Clinical and imaging characteristics of localized megalencephaly: a retrospective comparison of diffuse hemimegalencephaly and multilobar cortical dysplasia.
BACKGROUND
Hemimegalencephaly is a well-known congenital malformation. However, localized megalencephaly, which may be one of the subtypes of hemimegalencephaly, has not been separately investigated. In the present study, we attempted to characterize the clinical and magnetic resonance (MR) imaging features of localized megalencephaly in comparison with ordinary diffuse hemimegalencephaly and multilobar cortical dysplasia.


METHODS
MR findings for 43 patients with hemimegalencephaly and ten with multilobar cortical dysplasia, which is the differential diagnosis of localized megalencephaly, were retrospectively reviewed. Clinical findings such as the onset and severity of seizures and imaging findings including the affected area of the brain, structures outside of the hemisphere, and interval morphological changes were examined.


RESULTS
Of the 43 patients, 11 showed signs of localized megalencephaly (25.6%). Localized megalencephaly was predominantly seen on the left side (72.7%) and had a tendency toward severe-grade seizures compared to multilobar cortical dysplasia. The frequencies of the extracerebral abnormalities in the diffuse hemimegalencephaly, localized megalencephaly, and multilobar cortical dysplasia groups were 84.4%, 36.4%, and 0.0%, respectively. There were three localized megalencephaly patients whose affected areas shrank and whose images were similar to those of multilobar cortical dysplasia.


CONCLUSIONS
Localized megalencephaly accounts for one quarter of all hemimegalencephaly cases in this study. The incidence of extracerebral abnormalities in patients with localized hemimegalencephaly was almost half that of patients with diffuse hemimegalencephaly. Extracerebral abnormalities were absent in patients with multilobar cortical dysplasia. Associated extracerebral abnormalities may be a clue to differentiating localized megalencephaly from multilobar cortical dysplasia.
Nakahashi
Masumi
M
Department of Diagnostic Radiology and Nuclear Medicine, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan.
Sato
Noriko
N
Yagishita
Akira
A
Ota
Miho
M
Saito
Yoshiaki
Y
Sugai
Kenji
K
Sasaki
Masayuki
M
Natsume
Jun
J
Tsushima
Yoshito
Y
Amanuma
Makoto
M
Endo
Keigo
K
D000293:Adolescent; D000328:Adult; D001921:Brain / Q000002:abnormalities* / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D054220:Malformations of Cortical Development / Q000473:pathology*; D012189:Retrospective Studies; D055815:Young Adult