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Information and FAQ's
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By the time a child is approximately 12 years of age, the corpus callosum functions essentially as it will in adulthood, allowing rapid interhemispheric interaction. However, callosal myelination continues into an individual's teens, so interhemispheric transfer may also improve.
Although the corpus callosum is not the only path connecting the hemispheres, it is by far the largest and most important. Other interhemispheric connections include the anterior commissure which is about 50,000 fibers, as well as the posterior commissure and the hippocampal commissure, both of which are smaller even than the anterior commissure.
All of these conditions (complete agenesis, partial agenesis, hypoplasia, and dysgenesis) fall under the larger designation of Disorders of the Corpus Callosum (DCC).
Often individuals with AgCC have some other much smaller interhemispheric connections (eg. the anterior commissure). While this may allow for some information transfer between the hemispheres, no other commissure has the same functionality as the corpus callosum.
Individuals with complete AgCC are likely to have Probst Bundles, which are large intra-hemispheric nerve bundles that are not seen in typical brains. We do not know how Probst Bundles are used.
Figure 2: Agenesis of the Corpus Callosum.
The arrow points to where the corpus callosum
Figure 3: Partial AgCC.
The arrow points to the part of the
corpus callosum that developed.
Complete agenesis, partial agenesis, hypoplasia, and dysgenesis all fall under the larger designation of Disorders of the Corpus Callosum (DCC). Currently, there is currently very little research comparing these conditions and most of the cognitive research to date has focused on AgCC/ACC (not hypoplasia or other forms of dysgenesis).
However, the possibility of prenatal detection is relatively new, so there are many people who were diagnosed when they received a brain-scan for some other purpose.
- Prenatal infections or viruses (for example, rubella)
- Chromosomal (genetic) abnormalities (for example, trisomy 8 and 18, Andermann syndrome, and Aicardi syndrome)
- Toxic metabolic conditions (for example, Fetal Alcohol Syndrome)
- Blockage of the growth of the corpus callosum (for example, cysts)
In some cases, genetic causes and syndromes can be identified by a neurogeneticist or a neurologist. However, many times, the specific cause is unknown. For families concerned about heritability of this condition, genetic testing and a genetic counselor may be helpful. However, for the child with AgCC, the cause is often of less concern than the treatment.
While AgCC cannot be cured, it can be treated. Behavioral and cognitive interventions from early childhood on may be help the individual with AgCC maximize his or her abilities and learn ways to compensate for deficits. Treatments may involved occupational therapy, speech therapy, social skills training, academic assistance, job coaching, as well as medical interventions for complications such as seizures. Neuropsychologists, educational psychologists, physicians, and allied health professionals should be consulted for individual evaluations and recommendations regarding treatment. Learning to live as best as one can with AgCC is the goal, just as we all must learn to live with our personal limits and challenges.
AgCC may occur as an isolated condition or in combination with other cerebral or genetic abnormalities. Cerebral (brain) abnormalities that are often seen with corpus callosum disorders include Arnold-Chiari malformation and Dandy-Walker syndrome, Andermann syndrome (with progressive neuropathy), schizencephaly (clefts or deep divisions in brain tissue), holoprosencephaly (failure of the forebrain to divide into lobes), hydrocephaly, and migrational anomalies. AgCC is also associated with several chromosomal anomalies, including trisomy 13 and 18. When the corpus callosum disorder is part of a broader genetic syndrome, specific medical complications may appear. For example, girls may have a gender-specific condition called Aicardi's syndrome, which causes severe mental retardation, seizures, abnormalities in the vertebra of the spine, and lesions on the retina of the eye. Finally, AgCC can also be associated with malformations in other parts of the body, such as midline facial defects, visual system malformations, and heart defects.
In infancy, these may include feeding problems, as well as delays in holding the head erect, sitting, standing, and walking. There may be impairments in hand-eye coordination, speech, and visual and auditory memory. In mild cases, symptoms such as repetitive speech, social awkwardness, rigid thinking, poor problem solving, and odd communication patterns may appear in elementary school years.
The impact of AgCC may become more evident as a child reaches puberty. In a typical brain, corpus callosum functioning becomes much more efficient around ages 10-12, as the callosum mylenates. As the corpus callosum becomes increasingly functional in their typically developing peers, children with AgCC often appear to fall behind. Particular areas of difficulty are social understanding, social communication, comprehension of non-literal language (for example vocal inflection and proverbs), problem solving, executive skills (for example organization, flexibility in response to change, and planning), emotion recognition in others, self-awareness and personal insight. People with AgCC may appear somewhat rigid in their interests and socially simple. In this sense, AgCC symptoms may "get worse" with age ... however, often these individuals learn coping skills well into adulthood, so they may also "get somewhat better" with age eventually.
The nature of cognitive and social symptoms in AgCC, as well as the neuro-mechanics involved, is the primary focus of the Caltech Corpus Callosum Program . For more information see the Research section.
Part of the dilemma of our clinical diagnostic system is that by focusing on symptom clusters, we may actually be grouping people together who have similar symptoms for different reasons. This is not ideal, however it is the best system there is right now. Thus, a child with AgCC (an anatomic diagnosis) may also qualify for one of these behavioral diagnoses. Meanwhile, researchers will continue to examine how those behaviors may be linked to the AgCC.
Since the symptoms vary from person to person, the best way to find out how AgCC will affect your child would be to talk with your physician and allied health professionals to discuss the symptoms your child is experiencing and the behaviors he/she is exhibiting. Family support networks can also provide opportunities to compare experiences and figure out what may lay ahead for your child. For more information about support networks contact the National Organization for Disorders of the Corpus Callosum and the ACC Network .
Prior to participation, the procedures and risks will be discussed so that you can make an informed choice about participating. Read the criteria for participation carefully and then contact the researchers about your interest. For more information please see the Participation section.