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|Year : 2015 | Volume
| Issue : 6 | Page : 997-998
MR imaging and MR diffusion tensor imaging in mega corpus callosum
Prem Kumar Jaisankar, Rajeswaran Rangasami
Department of Radiology, Sri Ramachandra University, Chennai, Tamil Nadu, India
|Date of Web Publication||20-Nov-2015|
Dr. Prem Kumar Jaisankar
Department of Radiology, Sri Ramachandra University, Porur, Chennai - 600 116, Tamil Nadu
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Jaisankar PK, Rangasami R. MR imaging and MR diffusion tensor imaging in mega corpus callosum. Neurol India 2015;63:997-8
A 6-year-old boy was referred for MRI of the brain in the evaluation of global developmental delay. He was born from nonconsanguineous parents by normal vaginal delivery without any postnatal complications. All his milestones were delayed, and he was undergoing special training from the age of 5 years. There was no history of seizures. His MRI showed a thickened corpus callosum [Figure 1]a and [Figure 1]b, with few areas of pachy-polymicrogyria in the left temporal and parietal region [Figure 1]c. The thickness of corpus callosum was diffusely increased, measuring 13.4 mm in the genu (normal: 8.8–10.7 mm), 8.3 mm in the body (normal: 4.8–-5.9 mm), 8.5 mm in the isthmus (normal: 3–4 mm), and 10 mm in the splenium (normal: 8.5–10.6 mm). Diffusion tensor imaging (DTI) showed that the thickening was due to anomalous midline longitudinal fibers [Figure 1]d and [Figure 1]e. Based on the aforementioned features, a radiological diagnosis of mega corpus callosum (MCC) was made.
|Figure 1: a) Axial T2; and, b) sagittal T1 weighted images show increased thickness of the corpus callosum (arrow); c) T2 coronal image shows areas of pachy-.polymicrogyria pattern in the left temporal and parietal region (arrowhead). MR diffusion tractography; d) top.down axial; and, e) sagittal images show the green longitudinal supracallosal fibers (open arrow) responsible for the thickening; f) Sagittal T1.weighted image showing normal corpus callosum|
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Corpus callosum develops between 8 and 20 weeks of gestation. In contrast to malformations like partial or complete agenesis of corpus callosum, which are common, MCC is extremely rare. MCC can be associated with other disorders such as megalencephaly and polymicrogyria. Corpus callosal thickening can be associated with global developmental delay, facial dysmorphism, mental retardation, microcephaly, and visual symptoms. Corpus callosum is vital for communicating and integrating motor and somatosensory information between the hemispheres and for bilateral motor coordination and function. DTI is a new MRI technique that uses anisotropic diffusion to estimate the axonal organization of the brain and also for studying the white matter tracts. Color coding can be done according to the direction of the tracts. Diffusion tractography findings in MCC are sparsely reported.
A healthy corpus callosum is coded red, as it contains transverse fibers connecting both cerebral hemispheres [Figure 1]f. Rollins et al., postulated that the thickening of corpus callosum in MCC was due to the presence of anomalous longitudinal midline supracallosal fibers. Longitudinal supracallosal fibers are not visualized in healthy individuals. These fibers are thought to be commissural axons that went astray during axonal migration. These fibers are likely to represent heterotopic cingulum or aberrant callosal axons. Cases of isolated MCC without any associated malformations are also reported, and they carry a better prognosis.
In conclusion, MCC is a rare clinical entity that may or may not present with other disorders like megalencephaly and polymicrogyria. MRI shows increased dimensions of its various parts. Diffusion tractography shows that the thickening is due to anomalous midline longitudinal fibers.
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