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. Author manuscript; available in PMC: 2017 Jan 23.
Published in final edited form as: Neurosurg Rev. 2014 Feb 5;37(3):389–405. doi: 10.1007/s10143-014-0527-9

Table 2.

Three-tiered ILAE classification system of FCD distinguishes isolated forms (FCD types I and II) from those associated with another principal lesion (FCD type III)

FCD type I (isolated) Focal cortical dysplasia with
abnormal radial cortical
lamination (FCD type Ia)		 Focal cortical dysplasia with
abnormal tangential cortical
lamination (FCD type Ib)		 Focal cortical dysplasia with
abnormal radial and tangential
cortical lamination (FCD type Ic)
FCD type II (isolated) Focal cortical dysplasia
with dysmorphic
neurons (FCD type IIa)		 Focal cortical dysplasia with
dysmorphic neurons and
balloon cells (FCD type IIb)
FCD type III (associated
with principal lesion)		 FCD type III (associated
with principal lesion)		 Cortical lamination abnormalities
in the temporal lobe associated
with hippocampal sclerosis
(FCD type IIIa)		 Cortical lamination
abnormalities adjacent
to a glial or glioneuronal
tumor (FCD type IIIb)		 Cortical lamination
abnormalities adjacent to
vascular malformation
(FCD type IIIc)

FCD type III (not otherwise specified): if clinically/radiologically suspected principal lesion is not available for microscopic inspection. Please note that the rare association between FCD types IIa and IIb with hippocampal sclerosis, tumors, or vascular malformations should not be classified as FCD type III variant. Reprinted with permission from Blümcke et al. [19]