Diagnosing Disorders of the Corpus Callosum (DCC) Things to consider and things to expect
The views below represent a combination of the clinical experience of the scientific advisory board and published literature. This is not meant to supplant a clinician’s own judgment or practice parameters from the medical societies – such as the American Academy of Pediatrics and the American Academy of Neurology – whose members care for patients with callosal disorders. Please don’t hesitate to tell us if our suggestions were helpful or if and how our statements need modification by sending your suggestions to the attention of the scientific advisory board at: firstname.lastname@example.org.
This discussion is divided into five main sections:
When would a callosal disorder be suspected and hence an MRI ordered?
In this case we suggest turning first to the guidelines issued by the American Academy of Neurology for the evaluation of a child with global developmental delay (Shevell, et al., Practice parameter: Evaluation of
the child with global developmental delay, Neurology. 2003;60:367-380 | doi: 10.1212/01.WNL.0000031431.81555.16). Many patients with DCC have delay in at least two domains and would qualify for an MRI on this basis. Also, a number of patients with callosal disorders have epilepsy or non-febrile seizures and would require an MRI for that evaluation (reference article; Fenlon & Richards, Contralateral targeting of the corpus callosum in normal and pathological brain function, Trends in Neurosciences. 2015;38:264-272 | doi: 10.1016/j.tins.2015.02.007). There is also a subset of patients with callosal disorders who are diagnosed by in utero imaging. There are clearly benefits to obtaining an MRI after birth to better understand overall brain anatomy as that may help with anticipatory guidance. The individuals with DCC who are not detected by the above methods fall into a category with less clinical impairment and many in the past have not been scanned. Thus, we have seen DCC identified by scans performed for head trauma or headaches, common conditions but unrelated to the DCC. Additionally, some patients are scanned later by clinicians who are ultimately convinced that the child’s delay will not resolve and thus he/she has a fixed impairment. Because there is this group of DCC patients who go undiagnosed we recommend extending the AAN guidelines to obtain brain MRIs of children who have mild to moderate cognitive, motor and/or social delays that are not resolving by preschool years. These problems are observed frequently in our DCC patients and research participants and were seen in patients with isolated DCC who were identified by prenatal ultrasound (Moutard et al), and this observation is the basis for decreasing the threshold for pursuing a diagnostic MRI scan on these patients.
Early detection is directly related to long term benefit for the patient. Therapies that target inter-hemispheric coordination at young ages are especially beneficial. All individuals with DCC are affected by their condition. Early intervention affects the range and severity of the deficits.
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If ordering an MRI, what sequences should be collected?
Patients with ACC should have a standard MR imaging protocol for children with developmental delay. This consists of 3-D reformatable 1mm Sagital or coronal SPGR images.
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What anatomic findings and other organ systems should be considered in a full evaluation once a callosal disorder is identified?
A. Brain anatomic findings: DCC has also been associated with other commissural malformations, including of the anterior and hippocampal commissures. Probst Bundles are longitudinal bundles of white matter that are medial to the lateral ventricles of individuals with complete agenesis and presumably would have formed the corpus callosum. We find that DCC individuals who are missing their anterior commissure will likely have more impaired developmental outcomes. Other cerebral malformations including lissencephaly, polymicrogyria and heterotopia can also be seen with DCC. For a more detailed discussion of associated cerebral anomalies, we recommend this article (Hetts et al., Anomalies of the Corpus Callosum: An MR Analysis of the Phenotypic Spectrum of Associated Malformations, American Journal of Roentgenology. 2006;187:1343-1348 | doi: 10.2214/AJR.05.0146).
B. Extraneural findings: Patients with DCC frequently have involvement of other organ systems. All DCC patients should be evaluated by an ophthalmologist for vision and for involvement of the optic nerves. Additionally, if there is any language impairment (delay or dysarthria), hearing should be formally evaluated. Patients with DCC can develop hearing loss (mitochondriopathies and Chudley McCullough syndrome) post-natally and this should also be watched for. Twenty percent (20%) of patients with DCC have cardiac anomalies and therefore all DCC patients should have a careful cardiac evaluation. Many other organ systems can be involved, these include renal & genitourinary, musculoskeletal and vascular. Patients with DCC can also have chromosomal anomalies; at least a single visit to a geneticist would be recommended for any individual with DCC. Overall DCC patients frequently have involvement of other organ systems and this observation should guide a careful systems analysis of each patient.
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What are some of the potential etiologies for a callosal disorder?
Empiric evidence suggests that over 5% of patients with DCC will have an affected family member. This suggests that DCC can be caused by complex genetic interactions and sporadic genetic disorders (chromosomal deletions & duplications). The only environmental cause of DCC that is understood is alcohol exposure. These patients typically have the facial features of fetal alcohol syndrome, have microcephaly and severely diminished white matter volume. The genetic causes of DCC are many, although most disorders have only a handful of cases reported with DCC. In general, all DCC patients should undergo high-resolution karyotype analysis and sub-telomeric probes. More specific testing should be considered in conjunction with other clinical or anatomic findings. For a more detailed discussion of the genetics of DCC, we refer you to a recent review (Paul et al., Agenesis of the corpus callosum: Genetic, developmental and functional aspects of connectivity, Nature Reviews Neuroscience. 2007;8:287-299 | doi:10.1038/nrn2107) that summarizes these issues.
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What anticipatory guidance can be provided to families?
If this is a new diagnosis, then expect shock, denial, anger, and sadness as you would with any other difficult medical condition. If this is not a new diagnosis, then expect the possibility that the individual’s or family’s knowledge of DCC is incomplete or misinformed. DCC is a medical condition that has a broad spectrum of possible developmental delays all of which may range from mild to severe. The developmental problems always involve difficulty with abstract reasoning, problem solving, and social comprehension. These delays worsen near adolescence (typically ages 9-11) when the normal corpus callosa of the individual’s peers becomes much more efficient.
This is an overview of the behavioral characteristics which are often evident in individuals with DCC:
- Delays in attaining developmental milestones (e.g, walking, talking, reading). Delays may range from very subtle to highly significant.
- Clumsiness and poor motor coordination, particularly on skills that require coordination of left and right hands or feet (e.g. swimming, bike riding, tying shoes, driving).
- Hypersensitivity to particular sensory cues (e.g. food textures, certain types of touch) but often with a high tolerance to pain.
- Difficulties processing multidimensional tasks including language in social situations (e.g. jokes and metaphors), appropriate motor responses to visual information (e.g. stepping on others’ toes, handwriting runs off the page), and the use of complex reasoning, creativity and problem solving (e.g. coping with middle school and high school math and science or budgeting).
- Social challenges due to difficulty imagining potential consequences of behavior, insensitivity to the thoughts and feelings of others, and misunderstanding social cues (e.g. being vulnerable to suggestion and not recognizing emotions communicated by facial expressions or tone of voice).
- Mental and social processing problems become more apparent with age, with problems particularly evident from junior high school into adulthood.
- Limited insight into their own behavior, social problems, and mental challenges.
Advise affected individuals and their families that regardless of the nature or severity of the affected individual’s own developmental problems, therapy is available to improve the outcome. All are encouraged to contact the NODCC. Those younger than three years of age should contact Early Intervention Services for evaluation. Those with known deficits in motor, coordination, or speech can be referred to appropriate therapists by their physician.
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