Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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December 5, 2011
Agenesis of Corpus Callosum
- Agenesis of corpus callosum (callosal dysgenesis) accounts for 4% of CNS malformations.
- Occurs as an isolated anomaly. Commonly associated with CNS malformations.
- A myriad of CNS abnormalities may have callosal dysgenesis as part of their phenotype, including chromosomal abnormalities (trisomy 13), midline abnormalities (Dandy-Walker and Arnold-Chiari malformation), and syndromes associated with mutations in neural adhesion molecules guiding axon growth and migration.
- The etiology is due to a failure of axonal formation or migration and may be induced by environmental factors such as fetal alcohol exposure (affecting neuronal cell adhesion molecules), intrauterine infections, and inborn errors of metabolism such as phenylketonuria.
- Presentation is usually in childhood. Most children are normal at birth but begin to show progressive signs of subtle cognitive deficits. Prenatal diagnosis is possible using intrauterine ultrasound or MR imaging.
- Key Diagnostic Features: Parallel, widely spaced lateral ventricles. Dilated occipital horns (colpocephaly). Radially arranged gyri "pointing" to the 3rd ventricle seen on sagittal T1WI, as well as absence of the cingulate gyrus. Coronal sections show characteristic "trident-shaped" anterior horns with a "moose head" appearance, vertical hippocampi, and "keyhole" shaped temporal horns.
- DDx: Destruction of the corpus callosum, e.g., Surgery-callosotomy; stretched corpus callosum, e.g., hydrocephalus-thinned corpus callosum but all parts present; and immature corpus callosum
- Rx: Treat associated endocrine abnormalities or seizures
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