T1, T2 and T1 inversion recovery axial image in 16 year old female patient with seizures showing smooth, nodular area, isointense to grey matter seen on all the sequences and present all along the margin of the bilateral lateral ventricles (subependymal regions) consistent with gray matter heterotopia.The lesion is better depicted in T1 inversion recvoery image.
Discussion:
Definition: It is a type of cortical dysplasia (neuronal migrational anomaly) where in clumps of normal grey matter being located in the wrong part of the brain. Clinical features: Asymptomatic to profound seizures and it is usually detected incidentally on brain MRI. Various manifestations include severe seizure disorder, loss of motor skills, and mental retardation. Fatalities are practically unknown, other than the death of unborn male fetuses with a specific genetic defect.
Types of Heterotopia:
- Periventricular or subependymal: It can be seen as small single node or a large number of nodes, can exist on either or both sides of the brain at any point along the higher ventricle margins, can be small or large, single or multiple, and can form a small node or a large wavy or curved mass
- Focal Subcortical: form as distinct nodes in the white matter, "focal" indicating specific area.
- Band Form: "Band" heterotopia form in the white matter beneath the cortex, but the gray matter is more diffuse and is symmetric between the hemispheres.
Imaging: CT or MRI
CT scan: The density will be similar to that of the gray matter.
MRI: The signal intensity will be similar to gray matter in all the sequences. T1 inversion recovery sequence will better depict the lesion.