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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

From: Background frequency can enhance the prognostication power of EEG patterns categories in comatose cardiac arrest survivors: a prospective, multicenter, observational cohort study

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
  1. Values are expressed as number (%)
  2. EEG, electroencephalography; ROSC, return of spontaneous circulation
  3. aA total of 13 patients dead < 72 h after ROSC were categorized as absent ocular reflexes
  4. bTwo patients dead < 48 h after ROSC were categorized as motor component ≤ 3. Similarly, 13 patients dead < 72 h were categorized as motor component ≤ 3