Morphological studies of the corpus callosum by MRI in children with malformative syndromes

Children born to women treated for hypothyroidism during pregnancy show abnormal corpus callosum development

BACKGROUND

Thyroid hormone (TH) is essential for the developing brain, and because the fetal thyroid develops relatively late in gestation, the maternal TH supply is critical for fetal brain development. However, if the mother has hypothyroidism during pregnancy, fetal brain and neuropsychological development may be compromised. Rodents experiencing maternal TH insufficiency show abnormal corpus callosum (CC) morphology, but it is not known if children born to women treated for hypothyroidism (HYPO) show similar effects. The purpose of the current study was to investigate HYPO for CC morphology and morphometry and to determine whether any specific CC abnormalities were associated aspects of maternal hypothyroidism and were correlated with reduced neuropsychological functioning in the children.

METHODS

ANALYZE software was used to trace CCs in archived magnetic resonance imaging scans from 22 HYPO and 22 matched controls. Areas of two sub-regions and six segments and different shape metrics (angles, lengths, ratios) were determined. CC parameters were correlated with maternal thyrotropin (TSH) values and number of hypothyroid trimesters as well as the child's neuropsychological test performance.

RESULTS

HYPO showed a smaller anterior CC and genu and larger posterior CC and splenium areas than controls as well as shape abnormalities in genu and splenium. Results were correlated with the duration of maternal hypothyroidism. Executive function skills were positively associated with genu size in HYPO, while verbal comprehension skills were negatively associated with splenium and overall posterior CC sizes.

CONCLUSIONS

Maternal hypothyroidism contributes to CC abnormalities in the offspring, and effects differ for anterior versus posterior CC regions.

Malformations of Cortical Development in Patients with Midline Facial Defects and Ocular Hypertelorism

Objectives

We studied the neuroimaging and neurophysiological aspects of 17 patients with midline facial defects with ocular hypertelorism (MFDH).

Methods

The investigation protocol included a previous semistructured questionnaire about family history; gestational, neonatal, and postnatal development; and dysmorphologic and neurologic evaluation. Recognized monogenic disorders and individuals with other well-known conditions were excluded. All patients had high resolution magnetic resonance imaging (MRI) with multiplanar reconstruction (MPR) and routine electroencephalograms (EEGs).

Results

We detected abnormalities in five patients whose MRIs had been previously reported as normal. MRI showed central nervous system (CNS) structural abnormalities in all patients, which included commissural alterations in 16/17 (94%), malformations of cortical development in 10/17 (58%), disturbances of neural tube closure in 7/17 (42%), and posterior fossa anomalies in 6/17 (35%). Some patients had more than one type of malformation occurring at different stages of the embryonary process. EEGs showed epileptiform activity in 4/17 (24%) and background abnormalities in 5/17 (29%) of patients.

Conclusion

This study clearly demonstrated the presence of structural and functional neurologic alterations related to MFDH. Therefore, the CNS anomalies cannot be considered incidental findings but an intrinsic part of this condition, which could be related to environmental effects and/or genetic mutations. These findings would provide a basis for future investigations on MFDH and should also be considered when planning rehabilitation.

Many infants prenatally exposed to high levels of alcohol show one particular anomaly of the corpus callosum

INTRODUCTION

Effects of prenatal alcohol exposure on the brain are seen at every age. The earlier they can be quantified, the better the prognosis for the affected child. Here we show measurable alcohol effects at birth on a structure currently used for nosology only much later in life.

METHODS

Midline shape of the corpus callosum was imaged in infants via averaged unwarped transfontanelle ultrasound. We compared measures of these shapes among 23 infants prenatally exposed to high levels of alcohol and 21 infants unexposed to alcohol or only lightly exposed.

RESULTS

A particular feature of the corpus callosum, the appearance of a "hook" (obtuse angle) between the splenium and the long diameter of the arch in this plane, is strongly associated with prenatal alcohol exposure. In half of the high-exposed infants, the splenium angle is larger than in any of the unexposed brains. Simply characterizing this angle as less than or greater than 90 degrees detects 12 of the 23 exposed infants as anomalous with only 1 false positive among the unexposed. This apparently direct effect of prenatal ethanol exposure on the details of the callosum in about half the at-risk subjects cannot be attributed to any of several plausible competing exposures or other confounding factors applying during or after gestation.

CONCLUSION

An average of the images for the unexposed subjects has the geometry of textbook images of normal babies; but the average for the subgroup of high-angle subjects may serve as a template or guide to this regional damage parallel to the familiar photographic exemplars that help to assess facial signs.

Imagerie par résonance magnétique du retard mental non spécifique

Mental retardation is considered idiopathic or not otherwise specified when no etiological diagnosis can be identified in spite of comprehensive history, physical examination and metabolic or genetic investigations. In such cases, brain MRI is indicated for patients with abnormal head size or shape, craniofacial malformation, somatic anomalies, neurocutaneous findings, seizures, focal neurological findings or behavioral and/or developmental problems. Brain anomalies are now considered a main category for the etiology of mental retardation. MRI evaluation should include axial images of the entire brain, sagittal images through the midline structures, and coronal images of the posterior fossa or entire brain. MRI allows detection of major and or minor cerebral anomalies or malformations, sometimes multiple. In the literature, the most frequently involved structures include: 1/ corpus callosum (hypoplasia, short corpus callosum and verticalized splenium), 2/ septum pellucidum (cavum septum pellucidum or cavum vergae), 3/ ventricles (ventriculomegaly), 4/ cerebral cortex (cortical dysplasia), 5/ cerebellum (hypoplasia), and 6/ extra-axial CSF spaces (enlargement). In our patient population, dysplasia involving the cerebellum and vermis have been identified, a finding that has not yet been described in the literature. MRI allows detection of multiple minor morphological anomalies. Most have classically been considered as normal variants but they may in fact be markers of cerebral dysgenesis and are currently the only anomaly detected in the work-up of patients with mental retardation. Their role in the pathogenesis of mental retardation is under evaluation.

Asymmetry analysis of cingulum based on scale-invariant parameterization by diffusion tensor imaging

Current analysis of diffusion tensor imaging (DTI) is based mostly on a region of interest (ROI) in an image dataset, which is specified by users. This method is not always reliable, however, because of the uncertainty of manual specification. We introduce an improved fiber-based scheme rather than an ROI-based analysis to study in DTI datasets of 31 normal subjects the asymmetry of the cingulum, which is one of the most prominent white matter fiber tracts of the limbic system. The present method can automatically extract the quantitative anisotropy properties along the cingulum bundles from tractography. Moreover, statistical analysis was carried out after anatomic correspondence specific to the cingulum across subjects was established, rather than the traditional whole-brain registration. The main merit of our method compared to existing counterparts is that to find such anatomic correspondence in cingulum, a scale-invariant parameterization method by arc-angle was proposed. It can give a continuous and exact description on any segment of cingulum. More interestingly, a significant left-greater-than-right asymmetry pattern was obtained in most segments of cingulum bundle (-50-25 degrees), except in the most posterior portion of cingulum (25-50 degrees).

Macrocephaly, corpus callosum morphology, and autism

Although the cause of autism is undetermined, a general consensus has been that some type of early aberrant neural development underlies the disorder. Given the increased prevalence of macrocephaly in autism, one theory of abnormal neural development implicates early brain growth resulting in larger brain and head size in autism. Surface area measurements of the midsagittal section of the corpus callosum can be used as an index of neural development and white-matter integrity because the corpus callosum is the major white-matter structure that interconnects the two cerebral hemispheres. The purpose of this study was to obtain corpus callosum surface area, shape, and contour in a sample of non-mentally retarded autistic subjects with macrocephaly (n = 12) and compare them with those of matched (n = 8), typically developing control subjects with benign macrocephaly. No significant differences were found in surface area, shape, or contour between groups, nor did corpus callosum surface area relate to measures of IQ or picture vocabulary. These findings suggest no unique difference in overall regional corpus callosum surface area in autism with macrocephaly.

Angular analysis of corpus callosum in 18 patients with frontonasal dysplasia

Considering the rarity of the frontonasal dysplasia (FD) and the few reports about it in a large casuistry using magnetic resonance image (MRI), we describe the results of the angular analysis of the corpus callosum of 18 individuals with FD (7 male, 11 female), using an easily-reproductive method. Group I had 12 individuals with isolated form and Group II had 6 individuals with FD syndromic with unknown etiology. The results are presented in set. Comparing with the control group, patients with FD presented alpha angle increase and beta and gamma angles reduction (p<0.05). Alpha and gamma angles express the relationship between the anterior portion of corpus callosum and the floor of 4th ventricle. Considering the embryonary development, these findings would occur secondarily to failure during the development of nasal capsula. Thus, angular anomaly in corpus callosum would be a usual finding, and not fortuitous in patients with FD.

MRI in children with mental retardation

BACKGROUND

In mental retardation (MR) an aetiological diagnosis is not always obtained despite a detailed history, physical examination and metabolic or genetic investigations. In some of these patients, MRI is recommended and may identify subtle abnormal brain findings.

OBJECTIVE

We reviewed the cerebral MRI of children with non-specific mental retardation in an attempt to establish a neuroanatomical picture of this disorder.

MATERIALS AND METHODS

Thirty children with non-specific MR were selected to undergo cerebral MRI. The examination included supratentorial axial slices, mid-sagittal images and posterior fossa coronal images. Brain malformations, midline and cerebellar abnormalities were studied.

RESULTS

In 27 of 30 patients, the neuroimaging evaluation revealed a relatively high incidence of cerebral and posterior fossa abnormalities. The most frequent were: dysplasia of the corpus callosum (46%; hypoplasia, short corpus callosum and vertical splenium), partially opened septum pellucidum and/or cavum vergae (33%), ventriculomegaly (33%), cerebral cortical dysplasia (23%), subarachnoid space enlargement (16.6%), vermian hypoplasia (33%), cerebellar and/or vermian disorganised folia (20%), and subarachnoid spaces enlargement in the posterior fossa (20%). Other anomalies were: enlarged Virchow-Robin spaces (10%), white matter anomalies (10%) and cerebellar or vermian atrophy.

CONCLUSIONS

MRI has shown a high incidence of subtle cerebral abnormalities and unexpected minor forms of cerebellar cortical dysplasia. Even if most of these abnormalities are considered as subtle markers of brain dysgenesis, their role in the pathogenesis of mental retardation needs further investigation.

Second trimester prenatal alcohol exposure alters development of rat corpus callosum

Prenatal alcohol exposure produces many developmental defects of the central nervous system (CNS), such as in the corpus callosum (CC). This study was designed to observe the effect of prenatal alcohol exposure during the second trimester equivalent on the development of dendritic arbors of CC projection neurons (CCpn) in rat visual cortex. In addition, the effect of second trimester equivalent prenatal alcohol exposure on brain weight was determined. Pregnant dams received 1.2-6.0 g/kg ethanol (EtOH) during gestational day (G) 11-20. Controls consisted of normal and nutritionally matched pairfed (PF) dams. Pups were sacrificed on the day of birth, G26, G29 and G33. DiI crystals were placed in the midsagittal CC bundle to retrogradely label CCpn. Images of visual cortex were obtained from tissue slices using a confocal laser scanning microscope. The number and length of apical and basilar dendrite branches were determined. The results show that prenatal alcohol exposure restricted to the second trimester equivalent alters the development of the CCpn dendritic arbor and the brain weight in a blood alcohol concentration (BAC)-dependent manner. The alteration in the EtOH CCpn is manifested as an increase in the number and length of CCpn apical and basilar dendrite branches, while brain weight is reduced compared with Controls.

White-matter alterations and callosal abnormalities in syndromic patients with mental retardation

The aim of this study was to evaluate the frequency of callosal abnormalities and white matter alterations in syndromic patients. The authors report on the cerebral magnetic resonance imaging (MRI) morphologic analysis of the corpus callosum and white matter in 73 normal subjects and 61 syndromic patients. The study of the corpus callosum was carried out by MRI using different morphometric methods: measurement of the dimensions of length and thickness of genu, body, and splenium; measurement of angles obtained using the sagittal plane; and application of the proportional grid of Talairach. The evaluation of the white matter was carried out by applying a subjective grading scale. Abnormalities of the corpus callosum were found in about 50% of the syndromic subjects; in half of these cases, the abnormalities were associated with white matter alterations. In five syndromic patients (8.2%), the white matter alterations were not associated with corpus callosum abnormalities. This study shows that corpus callosum abnormalities are frequent in syndromology regardless of the syndrome type.

Minor cerebral alterations observed by magnetic resonance imaging in syndromic children with mental retardation

OBJECTIVE

To evaluate the anomalies of the central nervous system (CNS) by magnetic resonance imaging (MRI) in normal subjects and in syndromic patients.

METHODS AND MATERIAL

Seventy-three normal subjects and 50 different syndromic patients with mental retardation (from 3 months to 16 years) were studied utilizing several morphometric parameters (degree of myelination of the white matter, evaluation of liquoral spaces, septo-caudate distance, Evans index, Aboulezz method, and length, width and angles of corpus callosum).

RESULTS

A high frequency of anomalies of the corpus callosum, the Chiari anomaly and alterations either of the white matter or of the ventricular and periencephalic system have been observed.

CONCLUSION

The authors point out the importance of cerebral MRI in the study of CNS in patients with malformation syndromes. The present research, carried out on a large number of both normal subjects and patients with malformation syndromes, represents one of the first systematic studies in this field.

Minimal surface: a useful paradigm to describe the deeper part of the corpus callosum?

The aim of this magnetic resonance imaging study was to find a geometrical characterization of the deeper part of the corpus callosum. Its shape was studied in 12 middle-aged persons free of white matter pathology. Profiles of curvatures were measured showing that this surface was close to a minimal one, especially at the genu and near the splenium. To assess the effect of a white matter pathology on these geometrical features, the same measurements were performed in an extra group of nine patients with definite multiple sclerosis. The hypothesis of curvatures profiles parallelism for the two groups could be rejected at the 0.05 confidence level for the mean curvatures but not for the Gaussian ones. Curvatures profiles may give indications on balance between the cortex and the fiber bundles growth rates during the development and on large scale modifications co-occurring with multilocular white matter pathologies.

Hearing, speech, language, and vestibular disorders in the fetal alcohol syndrome: a literature review

Fetal alcohol syndrome (FAS) is characterized in part by mental impairment, as well as craniofacial and ocular anomalies. These conditions are traditionally associated with childhood hearing disorders, because they all have a common embryonic origin in malformations of the first and second branchial arches, and have similar critical periods of vulnerability to toxic insult. A review of human and animal research indicates that there are four types of hearing disorders associated with FAS. These are: (1) a developmental delay in auditory maturation, (2) sensorineural hearing loss, (3) intermittent conductive hearing loss due to recurrent serous otitis media, and (4) central hearing loss. The auditory and vestibular systems share the same peripheral apparatuses (the inner ear and eighth cranial nerve) and are embryologically and structurally similar. Consequently, vestibular disorders in FAS children might be expected. The evidence for vestibular dysfunction in FAS is ambiguous, however. Like other syndromes associated with craniofacial anomalies, hearing disorders, and mental impairment, FAS is also characterized by a high prevalence of speech and language pathology. Hearing disorders are a form of sensory deprivation. If present during early childhood, they can result in permanent hearing, language, and mental impairment. Early identification and intervention to treat hearing, language, and speech disorders could therefore result in improved outcome for the FAS child. Specific recommendations are made for intervention and future research.

Regional MRI measurements of the corpus callosum: a methodological and developmental study

A technique for quantifying the midsagittal size and shape of the corpus callosum (CC) from magnetic resonance brain scans is presented. The technique utilizes the distances to the ventral and dorsal boundaries of small sectors of the CC from a reference point to compute the size and shape parameters of the CC and its subdivisions. Intrarater and interrater interclass correlation coefficients for the area measurements ranged from 0.88 to 0.99. Correlations between these automated measures and those obtained by pixel counting were equally high. The corpus callosa of 104 (57 male and 47 female) right-handed healthy children and adolescents, ages 4-18, were examined in relation to age and sex. Corpus callosum growth was most striking for the splenium and isthmus with some changes in the midbody regions. The area and perimeter of these regions increased, shapes became more compact, and the boundaries became more regular with age. The length and curvature at the anterior and posterior regions of the CC increased more rapidly in males than in females. These significant and consistent results indicate that the method is reliable and sensitive to developmental changes of the CC.

Shape of the human corpus callosum in childhood. Elliptic Fourier analysis on midsagittal magnetic resonance scans

RATIONALE AND OBJECTIVES

The authors previously investigated the midsagittal magnetic resonance images of neurologically intact adults, and analyzed the shape of corpus callosum from a mathematic standpoint. Significant effects of age were demonstrated, without significant sex differences. In the current study, the same mathematic method was applied to analyze the sex and age shape differences of the human corpus callosum in childhood.

METHODS

On the midsagittal magnetic resonance images of 84 neurologically intact children (39 boys, 45 girls, aged 4 months to 15 years) the outline of the corpus callosum was identified. Its shape was quantified using elliptic Fourier analysis, which allows for global evaluation of the shape of organs identified by their outlines independently from size, spatial orientation, and relationship to reference planes. Subjects were grouped by sex and age.

RESULTS

The shape of the corpus callosum within age and sex classes in childhood was more homogeneous than in adulthood. A significant effect of age was demonstrated by the analysis of variance; however, no significant sex differences were found.

CONCLUSIONS

Corpus callosum shape in midsagittal magnetic resonance images was strongly influenced by central nervous system development and aging, but the influence of sex was not sufficient to be detected by current standard magnetic resonance imaging technology, and by the available sample sizes. The current investigation supplies data on the normal callosal shape in the first two decades of life, thus completing previous analysis.

Abnormalities of the corpus callosum in children prenatally exposed to alcohol

For 20 years, it has been known that fetal alcohol syndrome (FAS) is associated with abnormal brain development. Early autopsy studies point to the corpus callosum as one area affected by heavy alcohol exposure. Little is known, however, about the integrity of the brain in alcohol-exposed children who survive the perinatal period. This study was designed to assess the corpus callosum in living children exposed to high doses of alcohol prenatally. Thirteen children with histories of significant prenatal alcohol exposure and 12 normal control children were evaluated using magnetic resonance imaging. Using the midsagittal section, images were measured for the area of the corpus callosum using a computer-assisted measurement technique. In addition to the overall area, five equiangular regions were determined for each corpus callosum. Of the 13 alcohol-exposed children assessed, two had agenesis of the corpus callosum. The remaining alcohol-exposed children had significantly smaller overall callosal areas, as well as smaller regional areas of four of the five callosal regions, when compared with the normal control children. Importantly, when corrected for brain size, three of the five callosal regions were still smaller in the alcohol-exposed children, although overall area of the corpus callosum was no longer significantly different. These results suggest that prenatal exposure to high levels of alcohol is associated with abnormalities of the corpus callosum. They verify callosal agenesis in children with FAS, which previously had only been noted in autopsy reports.(ABSTRACT TRUNCATED AT 250 WORDS)

Morphometric study of the corpus callosum in Fukuyama type congenital muscular dystrophy by magnetic resonance imaging

The corpus callosum (CC) of 24 Fukuyama type congenital muscular dystrophy (FCMD) patients were studied using midsagittal MRI and the results were compared with those of 20 age-matched controls. The measurements included the thickness of the genu, body and splenium; the length, height and five specific angles of the CC. The cephalic index was also measured on axial MRI. The correlations among CC length, CC height, the five angles and the cephalic index were evaluated. One case of FCMD was found to have CC agenesis. The thickness of the genu, body, splenium and CC length were significantly reduced in FCMD. In addition, in FCMD, the CC height was increased, angle alpha was greater, angle delta reduced and the CC configuration more rounded, showing a high arch on imaging. No significant correlations among CC length, CC height, the five specific angles and the cephalic index were found in any of the FCMD data. These observations demonstrated the fact that CC development in FCMD is uniquely abnormal, and abnormal CC configuration does not have any correlation with altered cephalic index.

MRI study of the corpus callosum using the Talairach grid

The authors show how the Talairach grid may be applied to MRI for the study of the topography of the corpus callosum. Thirty-eight patients with malformative syndromes and 53 controls were studied to demonstrate the reliability of this method.