Paediatric Imaging

Cystic encephalomalacia

an irregular cystic area in the brain parenchyma which is characterised by the presence of multiple glial septations surrounded by astrocytic proliferation. This may be caused by infarction, infection or trauma. They may be focal or diffuse and their distribution will depend on the cause and severity of the injury and the post conceptual age of the patient. Encephalomalacia caused by infarction may be in the distribution of a major cerebral artery. If the injury is caused by mild to moderate hypotension the areas of encephalomalacia may lie in the boundary zones between the major cerebral arteries, whereas severe hypotension may result in widespread cystic encephalomalacia with sparing of the deep periventricular white matter only. The presence of reactive astrocytosis and glial septations distinguishes cystic encephalomalacia from an area of porencephaly and indicates that the injury occurred late in gestation, in the perinatal period, or after birth.

On imaging the cavities are best seen on MRI (Fig.1) where the amount on septation is better appreciated than on CT. The presence of astrocytosis causes low signal on T1- and high signal on T2-weighted sequences and may only be evident on MRI. These irregular septated cavities are also well seen on ultrasound. Calcification may be present and is best appreciated on CT.

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Fig.1

MRI of a child who had severe encephalitis. The scan demonstrates severe cystic encephalomalacia.
Cystic encephalomalacia, Fig.1