Focal cortical dysplasia type IIa and IIb: MRI aspects in 118 cases proven by histopathology.
BACKGROUND
This study aims to review the magnetic resonance imaging (MRI) aspects of a large series of patients with focal cortical dysplasia type II (FCD II) and attempt to identify distinctive features in the two histopathological subtypes IIa and IIb.


METHODS
We retrospectively reviewed the MRI scans of 118 patients with histological proven FCD IIa (n = 37) or IIb (n = 81) who were surgically treated for intractable epilepsy.


RESULTS
MRI was abnormal in 93 patients (79 %) and unremarkable in 25 (21 %). A dysplastic lesion was identified in 90 cases (97 %) and classified as FCD II in 83 and FCD non-II in seven cases. In three cases, the MRI diagnosis was other than FCD. There was a significant association between the presence of cortical thickening (p = 0.002) and the "transmantle sign" (p < 0.001) and a correct MRI diagnosis of FCD II. MRI positivity was more frequent in the patients with FCD IIb than in those with FCD IIa (91 % vs. 51 %), and the detection rate of FCD II was also better in the patients with type IIb (88 % vs. 32 %). The transmantle sign was significantly more frequent in the IIb subgroup (p = 0.003).


CONCLUSIONS
The rates of abnormal MRI results and correct MRI diagnoses of FCD II were significantly higher in the IIb subgroup. Although other MRI stigmata may contribute to the diagnosis, the only significant correlation was between the transmantle sign and FCD IIb.
Department of Neuroradiology, Ospedale Cà Granda Niguarda, Piazza Ospedale Maggiore 3, 20162 Milano, Italy. Nadia.Colombo@OspedaleNiguarda.it
Nadia
N
Colombo
Laura
L
Tassi
Francesco
F
Deleo
Alberto
A
Citterio
Manuela
M
Bramerio
Roberto
R
Mai
Ivana
I
Sartori
Francesco
F
Cardinale
Giorgio
G
Lo Russo
Roberto
R
Spreafico
D000293:Adolescent; D000328:Adult; D001921:Brain / Q000473:pathology*; D001927:Brain Diseases / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D004827:Epilepsy; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D054220:Malformations of Cortical Development / Q000473:pathology*; D065703:Malformations of Cortical Development, Group I; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult