Computer-assisted three-dimensional reconstruction of the corticospinal system as a reference for CT and MRI.

We present a three-dimensional (3D) anatomical computer-graphics model of the corticospinal system acquired from equidistant serial anatomical slices of six intracranially-fixed human brains. This model is part of a neuroanatomical reference system (NeuRef) which enables 3D visualization of the brain and shows the relationship of its components such as anatomical structures, functional fibre tracts and arteries. Sections through the models can be matched with corresponding CT or MR images. This allows the probable localisation of corticospinal fibres on CT or MRI.

3D reconstructions of neurofunctional structures for neuroimaging.

An improved method for computer-aided 3D reconstruction of neuroanatomical structures derived from intracranially fixed human brains is demonstrated. The embedded brains are cut into slices. The sliced surfaces are photographed. The outlines of the neuroanatomical structures are drawn onto transparencies which are scanned. The surfaces of the structures are 3D reconstructed with the triangulation method. The cortical structures of the human brain are complex, resulting in possible ambiguities for triangulation which must be solved interactively. These surface reconstructions allow for 3D visualization of the brain and its components comparable with intravital conditions found in clinical neuroimaging.

Computer-assisted 3D reconstruction of the terminal branches of the cerebral arteries. III. Posterior cerebral artery and circle of Willis.

We present a three-dimensional anatomical computer model of the terminal branches of the posterior cerebral artery and circle of Willis, acquired from equidistant serial anatomical slices of three brains. The reconstructions provide a clear picture from all angles of the complicated course of the terminal branches of the cerebral arteries. This can help to identify the arteries in conventional and magnetic resonance angiography. Our rendition of the cerebral arteries can be matched with CT, MR und PET images to indicate the areas of extension of the individual branches, allowing neuromorphological and functional correlations.

Computer-assisted 3D reconstruction of the terminal branches of the cerebral arteries. I. Anterior cerebral artery.

We present a three-dimensional anatomical computer model of the terminal branches of the anterior cerebral artery, acquired from equidistant serial anatomical slices of three brains. The reconstructions provide a clear picture from all angles of the complicated course of the terminal branches of the cerebral arteries, which can help to identify them on conventional and magnetic resonance angiography. Our rendition of the cerebral arteries can also be matched with CT, MR or PET images to indicate the areas of extension of individual branches, allowing neuromorphological and functional correlations.

Computer-assisted 3D reconstruction of the terminal branches of the cerebral arteries. II. Middle cerebral artery.

We present a three-dimensional anatomical computer model of the terminal branches of the middle cerebral artery, acquired from equidistant serial anatomical slices of three brains. The reconstructions provide a clear picture from all angles of the complicated course of the terminal branches of the cerebral arteries, which can help to identify them on conventional angiography and magnetic resonance angiography. The arteries can also be matched with CT, MR or PET images to indicate the areas of extension of individual branches, allowing neuromorphological and functional correlations.

Computer-assisted 3D-reconstruction and statistics of the limbic system. 1. Computer-assisted 3D-reconstruction of the hippocampal formation, the fornix, and the mamillary bodies.

The hippocampal formation of eight perfusion-fixed human brains was examined using new methods according to stereotactic and morphometric principles (macrovibratome and computer-aided 3D reconstruction). The reconstructions form part of a neuroanatomical reference system (NeuRef). This reference system allows for 3D visualisation of the brain and its components on a computer graphic workstation, as well as for the presentation of the union set based on a neuroanatomical structure taken from this sample of brains. This retrievable knowledge of neurofunctional systems is important for the preoperative planning of neurosurgeons and the adjustment of radiotherapy.

Computer-assisted 3D-reconstruction and statistics of the limbic system. 2. Spatial statistics of the hippocampal formation, the fornix, and the mammillary bodies.

A statistical method is described to show the distribution of neuroanatomical structures within a Cartesian coordinate system from any given number of examinations. The algorithm is based on polygons derived from the outlines of neuroanatomical structures in parallel canthomeatal-orientated cutting planes. These polygons are transformed in virtual voxels, rotated into the bicommissural coordinate system, and projected onto the three main planes of this coordinate system. Areas with the same probability for the structures examined are given in these planes. As an example this method is applied to the hippocampal formation and the results attained are shown.

[Three-dimensional reconstructions in neuroanatomy]. / Dreidimensionale Rekonstruktionen in der Neuroanatomie.

Computer-aided 3D reconstructions of neurofunctional systems and structures are generated as a reference for neuroimaging (CT, MRI, PET). The clinical application of these 3D reconstructions requires a coordinate system and conditions resembling the intravital neuroanatomy as far as possible. In this paper the neuroanatomical Reference System (NeuRef) of the Department of Neuroanatomy of Hannover Medical School is presented. This consists of methods to record brain structures from serial sections with minimal error (less than 1 mm) and to display 3D brain models derived from such a data base. In addition, NeuRef is able to generate sections through, for instance, the visual and pyramidal system and to transfer these data onto a corresponding CT image. Therefore, this method can serve as a diagnostic aid in neuroradiology, in operation planning, and radiotherapy. It can also be used in PACS.

Quantitative changes during the postnatal maturation of the human visual cortex.

Postnatal development of the human visual cortex is characterized by an overshooting growth pattern of its volume with a maximum at 8 postnatal months and by loss of a substantial proportion of its neurons. The highest rate of reduction in neuronal numbers is observed in layers II-IVa, with other layers showing a more gradual postnatal decrease.

Morphometric study on the postnatal growth of the hippocampus in Australian Aborigines and Caucasians.

In an autopsy study on Australian Aborigines (29 males, 27 females) and Caucasians (57 males, 37 females) the postnatal growth of the hippocampus was studied and described by mathematical growth functions. For male adults no significant difference in hippocampal volume was found. In contrast, hippocampal volume was significantly smaller for Aboriginal females compared to Caucasian females. Growth analysis showed slower growth rates and later half-value times for Aborigines compared to Caucasians. These results are discussed in relation to secular changes of growth parameters of the human brain during the last century, the socioeconomic and health status of Aborigines, and sexual differences in development and plasticity of the hippocampus.

A new anatomical representation of the human visual pathways.

A three-dimensional, computer-aided reconstruction of the intracranial parts of the visual system, optic nerve, optic chiasm, optic tract, lateral geniculate body, optic radiation and striate area on the basis of anatomical serial cuts is presented in this paper. The computer-graphic representation simulates the illumination of a three-dimensional reconstruction. This study depicts for the first time a detailed anatomical reconstruction and illustrative representation of the striate area. An interactive investigation of the structure on the screen as well as a demonstration of the intracranial relationships between different neuroanatomical structures and comparisons with magnetic resonance, computed tomographic, and positron emission tomographic images is possible, providing that the neuroimaging uses the identical Cartesian coordinate system [22].

Morphometric study on the postnatal growth of the cerebellum of Australian aborigines and Caucasians.

In an autopsy study on 29 male Aborigines and 57 male Caucasians, macroscopic and microscopic parameters of postnatal cerebellar development were determined and described by mathematic growth functions. For the whole cerebellum and its cortical layers volume measurements revealed delayed maturation for Aborigines compared to Caucasians. Despite the slower development in childhood, significantly smaller values for adult Aborigines compared to Caucasians were observed only for the whole cerebellum and the Purkinje cell sheet. Similarly, postnatal changes in Purkinje cell size showed prolonged growth phases in Aborigines compared to Caucasians. Calculations of absolute cell numbers for individual layers demonstrated later half-value times and slower growth rates for cell numbers in the internal granular and molecular layers consistent with the findings for the corresponding layer volumes. For Caucasians, the growth curve for the absolute cell number in the internal granular layer showed a maximum about 21 months postnatally and subsequently decreased towards adulthood by about 18%. No such overshoot could be demonstrated for Aborigines. In relation to absolute cell numbers in adulthood, this could indicate a smaller number of granule cells migrating from the external to the internal granular layer as well as less pronounced granule cell death in Aborigines compared to Caucasians. The external granular layer of Caucasians increased in volume postnatally to reach a maximum at about 4 months and subsequently decreased until its disappearance at approximately 2 years of age. The number Purkinje cells decreased marginally postnatally in both populations. These results were discussed in relation to secular changes of growth parameters of the cerebellum during the last century and the socioeconomic and health status of Aborigines.

Morphometric study on the postnatal growth of non-cortical brain regions in Australian aborigines and Caucasians.

In an autopsy study on 29 male and 27 female Aborigines and 57 male and 37 female Caucasians the volumes of a large number of brain regions were determined and fitted to logistic growth functions. For Aboriginal adults significantly smaller values were found for weight and volume of the whole brain, cerebrum, and cerebellum and for the volumes of cerebral white matter, thalamus, amygdaloid body (females only), and globus pallidus (males only). No significant differences were found for caudate nucleus, putamen, amygdaloid body (males only), and globus pallidus (females only). Almost every region studied showed later half-value times, slower growth rates, and prolonged growth phases for Aborigines compared to Caucasians. These results are discussed in relation to secular changes of growth parameters of the human brain during the last century, timing of growth phases for each area, and the socioeconomical and health status of Aborigines.

Localisation of the corticospinal fibres in the internal capsule in man.

The myelogenetic development of the corticospinal fibres in the internal capsule was studied using eight brains of the Yakovlev Collection and two brains of the collection in Hannover Medical School. The myelin sheaths of the corticospinal fibres stained by the Loyez method can best be seen in the third postnatal month. During their course through the internal capsule their relative position changes. In the superior portion of the internal capsule, at the level of the interventricular foramen, the pyramidal tract is located in the middle of the posterior limb and in the inferior portion, at the level of the subthalamic nucleus and metathalamus, in the posterior third of the posterior limb. The classical concept of the localisation of the pyramidal tract has, therefore, to be revised for the inferior portion of the internal capsule. The result of this study confirms those of stereotactic, neuropathological and macroscopic observations and underlines the importance of the Yakovlev Collection for the neurosciences.

The human pattern of gyrification in the cerebral cortex.

The degree of cortical folding found in adult human brains has been analyzed using a gyrification index (GI). This parameter permits the description of a mean value for the whole brain, but also a local specific analysis of different brain regions. Correlation analyses of the GI with age, body weight, body length, brain weight and volume of the prosencephalon and the cortex show no significant results. GI values do not differ significantly between male and female brains, right and left hemispheres or right and left sides of the superior temporal plane. The GI shows maximal values over the prefrontal and the parieto-temporo-occipital association cortex. A comparison between the rostro-caudal GI patterns of human brains and those of prosimians and Old World monkeys shows the largest difference over the prefrontal cortex. The mean GI increases from prosimians to human brains with the highest values for non-human primates being in the pongid group.

A quantitative study of Australian aboriginal and Caucasian brains.

The brain volumes of 8 male Australian Aborigines and 11 male Caucasians were determined. Total brain volume was significantly smaller for Aborigines (1199 +/- 84 ml) compared to Caucasians (1386 +/- 98 ml). Significantly smaller volumes were also found for cerebellum, prosencephalon-mesencephalon unit, cerebral cortex, frontal cortex, parieto-occipitotemporal cortex, and hippocampus. Volumes of ponsmedulla oblongata unit (21 +/- 3 ml for Aborigines and 22 +/- 3 ml for Caucasians) and visual cortex (14.9 ml +/- 2.6 ml and 14.6 +/- 2.2 ml, respectively) did not differ significantly. The striate cortex extended further onto the lateral surface of the occipital lobe in Aboriginal brains. The frontal portion of cerebral cortex was larger in Aboriginal than in Caucasian brains. According to the specific growth periods for the areas studied, these differences could be explained by the higher incidence of malnutrition and infectious diseases for Aboriginals during the development of the brain in early childhood, especially after the 6th postnatal month. However, genetic influences cannot be excluded. The results for the visual cortex of Aborigines might represent an adaptation to living conditions in the bush and desert regions of Australia.

The morphology of Australian aboriginal brains--documentation of eight cases.

Cortical morphology of the brains of eight Western Australian Aboriginals was documented. Sulcal patterns permitted classification of the brains into separate groups. Characteristic patterns were found for the shape of the prosencephalon and for the insular, parietooccipital, and frontal cortex in the aboriginal group. The length of the frontal, parietal, and occipital lobes and the width of the temporal lobes was measured. Length, width, and height of the Aboriginal prosencephalons were compared to measurements of eleven Caucasian brains. Postmortem changes, genetic differences, and factors influencing brain development were discussed.