HOLOPROSENCEPHALY - AN ANALYSIS OF CALLOSAL FORMATION AND ITS RELATION TO DEVELOPMENT OF THE INTERHEMISPHERIC FISSURE

PURPOSE: To correlate the degree of hemispheric fusion in holoprosence phaly with degree of callosal formation, with degree of thalamic and b asal ganglia fusion, and with presence or absence of dorsal cyst. METH ODS: MR, CT, and ultrasonography from 19 patients with holoprosencepha ly was retrospectively reviewed. The imaging studies were graded accor ding to extent of the hemispheric fusion, thalamic fusion, corpus stri atum fusion, callosal formation, and the presence or absence of a dors al cyst. These factors were statistically correlated with each other u sing Kendall rank correlation coefficient. RESULTS: There were signifi cant correlations between hemispheric fusion and failure of corpus cal losum formation, presence of dorsal cyst and failure of corpus callosu m formation, and hemispheric fusion and presence of dorsal cyst. Addit ional correlations were noted between thalamic fusion and corpus stria tum fusion. CONCLUSIONS: Our results suggest that the presence of an i nterhemispheric fissure is necessary for callosal formation, and the p resence of a dorsal cyst may interfere with callosal formation in holo prosencephaly.