythmical temporal discharge (n = 3), and wicket spikes (n = 1). Subclinical rhythmical epileptiform discharges of adults (SREDA) were found in two subjects. Burst patterns during drowsiness occur sufficiently often in routine clinical EEG recordings to warrant their careful analysis.

KEY WORDS.:

• Burst patterns
• clinical recordings
• drowsiness
• EEG.