3T MRI improves the detection of transmantle sign in type 2 focal cortical dysplasia.
OBJECTIVE
Type 2 focal cortical dysplasia (FCD2) is one of the main causes of refractory partial epilepsy, but often remains overlooked by MRI. This study aimed to elucidate whether 3T MRI offers better detection and characterization of FCD2 than 1.5T, using similar coils and acquisition time.


METHODS
Two independent readers reviewed the 1.5T and 3T MR images of 25 patients with histologically proven FCD2. For both magnetic fields, the ability to detect a lesion was analyzed. We compared the identification of each of the five criteria typical of FCD2 (cortical thickening, blurring, cortical signal changes, subcortical signal changes, and "transmantle" sign) and artifacts, using a four-point scale (0-3). Interobserver reliability for lesion detection was calculated.


RESULTS
Seventeen lesions (68%) were detected at 3T, two of which were overlooked at 1.5T. Interobserver reliability was better at 3T (κ = 1) than at 1.5T (κ = 0.83). The transmantle sign was more clearly identified at 3T than 1.5T (mean visualization score: 1.72 vs. 0.56; p = 0.002).


CONCLUSIONS
The use of 3T MRI in patients suspected of type 2 FCD improves the detection rate and the lesion characterization owing to the transmantle sign being more clearly seen at 3T. This point is of interest, since this feature is considered as an MR signature of FCD2.
Department of Neuroimaging, Sainte-Anne Hospital Center, Paris Descartes Sorbonne Paris Cité University, Paris, France.
Charles
C
Mellerio
Marc-Antoine
MA
Labeyrie
Francine
F
Chassoux
Pauline
P
Roca
Odile
O
Alami
Monique
M
Plat
Olivier
O
Naggara
Bertrand
B
Devaux
Jean-François
JF
Meder
Catherine
C
Oppenheim
D000293:Adolescent; D000328:Adult; D001921:Brain / Q000473:pathology*; D001927:Brain Diseases / Q000175:diagnosis* / Q000473:pathology; D004827:Epilepsy; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D054220:Malformations of Cortical Development / Q000175:diagnosis* / Q000473:pathology; D065703:Malformations of Cortical Development, Group I; D008875:Middle Aged; D059906:Neuroimaging / Q000379:methods*; D015203:Reproducibility of Results; D055815:Young Adult
Focal cortical dysplasia; Intractable epilepsy; MR imaging; Transmantle sign