What is the diagnosis?
Double cortex syndrome (also known as band heterotopia).
What other congenital cortical malformation is associated with subcortical band heterotopia?
Lissencephaly type I (classic). In fact the two conditions are due to similar mutations and form a spectrum.
What is the most common genetic abnormality and what impact does it have on demographics of affected individuals?
DXC gene located on the X chromosome tends to present as band heterotopia in females, whereas in males it presents with lissencephaly.
What MR spectroscopy abnormality are you likely to find in the abnormal heterotopic grey matter?
Reduced NAA due to neuronal dysfunction.
MRI of an 8 year old demonstrates a continuous ribbon of grey matter seen just deep to the cortex, separated from it with a thin layer of white matter. The overlying brain demonstrates some shallowness of sulci. Incidental cavum septum pellucidum et vergae is noted.