Publication

Abstract : A 5-month-old infant with macrocephaly and dysmorphism presented with seizures. Magnetic resonance imaging of the brain showed fused lateral ventricles and the absence of mid-line structures (inter-hemispheric fissure, septum pellucidum, and corpus callosum). A large dorsal cyst was seen, pushing the thin strip of the remaining fused cerebral cortex anteriorly. Imaging was suggestive of alobar holoprosencephaly [Figure 1a]. The electroencephalogram (EEG) showed a decreasing gradient of electrical potentials from the frontal electrode to the occipital electrode, with an almost isoelectric line over the most posterior leads [Figure 1b]. The electrical isolation of the posterior electrodes from the thin strip of the cerebral cortex by the huge dorsal cyst might be considered as the most plausible hypothesis for this unusual EEG pattern.[12]