An autopsy case with various cerebral malformations was studied and discussed on the pathogenesis. The patient was a 17-year-old female who developed tonic seizures around the age of 1 month and was treated under a diagnosis of infantile spasms. A CT scanning revealed agenesis of corpus callosum, subtentorial arachnoid cyst and brain atrophy. Neuropathologically multiple malformations were observed in the brain, polymicrogyria, pachygyria, cerebral gray matter heterotopia, partial agenesis of corpus callosum, hypoplasia of cerebellar vermis and arachnoid cyst. The most remarkable finding was chronic inflammation represented by infiltration of lymphocytes and foamy macrophages, fibrosis and vascular hyalinization in the arachnoid membrane as well as in the choroid plexus of the third ventricle. Proliferation of astrocytes with intracytoplasmic eosinophilic inclusions was also found in the areas of polymicrogyria and heterotopia. The infratentorial cyst was walled by scarring cerebellar tissue with a focal inflammation which was probably caused by an encephaloclastic process. The diversity in these cerebral malformations suggests that etiology might be polyphasic in time and infectious in nature during the intrauterine period of cerebral development.