A 2 year old girl presents following a first seizure. She has a history of global developmental delay. There is no previous neuroimaging for comparison.
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There is a thick band of abnormal T1 hyperintense, T2 hypointense signal intensity deep to the cerebral cortex. It parallels the cortex in contour and signal intensity. There is diminished overlying gyral sulcation. Many of the cortical sulci are shallow. There is mild enlargement of the lateral and third ventricles.
This is an example of band heterotopia, a malformation of cortical development that is due to arrested neuronal migration. Subcortical band heterotopia is strongly linked with lissencephaly and in the most recent classification system for malfomations of cortical development they are grouped together as lissencephaly type I - subcortical band heterotopia spectrum.
Band heterotopia is characterized on CT and MRI as a band of grey matter located deep to, and roughly paralleling, the cortex, with either normal or pachygyric overlying cortex.