Blumcke classification of focal cortical dysplasia

Blumcke et al. proposed the widely adopted International League Against Epilepsy (ILAE) consensus classification system for focal cortical dysplasia in 2011 ², which shares many features with the previously described classification systems by Palmini (2004) and Barkovich (2005). 

In 2022, an updated proposed consensus classification of focal cortical dysplasia, which builds upon the existing 2011 classification, was published ³.

This update adds white matter abnormalities and a grouping for lesions that do not fulfill other groupings. It also proposes an integrated multi-layered classification that adds genetic and neuroimaging information, coming to an integrated diagnosis ³.

Terminology

Unfortunately, as is the case with many classification systems that have developed in parallel or as iterations and revisions of existing classifications, there is significant overlap between the various classification systems with the same terminology used slightly differently. As such, it is important to state which classification system is being used when using these terms.

Classification

The following is based on the 2022 ILAE classification with the 2011 description in brackets when different ^2,3.

• type I: focal cortical dysplasia with abnormal cortical lamination

  • a: abundant microcolumns (radial cortical lamination)

  • b: abnormal layering (tangential 6-layer cortical lamination)

  • c: vertical and horizontal abnormalities (radial and tangential cortical lamination)

• type II: focal cortical dysplasia with dysmorphic neurons (Taylor dysplasia)

  • a: without balloon cells

  • b: with balloon cells

• type III: cortical dyslamination associated...

  • a: with hippocampal sclerosis

  • b: adjacent to brain tumor (glial or glioneuronal tumor)

  • c: adjacent to vascular malformation

  • d: adjacent to other lesions acquired in early life (e.g. stroke)

• white matter: mild malformations of cortical development with...

  • excessive heterotopic neurons

  • oligodendroglial hyperplasia

• no definite FCD on histopathology

Layered integrated diagnosis

• layer 1A: histopathology diagnosis

  • description of architectural and/or cytoarchitectural histopathology

  • H&E stain and immunohistochemistry

• layer 1B: ILAE histopathological subtype

  • assign classification type

• layer 2: genetic findings

  • describe relevant genetic findings, or “not available (NA)”

• layer 3: neuroimaging findings

  • comment as to whether MRI is normal or abnormal

  • include technical specification (e.g. imaging protocol, sequence, magnet strength)

• integrated diagnosis

  • combine layers 1-3 into a single summative diagnosis