Table 3 Electroencephalography findings and clinical examinations of the study patients in the early and late electroencephalography groups according to neurologic outcome at 1 month
EEG findings and clinical neurological examinations | Patients with EEG < 72 h (N = 353) | Patients with EEG of 72 h to 7 days (N = 136) | ||||
|---|---|---|---|---|---|---|
Good neurologic outcome (n = 110) | Poor neurologic outcome (n = 243) | P value | Good neurologic outcome (n = 38) | Poor neurologic outcome (n = 98) | P value | |
EEG background frequency | < 0.001 | < 0.001 | ||||
Dominant alpha waves | 69 (62.7%) | 15 (6.2%) | 14 (36.8%) | 8 (8.2%) | ||
Dominant theta waves | 36 (32.7%) | 51 (21.0%) | 20 (52.6%) | 20 (20.4%) | ||
Dominant delta waves | 5 (4.5%) | 62 (25.5%) | 4 (10.5%) | 19 (19.4%) | ||
Undetermined | 0 (0%) | 115 (47.3%) | 0 (0%) | 51 (52.0%) | ||
Categorization | < 0.001 | < 0.001 | ||||
Highly malignant pattern | 0 (0%) | 144 (59.3%) | 0 (0%) | 55 (56.1%) | ||
Malignant pattern | 24 (21.8%) | 64 (26.3%) | 10 (26.3%) | 26 (26.5%) | ||
Benign | 86 (78.2%) | 35 (14.4%) | 28 (73.7%) | 17 (17.3%) | ||
Highly malignant pattern | 0 (0%) | 144 (59.3%) | < 0.001 | 0 (0%) | 55 (56.1%) | < 0.001 |
Suppressed background without discharges | 0 (0%) | 106 (43.6%) | < 0.001 | 0 (0%) | 48 (49.0%) | < 0.001 |
Suppressed background with continuous periodic discharges | 0 (0%) | 8 (3.3%) | 0.061 | 0 (0%) | 2 (2.0%) | > 0.999 |
Burst-suppression | 0 (0%) | 30 (12.3%) | < 0.001 | 0 (0%) | 5 (5.1%) | 0.322 |
Malignant rhythmic or periodic features | 6 (5.5%) | 38 (15.6%) | 0.007 | 7 (18.4%) | 16 (16.3%) | 0.770 |
Periodic discharges (≥ 50%) | 2 (1.8%) | 17 (7.0%) | 0.046 | 3 (7.9%) | 8 (8.2%) | > 0.999 |
Rhythmic spike-and-wave (≥ 50%) | 3 (2.7%) | 18 (7.4%) | 0.085 | 1 (2.6%) | 6 (6.1%) | 0.673 |
Unequivocal seizures or status epilepticus | 3 (2.7%) | 34 (14.0%) | 0.001 | 6 (15.8%) | 10 (10.2%) | 0.382 |
Malignant background | 18 (16.4%) | 46 (18.9%) | 0.562 | 3 (7.9%) | 18 (18.4%) | 0.129 |
Discontinuous (> 10% suppression) | 2 (1.8%) | 8 (3.3%) | 0.730 | 1 (2.6%) | 5 (5.1%) | > 0.999 |
Low voltage (< 20 μV) | 14 (12.7%) | 33 (13.6%) | 0.827 | 2 (5.3%) | 12 (12.2%) | 0.349 |
Reversed anteroposterior gradient | 2 (1.8%) | 9 (3.7%) | 0.513 | 0 (0%) | 3 (3.1%) | 0.560 |
Absent pupillary reflex at ≥ 72 h after ROSCa | 5 (4.7%), n = 107 | 158 (67.8%), n = 233 | < 0.001 | 2 (5.3%), n = 38 | 62 (63.9%), n = 97 | < 0.001 |
Absent corneal reflex at ≥ 72 h after ROSCa | 16 (20.3%), n = 79 | 170 (85.9%), n = 198 | < 0.001 | 5 (16.1%), n = 31 | 59 (79.7%), n = 74 | < 0.001 |
Motor component of the Glasgow Coma Scoreb | ||||||
≤ 3 at 48 h after ROSC | 83 (77.6%), n = 107 | 238 (98.8%), n = 241 | < 0.001 | 28 (77.8%), n = 36 | 96 (99.0%), n = 97 | < 0.001 |
≤ 3 at 72 h after ROSC | 55 (50.5%), n = 109 | 233 (97.9%), n = 238 | < 0.001 | 16 (45.7%), n = 35 | 96 (98.0%), n = 98 | < 0.001 |