Table 3 Chronological magnetic resonance imaging findings in anoxic/hypoxic encephalopathy
From: Clinical review: Prognostic value of magnetic resonance imaging in acute brain injury and coma
| Â | Acute phase (<24 hours) | Early subacute phase (24 hours to day 13) | Late subacute phase (days 14 to 20) | Chronic phase (>21 days) |
|---|---|---|---|---|
Characteristics | Brain swelling | Brain swelling | Absence of brain swelling | Diffuse atrophy and dilatation of the ventricles |
DWI | Hypersignals in the cortex, in the thalamus and in the basal ganglia | Hypersignals in the cortex, in the thalamus and in the basal ganglia | Progressive disappearance of hypersignals found previously | Normal |
T2 | Hypersignals in the cortex, in the thalamus and in the basal ganglia | Hypersignals in the cortex, in the thalamus and in the basal ganglia. Possible subcortical hyposignals | Hypersignals of the cortex, the thalamus, the basal ganglia and the pons | Normal or possible hypersignals of the cortex, the thalamus, the basal ganglia and the pons |
T1 | No abnormalities | No abnormalities | Possible spontaneous subcortical and basal ganglia hypersignals | Can be normal |
T1 with gadolinium enhancement | No abnormalities | Possible subcortical enhancement suggestive of cortical laminar necrosis | Possible subcortical enhancement suggestive of cortical laminar necrosis | No abnormalities |
Comments | DWI seems more sensitive to mild hypoxic/anoxic injury in the first hours, and the hypersignal in cerebral cortex seems more precocious than in the basal ganglia | Hypersignals on both DWI and T2 become more intense, particularly in the thalamus and the basal ganglia | In some cases, appearance of diffuse white matter, abnormalities of delayed anoxic leukoencephalopathy on both DWI and T2 | In some cases, hypersignals of the cortex and hyposignals in the subcortical zone on both T2 and T1, suggestive of cortical laminar necrosis |