CLINICAL HISTORY:
16 year-old boy with history of intractable seizure. MRI was performed as part of workup. (4 images: axial T1, axial T2, axial FLAIR, coronal FLAIR)
DIAGNOSIS:
Subcortical band heterotopia
DISCUSSION:
MRI demonstrates a band of isotense signal within bilateral subcortical white matter giving rise to a double-cortex appearance. It is characteristic of subcortical band heterotopia.
Band heterotopia is a neuronal migration disorder. The bands of grey matter are interposed between the cortical mantle and lateral ventricles, with normal white matter present on either side. The thickness and extent of band may vary. The appearance of the overlying cortical mantle may be normal, show simplified gyral pattern or true pachygyria.
It most commonly affects females and most occurrences seem to be X-linked. The responsible gene is called doublecortin (DCX) (Xq22.3-q23). Much less frequently, the LIS1 (17p13.3) gene is implicated.
Intractable seizure is a feature with eventually 95% of patients developing epilepsy. These seizures are often refractory to medical therapy. Surgical treatment such as callosotomy may be performed in selected cases.
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