Ipsilateral Rhythmic Theta Activity (Intrinsic Epileptogenicity); Malformation of Cortical Development (MCD), Left Hemisphere. A 3-year-old left-handed girl
with intractable epilepsy, severe global developmental delay associated with malformation of cortical development in the left hemisphere. She had a
history of infantile spasms at 4 months of age. She presented with daily episodes of asymmetric epileptic spasms. MRI demonstrates left frontal cortical
dysplasia (open arrow) and left frontal periventricular nodular heterotopia (PNH) (small arrows). Interictal PET shows diffuse hypometabolism in the left
hemisphere, maximally expressed in the frontal region (arrow). EEG demonstrates very frequent runs of rhythmic theta and alpha activity in the left frontocentral region, with spreading to the midline and, to a lesser degree, to the right centro-parietal region.
Source: Epileptic Encephalopathy, Atlas of Pediatric EEG
In a series of 132 patients with cortical dysgenesis, 15% had nodular heterotopias.1 Nodule formation may be the result of (1) failure of a stop signal in the
Citation: Laoprasert P. Atlas of Pediatric EEG; 2011 Available at: http://mhmedical.com/ Accessed: July 31, 2017
germinal periventricular region, leading to cell overproduction, and (2) early transformation of radial glial cells into astrocytes, resulting in defective
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neuronal migration. The intrinsic interictal epileptiform activity of nodules may be due to an impaired intranodular GABAergic system.94 Two electroclinical
patterns of PNH emerged: (1) simple PNH, characterized by normal intelligence and seizures, usually partial, that begin during the second decade of life—
the seizures never become frequent and tend to disappear or become very rare, and the EEG shows focal abnormalities—and (2) PNH plus, characterized