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Etemadifar et al. Imaging of demyelinated corpus callosum

of demyelinating lesions of callosal tract, however It comprises four parts: (1) the reflected anterior
there are microstructural pathologic alterations in portion, or the rostrum; (2) the genu, or the anterior
the CC that cannot be assessed with conventional bulbar end; (3) the splenium, or the posterior rounded
MRI. Furthermore, in some demyelinating diseases end; (4) the body, which lies between the genu and
including MS, normal appearing white matter (NAWM) the splenium. The anterior half of human CC (genu,
has been reported to have noticeable histological rostrum, body) contains fibers interconnecting frontal
abnormality. Advanced MRI techniques such as association cortical areas and the isthmus mostly
[1]
diffusion tensor imaging (DTI) and MR spectroscopy contains primary motor, somatosensory and auditory
have been employed to evaluate changes in NAWM fibers. In the splenium, primary visual, association
and histological changes in active lesional areas. [2,3] temporooccipital and parietal commissural fibers are
The DTI is an advanced MR imaging technique that mixed, forming a single segment with the hippocampal
provides quantitative information regarding structural commissure through which parahippocampal fibers
features of central nervous system (CNS). It allows cross. Large diameter fibers are densest in the isthmus
the calculation of many parameters, including: and the posterior splenium, whereas small fibers are
mean diffusivity, which is a directionally averaged more numerous in the genu and anterior splenuim.
measurement of the apparent diffusion coefficient The MR imaging characteristics of CC are similar
(ADC) and fractional anisotropy (FA), which to those of white matter: high signal intensity on T1
summarizes the orientation-based dependence weighted images and low signal intensity relative to
of diffusivity. Many authors have investigated gray matter on both T2 weighted and proton density-
[4]
pathologic features of CC in different demyelinating weighted images. Measurement in the mid-sagital
diseases through various imaging methods, especially plane has been subject to extensive investigations.
MR imaging. They mostly focused on functional MRI, Normal MR imaging features of CC were reported by
DTI, MR spectroscopy in recent years of research. Okamoto et al. They showed focal thinning is seen
[17]
This study aimed to provide a short review of superiorly at the junction of body and splenium in 25%
different pathologic features of CC in neuroimaging of healthy individuals and considered to be a normal
of demyelinating disorders of CNS, which are mostly variation. On axial sections parallel to canthomeatal
auto-inflammatory types. It also shows the role of line at the high ventricular level, the body of CC is
these features in prognosis of these disorders to sectioned longitudinally, displaying a broad band of
help further discrimination and comparison between white matter bordered by the upper outer corners of
such diseases. [5,6] Cognitive dysfunction is one of lateral ventricles.
the major factors affecting the social functioning and
quality of life of patients suffering from demyelinating Function
disorders especially MS patients and It is one of the The function of the CC has been investigated for
most important factors which can be closely related centuries, suggesting it’s correlation with intelligence.
to neuroimaging features of MS. This can play a key- The earliest studies during the 16th century believed
role to help determine the outcome of the disease and it to be the “seat of the soul”. It took until the 18th
also their response to possible routine therapies. [7-11] century for Franz Joseph Gall and Johann Spurzheim,
In this article, we review different aspects of imaging dissecting alcohol fixed brains, to describe bundles of
and involvement patterns of CC in various CNS axons passing through the callosal white matter and
demyelinating disorders to determine more helpful connecting the 2 hemisphere. It’s known functions
ways of discrimination of such diseases and also, include: (1) inter-hemispheric exchange of information;
to demonstrate the role of white matter lesions (2) facilitation of some cortical activities; (3) inhibition
(particularly in CC) in evaluation of prognosis of these of some cortical functions and integration of inputs
demyelinating disorders. [12-16] To our knowledge there reaching one or both hemispheres.
was no article previously, discussing and comparing
CC features in different CNS demyelinating disorders One of the latest contributions in assessment of
similar to ours. physiology and function of the CC in different
analytical studies is functional MRI. [18-20]
NORMAL CC
CC IN MULTIPLE SCLEROSIS
Anatomy
The CC is a prominent band of compact white matter MRI
composed of transversely oriented nerve fibers by MS is the most common autoimmune disease of
which every part of one hemisphere is connected the CNS and it’s characterized by inflammation,
with corresponding part of the other hemisphere. demyelination and degenerative changes. The CC
70 Neuroimmunology and Neuroinflammation ¦ Volume 4 ¦ April 27, 2017