ADC pseudonormalisation

Dr Henry Knipe and A.Prof Frank Gaillard et al.

ADC pseudonormalisation is a normal phase encountered in the subacute stage of ischaemic stroke and represents an apparent return to normal healthy brain values on ADC maps which does not however represent resolution of ischemic damage.

ADC pseudonormalisation is seen typically between around 1 week following ischaemic stroke and is thought to be due to a combination of cell wall breakdown and increase of extracellular oedema (both of which result in facilitated diffusion - increased ADC values) 2. At some point these processes, combined with residual true abnormal restricted diffusion due to cellular swelling results in ADC values returning to those of normal healthy brain. 

It is important to realize that at the point that ADC values normalize DWI images (e.g. B = 1000) will continue to show increased signal due to T2-shine through. It is only later (e.g. 10-15 days) that DWI pseudonormalisation occurs, when ADC values are higher than normal, offsetting gradually waning T2 signal. 

Note: ADC pseudonormalisation should not be confused with early DWI reversal (a.k.a. diffusion lesion reversal), which is seen early in the course of ischaemic infarction, particularly in the setting of reperfusion therapy. Nor should it be confused with T2 washout seen a little later. 

Stroke and intracranial haemorrhage
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rID: 41740
Synonyms or Alternate Spellings:
  • ADC pseudonormalization

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