Terminology of the Thalamus and its Representation in a Part-Whole Relation

In stereotaxic neurosurgery, a variety of operative procedures focus on thalamic targets. The nomenclature of thalamic nuclei and sub-nuclei, however, has not yet been settled. In clinical and laboratory environments several terminologies coexist. This is an obstacle to both communication and a better understanding of recent electrophysiological findings. In the late 1980s, the application of new histochemical and immunohisto-chemical methods led to a deeper insight into existing correlations between the nomenclatures. As a uniform terminology of the thalamus is still lacking, we created a knowledge-based system (thalamus) which gives a comprehensible survey about the most important terminologies. The different nomenclatures are related to each other by organizing them in a component-integral relation. This part-whole relation contains both the knowledge on the subdivisions of the thalamus as well as the knowledge on the correlations between the various nomenclatures.

Tropicamide (1%): an effective cycloplegic agent for myopic children

PURPOSE

To evaluate the cycloplegic effect of 1% tropicamide in myopic children and to determine whether its efficacy is associated with age, gender, iris color, ethnicity, magnitude of the refractive error, or latent error.

METHODS

Four hundred sixty-nine children enrolled in the Correction of Myopia Evaluation Trial (COMET; a multicenter, randomized, double-masked clinical trial evaluating the rate of progression of juvenile-onset myopia in children wearing progressive-addition versus single-vision lenses) were given 1 drop of proparacaine in each eye followed 1 minute later by 1 drop of 1% tropicamide and then a second drop of 1% tropicamide 4 to 6 minutes later. Five accommodative responses to 20/100 letters located at 4 m and 33 cm were obtained in each eye with an autorefractor, 20 minutes after the second drop. Residual accommodation was calculated as the difference between the mean spherical equivalent responses obtained at the two distances. An examiner graded iris color, and ethnicity was reported by the children's parents or guardians.

RESULTS

The mean residual accommodation was small: 0.38 +/- 0.41 diopters (D) in the right eye and 0.30 +/- 0.41 D in the left eye. Small but statistically significant differences in residual accommodation were associated with ethnicity, but not with any of the other factors.

CONCLUSIONS

Tropicamide (1%) is an effective cycloplegic agent in myopic children.

Control measures for wastewater treatment plants during storm flow

In the context of the development of treatment plant control techniques, three measures for maintaining a high efficiency of treatment plants during rainfall events were tested. The three measures are increasing the nitrification volume by operating a facultative aeration, bypassing the primary sedimentation and adding flocculants before secondary sedimentation. Ammonia concentrations and ammonia loads were used in combination with rainfall forecasts as the criteria for putting the measures into operation. A simulation based on the Activated Sludge Model No. 1 and a pilot scale plant were used for testing the measures. The results show that all three measures may be suitable to cope with peak loads of treatment plants during rainfall events.

The Morel stereotactic atlas of the human thalamus: atlas-to-MR registration of internally consistent canonical model

In 1997, Morel, Magnin, and Jeanmonod presented a microscopic stereotactic atlas of the human thalamus. Parcellations of thalamic nuclei did not only use cyto- and myeloarchitectonic criteria, but were additionally corroborated by staining for calcium-binding proteins, which bears functional significance. The atlas complies with the Anglosaxon nomenclature elaborated by Jones and the data were sampled in three orthogonal planes in the AC-PC reference space. We report on the generation of three-dimensional digital models of the thalamus based on the three sets of sections (sagittal, horizontal, and frontal). Spatial differences between the three anatomical specimens were evaluated using the centers of gravity of 13 selected nuclei as landmarks. Subsequent linear regression analysis yielded equations, which were used to normalize the frontal and horizontal digital models to the sagittal one. The outcome is an internally consistent Canonical Model of Morel's atlas, which minimizes the linear component of the variability between the three sectioned anatomical specimens. In addition, we demonstrate the feasibility of the atlas-to-MRI registration in conjunction with on-line visualization of the trajectory in the digital models.

Evidence of a smaller left hippocampus and left temporal horn in both patients with first episode schizophrenia and normal control subjects

Findings from cerebral magnetic resonance imaging (MRI) studies in schizophrenia indicating temporal lobe involvement have been inconsistent and controversial. In a prospective study, we quantified the volumes of temporal lobe structures in 20 male patients with first episode schizophrenia (FES; mean+/-S.D.=27.4+/-4. 8 years) and 20 healthy age-matched male control subjects (27.7+/-3. 1 years). Measurements were performed on contiguous 2.2-mm coronal MRI slices, which included, as well as the temporal lobe, the amygdala, the hippocampal formation, and the temporal horn of the lateral ventricle. The definition of the borders of the structures relied on measurement guidelines derived from mutual comparisons of MRI and histological data. The definition of the hippocampus-amygdala interface was also validated in a correlated triplanar display. We did not detect any significant volume reductions of the measured structures in the FES group, as compared with healthy control subjects, on either side. Comparisons within groups, however, revealed that in both the patients and the healthy volunteers the hippocampal formations showed a significant right-sided bias (+9%, P=0.004, in the FES group; +12%, P=0.0003 in the control subjects). A significant volume difference in favor of the right hemisphere was also observed in the temporal horns of the lateral ventricles (+17%, P=0.02 in the patients with FES; +34%, P=0. 003, in the control group). There was only a nonsignificant trend for a larger temporal horn on the left side in patients with schizophrenia as compared with the control subjects. Our findings do not indicate a loss or reversal of the normal volume asymmetry pattern in the FES group.

One atlas - three anatomies: relationships of the Schaltenbrand and Wahren microscopic data

The stereotaxic atlas of Schaltenbrand and Wahren is widely used for orientation in functional neurosurgery of the human diencephalon. As the sagittal, frontal, and horizontal microscopic series were gathered from three different cerebral hemispheres, loci with the same ACPC (anterior commissure-posterior commissure) coordinates are not exactly anatomically corresponding. We compared the 3-D position of 21 anatomical structures in the three series based on their digitally interpolated solid volume representations. Regression analysis of the centres of gravity revealed strong linear correlations between series (0.944< or = Pearson's r< or = 0.976, alpha<0. 0001). Thus calculation of anatomically corresponding sites based on the regression equations seems justified. Volumetry revealed that the sagittally sectioned thalamus is approximately 10% larger than the frontally and 40% larger than the horizontally sectioned thalamus. So as to match it to the sagittal series, the frontal series has to be widened in lateral direction by 19%, in anteroposterior and dorsobasal (vertical) direction it has to be compressed by 5 and 9%, respectively. In contrast, the distance of structures from the midline in the horizontal and sagittal series is very similar. The horizontal series is, however, 25% smaller than the sagittal one in anteroposterior and 17% in vertical direction. On average, thalamic nuclei in the right hemisphere of brain LXXVIII (horizontal microscopic series) were located 2 mm more anterior as compared with the left side (sagittal series), which fact may be explained by difference in size and/or asymmetry. Spatial overlap between corresponding thalamic nuclei from the three series amounted to only 0-28% when superimposed in the ACPC reference space. Linear transformation towards an average led to significant increase (0-37%, p<0.001) of the overlap and ameliorated the quality of the fit of thalamic borders. Limited increase of the overlap is in part due to pronounced differences in the size of thalamic nuclei between the series.

A brainstem stereotactic atlas in a three-dimensional magnetic resonance imaging navigation system: first experiences with atlas-to-patient registration

OBJECT

The authors describe a computer-resident digital representation of a stereotactic atlas of the human brainstem, its semiautomated registration to sagittal fast low-angle shot three-dimensional (3-D) magnetic resonance (MR) imaging data sets in 27 healthy volunteers and 24 neurosurgical patients, and an analysis of the subsequent transforms needed to refine the initial registration.

METHODS

Contour drawings from the atlas, which offer the 70th percentile of variation of anatomical structures, were interpolated into an isotropic 3-D representation. Initial atlas-to-patient registration was based on the fastigium/ventricular floor plane reference system. The quality of the fit was evaluated using superimposition of the atlas and MR images. If necessary, the atlas was tailored to the individual anatomy by using additional transforms. On average, the atlas had to be stretched by 2 to 6% in the three directions of space. Scale factors varied over a broad range from -8 to +19% and the benefit of visual interactive control of the atlas-to-patient registration was evident. Analysis of distances within the pons measured in the midsagittal MR imaging slices and the required scale factors revealed significant correlations that may be used to reduce the amount of user interaction in the coregistration substantially. In 70.6% of the cases, the atlas had to be shifted in a cranial direction along the brainstem axis (in 25.5% of cases 3-4 mm, in 45.1% of cases 1-2 mm). This was due to a more caudal position of the fastigium cerebelli on the MR images compared with the atlas.

CONCLUSIONS

This observation, in conjunction with the variability of the height of the fourth ventricle in our MR imaging data (range 6.1-15.2 mm, mean 10.1 mm, standard deviation 1.8 mm) calls into question the role of the fastigium cerebelli as an anatomical landmark for localization within the brainstem.

Global aphasia-with and without hemiparesis. A linguistic and CT scan study

The location and size of brain lesions were compared between two groups of patients showing persisting global aphasia according to the criteria of the Aachen Aphasia test (AAT). The first group comprised 8 patients suffering from severe hemiparesis for more than 18 months. The 10 patients of the second group showed either no hemiparesis at all, or motor disturbance at the onset of the disorder with complete remission within 1 year. The sizes of the brain lesions were determined by means of CT scans. The location of the lesions was defined by a statistical model of the brain with labelled anatomical structure, which allowed an interindividual comparison. In the CT scans, the infarcted areas of the brains of patients with hemiparesis always extended to the wall of the lateral ventricle, thus including the whole corona radiata with the pyramidal tract. The infarcted areas of the patients without hemiparesis and with transient hemiparesis spared parts of the deep white matter. The data obtained via CT scans are of prognostic value for patients with transient hemiparesis, since determination of the extent of the lesion by means of CT permits an initial estimate on the possible later degree and quality of the motor recovery.

Somatotopy of human hand somatosensory cortex revealed by dipole source analysis of early somatosensory evoked potentials and 3D-NMR tomography

Somatosensory evoked potentials (SEPs) to median nerve and finger stimulation were analyzed by means of spatio-temporal dipole modelling combined with 3D-NMR tomography in 8 normal subjects. The early SEPs were modelled by 3 equivalent dipoles located in the region of the brain-stem (B) and in the region of the contralateral somatosensory cortex (T and R). Dipole B explained peaks P14 and N18 at the scalp. Dipole T was tangentially oriented and explained the N20-P20, dipole R was radially oriented and modelled the P22. The tangential dipole sources T were located within a distance of 6 mm on the average and all were less than 9 mm from the posterior bank of the central sulcus. In 6 subjects the tangential sources related to finger stimulation arranged along the central sulcus according to the known somatotopy. The radial sources did not show a consistent somatotopic alignment across subjects. We conclude that the combination of dipole source analysis and 3D-NMR tomography is a useful tool for functional localization within the human hand somatosensory cortex.

Terminology of the thalamus and its representation in a part-whole relation

In stereotaxic neurosurgery, a variety of operative procedures focus on thalamic targets. The nomenclature of thalamic nuclei and subnuclei, however, has not yet been settled. In clinical and laboratory environments several terminologies coexist. This is an obstacle to both communication and a better understanding of recent electrophysiological findings. In the late 1980s, the application of new histochemical and immunohistochemical methods led to a deeper insight into existing correlationships between the nomenclatures. As a uniform terminology of the thalamus is still lacking, we created a knowledge-based system (THALAMUS) which gives a comprehensible survey about the most important terminologies. The different nomenclatures are related to each other by organizing them in a component-integral relation. This part-whole relation contains both the knowledge on the subdivisions of the thalamus as well as the knowledge on the correlations between the various nomenclatures.

Verification of the Schaltenbrand and Wahren stereotactic atlas

The Schaltenbrand and Wahren stereotactic atlas was critically re-examined focusing on the technical quality and the consistency of the horizontal, sagittal and frontal microscopic cut series. From each series, both an isotropic contour and a solid volume model represented by a 256 matrix with an edge length of 6.4 cm were created using 3D-interpolation. Reslicing of the solid volumes in corresponding orthogonal planes enabled thorough direct comparison of the three series. In a 3D-navigation system prototype, the contour models can be matched to MRI and CT series. Different procedures for rigid matching including landmark matching were implemented. As regards the verification criteria, the frontal Schaltenbrand and Wahren series yielded the most comprehensible results whereas in the horizontal and sagittal series artifacts appear more pronounced.

Superimposition of an average three-dimensional pattern of brain structures on CT scans

A method is described for the superimposition of an averaged telencephalic anatomical model and individual CT scans. The model is digitally available and derived from 3-D measurements of 30 post-mortem brains. It is averaged in size in relation to the midintercommissural point. The midintercommissural point in the individual brain is gained from reformed parasagittal projection images. The model is adjusted to the individual CT scan series by scaling and rotating according to the best fit and correspondence of the position of the central sulcus. The method needs no invasive neuroradiological techniques but is based on current computer algorithms.

A quantitative approach to spatial variation of human cerebral sulci

The surfaces and the sulci of the lateral hemispheres of 30 postmortem brain specimens were three-dimensionally measured. The coordinates of all the structures registered constitute a digital brain model. The models were scaled linearly until they fitted a defined cuboid. Then all the models within the reference volume, each represented by a set of points, were considered together. The reference volume was divided into small cubic volume elements (voxels). Two parameters of the voxels were studied: the point density of each structure per voxel and the contribution index which designates how many of the hemispheres contribute points to a certain voxel. The latter parameter may serve as an index for the presence probability of a sulcus, which means the probability with which a sulcus will be contained in a defined volume element. The presence probability of a sulcus corresponds well with its first appearance in embryological development. Spatial variation in the early developing principal sulci is far less than in those which develop in later stages. As regards some defined regions of the brain, statements about the probable location of cortical areas in relation to the commissural system can be made.

A new method in computer-assisted imaging in neuroanatomy

A procedure is described yielding computed images of postmortem brains with high topographic accuracy. Structures of the brain are traced and registered by means of a digitizer capable of measuring coordinates three-dimensionally. The information corresponding to one brain model is stored on a flexible disk with a capacity of 256 Kbytes. According to the output desired, the resulting brain images are either completely or partially displayed on the computer screen as stereo pairs. The brain models possess a local fidelity of about 1 mm. The images are useful in simultaneously studying superficial and central parts of the brain, spatial relationships of the various structures and the projection of deep structures onto the surface of the brain. A RAM of about 100 Kbytes is necessary for a program enabling the user to perform stereo projections, three-dimensional transformations and other image manipulations. The special features of anatomical computer imaging as compared to computed tomography (CT) and nuclear magnetic resonance imaging (NMR) are outlined. A combination of these different techniques seems to improve clinical diagnosis.

Fractures of the hip in childhood

Twenty hip fractures in 19 children aged 2 1/2 to 18 were analyzed in a ten-year retrospective review at the University of Alabama Hospitals in Birmingham, Ala. There was one epiphyseal, one intertrochanteric, 4 subtrochanteric, and 14 intracapsular fractures. The mechanism of injury was usually severe trauma with 31% of the patients sustaining other associated major injuries. Avascular necrosis occurred in three intracapsular fractures (23%), all seemingly related to inadequate internal fixation. Coxa vara occurred in 30% of the patients; all were treated by closed methods, and delayed union and nonunion occurred in 10% of the series. Nine patients developed discrepancies of limb length between 1/2 and 13/4 inches. It was thought that intracapsular fractures should be treated with prompt open reduction and internal fixation with multiple pins; whereas, extracapsular fractures may be treated by either open or closed methods.