Several experimental spinal cord models have been introduced in rats. Most models try to mimick the spinal trauma situation in humans. In this pathology, early alterations are most likely related to trauma-induced membrane dysfunction, but secondary damage to the microvasculature may also play a role. In addition, platelet aggregation and edema formation also seem to be early consequences of impact injury. Experimental compression of the spinal cord can be performed using mechanical impact, inflable epidural cuff or balloon or crushing of the cord. Most recent variants of the weight-drop techniques have resulted in a more uniform unjury, though the approach is still invasive and the morphological evaluation is often impossible, due to extreme vacuolisation of the neural structures. In these models all fysiopathological phenomena mentioned above play a role. Recently a photochemically induced spinal cord infarction model was described which tried to separate the different pathophysiological meachanisms involved. We introduce a variation of the pathochemical infarction, the photochemical spinal cord micro-infarction. Rose bengal (20 mg/kg) was injected intravenously in anesthetized male Wistar rats. A l m m diameter optic fiber was inserted between the laminae L1-L2 and D7-D8 on the right side. This fiber was advanced to the dura, which was not opened. A Schott KL 1500 light source equipped with a 150 watt Osram Xenophot lamp was connected to this optic fiber and illumination lasted for 20 minutes. This method has several advantages: the lesion is unilateral so that the opposite side can serve as a control for histological, neurological and electrophysiological studied, the morphological changes are primarily situated in the gray matter and are discrete so that grading of the lesion is possible and an eventual pharmacological influence on the lesion can be detected. clinically reversible as well as irreversible deficits can be induced.

We describe a series of 12 patients who suffered from lesions adjacent to the classic Broca and Wernicke areas and were examined by magnetoencephalography (MEG) for presurgical language localization while performing a protocol of different language tasks. In these patients very large MEG activity of up to 5 pT was observed, which was located not only in the adjacent language processing brain areas but also in more distant areas, which are part of the language processing neuronal network. The high amplitude and the focal spatial extent of this activity allowed MEG source localization from the unaveraged data. In nine patients sources of this high amplitude activity were even found in the homologous language areas on the contralateral, the nondominant side of the brain. The physiological interrelationship of these large MEG changes needs to be investigated in more detail in further studies especially in the context of possible mechanisms for brain plasticity to overcome inhibitory activity of the impaired language area.

Object: The aim of this study was to investigate whether diffusion tensor imaging (DTI) can be integrated into functional navigation for the intraoperative visualization of the pyramidal tract. Methods: A single-shot spin-echo diffusion-weighted echo planar imaging sequence on a 1.5 T magnetic resonance (MR) scanner was used for DTI. One null image and six diffusion-weighted,images (high B value 1000 mm/s(2)) were obtained. Color-encoded fractional anisotropy maps of the principal eigenvector rendered as a boxoid within each voxel were used for segmentation of the pyramidal tract. The segmented images were rigidly registered with a T-1-weighted gradient echo 3D dataset for navigation in 16 patients with gliomas. In tumors adjacent to the motor cortex (n = 6) data from functional MR imaging were co-registered. Results: The whole DTI processing lasted about 25-30 minutes in each case. In all cases DTI could be integrated into the navigational dataset resulting in an intraoperative visualization of the pyramidal tract by microscope-based navigation. Navigational accuracy measured as the target registration error was 1.2 +/- 0.46 mm. Registration of fractional anisotropy maps with the 3D navigational dataset was possible with an error of less than 2 mm. Co-registration with fMRI was consistent with DTI data. A neurological deterioration was observed only in one patient. Conclusions: DTI can be reliably integrated into navigational datasets. Thus, microscope-based neuronavigation can be used for an intraoperative visualization of the course of the pyramidal tract. However, a possible shifting of the pyramidal tract has to be taken into account after major tumor parts are removed.

Kürzlich konnten wir und andere zeigen, daß die Quellen spontaner langsamer magnetischer Aktivität bei kortikalen Läsionen schalenförmig um die Läsion angeordnet sind (Vieth et al. 1992; Gallen et al. 1992). Vergleichbare Untersuchungen hinsichtlich spontaner fokaler Beta-Aktivität (12,5–30 Hz) oder der pathologischen Spontanaktivität bei Marklagerläsionen wurden unseres Wissens bisher nicht unternommen. Wir untersuchten daher die pathologische Spontanaktivität im Beta-Frequenzbereich bei Läsionen des Kortex und des Marklagers im Vergleich mit der langsamen magnetischen Aktivität (2–6 Hz). Die Frage war, wie eng die Schwerpunkte von Beta-Aktivität mit kortikalen Läsionen zusammenhängen und mit denen der langsamen Aktivität übereinstimmen, und wo andererseits sich pathologische Aktivität bei Marklagerläsionen zeigt.

In this study the authors investigated several approaches to localize cortical areas activated during speech processing. The event-related activation was elicited by visually presented stimuli. One paradigm consisted of written mono syllable nouns where the subjects were asked to read the words and imagine the described object. Another task was to silently name objects presented to them. The magnetic evoked activity of 13 normal subjects (9 right handed, 4 left handed) was recorded with the 37 channel biomagnetic system KRENIKONR (Siemens). The time course of the averaged evoked signals showed a high inter-individual variability. However they had two features in common, a wave starting at approximately 350 ms and a wave starting at 500 ms after the stimulus onset. The cortical representation of the waves in the cases with a high signal to noise ratio was found in the Wernicke's area and Broca's area respectively

Die Positronen-Emissions-Tomographie (PET) und die Magnetoenzephalographie (MEG) geben auf unterschiedliche Weise Informationen über die Funktion des Gehirns: PET kann Veränderungen der Hirndurchblutung meßen, während MEG Änderungen magnetischer Felder erfaßt.