Table 2.

The current three-tired ILAE classification system of FCD [5]

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)	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)	Cortical lamination abnormalities adjacent to any other lesion acquired during early life, e.g., trauma, ischemic injury, encephalitis (FCD type IIId)

FCD type III (NOS) : if clinically/radiologically suspected principal lesion is not available for microscopic inspection. Please note that the rare association between FCD type IIa and IIb with hippocampal sclerosis, tumors, or vascular malformations should not be classified as FCD type III variant. ILAE : international league against epilepsy, FCD : focal cortical dysplasia, NOS : not otherwise specified