Statistical shape analysis of temporal lobe in mesial temporal sclerosis patients

Protocol to quantify bird nest morphology via image analyses using linear measurements and geometric landmarks

Here, we present a protocol to quantify bird nest morphology via image analyses. We describe steps for collecting linear size measurements, placing geometric landmarks, and undertaking generalized Procrustes analysis to extract coordinate data. This protocol was designed to measure within- and among-individual variation in the morphology of dome nests built by captive zebra finches using coconut fiber in a laboratory environment. For complete details on the use and execution of this protocol, please refer to Whittaker et al.1.

Statistical shape analysis of the lentiform nucleus of children of different age groups: a retrospective study

The basal nuclei are important during infancy because of the significant development of motor skills. The main aim of this study was to evaluate the shape differences of the lentiform nucleus between different age and gender groups. A total of 126 children's axial magnetic resonance image series were included in the presented study. These images were grouped between 1 and 5 yr old. Right and left lentiform nuclei are marked with selected landmarks using TPSDIG v2.04. Statistical shape analyses were examined by a Generalized Procrustes Analysis. Our results showed that there was no statistically significant difference in lentiform nucleus shape between genders. However, there was a difference between the shapes of the right and left lentiform nuclei between the 1-yr and 5-yr age groups. These results demonstrated the shape changes in the lentiform nucleus during the first 5 yr of life. Further clinical studies based on our results may be used to gather more detailed information about movement disorders and neuronal development.

Longitudinal Morphometric Changes in the Corticospinal Tract Shape After Hemorrhagic Stroke

Deep intracerebral hemorrhage (ICH) exerts a direct force on corticospinal tracts (CST) causing shape deformation. Using serial MRI, Generalized Procrustes Analysis (GPA), and Principal Components Analysis (PCA), we temporally evaluated the change in CST shape. Thirty-five deep ICH patients with ipsilesional-CST deformation were serially imaged on a 3T-MRI with a median imaging time of day-2 and 84 of onset. Anatomical and diffusion tensor images (DTI) were acquired. Using DTI color-coded maps, 15 landmarks were drawn on each CST and the centroids were computed in 3 dimensions. The contralesional-CST landmarks were used as a reference. The GPA outlined the shape coordinates and we superimposed the ipsilesional-CST shape at the two-time points. A multivariate PCA was applied to identify eigenvectors associated with the highest percentile of change. The first three principal components representing CST deformation along the left-right (PC1), anterior-posterior (PC2), and superior-inferior (PC3) respectively were responsible for 57.9% of shape variance. The PC1 (36.1%, p < 0.0001) and PC3 (9.58%, p < 0.01) showed a significant deformation between the two-time points. Compared to the contralesional-CST, the ipsilesional PC scores were significantly (p < 0.0001) different only at the first-timepoint. A significant positive association between the ipsilesional-CST deformation and hematoma volume was observed. We present a novel method to quantify CST deformation caused by ICH. Deformation most often occurs in left-right axis (PC1) and superior-inferior (PC3) directions. As compared to the reference, the significant temporal difference at the first time point suggests CST restoration over time.

Statistical shape analyses of corpus callosum changes at preoperative and postoperative scaphocephaly patients

PURPOSE

Scaphocephaly is the premature closure of the sagittal suture. The treatment strategies mainly focus on correcting the shape of the head, but there are very limited studies examining changes in brain structure. This study aimed to investigate shape differences in the shape of corpus callosum regarding the pre-treatment and post-treatment term at scaphocephaly patients.

METHODS

Cranium shape data were collected from the two-dimensional digital images. The generalized Procrustes analysis was used to obtain mean shapes in the pre- and postoperative phases. The shape deformation of the corpus callosum from the pre- to postoperative phases was evaluated using the thin plate spline method.

RESULTS

There is an enlargement of the splenium part of corpus callosum in the late group. In the early group, corpus callosum genu and body enlargement were observed in the postoperative period compared to the preoperative period, followed by a narrowing of the isthmus region.

CONCLUSION

This study showed structural deformations in the corpus callosum in scaphocephaly patients using head shape with the landmark-based geometric morphometric method by taking into consideration the topographic distribution. An enlargement at the splenium part of corpus callosum exposes after the cranial vault expansion depending on time.

Statistical Shape Analysis of Cerebellum in Patients With Chiari Malformation I

The surgical procedure is viewed as a typical treatment choice for patients with Chiari malformation (CM). Decompression is the preferred method for surgery, but it is not always possible to understand whether decompression has been successful especially in an early period. The present study focuses on investigating the shape differences in the cerebellums of Chiari patients compared with healthy controls, and to assess the clinical application of this situation whether if present. The MRI scans were reviewed retrospectively. Cerebellar data were obtained from the digital images and 9 anthropometric landmarks were marked on each image. Shape difference was assessed by performing Generalized Procrustes analysis. The cerebellar shape deformation from control to the patient was evaluated performing the Thin Plate Spline approach. There is a statistically significant cerebellar shape difference between groups. Highest deformation was determined at the cerebellar tonsillar inferior area, posterior of the uvula, and anterior of inferior medullary velum. The present study demonstrated cerebellar shape differences in CM I patients using a landmark-based geometric morphometric approach, considering the topographic distribution of cerebellum for the first time.

Statistical shape analyses of trigonocephaly patients

PURPOSE

Surgery is the first treatment option for patients with metopic craniosynostosis. Fronto-orbital advancement is the preferred method for correction of isolated trigonocephaly, but it is hard to understand whether surgery has been successful mainly in an early period. We aim to investigate the shape differences in the head shapes of trigonocephaly patients compared between preoperative and postoperative term.

METHODS

Cranial shape data were collected from the two-dimensional digital images. The Generalized Procrustes analysis was used to obtain mean shapes of the preoperative and postoperative term. The shape deformation of the frontal calvarium from preoperative to the postoperative term was evaluated using the thin-plate spline (TPS) method.

RESULTS

There was significant cranial shape difference between preoperative and postoperative term. The high-level deformations for preoperative to postoperative term determined seen in TPS graphic. Highest deformation was observed at the bifrontal dimension especially at nasion and posterior edge of the forehead.

CONCLUSIONS

In this study, we showed that the shape difference and structural deformation of the calvarium were correlated with the metopic craniosynostosis. The present study also shows that preoperative and postoperative head shapes of patients with trigonocephaly can be compared using the landmark-based geometrical morphometric method by taking into consideration the topographic distribution.

Identifying Morphological Patterns of Hippocampal Atrophy in Patients With Mesial Temporal Lobe Epilepsy and Alzheimer Disease

Purpose: Mesial temporal lobe epilepsy (MTLE) and Alzheimer's disease (AD) are two distinct neurological disorders associated with hippocampal atrophy. Our goal is to analyze the morphologic patterns of hippocampal atrophy to better understand the underlying pathological and clinical characteristics of the two conditions.

Methods: Twenty-five patients with AD and 20 healthy controls with matched age and gender were recruited into the AD group. Twenty-three MTLE patients and 28 healthy controls with matched age and gender were recruited into the MTLE group. All subjects were scanned on 3T-MRI scanner. Automated volumetric analysis was applied to measure and compare the hippocampal volume of the two respective groups. Vertex-based morphologic analysis was applied to characterize the morphologic patterns of hippocampal atrophy within and between groups, and a correlation analysis was performed.

Results: Volumetric analysis revealed significantly decreased hippocampal volume in both AD and MTLE patients compared to the controls. In the patients with AD, the mean total hippocampal volume was 32.70% smaller than that of healthy controls, without a significant difference between the left and the right hippocampus (p < 0.05). In patients with MTLE, a significant reduction in unilateral hippocampal volume was observed, with a mean volume reduction of 28.38% as compared with healthy controls (p < 0.05). Vertex-based morphologic analysis revealed a generalized shrinkage of the hippocampi in AD patients, especially in bilateral medial and lateral regions. In MTLE group, atrophy was seen in the ipsilateral head, ipsilateral lateral body and slightly contralateral tail of the hippocampus (FWE-corrected, p < 0.05).

Conclusions: MTLE and AD have distinctive morphologic patterns of hippocampal atrophy, which provide new insight into the radiology-pathology correlation in these diseases.

MRI morphology of the hippocampus in drug-resistant temporal lobe epilepsy: Shape inflation of left hippocampus and correlation of right-sided hippocampal volume and shape with visuospatial function in patients with right-sided TLE

We sought to quantify the morphology in vivo of hippocampi in patients with drug resistant temporal lobe epilepsy (TLE) via magnetic resonance imaging (MRI), prior to temporal lobe resection, and the correlation of surface-based shape analysis of morphology and clinical cognitive function. Thirty patients with drug-resistant TLE and twenty healthy controls underwent clinical neuropsychological testing, and brain MRI at Lund University Hospital prior to hippocampal resection. A neuroradiologist categorised radiological findings into normal hippocampus, subtle changes or definite hippocampal sclerosis. We manually segmented MRI of the hippocampus of participants using ANALYZE 11.0 software; and analysed hippocampal shape using SPHARM-PDM software. For radiologist visual-ratings of definite left hippocampal sclerosis in those with left-sided TLE, hippocampal volumes were significantly smaller compared to normal controls. In right-sided TLE we found contralateral shape inflation of the left hippocampus, partially confirming previous shape analytic studies of the hippocampus in TLE. We found significant correlation of volume and surface deflation of the right hippocampus in right-sided TLE with reduced performance on the two right-lateralised visuospatial memory tests, the Rey Complex Figure Test (Immediate and Delayed recall) and the Recognition Memory Test for faces. Decreased hippocampal volume was correlated with poorer performance on these tasks. The morphology of the hippocampus can be quantified via neuroimaging shape analysis in TLE. Contralateral shape inflation of the left hippocampus in right-sided TLE is intriguing, and may result from functional compensation and/or abnormal tissue. In right-sided TLE, hippocampal structural integrity, quantified as hippocampal shape, is correlated with lateralised visuospatial function.

Statistical Shape Analysis of Subthalamic Nucleus in Patients with Parkinson Disease

OBJECTIVE

Subthalamic nucleus (STN) is the most targeted localization in the treatment of Parkinson disease (PD) with deep brain stimulation. However, no studies have been found in the literature about possible shape changes of STN in the literature. We aimed to investigate possible shape changes in the STN and the relationship between shape changes and disease duration in PD patients by using statistical analysis.

METHODS

Patients who were diagnosed with idiopathic PD and controls were enrolled in this study. Age, sex, and disease duration of all cases were recorded. Turbo-spin-echo T2-weighted axial series parallel to the skull base in each case containing midbrain images were obtained, including the whole STN. Standard anatomic landmarks were selected and marked on each digital image using a special software in all cases. Statistical geometric shape and deformation analysis of STN was performed in 2 groups.

RESULTS

Forty-three patients with PD and 50 age/sex-matched controls were enrolled in this study. There were statistically significant left and right STN shape differences between the groups. Maximum deformation was seen in the dorsolateral parts of both STNs. General shape variability of the STNs was found on the left (0.096) and right (0.049).

CONCLUSIONS

Significant shape differences and remarkable deformation of STN are seen in patients with PD compared with controls. Maximum deformation was observed in the dorsolateral part of the STN, and with the increase in the duration of the PD, shape differences and deformations became more prominent.

A potential pitfall in studies of biological shape: Does size matter?

The number of published studies using geometric morphometrics (GM) for analysing biological shape has increased steadily since the beginning of the 1990s, covering multiple research areas such as ecology, evolution, development, taxonomy and palaeontology. Unfortunately, we have observed that many published studies using GM do not evaluate the potential allometric effects of size on shape, which normally require consideration or assessment. This might lead to misinterpretations and flawed conclusions in certain cases, especially when size effects explain a large part of the shape variation. We assessed, for the first time and in a systematic manner, how often published studies that have applied GM consider the potential effects of allometry on shape. We reviewed the 300 most recent published papers that used GM for studying biological shape. We also estimated how much of the shape variation was explained by allometric effects in the reviewed papers. More than one-third (38%) of the reviewed studies did not consider the allometric component of shape variation. In studies where the allometric component was taken into account, it was significant in 88% of the cases, explaining up to 87.3% of total shape variation. We believe that one reason that may cause the observed results is a misunderstanding of the process that superimposes landmark configurations, i.e. the Generalized Procrustes Analysis, which removes isometric effects of size on shape, but not allometric effects. Allometry can be a crucial component of shape variation. We urge authors to address, and report, size effects in studies of biological shape. However, we do not propose to always remove size effects, but rather to evaluate the research question with and without the allometric component of shape variation. This approach can certainly provide a thorough understanding of how much size contributes to the observed shaped variation.