Classic SDH stages in CT and MRI (at 1.5T)a
| Characteristics | Stage | ||||
|---|---|---|---|---|---|
| Hyperacute | Acute | Early Subacute | Late Subacute | Chronic | |
| Assumed time rangeb | Min: 0 hr | Min: 1 day | Min: 2 days | Min: 1 wk | Min: 2 wk |
| Max: 24 hr | Max: 3 days | Max: 2 wk | Max: 3 wk | ||
| NECTc | ↓/↔ | ↑ | ↑ | ↔ | ↓ |
| MRIc (T1) | ↔ | ↔ | ↑ | ↑ | ↓ |
| MRIc (T2) | ↑ | ↓ | ↔/↑ | ↑ | ↑ |
| Hb state | Oxy-Hb | Desoxy-Hb | Met-Hb | Met-Hb | Ferritin/hemosiderin |
| Hb localization | Intracellular | Intracellular | Intracellular | Extracellular | Extracellular |
| Fe oxidation state | Fe2+ | Fe2+ | Fe3+ | Fe3+ | Fe3+ |
| Pathophysiology | Unclotted blood | Clotted blood, clot retraction | Max clot retraction, erythrocytes predominantly (still) intact, oxidative denaturation of the desoxy-Hb into met-Hb | Lysis of erythrocytes, thereby increase of extracellular met-Hb, start of disintegration to heme and globin, Fe3+ is stored within the macromolecule ferritin and the phagocytic product hemosiderin, respectively | In contrast to intraparenchymal hematomas, removal of ferritin and hemosiderin within the extra-axial space is accelerated due to the missing blood-brain barrier (therefore ↑ in T2) |
Note:—NECT indicates nonenhanced CT; Hb, hemoglobin; ↑, hyperdense/hyperintense; ↓, hypodense/hypointense; ↔, isodense/isointense; Min, minimum; Max, maximum; Desoxy-Hb, Desoxy-Hemoglobin; Oxy-Hb, Oxy-Hemoglobin; Met-Hb, Met-Hemoglobin.
↵a According to Hedlund,22 Vezina,28 Lee et al,61 Duhem et al,62 Tung,63 Cramer et al,64 Bradley,65 and Bergström et al.66
↵b Due to insufficient data base, the time intervals stated do not represent absolute borders—that is, the ranges may be exceeded or undercut in single cases.
↵c Density/signal intensity compared with cortical brain tissue.