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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

  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
  1. DWI, diffusion weighted imaging; T1, T1 weighted sequence; T2, T2 weighted sequence. Adapted from [66,67].