Figure 6.

Periventricular nodular heterotopia (PNH). (A) An axial magnetic resonance imaging (MRI) scan shows nodules of gray matter intensity (arrows) along the left lateral ventricles, a characteristic appearance of PNH. (B) A schematic illustrating the mechanism of PNH formation. Disruption of neuroependyma, possibly because of disrupted vesicular trafficking, results in “gaps” in the membrane and disrupted neuroependymal attachment of the radial glial cells (RGCs). Neurons produced in the ventricular zone are not connected to the RGCs and are unable to migrate, remaining at or near the ventricular border as nodules of neurons.