Table 2 Electroencephalography patterns and findings of the study patients according to electroencephalography timing
EEG findings | Total (N = 489) | Patients with EEG < 72 h (N = 353) | Patients with EEG of 72 h to 7 days (N = 136) | P value |
|---|---|---|---|---|
EEG background frequency | 0.220 | |||
Predominant alpha waves | 106 (21.7%) | 84 (23.8%) | 22 (16.2%) | |
Predominant theta waves | 127 (26.0%) | 87 (24.6%) | 40 (29.4%) | |
Predominant delta waves | 90 (18.4%) | 67 (19.0%) | 23 (16.9%) | |
Undetermined | 166 (33.9%) | 115 (32.6%) | 51 (37.5%) | |
Categorization | 0.934 | |||
Highly malignant pattern | 199 (40.7%) | 144 (40.8%) | 55 (40.4%) | |
Malignant pattern | 124 (25.4%) | 88 (24.9%) | 36 (26.5%) | |
Benign | 166 (33.9%) | 121 (34.3%) | 45 (33.1%) | |
Highly malignant pattern | ||||
Suppressed background without discharges | 154 (31.5%) | 106 (30.0%) | 48 (35.3%) | 0.261 |
Suppressed background with continuous periodic discharges | 10 (2.0%) | 8 (2.3%) | 2 (1.5%) | 0.733 |
Burst-suppression | 35 (7.2%) | 30 (8.5%) | 5 (3.7%) | 0.064 |
Malignant rhythmic or periodic features | 67 (13.7%) | 44 (12.5%) | 23 (16.9%) | 0.2 |
Periodic discharges (≥ 50%) | 30 (6.1%) | 19 (5.4%) | 11 (8.1%) | 0.264 |
Rhythmic spike-and-wave (≥ 50%) | 28 (5.7%) | 21 (5.9%) | 7 (5.1%) | 0.732 |
Unequivocal seizures or status epilepticus | 53 (10.8%) | 37 (10.5%) | 16 (11.8%) | 0.683 |
Malignant background | 85 (17.4%) | 64 (18.1%) | 21 (15.4%) | 0.527 |
Discontinuous (> 10% suppression) | 16 (3.3%) | 10 (2.8%) | 6 (4.4%) | 0.399 |
Low voltage (< 20 μV) | 61 (12.5%) | 47 (13.3%) | 14 (10.3%) | 0.365 |
Reversed anteroposterior gradient | 14 (2.9%) | 11 (3.1%) | 3 (2.2%) | 0.766 |