[Neurological chief complaints in an emergency room]. / Neurologische Leitsymptome in einer Notaufnahme.

Neurological chief complaints often lead patients into the emergency room. In order to establish standard emergency workups it is important to know the frequency of neurological chief complaints. Therefore, we performed a retrospective study on 4,132 consecutive neurological patients in the emergency room over a 1-year period. The most frequent chief complaint was headache (20%) followed by motor deficit (13%), vertigo (12%) and epileptic seizure (11%). In conclusion, the neurological workup in the emergency room can be optimized by establishing clinical decision-making rules for the four most frequent chief complaints.

A flow sensitive alternating inversion recovery (FAIR)-MRI protocol to measure hemispheric cerebral blood flow in a mouse stroke model.

Blood flow imaging is an important tool in cerebrovascular research. Mice are of special interest because of the potential of genetic engineering. Magnetic resonance imaging (MRI) provides three-dimensional noninvasive quantitative methods of cerebral blood flow (CBF) imaging, but these MRI techniques have not yet been validated for mice. The authors compared CBF imaging using flow sensitive alternating inversion recovery (FAIR)-MRI and (14)C-Iodoantipyrine (IAP)-autoradiography in a mouse model of acute stroke. Twenty-nine male 129S6/SvEv mice were subjected to filamentous left middle cerebral artery occlusion (MCAo). CBF imaging was performed with (14)C-IAP autoradiography and FAIR-MRI using two different anesthesia protocols, namely intravenous infusion of etomidate or inhalation of isoflurane, which differentially affect perfusion. Using (14)C-IAP autoradiography, the average CBF in ml/(100 g*min) was 160+/-34 (isoflurane, n=5) vs. and 59+/-21 (etomidate, n=7) in the intact hemisphere and 43+/-12 (isoflurane, n=5) vs. 36+/-12 (etomidate, n=7) in the MCAo hemisphere. Using FAIR-MRI, the corresponding average CBFs were 208+/-56 (isoflurane, intact hemisphere, n=7), 84+/-9 (etomidate, intact hemisphere, n=7), 72+/-22 (isoflurane, MCAo hemisphere, n=7) and 48+/-13 (etomidate, MCAo hemisphere, n=7). Regression analysis showed a strong linear correlation between CBF measured with FAIR-MRI and (14)C-IAP autoradiography, and FAIR-MRI overestimated CBF compared to autoradiography. FAIR-MRI provides repetitive quantitative measurements of hemispheric CBF in a mouse model of stroke.

No evidence for early decrease in blood oxygenation in rat whisker cortex in response to functional activation.

Using optical methods through a closed cranial window over the rat primary sensory cortex in chloralose/urethane-anesthetized rats we evaluated the time course of oxygen delivery and consumption in response to a physiological stimulus (whisker deflection). Independent methodological approaches (optical imaging spectroscopy, single fiber spectroscopy, oxygen-dependent phosphorescence quenching) were applied to different modes of whisker deflection (single whisker, full whisker pad). Spectroscopic data were evaluated using different algorithms (constant pathlength, differential pathlength correction). We found that whisker deflection is accompanied by a significant increase of oxygenated hemoglobin (oxy-Hb), followed by an undershoot. An early increase in deoxygenated hemoglobin (deoxy-Hb) proceeded hyperoxygenation when spectroscopic data were analyzed by constant pathlength analysis. However, correcting for the wavelength dependence of photon pathlength in brain tissue (differential pathlength correction) completely eliminated the increase in deoxy-Hb. Oxygen-dependent phosphorescence quenching did not reproducibly detect early deoxygenation. Together with recent fMRI data, our results argue against significant early deoxygenation as a universal phenomenon in functionally activated mammalian brain. Interpreted with a diffusion-limited model of oxygen delivery to brain tissue our results are compatible with coupling between neuronal activity and cerebral blood flow throughout stimulation, as postulated 110 years ago by C. Roy and C. Sherrington (1890, J. Physiol. 11:85--108).

Physical model for the spectroscopic analysis of cortical intrinsic optical signals.

We used Monte Carlo simulations and the diffusion approximation to estimate correction terms for the analysis of reflectance spectra of cortical intrinsic optical signals. These corrections depend on scattering and absorption properties, i.e. they are dependent on assumptions on the tissue blood content and oxygen saturation. The analysis was applied to reflectance spectra acquired during whisker barrel stimulation in the rat where attenuation spectra were converted to changes in oxygenated and deoxygenated haemoglobin concentration. The description of the experimental data as judged by the residual and sensitivity to variations of wavelength was considerably improved when the correction terms were included. Inclusion of the correction does have a considerable impact on the time course of deoxyhaemoglobin concentration changes. In contrast to the calculation without correction terms, there is no indication for an early increase in deoxyhaemoglobin ('early dip'). This finding might further current interpretation of the coupling between neuronal activation and oxygen extraction and supply.

Very slow oscillatory activities in lateral geniculate neurons of freely moving and anesthetized rats.

In urethane anesthetized rats many lateral geniculate neurons display a strong very slow oscillatory behavior in the range of 0.025-0.01 Hz. One of the aims of the present study was to determine whether very slow oscillatory activity in this range can also be obtained in barbiturate anesthetized and in awake animals, respectively. Although very slow oscillations were found in geniculate neurons both during awakeness and during anesthesia, significant differences in peak frequencies of oscillations under the three experimental conditions (barbiturate, urethane, awake) were demonstrated. In addition, we have tested the influence of glutamate antagonists and GABA agonists as well as antagonists on the very slow oscillatory activity in urethane anesthetized rats. Very slow oscillatory activity which could be blocked by the continuous illumination of the eyes was re-induced by iontophoresis of NMDA and non-NMDA glutamate antagonists. GABA(A) as well as GABA(B) agonists also caused a significant re-induction of very slow oscillatory activity under light conditions. In the dark, muscimol, a GABA(A) agonist, significantly enhanced the very slow oscillatory activity, i.e. muscimol either induced it or reduced the frequency of very slow oscillations. For the whole sample, GABA antagonists did not have a significant influence on the very slow oscillatory activity. Autocorrelation analysis based on the spike interval histograms and determination of the spectrum of autocorrelograms revealed the significance of periodicity.