J Korean Neurosurg Soc.  2019 May;62(3):288-295. 10.3340/jkns.2019.0025.

Pathological Classification of Focal Cortical Dysplasia (FCD) : Personal Comments for Well Understanding FCD Classification

Affiliations
  • 1Department of Pathology, Severance Hospital, Yonsei University College of Medicine, Seoul, Korea. paxco@yuhs.ac
  • 2Yonsei Institute of Pharmaceutical Sciences, College of Pharmacy, Yonsei University, Incheon, Korea.

Abstract

In 2011, the International League against Epilepsy (ILAE) proposed a first international consensus of the classification of focal cortical dysplasia (FCD). This FCD classification had been widely used in worldwide. In this review paper, the authors would like to give helpful comments for better understanding of the current FCD classification. Especially, the basic concepts of FCD type I, such as "radial", "tangential" and "microcolumn" will be discussed with figures. In addition, the limitations, genetic progress and prospect of FCD will be suggested.

Keyword

Focal cortical dysplasia; Histology; Classification; Embryology; Pathology

MeSH Terms

Classification*
Consensus
Embryology
Epilepsy
Humans
Malformations of Cortical Development*
Pathology

Figure

  • Fig. 1. The low power view of normal neocortex (NeuN, ×40) and a Korean folding pan (inlet). The imaginary white lines show the direction of radial migrations of neural cells. The lines look like the bones of a folding pan (inlet). The cortical six-layers were seen with red imaginary lines. The red imaginary lines show the tangential composition of neocortex. In the normal neocortex, it is unusual that the neuronal cells exactly align along the white imaginary lines.

  • Fig. 2. The low power view of the neocortex in FCD type Ia (NeuN, ×40). In contrast to the normal neocortex, many neuronal cells in FCD type Ia show linear alignment as shown in the dot-line box. FCD : focal cortical dysplasia.

  • Fig. 3. In high power view of the box (NeuN, ×200), the so-called many microcolumns, which were defined more than eight neurons aligned in a vertical direction, are noted (red boxes).

  • Fig. 4. The low power view of FCD type Ib (NeuN, ×40). The cortical sixlayers are deranged (too chaotic) compared to those in normal neocortex (Fig. 1). FCD : focal cortical dysplasia.

  • Fig. 5. The histopathological findings of FCD type IIa. The low power view (A; H-E, ×40) shows cortical dyslamination which means derangement of normal neocortical six-layers. High power view shows many large dysmorphic neurons with coarse Nissl substances. The size of dysmorphic neuron cytoplasm is more than 20 µm (B; H-E, ×400; black bar, 20 µm). Dysmorphic neurons are highlighted by immunostaining with nonphosphorylated neurofilament (C; SMI132, ×200). FCD : focal cortical dysplasia.

  • Fig. 6. The histopathological findings of FCD type IIb. The low power view (A; H-E, ×40) shows cortical dyslamination as FCD type IIa. High power view shows many large dysmorphic neurons with coarse Nissl substances (B; H-E, ×400; black bar, 20 µm) and balloon cells showing eosinophilic homogenous cytoplasm (C; H-E, ×400; black bar, 20 µm). FCD : focal cortical dysplasia.

  • Fig. 7. FCD type IIIa is a hippocampal sclerosis (ILAE type Ia) showing neuronal loss in CA4, 3, 2 and 1 (A; NeuN, ×12) with associating FCD type Ib which shows a breakdown of cortical tangential composition in overlying cortex (B; NeuN, ×40). FCD : focal cortical dysplasia.

  • Fig. 8. FCD type IIIb is combined with a low grade-epilepsy associated tumor (LEAT). Diagnosis of “the associated tumor” in this case is dysembryoplastic neuroepithelial tumor (DNT) (A; H-E, ×12 and B; H-E, ×200). Overlying cortex shows FCD type Ia (C; NeuN, ×40) characterized by microcolumns (D; red box; NeuN, ×200). FCD : focal cortical dysplasia.


Reference

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