[Differential diagnosis of Parkinson's syndromes--an overview]. / Differenzialdiagnostische Massnahmen bei Parkinsonsyndromen--eine Ubersicht.

With regard to aging of the general population non-neurologists are more frequently confronted with patients presenting with parkinsonian symptoms. The central task concerning treatment and prognosis in such cases is to differentiate idiopathic Parkinson's disease from secondary Parkinson syndromes and so called Parkinson-Plus-Syndromes. Besides clinical presentation neuroimaging techniques have been established in recent years, which can help with correct classification in early disease stages and difficult cases. In this article, we review the current clinical pathways for differential classification of parkinsonian symptoms with a special emphasis on clinical assessment and neuroimaging techniques like NMR and transcranial sonography.

Aortic calcification on plain chest radiography predicts embolic complications during carotid artery stenting.

BACKGROUND AND PURPOSE: Aortic arch calcification (AC) on conventional angiograms has recently been shown to be associated with embolic complications during carotid artery stenting (CAS). Because conventional angiography is not routinely carried out in patients prior to CAS, a less invasive, commonly available diagnostic modality is warranted to identify AC. METHODS: We investigated the occurrence of AC on routinely acquired chest radiographs and its influence on diffusion-weighted imaging (DWI) lesions as surrogate markers for stroke. RESULTS: A total of 152 patients (mean age: 67.5 +/- 8.9 years, 112 men) underwent CAS and completed pre- and post-procedural DWI. AC larger than 1 cm in length was classified as relevant and could be detected in 63 patients (41.4%) on plain chest radiographs. In patients with AC, significantly more new DWI-lesions were found than in patients without AC [median 2; interquartile range (IQR): 0-7 vs. median 1, IQR: 0-2; P < 0.05]. After multivariate regression analysis, AC was independently associated with new post-procedural DWI lesions. DISCUSSION: AC is a common finding in patients with a high-grade carotid stenosis and predicts embolic complications during CAS. Since AC can be detected on plain chest radiography, this diagnostic tool is useful to identify high-risk patients for CAS.

Early treatment after a symptomatic event is not associated with an increased risk of stroke in patients undergoing carotid stenting.

A recently symptomatic carotid artery stenosis carries a high risk of subsequent ischaemic events and thus requires rapid treatment. We investigated the influence of the time delay between the last symptomatic event of a carotid stenosis and subsequent carotid artery stenting (CAS) with respect to the combined 30-day outcome of stroke and death. In a group of 320 patients undergoing CAS the median delay before the intervention was 19 days (interquartile range 10-36) and the combined 30-day complication rate was 8.4%. Time delay was not significantly associated with peri-procedural complications, regardless of whether this variable was dichotomized (<14 days and > or =14 days), separated into interquartile ranges or analysed as a continuous variable. Our results indicate that early CAS is not associated with an increased complication rate in patients with a recently symptomatic carotid stenosis. Thus, if CAS has been selected as the treatment modality for a patient, it should be performed as soon as possible to maximize the benefit of the intervention in reducing the risk of stroke.

Role of inelastic tunneling through the insulating barrier in scanning-tunneling-microscope experiments on cuprate superconductors.

The tunneling path between the CuO2 layers in cuprate superconductors and a scanning-tunneling-microscope tip passes through a barrier made from other oxide layers. This opens up the possibility that inelastic processes in the barrier contribute to the tunneling spectra. Such processes cause one or possibly more peaks in the second derivative current-voltage spectra displaced by phonon energies from the density of states singularity associated with superconductivity. Calculations of inelastic processes generated by apical O phonons show good qualitative agreement with recent experiments reported by Lee et al. Further tests to discriminate between these inelastic processes and coupling to planar phonons are proposed.

Full-counting statistics for voltage and dephasing probes.

We present a stochastic path integral method to calculate the full-counting statistics of conductors with energy conserving dephasing probes and dissipative voltage probes. The approach is explained for the experimentally important case of a Mach-Zehnder interferometer, but is easily generalized to more complicated setups. For all geometries where dephasing may be modeled by a single one-channel dephasing probe we prove that our method yields the same full-counting statistics as phase averaging of the cumulant generating function.

Noise and full counting statistics of incoherent multiple Andreev reflection.

We present a general theory for the full counting statistics of multiple Andreev reflections in incoherent superconducting-normal-superconducting contacts. The theory, based on a stochastic path integral approach, is applied to a superconductor-double-barrier system. It is found that all cumulants of the current show a pronounced subharmonic gap structure at voltages V=2Delta/en. For low voltages V< or =3. We show that this low-voltage result holds for a large class of incoherent superconducting-normal-superconducting contacts.

Frequency scales for current statistics of mesoscopic conductors.

We calculate the third cumulant of current in a chaotic cavity with contacts of arbitrary transparency as a function of frequency. Its frequency dependence drastically differs from that of the conventional noise. In addition to a dispersion at the inverse RC time characteristic of charge relaxation, it has a low-frequency dispersion at the inverse dwell time of electrons in the cavity. This effect is suppressed if both contacts have either large or small transparencies.

Stochastic path integral formulation of full counting statistics.

We derive a stochastic path integral representation of counting statistics in semiclassical systems. The formalism is introduced on the simple case of a single chaotic cavity with two quantum point contacts, and then further generalized to find the propagator for charge distributions with an arbitrary number of counting fields and generalized charges. The counting statistics is given by the saddle-point approximation to the path integral, and fluctuations around the saddle point are suppressed in the semiclassical approximation. We use this approach to derive the current cumulants of a chaotic cavity in the hot-electron regime.

Efficiency of mesoscopic detectors.

We consider a mesoscopic measuring device whose conductance is sensitive to the state of a two-level system. The detector is described with the help of its scattering matrix. Its elements can be used to calculate the relaxation and decoherence times of the system, and determine the characteristic time for a reliable measurement. We derive conditions needed for an efficient ratio of decoherence and measurement times. To illustrate the theory we discuss the distribution function of the efficiency of an ensemble of open chaotic cavities.