Clinical History
The patient presented with GTCC in the emergency department. She had a history of seizures for 20 years but did not take anti-epileptic drugs regularly. The patient had a suboptimal IQ level. There was no microcephaly.
Imaging Findings
MRI brain revealed a band-like subcortical lesion that had a similar signal intensity as grey matter on all sequences in all lobes of the bilateral cerebral cortex. The lesion was separated from the cortex by a thin band of white matter, appearing as "double cortex".
Pachygyria was noted in bilateral frontal lobes predominantly in the inferior frontal region. Central grey matter nuclei did not show any significant abnormality. Brain stem and cerebellum did not show any significant abnormality.
Discussion
Heterotopia represents the collection of normal neurons in an abnormal location due to abnormal neuronal migration. Patients present with epilepsy, delayed milestones and mental retardation. Heterotopia may be associated with pachygyria, agenesis of the corpus callosum, Chiari II malformation, arachnoid cyst, schizencephaly and cephalocele. [1]
There are three types of heterotopia: Periventricular heterotopia, subcortical heterotopia and band heterotopia. [1]
Periventricular heterotopias are located in the subependymal region of the lateral ventricle commonly in trigone and occipital horn. [1]
Subcortical heterotopias are located in subcortical and deep white matter and connected to cerebral cortex or ventricular wall. Subcortical heterotopias are either a nodular, curvilinear or mixed form. [1]
Band heterotopia is also known as 'double cortex syndrome'. It is a diffuse form of grey matter heterotopia. It is associated with lissencephaly type-I and genetic abnormality located on X chromosome. It is commonly attributed to abnormalities in DCX gene and LISI gene. [2]
On MR imaging, it shows the characteristic 3-layer. Cerebral cortex is separated from subcortical heterotopic grey matter by a band of white matter. Cerebral cortex may be pachgyric or normal. [1]
It is usually treated with antiepileptic drugs. [2]
Differential Diagnosis List
Band heterotopia
Cortical dysplasia
Lissencephaly