Luis E Bello-Espinosa MD (Dr. Bello-Espinosa of University of Calgary and Alberta Children's Hospital has no relevant financial relationships to disclose.)
Harvey B Sarnat MD FRCPC MS, editor. (Dr. Sarnat of the University of Calgary has no relevant financial relationships to disclose.)
Originally released January 19, 1998; last updated June 22, 2016; expires June 22, 2019

This article includes discussion of polymicrogyria, microgyria, micropolygyria, status verrucous deformans, layered polymicrogyria, unlayered polymicrogyria. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.


Polymicrogyria is a complex malformation of cortical development due to disorder of neuronal organization, in which the process of normal cerebral cortical development is disturbed either early in the stage of cortical organization or late in the stage of neuronal migration. The end result is an excessive number of fused small gyri separated by shallow sulci and abnormal lamination.

Key points


• Polymicrogyria is a cerebral malformation of cortical development with excessive folding of small, fused gyri with abnormal cortical lamination.


• The underlying etiologies are variable, including genetic disorders and vascular insults, resulting in a wide variety of neurologic signs and symptoms.


• High-resolution magnetic resonance imaging is the most reliable imaging modality for diagnosis and evaluating the extent of disease.


• Surgical resection of epileptogenic foci may provide good seizure control, with better developmental outcome in children.

Historical note and terminology

Originally coined in the early 1900s by Bielschowsky (Pascual-Castroviejo et al 2001), the term, “polymicrogyria” was largely replaced by the term “microgyria” by the middle of the century. Contemporary preference has seen a resurgence of the term “polymicrogyria,” which more accurately describes the findings in this disorder (Pascual Castroviejo et al 2003).

Classification: Several types with various manifestations and etiologies have been noted. Under the current classification of malformations of cortical development, the following types of polymicrogyria are noted (Barkovich et al 2005; Barkovich 2013).


(1) Bilateral frontal polymicrogyria (BFP)
(2) Bilateral frontoparietal polymicrogyria (BFPP)
(3) Bilateral perisylvian polymicrogyria (BPP)
(4) Bilateral parasagittal parieto-occipital polymicrogyria (BPPOP)
(5) Bilateral generalized polymicrogyria (BGP)
(6) Unilateral perisylvian polymicrogyria (UPP) (Barkovich et al 2005)

Outdated names used for polymicrogyria include microgyria, micropolygyria, and status verrucosus deformis (Crome 1952).

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