Porencephaly refers to –
Foetal alcohal syndrome
Dandy-walker-syndrome
Vascular lesion due to degenerative vessel disease and head injury
Neural tube defects
Porencephaly Refers to the presence of cysts or cavities within the brain, that may results from

Developniental defects (True porencephalic cysts).
Acquired lesions of infarction of tissues.        (i.e. Vascular lesions) - AV malformation or infarcts or (Pseudo-porencephalic cysts).

Defects of NeuronalMigration : malformations of cortical development
Lissencephaly        -          Also called agyria
Characterized by absence of cerebral convolutions and poorly formed sylvian fissure giving the appearance of 3-4 months fetal brain.
Schizencephaly       -        Presence of unilateral or bilateral clefts within the cerebral hemisphere due to an Abnormality of morphogenesis
Porencephaly        -          Presence of cysts cavities within the brain that result from developmental defects or acquired lesions including infarction of tissue.
Holoprosencephaly   -     Developmental disorder of brain that results from defective cleavage of prosencephalon.