This 38-year-old male had a seizure 22 years ago. This is a follow-up scan, and the patient has no recent seizures or head trauma. See what you can discern from the first two images before looking at the duplicate images 3 and 4 (with highlighted area on image 4).
Q1 – The finding represents:
(a) Subependymal heterotopia
(b) Giant cell astrocytoma
A1 – (a) Subependymal heterotopia
Q2 – Subependymal heterotopia can be all of the following, except:
(c) Associated with seizures
(d) Focal or diffuse
(e) A manifestation of tuberous sclerosis
Q3 – The following are all true of heterotopias, except:
(a) Can be nodular or diffuse
(b) Most commonly present with seizures
(c) May be associated with agenesis of the corpus callosum
(d) Spectroscopy is usually normal
The majority of cases of subependymal heterotopia are sporadic. Some are X-linked. Affected females have mild cognitive deficits. Affected males are spontaneously aborted or have severe deficits. Tuberous sclerosis patients have subependymal nodules, but they are not true heterotopias.
The most common clinical presentation is seizures and developmental delay.
Heterotopias can be diffuse as in this case or focal most commonly in the regions of the trigones or occipital horns.
Differential diagnosis includes tuberous sclerosis. Tubers are usually calcified and have higher T2 signal than normal brain tissue. There are often cutaneous stigmata such as adenoma sebaceum, shagreen patches, or ash leaf spots.
Gray matter heterotopias may be associated with agenesis of the corpus callosum as well as pachygyria, schizencephaly, poly microgyria and Chiari II.
Spectroscopy in grey matter heterotopias demonstrates a decreased NAA/CR ratio, although often mild.
A2 – (e) A manifestation of tuberous sclerosis
A3 – (d) Spectroscopy is usually normal
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1. Barkovich, Radiology 1992: 182, 493-499.
2. Mitchell et. al. Antenatal diagnosis of subependymal heterotopia, AJNR 2000:21 (2).