PURPOSE: The new International League Against Epilepsy (ILAE) classification for 
focal cortical dysplasia (FCD) differentiates between patients with isolated FCD 
(type 1) and FCD with an associated hippocampal sclerosis (HS) (type 3a). In 
contrast to the former FCD classification by Palmini, which considered only 
histologic features, the novel ILAE classification also relies on magnetic 
resonance imaging (MRI) findings and presumed pathogenesis. We investigated in a 
cohort of 100 patients with exclusively temporal FCD if the new subdivision of 
FCD is reflected in clinical characteristics.
METHODS: Thirty-one patients with FCD type 1 and 50 patients with FCD type 3a in 
the temporal lobe were included. In all patients MRI and histology of the FCD 
were available. Both patient groups were compared to 19 patients with temporal 
FCD type 2 with clearly different histologic appearance.
KEY FINDINGS: Patients with FCD type 1 and type 3a presented with similar 
clinical features in many respects. In univariate analyses, no statistically 
significant differences were found as to age at epilepsy onset (p = 0.07) and 
epilepsy surgery (p = 0.14), a normal appearing neocortical temporal lobe (p = 
0.08) or diagnosis of FCD by visual inspection of MRI (p = 0.08), preoperative 
seizure frequency (p = 0.06), and the predominance of an epigastric aura (p = 
0.08). The postoperative outcome was nearly identical 1 year (p = 0.8) and 2 (p 
= 0.8), 3 (p = 0.8), 5 (p = 0.7), and 8 (p = 1.0) years postoperatively. Only 
febrile seizures (p = 0.025) and an aura (p = 0.03) were significantly more 
frequently reported in patients with FCD type 3a. Similar results were obtained 
from a multivariate logistic regression analysis. Patients with FCD type 2 were 
more different: Compared to FCD type 3a, age at epilepsy surgery was 
significantly lower (p = 0.004) and auras (p = 0.005) were significantly less 
frequently reported. Epigastric auras (p = 0.04) and febrile seizures (p = 
0.025) occurred significantly less frequently in patients with FCD type 2 
without HS compared to FCD type 3a. The diagnosis of an FCD was significantly 
more frequently made (p = 0.03) by visual inspection of the MRI compared to FCD 
type 1.
SIGNIFICANCE: Clinical features did not allow to clear separation of temporal 
FCD types 1 and 3a. Statistically significant differences were seen in a history 
of febrile seizures and the occurrence of auras more common in FCD type 3a. 
However, FCD type 2 in the same localization but with different histology 
presented with further differences such as more frequent FCD diagnosis by visual 
inspection of MRI, earlier operation, and less frequent epigastric auras.