The corpus callosum is a midline structure connecting the two cerebral hemispheres. Axons arising from the superficial layers of the cerebral cortex cross the midline via the corpus callosum to the homotypic region of the contralateral cerebral cortex.
Agenesis of the corpus callosum is a congenital disorder in which the corpus callosum is partially or completely absent. It is a relatively rare condition occurring in about 1-5% of the population. Although dysgenesis of the corpus callosum commonly occurs in isolation, the condition may be associated with other disorders including Arnold-Chiari malformation, Dandy-Walker syndrome, and Aicardi’s syndrome. Interhemispheric cysts, holoprosencephaly, and midline facial defects are also common.
The clinical presentation of patients with agenesis of the corpus callosum ranges from subtle to severe. Some patients are asymptomatic with discovery of the disorder being an incidental finding on neuroimaging performed for other purposes.
Symptomatic infants most commonly present with developmental delay, seizures, and cerebral palsy. Obstructive hydrocephalus and macrocephaly secondary to intehemispheric cysts may be the initial presenting symptom. Delays in motor milestones, such as difficulties with sitting and walking or problems with chewing and swallowing, may also be observed. Other findings include hypotonia, speech and language delays, and mental retardation.
Antenatal diagnosis of agenesis of the corpus callosum is possible with prenatal ultrasound (US) after about 20 weeks gestation. Charactersitic findings include colpocephaly (abnormal enlargement of the occipital horns of the lateral ventricles) and abnormally parallel ventricular walls.
In the newborn, transcranial
CT imaging is also diagnostic and can demonstrate absence of the corpus callosum. Colpocephaly, parallel lateral ventricles, and interhemispheric cysts are common findings.
Confident diagnosis of agenesis of the corpus callosum and associated neuronal migration anomalies, which are often subtle on US or CT, requires MR imaging. Sagittal T1-weighted images clearly demonstrates absence or dysgenesis of the corpus callosum. Upward bulging of the roof of the third ventricle into the interhemispheric fissure is also often seen and can be mistaken for an interhemispheric cyst. The non-decussated callosal fibers, instead of crossing the midline, are seen on coronal and axial imaging to run along the medial borders of the lateral ventricles as the longitudinal callosal bundles of Probst. Other possible findings include an interhemispheric cyst and hydrocephalus.
There is no specific treatment for agenesis of the corpus callosum. Management involves symptomatic therapy such as medications for seizure control and social services for developmental delay or speech problems.
Prognosis varies with the extent of associated malformations or syndromes. The mental retardation, if present, is not progressive, and many patients can live normal lives.
1. Jeret JS, Serur D, Wisniewski KE: Clinicopathological findings associated with agenesis of the corpus callosum. Brain Dev 1987; 9(3): 255-64.
3. Lacey DJ: Agenesis of the corpus callosum. Clinical features in 40 children. Am J Dis Child 1985 Sep; 139(9): 953-5.
Bishoy Zakhary, Medical Student,
Phillip J. Silberberg, M.D., Dept of Radiology, Omaha Children’s Hospital,
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Case Number: 842436Last Updated: 2011-06-29 The reader is fully responsible for confirming the accuracy of this content.
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