These two entities are often considered together because of their similar appearance. However, they have separate origins. Porencephaly is a locally destructive brain lesion resulting from either a developmental anomaly or intraparenchymal insult. There are two types of porencephaly. Type I is generally due to an antepartum intraparenchymal hemorrhage. Type II lesions are usually developmental anomalies. Various causes of parenchymal damage have been reported, such as trauma or inherited disease. Schizencephaly is a full-thickness cleft of the cerebral mantle considered to be a migrational abnormality rather than a destructive process. The etiology may include encephaloclastic disorder, cytomegalovirus or genetic disorders such as triple X syndrome.

Sonographic findings:


Fig 1, Fig 2, Fig 3

  • a fluid-filled space within normal brain parenchyma, often communicating with the lateral ventricles
  • usually unilateral
  • often progressive changes to hydranencephaly (most severe form)
  • no pressure effect on the adjacent brain
  • the defect lined by white matter (demonstrated by MRI)


Fig 4

  • unilateral or bilateral cystic lesion
  • may or may not communicate with the lateral ventricle
  •  typically bilateral clefts in the fetal brain connecting the lateral ventricles with the subarachnoid space
  • absence of the cavum septum pellucidum is commonly seen
  • MRI is very helpful in confirming the diagnosis
  •  the defect is lined by gray matter (demonstrated by MRI)

–     The main differential diagnoses include arachnoid cyst, interhemispheric cyst in the case of agenesis of the corpus callosum, and dorsal sac in holoprosencephaly.

–     Usually diagnosable after 18 weeks.

Fig 1: Porencephaly  Transthalamic view: only small part of brain tissue left (*)

Fig 2: Porencephaly  Most of the brain tissue is absent, only small part of brain tissue left (*). (arrow = thalami)

Fig 3: Porencephaly  Some part of cerebral tissue is absent (*)

Fig 4: Schizencephaly  Cleft of cerebral tissue is absent (*) resulting in cystic brain lesion

Video clips of porencephaly / schizencephaly

Porencephaly: Transthalamic view: missing large piece of brain (*)

Porencephaly: Transverse scan of the head: fluid collection (*) in the large area of missing brain tissue

Associations: Rare.

Management: In continuing pregnancies, the fetus should be delivered in a tertiary center.

Prognosis: Depends on the size and location of the lesion; very poor for extensive porencephaly, and the bilateral form of schizencephaly.

Recurrence risk: Rare, though hereditary cases have been reported.