American Journal of Neuroradiology 28:678-682, April 2007
© 2007 American Society of Neuroradiology
PEDIATRICS
Hemimegalencephaly: A Study of Abnormalities Occurring Outside the Involved Hemisphere
a Department of Radiology, National Center Hospital for Mental, Nervous, and Muscular Disorders, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan
b Department of Child Neurology, National Center Hospital for Mental, Nervous, and Muscular Disorders, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan
c Department of Neuroradiology, Tokyo Metropolitan Neurological Hospital, Kokubunji, Tokyo, Japan
d Department of Radiology, Teikyo University School of Medicine, Itabashi-ku, Tokyo, Japan
e Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University School of Medicine, Kyoto, Kyoto, Japan
f Clinical Neuroscience, Medical Sciences for Control of Pathological Processes, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Japan
g Department of Psychiatry, Ibaraki Prefectural Tomobe Hospital, Ibaraki, Japan
Please address correspondence to Noriko Sato, MD, Department of Radiology, National Center Hospital for Mental, Nervous, and Muscular Disorders, National Center of Neurology and Psychiatry, 4-1-one Ogawahigashi-cyo, Kodaira, Tokyo, 287-8511 Japan; e-mail: snoriko{at}ncnp.go.jp
BACKGROUND AND PURPOSE: Hemimegalencephaly is a rare but well-known congenital malformation with ipsilateral enlargement of the hemicerebrum. However, very little is known about changes in structures outside the involved hemisphere in patients with this condition. We investigated morphologic abnormalities occurring outside the affected hemisphere by MR imaging in a large series of patients with hemimegalencephaly.
MATERIALS AND METHODS: MR imaging findings for 30 patients with hemimegalencephaly were retrospectively reviewed and evaluated for structures outside the involved hemisphere on routine MR images, such as cranial nerves (I, II, V), brain vessels, subdural and subarachnoid spaces, brain stem, and cerebellum, on both the ipsilateral and contralateral sides.
RESULTS: The ipsilateral olfactory and optic nerves were enlarged in 8 (26.7%) and 1 (3.3%) of the 30 patients, respectively, without enlargement on the contralateral side. No asymmetry was noted in the trigeminal nerves. Asymmetric vascular dilations in the ipsilateral cerebral hemisphere were observed in 12 of the 30 patients (40%), in deep cerebral vessels in 11 patients (36.7%), and in superficial cerebral vessels in 8 patients (26.7%). Ipsilateral brain stem and hemicerebellar asymmetric enlargement was detected in 2 patients (6.7%) and 14 patients (46.7%), respectively. Abnormal cerebellar folia were observed on the ipsilateral side in 6 patients (20%) and on the contralateral side in 3 patients (10%).
CONCLUSION: Ipsilateral olfactory nerve enlargement, cerebral vascular dilations, cerebellar enlargement, and bilateral or ipsilateral abnormal architecture of the cerebellar folia are often associated with hemimegalencephaly.
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