Patterns of neonatal hypoxic–ischemic brain injury

Macrocephalic infant, with absent cerebral hemispheres, in keeping with hydranencephaly.
Note the thalami, cerebellum and brain stem are normal.

A moderate size cyst in the right parieto-occipito-temporal junction measuring 5 x 4 x 6 cm has a small communication with the occipital horn of the right lateral ventricle. It follows CSF signal in all sequences, with no diffusion restriction or enhancement. It is not lined by a grey matter and is associated with a small amount of adjacent FLAIR hyperintensity. It exerts mild mass effect on the adjacent parenchyma with slight remodelling of the overlying calvarium noted.  

Grade I germinal matrix haemorrhage

Sagittal non-contrast 

Left sided intraventricular haemorrhage located at the caudothalamic groove, and extending into the occipital horn, without ventricular dilatation (grade II).

Subependymal hemorrhage extends to both lateral ventricles with formation of CSF/Blood level at occipital horns. Associated periventricular leukomalacia (PVL) more on the left side and moderate dilatation of all ventricular system are noted.
Diagnosis: Germinal matrix hemorrhage Grade III with communicating hypdrocephalus and periventricular leukomalacia

Grading of germinal matrix haemorrhage has taken several forms over the years. The most commonly used system is the sonographic grading system proposed by Burstein, Papile et al.

Classification

• grade I
  • restricted to subependymal region/germinal matrix which is seen in the caudothalamic groove
  • overall good prognosis 
• grade II
  • extension into normal sized ventricles and typically filling less than 50% of the volume of the ventricle
  • overall good prognosis 
• grade III
  • extension into dilated ventricles
  • ~20% mortality
• grade IV
  • grade III with parenchymal haemorrhage
  • 90% mortality 

Hypoxic-ischemic injury to gray matter (thalami and lentiform nuclei) demonstrates characteristic T1 hyper intensity and T2 hypo intensity

MRI

MRI is the most sensitive and specific imaging technique for examining infants with suspected hypoxic-ischemic brain injury. Conventional sequences can help exclude other causes of encephalopathy such as haemorrhage, cerebral infarction, neoplasms, or congenital malformations.
A number of patterns of injury are encountered (see patterns of neonatal hypoxic–ischaemic brain injury) with the following expected signal intensity changes:

• T1
  • grey matter: hyperintense
  • white matter: hypointense
• T2
  • grey matter: variable depending on the time of imaging and presence of haemorrhage
  • white matter: hyperintense
• DWI/ADC
  • diffusion restriction first week
  • ADC pseudonormalisation occurs at the end of the first week

Reference