Laminar heterotopia is a form of diffuse grey matter heterotopia, resulting in heterotopic grey matter, deep to the cortex, within the centrum semiovale 2.
There appears to be some disagreement or confusion in regards to whether or not laminar heterotopia is synonymous with band heterotopia with textbooks and articles variously grouping them together or separately.
Barkovich has the following to say on the matter 4: "It is the opinion of this author that the term laminar heterotopia is confusing. The way Friede 5 defines the term, it is synonymous with band heterotopia (also called double cortex). [...] Des Portes 6 refers to band heterotopia as subcortical laminar heterotopia. Radiologically, band heterotopia and subcortical heterotopia are distinct. Band heterotopia consist of smooth layers of gray matter that often follow the curvature of the overlying cortex. They are not convoluted nor are they contiguous with the overlying cortex. They do not contain blood vessels or CSF. Subcortical heterotopia usually consist of swirling, heterogeneous, curvilinear masses of gray matter often containing blood vessels and CSF. They are essentially always contiguous with the overlying cortex and the underlying ventricular surface."
Perhaps a way of avoiding confusion is to not use the term, but rather use:
- band heterotopia to denote subcortical smooth linear grey matter deep to the cortex separated from it by white matter
- subcortical heterotopia to denote discontinuous regions of grey matter (usually at least somewhat nodular) in the subcortical grey matter