Morphometric MRI evaluation of corpus callosum and ventricles in normal adults

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Morphometric MRI evaluation of corpus callosum and ventricles in normal

adults

Article in Neurological Research · December 2011

DOI: 10.1179/1743132811Y.0000000030 · Source: PubMed

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Published by Maney Publishing (c) W. S. Maney & Son Limited

Morphometric MRI evaluation of corpus

callosum and ventricles in normal adults

Pınar Karakas¸

1

, Zafer Koc¸

2

, Filiz Koc¸

3

, M Gu

¨lhal Bozkır

1

Department of Anatomy, Faculty of Medicine, C¸ukurova University,2Department of Radiology, Faculty of

Medicine, Bas¸kent University,3Department of Neurology, Faculty of Medicine, C¸ukurova University, Adana,

Turkey

Objectives: The aim of this study was to determine the normal values of subregions of corpus callosum and ventricles in healthy adult people in our population using magnetic resonance imaging (MRI) and to establish gender differences.

Methods: The MRI of 52 healthy individuals (29 females and 23 males) aged 20–50 years was obtained. The measurements were performed from MRI on a workstation. The midsagittal images were used for measurements of the subregions of corpus callosum and axial images were for lateral and third ventricles. Results: The mean values of the widths of genu, body, splenium, and height of the corpus callosum were 13.28¡2.10, 7.64¡1.07, 12.52¡1.35, and 25.47¡2.20 mm, respectively in females; whereas, the same measurements were 13.23¡2.41, 6.89¡2.12, 11.90¡1.94, and 25.03¡3.38 mm, respectively in males. Moreover, the mean value for the longitudinal dimension of the brain was 150.12¡5.04 mm, while that for the corpus callosum was 71.27¡3.70 mm in females. Additionally, the mean frontal horn width of the lateral ventricle and the transverse inner diameter of the skull were 34.06¡3.05 and 130.76¡6.71 mm in females and 34.03¡2.78 and 129.96¡10.61 mm in males, respectively. Due to these measurements, the values of Evans index which is reflecting the lateral ventricle enlargement were estimated to be 0.25¡1.90 and 0.25¡1.14 in females and males, respectively. According to our last measurement result, the mean values for the third ventricle width were 3.79¡0.85 and 4.12¡0.94 mm in females and males, respectively. These findings show that there are differences between the averages of some indices of corpus callosum of our population and the other populations.

Keywords: Corpus callosum, Lateral ventricle, MRI, Normal adult, Third ventricle

Introduction

The corpus callosum is the major transverse com-missure connecting the cerebral hemispheres and consists of subregions like genu, rostrum, trunk,

and splenium.1,2 It plays a key role in relaying

sensory, motor, and cognitive information between

homologous regions in the hemispheres.3,4Moreover,

its vulnerability to some toxins like alcohol and some white matter diseases like multiple sclerosis is also

important and not to be forgotten.2,5

The corpus callosum develops between 8 and 20 weeks of gestation. Inter-hemispheric crossing fibres begin to transverse the massa commisuralis in the genu region at 11–12 weeks post-conceptional age. Additionally, the rostrum develops at 18– 20 weeks post-conceptional age. Therefore, embry-ologically, the pioneer fibres of the future corpus callosum cross the midline in the 60–80 mm fetus

(12–13 weeks post-conceptional age) and it is effec-tively adult-like in the 140–60 mm fetus (18–20 weeks

post-conceptional age). It has emphasized that

agenesis of corpus callosum or absent rostrum may be rarely seen variations. Absent rostrum is usually found as a chance while evaluating magnetic

reso-nance imaging (MRI) for other purposes.6–8

The anatomy of the corpus callosum has received more interest due to increasing surgical interventions like callosotomies and treatment for some forms of

epilepsy.9,10Thus, some anatomical landmarks could

be found as reference points for microsurgery to this area. Therefore, a detailed morphometric measure-ment of corpus callosum is required. In addition, accurate measurements of the size of this structure in healthy adult people can provide the normal values and thus establish reference values to compare gender, racial differences and evaluate patients’ values.

Ventricular size is important for determination of many neurological diseases and ventricular enlarge-ment shows loss of brain parenchyma. Furthermore, Correspondence to: Pınar Karakas¸, Department of Anatomy, Faculty of

Medicine, C¸ ukurova University, Adana 01330, Turkey. Email: pkarakas@ cu.edu.tr

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measurements of the ventricular size are used in studies

of hydrocephalus following third ventriculostomy.11–15

Due to the literature findings, the majority of the reports about normal values for ventricular size involve

children and adolescents younger than 20 years.11,16,17

In this respect, the values of ventricular size in adults could be necessary for evaluating the pathologies from normal brains.

The aim of this study was to document the normal values of subregions of corpus callosum and lateral and third ventricles using MRI in healthy adult females and males in our population and to identify the gender differences, if any.

Materials and Methods

The research protocol of this study was approved by our institutional review board, and ethics committee approval also was obtained. Written informed con-sent was obtained from all individuals before MRI examination. This study is based on retrospective evaluation of cerebral MRI in consecutive 52 (29 females and 23 males) individuals aged 20–50 years (mean¡standard deviation of females: 35.64¡8.74 years; mean¡standard deviation of males: 36.11¡ 13.10 years) over a period of 2 years between March 2007 and March 2010. Inclusion criteria were no neurological signs, no intracranial lesions on MRI, and no history of neurological illness, current or past psychiatric illness, alcoholism, or drug use problems.

MRI was performed using a 1.5-T MRI system (Siemens; Avanto, Erlangen, Germany). A circularly polarized matrix coil was used for radiofrequency reception of the MRI signal. Routine brain MRI protocol including axial T2-weighted turbo spin echo (TSE) (TR/TE, 4500/118 ms; slice thickness, 6 mm; gap, 1.5 mm) and sagittal T1-weighted spin echo (SE)

(TR/TE, 450/11 ms; slice thickness, 5 mm; gap, 1.5 mm) was used.

Image analyses were performed randomly by two observers [observer 1, a radiologist (ZK) and observer 2, an anatomist (PK)]. The two observers reviewed MR images and performed all measure-ments in consensus. For intraobserver variability, all measurements were randomly performed by consen-sus in different sessions separated from the first evaluations by at least 3 weeks to minimize recall bias. Averages of the two measurements were used for final value of all measured region. The measure-ments were performed from digital MR images on a workstation (Advantage 4.4; GE Heathcare, Milwaukee, WI, USA) using caliper function with 62 magnification. Six measurements from subre-gions of the corpus callosum were determined using the midsagittal T1-weighted SE image as follows (Fig. 1):

(A) the width of the genu;

(B) the width of the body;

(C) the width of the splenium;

(D) the length of the corpus callosum from anterior

to posterior;

(E) the maximum height of the corpus callosum. A

line was taken between the inferior points of the rostrum and splenium. Another line parallel to this was taken the top point of corpus callosum. Distance between these lines was recorded; (F–G) the distance from the frontal to occipital pole

(the longitudinal dimension of the brain). Using axial T2-weighted TSE images, the following parameters were measured (Figs. 2 and 3):

Figure 1 Midsagittal T1-weighted SE MRI (TR/TE, 450/ 11 ms) of measurement sites of a normal adult. (A) The width of the genu. (B) The width of the body. (C) The width of the splenium. (D) The length of the corpus callosum from anterior to posterior. (E) The maximum height of the corpus callosum. (F–G) The distance from the frontal to occipital pole.

Figure 2 Axial T2-weighted TSE MRI (TR/TE, 4500/118 ms) of measurement sites of a normal adult. (H) The maximum width between the frontal horns of the lateral ventricles. (I) The maximum transverse inner diameter of the skull at the same level.

Karakas¸ et al. Morphology of corpus callosum and ventricles

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(H) the maximum width between the frontal horns of

the lateral ventricles (frontal horn width);

(I) the maximum transverse inner diameter of the

skull at the same level. After these measurements, Evans ratio (H/I) was calculated. It is assumed to reflect frontal horns ventricular enlargement;

(J) the maximum width of the third ventricle

mea-sured at the level of the section where Monro’s foramen was visible.

The data were divided into two groups due to gender and statistical analysis was performed with SPSS 10.0. From these measurements, means, standard deviations, minimum, and maximum values were

evaluated. The intraobserver variability agreement of measurements was calculated using Spearman’s rank correlation test.

Results

The dimensions of corpus callosum and ventricular size of healthy adults are shown in Table 1.

From the 52 MRI scans, various dimensions of corpus callosum and ventricular size were measured (Figs. 1–3). The mean values of the widths of genu, body, splenium, and height of the corpus callosum were 13.28¡2.10, 7.64¡1.07, 12.52¡1.35, and 25.47¡ 2.20 mm in females, respectively; whereas, the same measurements were 13.23¡2.41, 6.89¡2.12, 11.90¡ 1.94, and 25.03¡3.38 mm in males, respectively. Moreover, the mean value for the longitudinal dimension of the brain was 150.12¡5.04 mm, while that for the corpus callosum was 71.27¡3.70 mm in females, a ratio of .2 : 1. This ratio was also similar in males (the same longitudinal dimensions were 152.53¡5.43 and 73.05¡ 5.28 mm in males, respec-tively) (Fig. 1). Additionally, the mean frontal horn width of the lateral ventricle and transverse inner diameter of the skull were 34.06¡3.05 and 130.76¡ 6.71 mm in females and 34.03¡2.78 and 129.96¡ 10.61 mm in males, respectively (Fig. 2). Due to these measurements, Evans ratios were 0.25¡1.90 and 0.25¡1.14 in females and males, respectively. Accord-ing to our last measurement result, the mean values for the third ventricle width were 3.79¡0.85 mm in females and 4.12¡0.94 mm in males (Fig. 3). The intraobserver variability agreement of the measure-ments was found to be good (0.89–0.96) between the evaluation in different sessions by two observers in Figure 3 Axial T2-weighted TSE MRI (TR/TE, 4500/118 ms)

of measurement site of the third ventricle of a normal adult. (J) The maximum width of the third ventricle.

Table 1 Dimensions of corpus callosum and ventricular size (mm)

Dimensions Sex Mean¡standard deviation Minimum–maximum

A Female 13.28¡2.10 9.75–19.33 Male 13.23¡2.41 10.80–20.13 B Female 7.64¡1.07 5.86–9.40 Male 6.89¡2.12 3.90–12.63 C Female 12.52¡1.35 10.21–16.42 Male 11.90¡1.94 8.30–15.04 D Female 71.27¡3.70 64.50–79.10 Male 73.05¡5.28 65.71–84.90 E Female 25.47¡2.20 21.30–29.05 Male 25.03¡3.38 18.83–31.72 F–G Female 150.12¡5.04 143.80–159.80 Male 152.53¡5.43 141.02–160.82 H Female 34.06¡3.05 26.70–40.00 Male 34.03¡2.78 28.45–39.60 I Female 130.76¡6.71 110.10–145.10 Male 129.96¡10.61 107.30–143.87

Evans index Female 0.25¡1.90 0.21–0.29

Male 0.25¡1.14 0.24–0.28

J Female 3.79¡0.85 2.50–5.70

Male 4.12¡0.94 3.00–5.60

Note: A: the width of the genu; B: the width of the body; C: the width of the splenium; D: the length of the corpus callosum from anterior to posterior; E: the maximum height of the corpus callosum; F–G: the distance from the frontal to occipital pole; H: the maximum width between the frontal horns of the lateral ventricles; I: the maximum transverse inner diameter of the skull at the same level; Evans ratio: H/I; J: the maximum width of the third ventricle.

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consensus (minimum correlation coefficient50.89 for ‘maximum width of the third ventricle’, and max-imum50.96 for ‘distance from the frontal to occipital pole’).

Discussion

This study included various parameters of the corpus callosum and ventricular size in healthy adults and compared them with other populations. The radi-ologically created values of corpus callosum and ventricles in both genders are valid for morphologi-cally normal brains and malformations should there-fore be carefully determined.

The corpus callosum is a topographically orga-nized neural structure that is composed of the majority of the commisural fibres connecting the

two cerebral hemispheres.18,19Morphological

varia-bility in the corpus callosum is often found in diseases such as Alzheimer’s disease, depression,

autism, and schizophrenia.4,18,20 Furthermore,

stu-dies using postmortem material or MRI obtained some sex differences in the size of subregions of corpus

callosum.18,21,22 When we analyse our images, the

averages of the widths of genu, mid-body, and splenium were 13.28, 7.64, and 12.52 mm in females and 13.23, 6.89, and 11.90 mm in males, respectively. Females’ body and splenium values are found higher than males’. It is in concordance with most literature findings that suggested the splenium size difference

between genders.18,21,23–25 However, it was generally

declared that males have larger bodies than females.5

But we found the opposite. In a study consisting of Chinese adults, these values were 11.68, 6.33, and

11.53 mm, respectively.22Same dimensions were 9.91,

5.58, and 9.94 mm in Japanese individuals while they

were 11.2, 8, and 11.5 mm in Indian, respectively.10,26

Furthermore, Mourgela et al. reported the widths of genu and splenium to be 21.3 and 7.4 mm,

respectively.27According to these data, we found

di-fferences in all average values of Chinese, Japanese, and Indian compared with our results: they have lower values than us. Mourgela’s averages were significantly different from ours. The width of genu

was y8 mm greater than ours; however, the width

of splenium was 5 mm lower than us.

Some direct identifiable landmarks for corpus callosum could be useful for surgery; however, the variability of its morphology makes it difficult. During the callosotomy, rostral majority of the corpus callosum must be split to increase the clinical

success.9,28,29 Moreover, it was shown that during

microsurgery, there was distortion of the corpus callosum due to the flattening of the brain. This

situation resulted in increasing horizontal and

decreasing vertical dimensions of corpus callosum, by 15% of its total length and 20% of its maximum

height, respectively.9 Gonc¸alves-Ferreira et al.

eval-uated an average total length of 74.9 mm and a total height of 25.5 mm; whereas, they were 75.7 and

32.7 mm respectively in Indian.9,10 Moreover, they

were identified to be 70.7 and 24.5 mm respectively in Chinese population and 69.7 and 25.8 mm

respec-tively in Japanese.22,26From our study, these

dimen-sions were 71.2 and 25.4 mm in females whereas 73 and 25 mm in males, respectively. Due to these reports, we found some differences between other populations and our values: especially Indian have higher values than us. Conversely, the average total lengths of corpus callosum of Chinese and Japanese people were lower than ours. However, in this investigation, the average total length of corpus callosum was closer to the values given in classical

publications.9According to this paper, the

measure-ment of the maximum height of the corpus callosum shows that the depth of the surgical incision to have a complete sectioning of the rostral corpus callosum must be 25 mm.

The lengths of the brain were established to be 150.1 mm in females and 152.5 mm in males in our study group. In addition, when we investigated the ratio of the length of the brain to that of the corpus callosum, it was 2.1. This dimension result showed

similarity with other researches.10,27,30

Moreover, ventricular enlargement indicates loss of volume of brain parenchyma and this atrophy is associated with many neurological diseases like

dementia, stroke, Huntington’s disease, etc.12 It was

also notified that the most consistent structural neu-roimaging finding is enlargement of lateral and third

ventricles in schizophrenic patients.31,32Additionally,

it was informed that patients with multiple sclerosis had significantly larger ventricular sizes than healthy controls and showed an increase in size with

pro-gression of the disease.12,33,34 The linear

measure-ments of ventricles were made for evaluating the normative ventricles’ values in this paper. Lateral ventricles enlargement was evaluated by averages of Evans ratio and this ratio was found to be 0.25 in both genders in our investigation. These values were similar with those in previous reports from Norway

and England.13,33However, Evans ratio was reported

to be 0.26 and 0.27 in females and males, respectively

in Japanese.26From several studies about the average

of third ventricle width, they were reported to be 3 mm in females and 4 mm in males from Norway; whereas, Turner and colleagues obtained the same

dimension as 5.14 mm.13,33 Meanwhile, this width

was found to be 5.7 mm in Japanese people.26 Our

values for this distance are closer to that in the report from Norway.

In this study, we observe that there are differences between the averages of some indices of corpus

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callosum of Indian, Japanese, Chinese, and our population. However, in a study from Greece, we identify that there are also different averages from ours. Moreover, it is seen that ventricular dimen-sions are similar with those of European population. We think that these diversities may be a result of some factors such as race, genetic variables, indivi-dual constitution, and age. New, sex-specific norma-tive standards for radiological indices of corpus callosum and ventricular size in our population are presented. These linear measurements should be applicable for routine MRI reading without any need of an extra programme in a computer. Callosotomy is often performed using a restricted technique to access to intraventricular pathology and rostral subcallosal areas and to treat some

epilepsy forms.9Therefore, the precise knowledge of

subregions of corpus callosum could be helpful for the surgeon to have a good result. Furthermore, the assessment of ventricular size is generally obtained from subjective evaluation without determination of the normative standards and the effect of brain volume change during ageing in healthy people has to be taken into account in studies of different brain

pathologies.13It therefore becomes necessary to have

normal values for various racial groups, to compare with normal as well as pathological conditions. As a result, we believe that these normal reference values of corpus callosum and ventricles obtained from MRI are essential baseline data for interpreting pathological changes, planning surgery, and deter-mining presence and progress of some neurological diseases.

In conclusion, there are differences between the averages of some indices of corpus callosum of our population and the other populations. Ventricular dimensions of our population are similar with those of European population. New, sex-specific normative standards for radiological indices of corpus callosum and ventricular size in our population are applicable for routine MRI reading.

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