Wednesday, March 26, 2008

Hypoxic ischaemic brain injury

In evaluation of hypoxic ischaemic brain injury,
1. Diffusion weighted images are more sensitive than MR spectroscopy in acute setting
2. Most of the germinal matrix haemorrhage occur within 24 hours of birth
3. Cerberal cortex is more often involved in hypoxic injuries than deep grey structures in neonates and pre-term babies
4. Normal appearance on diffusion weighted images by the end of first week of hypoxic insult indicates reversal of hypoxic insults
5. Germinal matrix haemorrhage extending into ventricles is graded as IV

Answers: F, T, F, F, F

Notes: Diffusion weighted images are more sensitive than T1 and T2 weighted images, but MR spectroscopy is more sensitive than diffusion weighted images. MRS shows increased lactate in the deep gray matter, parieto-occipital region, and watershed zones as early as 2-8 hours. Germinal matrix haemorrhage is more often seen in pre-term babies born weighing less than 2000g and majority of the bleeds occur within 24 hours of birth. Deep grey structures are more often involved than cerebral cortex in both neonates and pre-term babies. Thalami, anterior vermis and dorsal brainstem are more frequently involved in pre-term babies, where as in full term neonates basal ganglia are more often involved. Diffusion-weighted images, although sensitive in diagnosing hypoxic damage, but they often underestimate the extent of the injury. Diffusion-weighted images also tend to normalise by end of the 1st week, but do not imply reversal hypoxic insult (pseuonormalization). Germinal matrix haemorrhages are graded into: Gr1 – subependymal haemorrhage without or minimal intraventiruclar bleed; gr 2 – germinal matrix and intraventricular haemorrhage without ventricular dilatation; gr 3 – gr 2 + ventricular dilatation; gr 4 – periventricular parenchymal haemorrhagic infarct

Reference: Huang BY et al. Hypoxic-Ischemic Brain Injury: Imaging Findings from Birth to Adulthood. RadioGraphics 2008;28:417-439