![]() ![]() The presence of the rostrum essentially excludes primary agenesis. In primary dysgenesis parts of the corpus callosum which form before the insult will be present whereas later parts will be absent. More recent studies, including using MR tractography, cast some doubt on this assertion, instead suggesting that the anterior body develops first and then continues bidirectionally, with the anterior portions (genu) developing earlier/more prominently than the posterior portions (splenium) 12,13. Traditionally, it was believed that development begins in the genu and progresses posteriorly with the rostrum appearing last. The development of the corpus callosum occurs between the 12 th and 16-20 th weeks of gestation 2,4. The hippocampal formations are usually hypoplastic, with resultant dilatation of the temporal horns of the lateral ventricles.ĭysgenesis (which may be complete or partial) is a result of encephalomalacia secondary to toxic, ischemic or traumatic events 2. The anterior commissure is usually present and often enlarged. These bundles of white matter are known as Probst bundles. The white matter tracts which usually cross the midline, instead are oriented vertically, separating the lateral ventricles widely, in a racing car sign configuration. PathologyĪgenesis is a result of an insult occurring at approximately 8-12 weeks gestation 2,4 resulting in failure to form the corpus callosum. The clinical picture in other cases is dictated by the associated abnormalities that are frequently found, especially in agenesis 4.Ĭhildren with agenesis may have dysmorphic facies, most commonly demonstrating hypertelorism 6. Isolated partial dysgenesis of the corpus callosum is often asymptomatic. congenital lactic acidosis (due to mitochondrial respiratory chain defects).hydrocephalus (30%): particularly the trigones and posterior horns of lateral ventricles = colpocephaly. ![]() other CNS associations: often multiple present.AssociationsĪssociated anomalies can be frequent and broad which includes: There appears to be a male predilection (M:F ~2:1) 6. Maternal alcohol consumption during pregnancy has been recognized as another risk factor 6. It may be as uncommon as 1:20,000 according to autopsy series 6. It should be noted however that in pediatric neuroradiology practice it may be seen in as many as 1% of referrals, clearly representing a significant selection bias, attributable to a large number of symptomatic associated abnormalities. A true estimate of incidence is difficult to establish as many isolated cases are asymptomatic.
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