RPS 411 - Paediatric neuroimaging and neuroanatomy

Purpose:

To define the changes in subfields and subregions of the hippocampus in normal ageing.

Methods and materials:

We examined 83 normal volunteers without neurological or psychiatric disorders divided into groups: 15-19, 20-24, 25-29, 30-39, 40-49, 50-59, 60-69 years old, and older than 70.

MR VBM was performed using 3D MPRAGE on MRI 1.5T XGV (Canon, Japan) with Freesurfer 6.0.

Results:

A comparative analysis using the Mann-Whitney criteria defined the increase of the whole hippocampal volume until the age of 29. Then until 39, there was no difference. After that first slow (until 69) and after 70, a quick decrease of 17% of a significance level, p≤0.05.

The most significant difference occurred in the CA3 Broadmann area increasing until 24 years old, 12% of a significance level, p≤0.05. Until 49, there was no difference. There was a decrease of 7% until 70 years, and after 70 years, a decrease of 19% of a significance level, p≤0,01. The same results we found in the CA1 Brodmann area: increasing until age 29 years then a slow decreasing. After 70 years, a decrease of 18% of a significance level, p≤0,05, was seen. A significant difference was found in the hippocampal sulcus of 20% of a significance level, p≤0.05.

In old age, a significance level, p≤0.05, was found in the decrease in the volume of the hippocampal tail of 23%, molecular layer of hippocampus (14%), and of the dentate gyrus (19%), fimbria (37%), and subiculum (16%).

Conclusion:

In our research, we found significant dynamics of differences in the whole volume of the hippocampus. The most significant changes were found in the CA1 and CA3 Broadmann areas, hippocampal sulcus, fimbria, hippocampal tail, subiculum, molecular layer of hippocampus, and dentate gyrus.

Limitations:

n/a

Ethics committee approval

Ethics committee approval obtained.

Funding:

No funding was received for this work.

Purpose:

The brainstem is involved in different types of hindbrain anomalies, which are nowadays increasingly detected by prenatal sonography. However, little is known about the proportions of different foetal brainstem segments and their evolution throughout pregnancy. This study aimed to assess the midsagittal two-dimensional area of brainstem substructures with foetal MRI.

Methods and materials:

Prenatal cases with normal brain development were retrospectively assessed. The midbrain, pons, and medulla oblongata were segmented using a T2-weighted median sagittal slice and ITK snap. The ratios of the brainstem substructures were calculated and correlated to gestational age.

Results:

148 brain-normal foetal MRI with a mean age of 25.26±4.12 gestational weeks (GW) showed a sufficient image quality to be assessed. The ratio midbrain:pons significantly decreased (p<0.01) from 0.6 to 0.5 between 18 and 40 GW, whereas the ratio pons:medulla oblongata increased significantly (p<0.01) from 1.5 to 1.8. The ratio midbrain:medulla oblongata remained 0.9 throughout gestation (p=0.91).

Conclusion:

Two-dimensional segmentation of brainstem substructures revealed that there was an increase in the size of pons compared to midbrain and medulla oblongata during the 2nd and 3rd trimester. Brainstem proportions at the early second trimester (midbrain:pons:medulla=3:4:3) differ from those postnatally (1:2:1), which has to be acknowledged when assessing the brainstem in foetal hindbrain malformations.

Limitations:

An inherently limiting factor of foetal imaging is the small size of the posterior fossa. The size and limited resolution make segmentation prone to partial volume effects. Although movement artefacts can be a limiting factor, we were able to bypass them by repeating the desired image plane.

Ethics committee approval

Ethics committee approval and written informed consent were obtained.

Funding:

No funding was received for this work.

Purpose:

To compare the apparent diffusion coefficient (ADC) values of different areas of the brain in foetuses with intrauterine growth restriction (IUGR) and control cases.

Methods and materials:

A total of 38 foetuses with IUGR and 18 control foetuses with similar gestational age were compared using a 3T magnetic resonance scanner. IUGR cases included 23 foetuses with clinical severity signs (group A) and 15 foetuses without these signs (group B). ADC values were measured in different brain regions and compared among the groups. Foetuses with brain structural abnormalities were excluded.

Results:

Foetal brain signal and anatomy were normal in all foetuses. Head circumference <5% was more common in IUGR compared to IUGR B (56.5% vs 13.3%, p<0.0001). In comparison to the normal group, the ADC values in IUGR foetuses were significantly lower in the cerebellar hemisphere (CH) (1.239 vs 1.280.5 x10-3 mm2/sec, p=0.045), thalami (1.205 vs 1.285 x10-3 mm2/sec, p=0.031), and caudate nucleus (CN) (1.319 vs 1.394 x10-3 mm2/sec, p=0.04). However, ADC values were not significantly different between IUGR subtypes. Pons had the lowest ADC values among all brain regions.

Conclusion:

In a comparison with a control group, ADC values of some brain areas (thalami, CN, and CH) were found to be significantly lower in IUGR foetuses, though there were not any significant differences in IUGR subtypes.

Limitations:

The specificity and sensitivity might be overestimated because the ADC value cut-off was calculated from our own cases.

Ethics committee approval

Institutional review board approval and parents' informed consent were obtained.

Funding:

No funding was received for this work.

Purpose:

Emerging research confirms our understanding of epilepsy as a network disorder that involves more widespread cortical compromise than previously assumed. However, little is known about the developed laminar-specific cortical disruption. We aimed to investigate the cortical laminar architecture of the neocortex beyond the measurement of cortical thickness using clinically feasible structural MRI.

Methods and materials:

Epilepsy patients with focal cortical dysplasia (FCD; n=9), periventricular nodular heterotopia (PVH; n=9), and age-matched healthy controls (HC; n=9) underwent T1 relaxation 3T-MRI, of which component probability T1-maps were utilised to extract a sub-voxel composition of 6 T1 cortical layers. 78 cortical areas of the automated anatomical labelling (AAL) atlas were divided into 1,000 equal-volume sub-areas and logistic regressions were performed to compare FCD/PNH patients to HC, with the T1-layers composing each sub-area as regressors. The significance maps were projected on MNI brain templates.

Results:

Widespread cortical dyslamination was observed in the patient groups compared to the HC. Out of 1,000 sub-areas, 291 bilateral hemispheric cortical sub-areas were found to predict FCD and 256 to predict PNH. For each of these sub-areas, we were able to identify the T1-layer, which contributed the most to the prediction.

Conclusion:

Our results reveal similar widespread cortical dyslamination in epilepsy patients with FCD and PNH, which supports the concept of epilepsy as a network disease, although intrinsic abnormalities of neuronal development may be a contributory factor. As the ability to assess structural and functional connections in the human brain increases through both diffusion tensor imaging and functional MRI, using qualitative and quantitative information of cortical laminar patterns in epilepsy patients as a sensitive imaging biomarker could potentially elucidate pathophysiologic mechanisms and facilitate patient management towards developing individually tailored treatment.

Limitations:

n/a

Ethics committee approval

Ethics committee approval obtained.

Funding:

No funding was received for this work.

Purpose:

According to the updated WHO 2016 classification of CNS tumours, diagnosis of a medulloblastoma now demands genetic subgroup information (in addition to histopathology), defining the tumour biology, therapy and prognosis more precisely. The aim of this study was to assess potential correlations of qualitative and quantitative MRI features for differentiation of genetic subtypes of medulloblastomas.

Methods and materials:

A retrospective single-centre analysis of all patients with medulloblastomas from 2015-2019 with available genetic subgroup information (WNT, SHH, and non-WNT/non-SHH) was conducted. Regarding qualitative MRI analysis, tumour location as well as presence/absence of contrast-enhancement, oedema, cysts, and signs of metastatic disease were evaluated. Quantitative MRI analysis consisted of manual region-of-interest (ROI) based on ADCmean calculation within the solid tumour. Statistical analysis included a comparison of ADCmean between the genetic subgroups and a correlation with histopathological and imaging features.

Results:

30 patients (8 female, mean age=12 years) were included. 3/30 tumours were WNT-activated (10%), 11/30 (37%) SHH-activated, and 16/30 (53%) were classified as non-WNT/non-SHH. The tumour was located centrally in 19/30 (63%) and laterally in 7/30 (23%) patients. Distinct contrast enhancement was present in 3/30 (10%), oedema in 6/30 (20%; exclusively SHH subtypes), cysts in 25/30 (83%), and signs of metastatic disease in 13/30 (43%) patients. ADCmean [10-6mm2/s] was 484 for WNT, 566 for SHH, and 624 for non-WNT/non-SHH subtypes (p>0.05). We found a significant negative correlation between ADCmean and the proliferation parameter ki67 (r=-0.469, p=0.009, n=30).

Conclusion:

In our study, peritumoral oedema was only present in SHH subtypes. Quantitative DWI analysis alone was not sufficient for the differentiation of genetic subtypes. However, a comparably lower ADC value was associated with a higher proliferation rate.

Limitations:

n/a

Ethics committee approval

n/a

Funding:

No funding was received for this work.

Purpose:

Imaging modalities like neurosonogram and CT have a limited role in evaluation. MRI with diffusion-weighted imaging shows features of viral encephalitis involving frontoparietal subcortical and deep white matter and corpus callosum.

Methods and materials:

10 neonates of Chikungunya encephalitis born of mothers with Chikungunya in the last 2 weeks prior to delivery underwent MRI evaluation included T1, T2, FLAIR diffusion-weighted, gradient echo, and post-contrast images. A neurosonogram was done in one child and a CT scan in another. Follow-up MRI was done at 1 month or 3 months, depending on the clinical evaluation of the neurodevelopmental delay.

Results:

2/10 neonates showed normal MRIs. All the cases showed bilateral involvement affecting frontal, parietal, and occipital lobes. The infratentorial compartment with the cerebellum and brain stem were not involved. T2 and FLAIR hyperintensities diffuse as well as discrete in appearance were seen in the subcortical and deep white matter periventricular location with sparing of the U fibres. Follow-up MRIs showed a significant reversal in diffusion restriction in the 1-month scan. Cystic encephalomalacia with ventricular dilatation was seen with a reduction in white matter volume in the 3-month follow-up scan in 2 cases.

Conclusion:

Encephalitis is the most common neurological presentation in the Chikungunya infected neonates after mother-to-child transmission. Neuro imaging is essential with MRI, with diffusion-weighted imaging being the primary imaging modality. DWI images may show changes prior to signal intensity changes on T2 images. DWI can also demonstrate progress as well as as prognosticate. Long-term MRI imaging is important in neonates who have neurodevelopmental delays.

Limitations:

n/a

Ethics committee approval

n/a

Funding:

No funding was received for this work.

Purpose:

Craniofacial dysmorphology varies significantly along a wide spectrum of severity in metopic cranial synostosis (MCS). This study aimed to quantify craniofacial changes to investigate their relationships with the severity of trigonocephaly.

Methods and materials:

Among 59 infants with MCS, we identified 3 groups according to the severity of trigonocephaly combining the metopic ridge and interfrontal angles (mild, moderate, and severe). We performed a quantitative analysis using high-resolution CT images evaluating: 1) cranial fossae dimensions; 2) vault indices and ratios: interparietal/intercoronal (IPD/ICD ratio), interparietal/intertemporal (IPD/ITD), cephalic index, vertico-longitudinal index; 3) orbito-facial distances (midfacial depth, maxillary height, upper facial index, orbital distances, globe protrusions), maxilla and orbital volumes; 4) supratentorial (ICV) and infratentorial (PCFV) cranial volume, supratentorial (WBV) and infratentorial (PCFBV) brain volume.

Results:

In all groups, middle skull base lengths and upper midface indexes (n-pr/af-af) were increased.

In moderate and severe groups, anterior hemifossae lengths were reduced, IPD/ICD and vertico-longitudinal index were changed, interzygomatic buttre distance, midfacial depth (af-ans), anterior, and mild and lateral interorbital distances were reduced and globe protrusions were increased.

The comparison between moderate and severe groups showed a worsening of globe protrusions and IPD/ICD in the severe group and only in the severe group were ICV and WBV resulted reduced.

Conclusion:

This morpho-volumetric study provides new insights in understanding the craniofacial changes occurring in infants at different severities of trigonocephaly. The increase of globe protrusions and the reduction of sovratentorial volumes found in the severe group reflect the severity of trigonocephaly; these patients might require early surgical cranial expansion.

Limitations:

A retrospective study

Ethics committee approval

n/a

Funding:

No funding was received for this work.

Purpose:

The head of the hippocampus (H) is classically described as having 2 -4 digitations both in ex-vivo specimens and in-vivo coronal MRI. Our aim was to develop a new MR-based classification of the anatomical variants of H in a large sample population of healthy subjects

Methods and materials:

Brain MRIs of 247 young healthy subjects (138 M, age 18-39) were analysed. The H was identified on coronal reformatted 3D T1-w MRI. The H of a subset of 100 subjects were analysed and classified according to number of sulci and number and size of digitations. This classification was used to assess the frequencies of anatomical variants in a larger subset of 247 subjects for hemisphere and sex. Statistically significant differences were assessed by Chi-Square or marginal homogeneity tests (level of significance ρ<0.05)

Results:

8 variants of the H were described. Class 0 (11.3%) describes a total lack of sulci and is subdivided in 0A (one digitation, 10.1%) and 0B (no digitations or “null variant”, 1.1%). Class 1 (25.6%, one single sulcus) is subdivided into 4 types according to location and width of the sulcus [1A (8.8%), 1B (12.8%), 1C (1.3%), and 1D (2.7%)]. Class 2 ("classical variant", 2 symmetrical sulci and 3 digitations equal in size) is the most frequent overall (63.0%). A statistically significant difference between the H classification of the two hemispheres was observed only in women (ρ=0.035) and overall (ρ=0.047). Variants prevalence did not differ between genders.

Conclusion:

We described a new morphologic classification of the H which should allow minimisation of the risk of misinterpreting anatomical variants as pathologic conditions.

Limitations:

Only T1w coronal images were assessed, not T2w.

Ethics committee approval

n/a

Funding:

No funding was received for this work.

Purpose:

Quantitative MRI has been proven to aid in identifying subtle volumetric changes in the brain. Studies have stated regional and global differences in shape, size, and volume between the caucasian and eastern populations. Chinese, Korean, and Japanese populations have also shown significant differences in brain shape and size between the western and eastern population. Our objective was to study the differences between the Indian and caucasian populations.

Methods and materials:

100 healthy control T1 3d MRIs of brains were collected from Indian and caucasian (XNAT database) populations, cross-matched between the ages of 20-85 years. A semi-automated clustering segmentation technique of ITK-SNAP was used to segment brain volumes. MRIs with motion artefacts were rejected to reduce error.

Results:

Data had a normal distribution between ages, with a skewness coefficient of 0.05. The age and gender-matched comparison of Indian (group 1) and caucasian (group 2) brains and intracranial volumes (ICV) showed significant differences. The average volumes for Indians were 1,122.48 ml (whole-brain) and 1,339.75 ml (ICV) as compared to 1,222.68 ml (whole-brain) and 1,482.87 ml (ICV) in caucasians. One way anova for brain and ICV were found significant at p<0.5.

Conclusion:

To our knowledge, this is the first large-scale study examining the differences in the volumes of brains and intracranial volumes between Indians and caucasians. The statistical analysis confirms the vast differences in the volumes of the brain in the two population. For the use of the quantitative analysis based on MRI to be clinically relevant, new references need to be build based on the type of population.

Limitations:

The relationship between brain volumes and ICV described here are based on cross-sectional data and await refinement in future analyses.

Ethics committee approval

n/a

Funding:

No funding was received for this work.

Purpose:

The role of postmortem magnetic resonance imaging (MRI) is becoming more important in forensic medicine. The purpose of this study was to assess the potential advantages in using 7 Tesla MRI versus 3 Tesla MRI in forensic medicine for the assessment of cerebral haemorrhages.

Methods and materials:

Decedents with cerebral haemorrhages (n=10) after blunt trauma or in accordance with a natural cause of death underwent head examinations using a 3 Tesla MRI unit and using a 7 Tesla MRI unit. The case selection was based on the detection of a cerebral haemorrhage on a previously performed computed tomography scan. The MRI protocol included 3D T2, T1, and susceptibility-weighted sequences. Additionally, high-resolution 3D in-phase gradient-echo sequences were performed for the visualisation of the bones. The images were visually compared by two radiologists.

Results:

7 Tesla MRI was superior to 3 Tesla MRI with regard to the detailed visualisation of anatomical structures due to the high contrast and high spatial resolution of the 7 Tesla MRI. Additionally, microhaemorrhages could be visualised on 7 Tesla MRI due to an increased susceptibility compared to 3 Tesla MRI. Overall, 7 Tesla MRI allowed for a more precise assessment of cerebral bleeding. A drawback of 7 Tesla MRI was the increased B1 inhomogeneities compared to 3 Tesla MRI, which caused signal differences across the brain. Small osseous fractures could be visualised on both MRI units, albeit 7 Tesla MRI presented a higher spatial resolution.

Conclusion:

7 Tesla MRI enables a more precise examination of cerebral haemorrhages, which may provide new opportunities for their radiological assessment in forensic as well as in clinical radiology.

Limitations:

A small number of cases.

Ethics committee approval

n/a

Funding:

No funding was received for this work.

Purpose:

During the radiological evaluation of the FLAIR sequence for postmortem cases, a wide variety of image contrast is observed, different from that encountered in living patients. We aimed at evaluating the impact of two variables (temperature and delay from death) suspected of having an influence on the optimal inversion time (TI) value, which allows obtaining the living patient-like image contrast.

Methods and materials:

In 24 postmortem cases, brain MRIs were performed and 3D FLAIR sequences with TI varying from 1,660 ms-900 ms, every 110 ms, were acquired. Two radiologists independently evaluated the images and were asked to choose which TI corresponded to the image of a standard patient-like FLAIR contrast. Rectal temperature and delay between the death of the cases and MRI were recorded. Pearson‘s correlation tests between the mean TI value, temperature, and delay were performed, as well as an evaluation of interobserver reliability with the prevalence-adjusted and bias-adjusted Kappa (PABAK).

Results:

The temperature ranged from 5.7°-29.7°, while the death-MRI delay ranged from 12.3h to 74.4h. The optimal TI value ranged from 1,330 ms-1,100 ms, with moderate interobserver reliability (PABAK=0.56, 95%CI [0.28-0.84]). The optimal TI value was significantly correlated with the temperature (Pearson R=0.70; p=0.0014) and the delay from death (Pearson R=-0.67; p=0.00027). Rectal temperature was inversely correlated with the delay from death (Pearson R=-0.79; p<0.00001).

Conclusion:

Postmortem brain FLAIR imaging contrast is significantly related to body temperature and delay from death. The TI value should be adapted to obtain living patient-like image contrast. A larger study cohort is needed to confirm these preliminary results and to evaluate whether the TI value could be used as an additional tool for dating the postmortem interval.

Limitations:

The size sample.

Ethics committee approval

n/a

Funding:

No funding was received for this work.