Table 2.
EEG features classified by background abnormalities, periodic and rhythmic activity, sharp waves, seizures, and status epilepticus. Note that the number of EEG findings may be higher than the number of patients as a given patient may have more than one finding.
| EEG Abnormality | Number of patients | Percentage of total patients (n = 617) | Percentage of abnormal EEGs in each category |
|---|---|---|---|
| Background Abnormalities (n = 659) | |||
| Diffuse slowing | 423 | 68.6 % | 64.2 % |
| Focal slowing | 105 | 17.0 % | 16.0 % |
| Slowing of PDR | 14 | 2.3 % | 2.1 % |
| Absent PDR | 63 | 10.2 % | 9.6 % |
| Attenuation | 8 | 1.3 % | 1.2 % |
| Discontinuous EEG | 13 | 2.1 % | 2.0 % |
| Asymmetry | 13 | 2.1 % | 2.0 % |
| Decreased reactivity | 20 | 3.2 % | 3.0 % |
| Periodic and Rhythmic patterns (n = 138) | |||
| Generalized PD | 35 | 5.7 % | 25.4 % |
| Lateralized/ multi-focal PD | 24 | 3.9 % | 17.4 % |
| Generalized PD with triphasic morphology. | 18 | 2.9 % | 13.0 % |
| SIRPIDS | 7 | 1.1 % | 5.1 % |
| Unclassified PD | 4 | 0.6 % | 2.9 % |
| Generalized RD | 32 | 5.2 % | 23.2 % |
| Lateralized/ multifocal RD | 16 | 2.6 % | 11.6 % |
| Unclassified RD | 2 | 0.3 % | 1.4 % |
| Epileptiform changes (n = 114) | |||
| Focal ED | 35 | 5.7 % | 30.7 % |
| Generalized ED | 27 | 4.4 % | 23.7 % |
| Multifocal ED | 13 | 2.1 % | 11.4 % |
| Unspecified ED | 5 | 0.8 % | 4.4 % |
| Seizures | 12 | 1.9 % | 10.5 % |
| Status epilepticus | 22 | 3.6 % | 19.2 % |
[PDR- posterior dominant rhythm, PD- periodic discharges, RD- rhythmic discharges, ED- epileptiform discharges].