New classification system of focal cortical dysplasia : application to practical diagnostic field

Abstract

Malformation of cortical development (MCD) is a well-known cause ofdrug-resistant epilepsy and focal cortical dysplasia (FCD) is the most commonneuropathological finding in surgical specimens from drug-resistant epilepsypatients. Palmini’s classification proposed in 2004 is now widely used tocategorize FCD. Recently, however, Blumcke et al. recommended a new systemfor classifying FCD in 2011. We applied the new classification system inpractical diagnosis of a sample of 117 patients who underwent neurosurgicaloperations due to drug-resistant epilepsy at Severance Hospital in Seoul, Korea.Among 117 cases, a total of 16 cases were shifted to other FCD subtypes underthe new classification system. Five cases were reclassified to type IIIa and fivecases were categorized as dual pathology. The other six cases were changedwithin the type I category. The most remarkable changes in the newclassification system are the advent of dual pathology and FCD type III. Thus, itwill be very important for pathologists and clinicians to discriminate betweenthese new categories. More large-scale research needs to be conducted toelucidate the clinical influence of the alterations within the classification of typeI disease. Although the new FCD classification system has several advantagescompared to the former, the correlation with clinical characteristics is not yetclear.