Table 1.
Summary of original studies on the features of raw EEG or qEEG. RAV, relative alpha variability; ADR, alpha/delta ratio; AT/D, alpha-theta/delta ratio; IIC, ictal-interictal continuum; GRDA, generalized rhythmic delta activity; mFS, modified Fisher scale; WFNS, World Federation of Neurosurgical Societies grading.
| Study type | N. of vasospasm or DCI / total N | SAH grade | EEG methods | EEG/qEEG features | |
|---|---|---|---|---|---|
| Parkes et al., 1971 | Prospective | 6/13 angiographic or clinical | All | 8-channel raw EEG | Increases in the percent time of theta and delta activity |
| Rivierez et al., 1991 | Retrospective | 104/151 angiographic | Fisher 1–3 | 8-channel raw EEG | Prognostic values of localized delta wave, delta diffuse wave, “axial bursts” |
| Labar et al., 1991 | Prospective | 8/11 clinical or radiographic | H-H 1–4 | 2-channel qEEG | Decreases in the total power |
| Vespa et al., 1997 | Prospective | 19/32 angiographic or sonographic | All | 8 electrodes, 10–20 system, qEEG | Decreases in RAV |
| Claassen et al, 2004 | Prospective | 9/34 angiographic, clinical, or radiographic | H-H 4–5 | F3–C3 and F4–C4, or Fp1–F3 and Fp2–F4, or F7–T3 and F8–T4 for the anterior circulation, P3–O1 and P4–O2, or T5–O1 and T6–O2 for the posterior circulation | Decreases in ADR, increases in the delta/total power ratio |
| Rathkrishnan et al., 2011 | Prospective | 8/12 clinical or radiographic | All H-H, mFS 3–4 | 20 electrodes, 10–20 System, qEEG. Analysis restricted to anterior quadrants | Composite alpha index (CAI) |
| Gollwitzer et al., 2015 | Prospective | 6/12 clinical or radiographic | All | 10 electrodes, 10–20 System, qEEG | Decreases in the alpha and theta powers |
| Rots et al., 2016 | Prospective | 11/21 clinical or radiographic | All | 8 electrodes, 10–20 system, qEEG | Decreases in either ADR, alpha power, alpha variability, combination of ADR and alpha variability |
| Kim, et al., 2017 | Retrospective | 53/124 clinical or radiographic | H-H 4–5, Fisher 3 | 10–20 system, qEEG | Late onset of any type of IICAs except GRDA |
| Rosenthal et al., 2018 | Prospective | 52/103 clinical or radiographic | H-H 4–5, mFS 3–4 | 10–20 System, qEEG | Worsening focal slowing, ADR, or RAV |
| Balança et al., 2018 | Retrospective | 9/15 radiographic | H-H or WFNS 4–5 | 10–20 system, qEEG | Decreases in AT/D |