|Mega corpus callosum and caudate nuclei with bilateral hippocampal malformation
|Rahşan Göçmen, Kader Karlı Oğuz
|From the Department of Radiology, University School of Medicine, Ankara, Turkey
|Keywords: • corpus callosum • dysgenesis• hippocampus
A thick corpus callosum is an extremely rare condition
with a limited number of reports in the literature. We
report an unusual case of a thick corpus callosum and
hypertrophic caudate nuclei with abnormal bilateral
hippocampal development in a 15-year-old female
who had mental and motor retardation.
The corpus callosum (CC) is the main interhemispheric commissure
in the brain. Although many cases with hypoplasia and atrophy
of the CC are seen in daily practice, a thick CC is an extremely
rare condition with a limited number of reports in the literature[1
With the best visualization in midsagittal images, magnetic resonance
imaging (MRI) is well suited for identifying abnormalities of the CC.
Herein, we present a case of mega CC and caudate nuclei with abnormal
bilateral hippocampal development.
The patient, a 15-year-old female, underwent cranial MRI for evaluation
of mental and motor retardation. She was the second child born at
term by normal vaginal delivery and without complication to healthy
non-consanguineous parents. There was no history of perinatal hypoxia.
Birth weight was 4500 g. There was no family history of neurological
illness. At the age of 6 months she presented with poor head control
and weak sucking reflex. No specific diagnosis was made at that time.
Following an operation for strabismus at 6 years of age, she attended a
special training center for 7 years.
When she presented at age 15 years, her examination revealed ataxic
gait, self-mutilation, and spontaneous fits of laughter, but no facial dysmorphism.
She was capable of forming sentences composed of only 2
words. Her parents did not describe any seizure activity.
Laboratory analysis of serum and urine, and electroencephalogram
were unremarkable. Her intelligence quotient according to the Stanford-
Binet scale was 47.
MRI of the brain was performed on a 3.0 Tesla MR system (Allegra,
Siemens Medical Systems, Erlangen, Germany), which included sagittal
and transverse T1-weighted (W) spin echo (SE) (TR/TE: 650/20 ms), and
transverse and coronal T2-W turbo spin-echo (TSE) (TR/TE: 4000/114
ms) images. The examination was performed under light sedation.
On visual inspection, a thick CC was present (Fig.
). To be objective,
morphometric analysis was performed in respect to length, thickness,
and area of the CC, and area of the supratentorial supracallosal
compartment (SSC) (Figs.
). Morphometric analysis of the CC was
performed on the midsagittal T1-W image. Length of the CC was normal
(88.6 mm; age-matched normal individual: 71.3 mm) (Figs.
values obtained were compared to normal values for her age in the literature[1
]. Thickness of the CC was diffusely increased; the genu, body,
and splenium were 17.6 mm (normal: 11 mm), 10.8 mm (normal: 6
mm), and 11.3 mm (normal: 11 mm) thick, respectively (Fig.
genu was affected most strikingly. Areas of the CC and SSC were 1492
and 8145 mm2
, respectively (Fig.
). The area of the CC was apparently
greater than that obtained from a recent study performed on adult Turkish females[2
the area of the SSC was normal (average
callosal and supratentorial supracallosal
areas were 608 and 8149 mm2
Click to Enlarge
|Figure 1: a-d. Midsagittal T1- weighted (TR/TE: 650/20 ms) MR image (a) of the patient shows a thick corpus callosum. Also note the enlarged
perivascular space in the splenium. The genu is thicker than the splenium. Measurement of corpus callosum thickness and length (b), and area
of the corpus callosum and supratentorial supracallosal compartment (c) are shown. For comparison, the MR image of a normal 15-year-old
female is shown (d).
No sulcation abnormality or migration
disorder was detected. Both caudate
nuclei were enlarged and rounded.
Additionally, the cavum septum
pellucidum et vergae was observed on
MRI examination (Fig.
Click to Enlarge
|Figure 2: a, b. Transverse T2- weighted (TR/TE: 4000/114 ms) turbo spin-echo MR image (a)
shows large, round caudate nuclei and the cavum septum pellucidum. Coronal T2- weighted
turbo spin-echo (TR/TE: 4000/114 ms; section thickness: 3 mm) MR image (b) shows
malrotation of both hippocampi.
On coronal T2-W images, bilateral
hippocampal malformation was noted.
They were small, short, round, and
placed medially, with vertical collateral
Formation of the CC occurs between
the 8th and 20th gestational weeks
when growth of the entire brain also
]. Development of the CC is greatly influenced by formation
of the brain hemispheres; thus,
CC abnormalities frequently coexist
with various kinds of structural brain
anomalies. Not infrequently, it is those
associated anomalies that cause clinical
symptoms in which isolated CC
agenesis is detectable only with sophisticated
psychoneurological tests. Brain
injuries, cerebral atrophy, and myelination
disorders may cause focal or
diffuse thinning of the CC. With some
exceptions, such as holoprosencephaly,
or syntelencephaly, morphological
analysis of the CC allows differentiation
between callosal hypodysgenesis
and destructive processes[4
measurements of the CC in the pediatric
population were defined by Iai et al.
]. Normal morphology of the
CC, with the splenium as the thickest
part, was altered in the present case in which the genu was thicker than the
splenium, i.e. the genu was predominantly
affected. Many descriptions of
CC configuration anomalies have been
published. Most of these reports were
of developmental failure, such as agenesis,
hypogenesis, or acquired atrophic
changes. A case with thick genu and
body portions, in addition to agenesis
of the splenium, was associated with
a largely open Sylvian fissure, perisylvian
and frontal polymicrogyria,
multiple heterotopias, and facial and
symmetric megalencephaly, a
thick CC, enlarged white matter, and
incomplete opercularization were reported
in 3 cases by Gohlich-Ratmann
]. Morphometric analysis of the
CC was made in 2 of these 3 cases and
the genu was found to be thicker than
the splenium in both. The authors suggested that thickening of the CC might
have occured as a consequence of bihemispheric
in the presented case, the area of the
CC was significantly increased despite
a normal SSC area. Hence, we cannot
attribute callosal hypertrophy to cerebral
overgrowth in our case. Moreover,
2 separate studies on type-1 neurofibromatosis
patients showed increased
callosal size in comparison to normal
individuals, which could not be explained
solely by the presence of macrocephaly[7
]. Increase in size and/or
number of axons in Rhesus monkeys
due to thickened myelin or decreased
apoptosis, which normally occur in the
CC in the sixth postnatal month, were
]. Our patient
did not have any neurocutaneous stigmata.
A study that examined MRI abnormalities
in 18 patients with Cohen
Syndrome (characterized by typical
facial and structural features, mental
retardation, microcephaly, ophthalmologic
and cheerful disposition) reported
a relatively enlarged CC as the main
]. Clinical findings did not
meet the diagnostic criteria of Cohen
syndrome in our patient. A thick and
short CC in 2 unrelated cases with
hypertricosis, hyperkeratosis, mental retardation, and facial dysmorphism
was reported by Poyhonen et al.[11
Prenatal diagnosis can be performed,
as was done by Cavichioni et al. in a
patient who suffered from facial dysmorphism
and Willm's tumor of the
Given that the 3 steps in callosal
development are commiseration, establishment
of the callosal fiber tracts,
and maturation, the unusually thick
CC in the presented case might have
resulted from an abnormality in the
maturation step or perhaps in postnatal
progressive myelination of the CC. Although it is known that many
neuronal migration and hippocampal
developmental abnormalities coexist
with CC dysgenesis, the presence of
bilateral hippocampal malrotation and
caudate nuclei hypertrophy in conjunction
with mega CC distinguishes
the presented case.
In conclusion, with the increased use
of MRI, a much higher incidence of CC
anomalies have been diagnosed and it appears
that further investigation of associated
abnormalities and their relationship
to a thick CC is needed. Thus, morphology
of the CC should be carefully scrutinized,
especially on midsagittal MRI in
children with motor and/or mental retardation,
facial dysmorphism, and seizure.
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