BACKGROUND AND PURPOSE: Malformation of cortical development (MCD) is a 
well-known cause of drug-resistant epilepsy and focal cortical dysplasia (FCD) 
is the most common neuropathological finding in surgical specimens from 
drug-resistant epilepsy patients. Palmini's classification proposed in 2004 is 
now widely used to categorize FCD. Recently, however, Blumcke et al. recommended 
a new system for classifying FCD in 2011.
METHODS: We applied the new classification system in practical diagnosis of a 
sample of 117 patients who underwent neurosurgical operations due to 
drug-resistant epilepsy at Severance Hospital in Seoul, Korea.
RESULTS: Among 117 cases, a total of 16 cases were shifted to other FCD subtypes 
under the new classification system. Five cases were reclassified to type IIIa 
and five cases were categorized as dual pathology. The other six cases were 
changed within the type I category.
CONCLUSIONS: The most remarkable changes in the new classification system are 
the advent of dual pathology and FCD type III. Thus, it will be very important 
for pathologists and clinicians to discriminate between these new categories. 
More large-scale research needs to be conducted to elucidate the clinical 
influence of the alterations within the classification of type I disease. 
Although the new FCD classification system has several advantages compared to 
the former, the correlation with clinical characteristics is not yet clear.