Simulation of cerebral hemodynamics for preoperative risk assessment.

BACKGROUND: An important part of the medical treatment of many cerebrovascular diseases is the occlusion of brain supplying arteries. Until now, the risk of this intervention can only be estimated by invasive diagnostics including the risk of cerebrovascular accidents. METHODS AND RESULTS: As a supporting tool, a computer model of the circle of Willis was designed. The model is based upon linear differential equations describing electrotechnical circuits extended non-linearly. By these means, time continuous simulations of different states and the online observation of all calculated state variables such as blood pressure and blood flow in every modeled vessel became feasible. For individual simulations, model parameters were determined by MR-angiography and boundary values by simultaneous Duplex-measurements in both carotid and vertebral arteries. State variables generated by the model behaved physiologically and the reaction of individual cerebrovascular systems in critical situations could be investigated by special scenarios. Inaccuracies concerning the determination of model parameters and boundary values of the used differential equations are likely to be resolved in the near future through a more careful and technically improved determination of these values. CONCLUSIONS: Computer models of subjects were created taking in account the individual anatomical and non-linear physical properties of real vascular systems supplying the brain. Thereby information could be obtained concerning the hemodynamic effects of an iatrogenic vascular occlusion.

MR blood oxygenation level-dependent signal differences in parenchymal and large draining vessels: implications for functional MR imaging.

BACKGROUND AND PURPOSE: One major limitation of current functional MR (fMR) imaging is its inability to clarify the relationship between sites of cortical neuronal activation, small parenchymal venules that are in close proximity to these sites, and large draining veins distant from the active parenchyma. We propose to use gradient-echo blood oxygenation level-dependent (BOLD) fMR time courses to differentiate large draining veins from parenchymal microvasculature. METHODS: In eight research subjects, five of whom presented with space-occupying lesions near the central sulcus, gradient-echo fMR imaging was performed during alternating periods of rest and motor activation. MR signal time courses from parenchymal regions and draining veins of different diameters, which were identified using contrast-enhanced T1-weighted scans, were evaluated. Percent signal changes (deltaS) and the time to the onset of MR signal rise (T0) were calculated. RESULTS: Mean delta(S) for all subjects was 2.3% (SD+/-0.7%) for parenchymal activation, 4.3% (SD +1.0%) for sulcal macrovasculature, and 7.3 (SD+/-1.1%) for large superficial bridging veins. The mean time to onset of MR signal increase was 4.4 seconds for parenchymal task-related hemodynamic changes and 6.6 seconds for venous hemodynamic changes, regardless of vessel size. Both the differences in delta(S) and T0 were statistically significant between venous and parenchymal activation (P < .0001). CONCLUSION: Gradient-echo fMR imaging reveals hemodynamic task-related changes regardless of vessel size and therefore might show macrovascular changes distal to the site of neuronal activity. MR-signal time-course characteristics (delta(S) and T0) can be used to differentiate between small parenchymal and larger pial draining vessels, which is especially important in presurgical planning of neurosurgical procedures involving functionally important brain regions. The knowledge about the differences in (delta)S and T0 between micro- and macrovasculature might lead to a more accurate description of the spatial distribution of underlying neuronal activity.

Effects of tracheostomy on human tracheobronchial mucosa: a scanning electron microscopic study.

The protective functions missing in the upper airways of tracheostomy patients lead to functional and morphological changes in the lower respiratory tract. To obtain detailed data from the surface of the tracheobronchial mucosa, a scanning electron microscopic study was performed. Mucosal biopsies were taken from different sites of the tracheobronchial tree in 5 healthy control subjects, 5 patients with tracheostomy after laryngectomy, and 5 tracheostomy patients not affected by a history of smoking. Following scanning electron microscopic examination, the specimens were evaluated morphometrically. The percentage ciliary border and the individual mucosal surface changes depended on the biopsy site and the degree of previous damage. Individual structural alterations consisted of squamous metaplasia, giant cilia, compound cilia, and microplicae. Giant cilia represented an impressive form of differentiation in chronic bronchitis recognizable by scanning electron microscopy.

Correlative histological and ultrastructural study of unusual changes in human tracheobronchial epithelium.

In tracheostomy patients with chronic bronchitis, scanning electron microscopy reveals detailed surface changes in the tracheobronchial mucosa. The principle of intermicroscopic correlation, i.e., the sequential examination of a specimen by different microscopic procedures, is illustrated with giant cilia. After re-embedding the scanning electron microscopic specimens and precisely locating a ciliary convolution by light microscopy in semithin section, the giant cilia were studied in ultrathin sections by transmission electron microscopy. The cilia were shown to be at least 9 microns long (normal ciliary length = 4-6 microns). Central and peripheral microtubular axonemal structures with a 9 + 2 arrangement were clearly shown in both longitudinal and cross section. Giant cilia, thus, most closely resemble outgrowths of normal cilia. If they are motile at all, they seem unlikely to effect a transport function coordinated in direction and time.

[Polyposis of the nasal cavity and sinuses]. / Die Polyposis nasi et sinuum.

In spite of many recent advances in basic science, the etiology and pathogenesis of nasal and paranasal polyps have still not been clarified. Well defined causal factors are hereditary diseases such as cystic fibrosis and primary ciliary dyskinesia. Allergic and non-allergic processes of the airways, particularly intrinsic asthma and intolerance to non-steroidal antiinflammatory drugs (NSAID), are implicated in the development of nasal polyposis. Histopathological studies of polyp tissue do not allow etiologic or prognostic conclusions, but are indispensable for the classification of structures involving clinical signs similar to nasal polyps. Causal antiallergic therapy is confined to the rare cases with an evident clinically relevant nasal allergy. Topical corticosteroids are effective in the treatment of nasal polyposis, but in extensive and obstructive polyps surgery is required. In severe polyposis of the ethmoid sinus endoscopically controlled endonasal ethmoidectomy is the surgical treatment of choice.

[Condition of the tracheobronchial mucous membrane in patients with long-term tracheostomy. A scanning electron microscopy study]. / Die tracheobronchiale Schleimhautbeschaffenheit bei Patienten mit Langzeit-Tracheostoma. Eine rasterelektronenmikroskopische Studie.

In patients with tracheostomy and lacking or non-patent larynx the nose has no longer any climatic function for the lower airways. The comparison of mucosal alterations in the tracheobronchial tree of 5 laryngectomized patients, 5 tracheostomized patients without chronic bronchitis prior to the operation, and 5 otherwise healthy persons, who served as a control group, allows conclusions on the protective function of the intact upper airways. The specimens obtained from the right upper lobe bronchus, the main carina, the middle third of the trachea and below the stoma are examined by means of a scanning electron microscope (SEM). The percentage of the ciliated components of the epithelium is evaluated with a semi-automatically functioning image analyser. In healthy subjects the ciliated cells are clearly reduced close to the main carina. After laryngectomy a reduction of cilia along the entire tracheobronchial tree is observed, whereas at the main carina they are more or less lacking. In patients without preexisting chronic bronchitis the ciliary carpet is also almost totally absent near the carina and the stoma, while it is qualitatively better in the right upper lobe bronchus and the middle trachea. The method presented here, with evaluation of the distribution and ciliary surface morphology, allows quantification of the tracheobronchial mucosal condition under various anatomical and clinical circumstances. If the protective function of the upper airways is missing, the alterations of the tracheobronchial mucosa depend on the extent of the preexisting damage and on the level where the specimen is taken.

[Contributions to the Structure of Hypercratine, another Alkaloid of Ruspolia hypercrateriformis.]. / Zur Struktur von Hypercratin, einem weiteren Alkaloid aus Ruspolia hypercrateriformis*

Besides the known pyrrolidine alkaloids ruspolinone ( 1), norruspolinone ( 2), and norruspoline ( 3) the "bispyrrolidine" alkaloid hypercratine was isolated from the roots of RUSPOLIA HYPERCRATERIFORMIS M. R. (Acanthaceae). After chemical and spectroscopic analysis of the new compound, structure 4 is suggested.

Determination of cognitive hemispheric lateralization by "functional" transcranial Doppler cross-validated by functional MRI.

BACKGROUND AND PURPOSE: Changes of blood flow velocity in the right and left middle cerebral artery (MCA) induced by cognitive demands are detectable by means of "functional" transcranial Doppler sonography (fTCD). Functional MRI (fMRI) is an alternative method for mapping brain activity. The purpose of this study was to determine whether fTCD can detect hemispheric lateralization and to cross-validate fTCD with fMRI. METHODS: Bilateral continuous MCA monitoring of 14 healthy, right-handed subjects with TCD was performed while the subjects underwent a visuospatial task, and the hemispheric blood flow velocity shift was calculated. Identical stimulus and response patterns were used in fMRI. Blood oxygenation level-dependent fMRI was performed with the use of a gradient-echo echo-planar sequence on a 1.5-T scanner. Statistical maps were computed on a voxel-by-voxel basis, hemispheric ratios for activated pixels were computed, and a group study was performed separately for the male and female subgroups. RESULTS: Statistical analyses (t test) showed a significantly higher mean peak blood flow velocity increase (P<0.05) of the right MCA (111.3+/-7.0%) compared with the left MCA (107.1+/-6.1%). fMRI demonstrated bilateral activation in the superior parietal lobulus (Brodmann area 7) with a right/left ratio of 1.95. Concordant differences between the female and male subgroups could be visualized with both methods. CONCLUSIONS: Both methods succeeded in discriminating a blood flow shift to the right hemisphere induced by a complex cognitive visuospatial task. fMRI cross-validates the findings of fTCD. Our study suggests that fTCD can investigate the close relationship between brain activity and blood flow and lateralize higher cognitive functions reliably.

Functional magnetic resonance mapping of sensory motor cortex for image-guided neurosurgical intervention.

PURPOSE: This paper describes the potentials of functional magnetic resonance imaging (fMRI) to map sensory motor cortex in patients with mass lesions near primary motor cortex and to guide neurosurgical procedures located close to eloquent brain regions. MATERIAL AND METHODS: 7 patients with mass lesions near the central sulcus and 10 healthy volunteers were studied using a blood oxygenation level dependent 2D multislice multishot T2* weighted gradient echo EPI sequence on a 1.5T Phillips Gyroscan during alternating epochs of rest and motor activation of hand, foot and tongue. Sites of neuronal activation were identified by statistical analysis of the signal time course using Kolmogorov Smirnov statistics. RESULTS: Neuronal activation following motor tasks consistently localised to the contralateral precentral gyrus and the supplementary motor area, even in the presence of local brain pathology. Additionally we could observe activation in primary sensory areas (post-central gyrus) and supplementary motor area (SMA) in some cases. CONCLUSION: fMRI is capable of mapping sensory motor cortex even in the presence of distorting brain lesions. Since this information will provide valuable information to the neurosurgeon during pre-operative planning, we consider this method for neurosurgical navigation a valuable tool in the routine diagnostic of intracerebral interventions.