The superficial palmar branch of the radial artery: a corrosion cast study.

BACKGROUND: Surgical procedures such as thenar flaps and radial artery (RA) harvesting call for an elaborate anatomical study of the RA's superficial palmar branch (SPB). The aim of this study was to describe the branching pattern of this vessel related to the morphometric characteristics and variations of this artery. MATERIALS AND METHODS: Twenty 4% formalin solution-injected hands were dissected. For the morphometric study we used another group of 35 human hands of adult persons, injected with methyl methacrylate fluid into the ulnar and radial arteries. As soon as polymerisation was completed, a 40% solution of potassium hydroxide was applied for corrosion. The vascular arterial casts were examined under the stereoscopic microscope and precise drawings of each specimen were made. RESULTS: In the majority of cases (75%) SPB passed superficially, over the abductor pollicis brevis muscle. The mean diameter of the SPB, very variable depending on its length and field of supply, was 1.52 ± 0.49 mm, ranging from 0.8 to 2.7 mm. Developed SPB type, was present in 31.4% of hands, with the diameter of 1.7 mm and larger (mean 1.95 mm), continuing distally to become the radialis indicis artery, with an average calibre of 1.2 mm, and with important branches to the thumb. In most hands (68.6%), the hypoplastic SPB, was present, with a mean diameter of 1.17 mm, and the field of supply within the thenar area. CONCLUSIONS: Knowledge of the SPB dominance and existence of anastomotic vessels in its field of supply are of importance to avoid the risk of possible ischaemic sequelae in the hand associated with harvesting the RA.

Sex differences of human corpus callosum revealed by polar coordinate system: magnetic resonance imaging study.

BACKGROUND: Evaluation of morphological and size changes related to various pathological conditions of the corpus callosum (CC) requires the data about sex dimorphism of the CC. The purpose of our study is to define potential morphological sex differences of the CC by the use of polar coordinate system as a system of measurements. MATERIALS AND METHODS: After division of the CC into three equal segments by the use of polar coordinate system, we investigated the length of the hemisphere (A-A'), the CC size as its midsagittal section area (CCA), the size of its segments (C1, C2, C3), thickness of the thinnest part of the CC (TCC) and the angular coordinate (a angle) of dorsal point of the TCC in a sample of 30 human brains magnetic resonance images (15 males and 15 females, age 20-50 years). RESULTS: We found significantly larger CCA, C3 segment and the TCC in males. Statistically significant correlation in both, males and females, was found between parameters of the CCA and of all of its segments (C1, C2, C3), the C1 and C2, the C2 and C3 segments, as well as like as between the C2 and TCC. Sex differences were also in findings of significant correlation between the C1 and C3 segments, between CCA and TCC, and of significant negative correlation between the a angle and A-A' only in females. CONCLUSIONS: We concluded that the use of polar coordinate system appropriately reflects the anatomical and encephalometric characteristics of human CC.

Pyramidal lobe of the human thyroid gland: an anatomical study with clinical implications.

The presence, position, extent, relationships to neighboring structures and size of the human pyramidal lobe were investigated in 58 human post-mortem specimens in order to determine the variability of this structure. The pyramidal lobe is found in 55.2% of cases as a single conical extension of the thyroid gland. It was present more often in male (53.1%) than in female (46.9%) specimens and located slightly more often on the left side of the midsagittal plane (53.1%). According to the origin and location of its base, we defined five types of pyramidal lobe, with the left-sided types (Types III and IV) being predominant. The pyramidal lobe was 22.6 mm long, 11.2 mm wide and 3.6 mm thick (mean values). The means of all measured parameters were higher in female than in male specimens (pyramidal lobe was 2.3 mm longer, 1.6 mm wider and 0.4 mm thicker in female specimens) but these differences were not significant. In addition, we found that the size of the pyramidal lobe was dependent on the presence of a fibrous or muscular band that may represent a fibrous remnant of the thyroglossal duct or the levator glandulae thyroideae muscle. The pyramidal lobe was four times longer and its base was two and a half times wider and three times thicker when it was associated with this band. We believe that our data can be used to perform safer and more effective partial thyroidectomy in order to preserve thyroid function after surgical treatment.

Brodmann's areas 17 and 18 brought into stereotaxic space-where and how variable?

Studies on structural-functional associations in the visual system require precise information on the location and variability of Brodmann's areas 17 and 18. Usually, these studies are based on the Talairach atlas, which does not rely on cytoarchitectonic observations, but on comparisons of macroscopic features in the Talairach brain and Brodmann's drawing. In addition, in this atlas are found only the approximate positions of cytoarchitectonic areas and not the exact borders. We have cytoarchitectonically mapped both areas in 10 human brains and marked their borders in corresponding computerized images. Borders were defined on the basis of quantitative cytoarchitecture and multivariate statistics. In addition to borders of areas 17 and 18, subparcellations within both areas were found. The cytoarchitectonically defined areas were 3-D reconstructed and transferred into the stereotaxic space of the standard reference brain. Surface rendering of the brains revealed high individual variability in size and shape of the areas and in the relationship to the free surface and sulci. Ranges and centers of gravity of both areas were calculated in Talairach coordinates. The positions of areas 17 and 18 in the stereotaxic space differed between the hemispheres. Both areas reached significantly more caudal and medial positions on the left than on the right. Probability maps were created in which the degree of overlap in each stereotaxic position was quantified. These maps of areas 17 and 18 are the first of their kind and contain precise stereotaxic information on both interhemispheric and interindividual differences.

Neuronal correlates of real and illusory contour perception: functional anatomy with PET.

Illusory contours provide a striking example of the visual system's ability to extract a meaningful representation of the surroundings from fragmented visual stimuli. Psychophysical and neurophysiological data suggest that illusory contours are processed in early visual cortical areas, and neuroimaging studies in humans have shown that Kanizsa-type illusory contours activate early retinotopic visual areas that are also activated by real contours. It is not known whether other types of illusory contours are processed by the same mechanisms, nor is it clear to what extent attentional effects may have influenced these results, as no attempt was made to match the salience of real and illusory stimuli in previous imaging studies. It therefore remains an open question whether there are any brain regions specifically involved in the perception of illusory contours. To address these questions, we have used 15O-butanol positron emission tomography (PET) and a novel kind of illusory contour stimulus that is induced only by aligned line ends. By employing a form discrimination task that was matched for attention and stimulus salience across conditions we were able to directly contrast perception of real and illusory contours. We found that the regions activated by illusory contour perception were the same as those activated by real contours. Only one region, located in the right fusiform gyrus, was significantly more strongly activated by perception of illusory contours than by real contours. In addition, a principal component analysis suggested that illusory contour perception is associated with a change in the correlation between V1 and V2. We conclude that different kinds of illusory contours are processed by the same cortical regions and that these regions overlap extensively with those involved in processing of real contours. At the regional level, perception of illusory contours thus appears to differ from perception of real contours by the degree of involvement of higher visual areas as well as by the nature of interaction between early visual areas.

Cytoarchitectural maps of the human brain in standard anatomical space.

The remarkable intersubject variability of the human cerebral cortex poses major problems for the systematic study of functional-structural relationships. Lack of homology and macroscopical landmarks between brains implies that one cannot in three or two dimensions find which part of one gyrus or sulcus matches which part of another subject's cerebral cortex. Furthermore, the frequent lack of correspondence between cytoarchitectural borders and the bottom of sulci invalidates correlations between gross morphology and microstructure. Therefore, we proposed that microstructural criteria should be used to define an anatomical space for comparison of individual brains and for establishing a probability map for each cytoarchitecturally defined area by quantitative means [Roland and Zilles, 1994; Trends Neurosci 17:458-467]. Here we examined the mapping of cytoarchitectural areas 4a, 4p, 3a, 3b, V1, and V2 into two commonly used anatomical standard reference spaces. Linear global transformations into Talairach space produced minimal overlap of corresponding cytoarchitectural areas. Global affine and nonaffine transformations into the anatomical space of the Human Brain Atlas (HBA) gave significantly larger volumes of overlap of corresponding cytoarchitectural areas. It is expected that local transformations can further improve the registration of corresponding cytoarchitectural areas and thereby define a common standard anatomical space in which to study variations in gross anatomical structure and function.