Clinical History
Hypotelorism, microcephaly, and seizures
Imaging Findings
Presented with hypotelorism, microcephaly, and seizures. MR imaging examination was performed at 0.5 Tesla.
Discussion
Classically, holoprosencephaly has three forms, alobar, semilobar, and lobar. In the alobar type there is a single ventricle, the thalami and basal ganglia are fused, and the interhemispheric fissure and corpus callosum are absent. In the semilobar type, similar changes are present, however, the cerebral hemispheres are relatively more developed. In the lobar type, the ventricles show relatively normal configuration, rostral frontal regions are fused, and the corpus callosum is absent or dysplastic. A variety of milder forms of the anomaly has been described including, holoprosencephaly associated with midline interhemispheric fusion (with atypical callosal dysgenesis), and holoprosencephaly manifesting with fusion of the gyri cinguli (with intact but thinned corpus callosum), and holoprosencephaly associated with aventriculi. The occurrence of holoposencephaly has been attributed to faulty mesenchyme formation, and abnormal persistence or maldifferentiation of the primitive meningeal tissue accounting for maldevelopment of the interhemispheric fissure, falx, and corpus callosum. It should be noted that the only condition associated with fusion between cerebral hemispheres of varying degrees is holoprosencephaly, and the infratentorial anomaly associated with fusion of the cerebellar hemispheres is rhombencephalosynapsis (with vermian dysgenesis).
Differential Diagnosis List
