Major neuropathological patterns of injury in HIE

Selective neuronal necrosis

• Neuronal necrosis selective to areas with high energy demands (selective vulnerability)
• Cerebral cortical necrosis  —  may be focal, bilateral, symmetric of diffuse. Neuronal damage is the greatest in the depth of the sulci. Pre- and postcentral gyri, calcarine cortex are often involved. Foci of necrosis in watershed zones of the main cerebral arteries results mainly from hypotension. Hippocampus is also vulnerable to damage.
• Deep gray matter  —  necrosis predominantly affects the neurons in thalamus and basal ganglia. Damage of the midbrain and brain stem nuclei may be associated
• Pontosubicular necrosis  —  selective neuronal necrosis affecting the pontine nuclei and subiculum of the hippocampus, rare pattern often coexist with intraventricular hemorrhage or periventricular leukomalacia.
• Global cerebral necrosis involving much of th cerebral cortex, brain stem and thalamus is seen in cases of severe birth asphyxia with a significant period of cariovascular arrest. Ischemic damage to spinal cord and cerebellum is frequent on these occasions although without cardio-respiratory arrest these areas may remain intact in spite of severe changes in the cerebral hemispheres.

White matter lesions

• Periventricular leukomalacia  —  common in preterm infants, see section PVL
• Cerebral white matter gliosis  —  the same period in risk as PVL (28 – 32 weeks), results from preferential injury to oligodendrocyte precursors. Severe damage results in marked decrease in the white matter volume, the corpus callosum is thin.

Combined grey and white matter lesions

• Parasagittal cerebral injury
• Bilateral necrosis of the cerebral cortex and subjacent white matter in the watershed areas between the three major cerebral arteries maximal over the parasagittal region particularly in the posterior parietal location
• classic pattern seen in full term infants
• Focal and multifocal infarcts
• Infarction with necrosis of grey and white matter in the region of single cerebral artery

Late stages of HIE in survivors

• Ulegyria  —  narrow and distorted cerebral gyri, often observed in the parasagittal areas. Sclerotic gyri contain few or no neurons being replaced by glial cells.
• Multifocal cystic encephalopathy  —  sponge-like brain with large septated cavities throught the cortex and white matter of both hemisheres. There is usually relative sparing of temporal lobe, basal ganglia and brain stem. Develops as the result of an hypoxic-ischemic insult near end of gestation or in the early postnatal period. Also occurs in herpes viral infection etc.
• Status mramoratus  —  marbled appearnace of striatum and/or thalamus, the appearance is caused by neuronal loss, astrogliosis and escessive myelination. This lesion develops up to the postnatal age of 6 – 9 months and is associated with complicated labor or acute febrile ilness during the first year of life.

Unifocal pseudocyst

• Cystic periventricular leukomalacia
• White matter hypoplasia  —  overall reduction in cerebral white matter volume, hydrocephalus e vacuo and thinning of corpus callosum
• Porencephaly  —  a pseudocyst which develops as a result of an ischemic brain injury in utero probably dating to the third trimestr, see Atlas of fetal pathology
• Hydranencephaly/basket brain  —  severe hypoxic-ischemic damage occuring toward the end of second trimestr, see Atlas of fetal pathology