Perspectives in Medicine最新文献

The optimal treatment strategy for patients with asymptomatic carotid artery stenosis (ACS) is still a matter of debate. Based on a simplistic view, all stenosed vessels should be cleaned, and the earlier the better. Due to the improvements of medical management in patients with high-grade ACS, there is uncertainty as how to best manage these patients. Consequently, the cost-effectiveness of CEA in patients with ACS has been questioned. Therefore, the question arises how best medical treatment changes the risk of stroke in patients with ACS. This overview discussed the therapeutic options for ACS from a neurological point of view.

Objective

We have introduced and improved a transducer holder, named the Sonopod, for transcranial color duplex sonography (TCDS) monitoring via both temporal/foraminal windows (TW/FW). The objective is to clarify clinical usefulness and identify problems in TCDS-Sonopod monitoring during the evaluation of brain tissue perfusion.

Methods

Brain tissue perfusion monitoring was evaluated in 11 patients (ages 31–94, mean 66). After a bolus intravenous Levovist^®, power modulation imaging (PMI) in all cases was evaluated in comparison with second harmonic imaging (SHI) in two cases at the diencephalic horizontal plain via the TWs on the basis of time–intensity curves (TICs) in five regions of interest (ROIs); bilateral basal ganglia (BG) and thalamus (Th), and contra-lateral temporal lobe (TL). After a SONOS5500 S3 transducer was installed in the Sonopod, acetazolamide (ACZ) cerebral vasoreactivity utilizing PMI was evaluated in 10 cases via the bilateral (five cases) and unilateral (five cases) TWs. A total of 30 TICs were evaluated before/after ACZ administration.

Results

(1) All patients could be monitored continuously by one examiner. (2) We confirmed that PMI proves superior to SHI in quantitative evaluation of the bilateral hemispheres via the unilateral TWs. (3) Brain tissue perfusion could be precisely quantified before/after ACZ in the same ROIs. (4) TIC base-line drifts during monitoring were observed in 4 (seven TICs) of 10 (30 TICs) patients. However, fixed-probe shifts during monitoring were easily readjustable and the TIC recovered to the base-line in all cases. (5) Due to re-fixation needed for contralateral TW monitoring, it was not possible to evaluate completely in the same ROIs.

Conclusions

TCDS-Sonopod monitoring succeeds in continuously and quantitatively evaluating precise and reproducible intracranial hemodynamics in the brain tissue.

Contrast Enhanced Carotid Ultrasonography (CCU) is capable of detecting angiogenesis within the carotid plaque as a potential index of plaque vulnerability. However, due to a lack of standard of examination technique and documentation, results are not sufficiently, reliably comparable.

To improve this situation and in order to support wide acceptance of this promising technique, experts in this field met in the Consensus conference in May 22, 2011, held during the 16th ESNCH Meeting (20–23 May 2011) in Munich, Germany, to discuss the limitations and problems and to determine guidelines for its proper use in scientific investigations and clinical practice.

The main results of this conference are presented here. The discussion is still in progress and individual conclusions may not reflect the opinion of all participants. It aims to provide a basis for a later comprehensive consensus statement.

Multiple sclerosis (MS) is a chronic inflammatory and neurodegenerative disease of the central nervous system (CNS). Its autoimmune origin has been recently challenged by a substantially different mechanism termed chronic cerebrospinal venous insufficiency (CCSVI), which has attracted worldwide attention in the scientific community, in the media and among MS patients. According to this hypothesis, a congestion of cerebrovenous outflow induces an increased intracranial pressure and a disintegration of the blood–brain barrier in perivenular regions promoting local iron deposition and activation of pro-inflammatory factors, ultimately leading to MS. After the initial report of a perfect association between CCSVI and MS, different independent groups were not able to replicate these results, casting doubts on the credibility of the CCSVI concept in MS. In spite of this, interventional procedures like venous angioplasty named the “liberation” treatment have been claimed as a cure of MS or at least as a major improvement of MS symptoms. As a result, an increasing number of MS patients are undergoing endovascular treatment, in spite of a lack of an evidenced-based benefit and recent reports of serious adverse events. This review represents a critical appraisal of the CCSVI hypothesis, discusses its basis, the diagnostic criteria and its relationship with MS.

With improvements in ultrasound (US) imaging equipment and refinements in scanning technique, an increasing number of peripheral nerves and related pathologic conditions can be identified. Modern US imaging supports the clinical examination and electrophysiologic testing in setting the diagnosis, and enhances this information by illuminating the morphological aspects and etiology of peripheral nerve pathology. US can readily be used for detection of nerve abnormalities caused by trauma, tumors, inflammation and a variety of nonneoplastic conditions, including compressive neuropathies. Well recognized advantages of the method such as the possibility of a dynamic examination, assessing long nerves segments in a short time, bed-side-availability, non-invasivity and low cost, make US the ideal imaging tool in peripheral nerve disease.

Because of the recent hypothesis of involvement of the venous hemodynamics in multiple sclerosis (MS), and because of the pitfalls of these studies, there is the need to achieve a definite conclusion from a large sample of subjects by using a strict and controlled neurosonological protocol. The aim of the advanced protocol, designed for a subgroup of the FISM study, is to analyze several items of the venous hemodynamics in order to obtain more pathophysiological data on venous circulation. Advanced Ultrasound Protocol: This is a multicenter, observational study. From a pool of about 1200 adults with MS, 400 healthy subjects and 400 subjects with other neurodegenerative disorders (2000 subjects in total) will be selected a population able to be examined by the advanced protocol. The examiner will always be blind on the clinical diagnosis, and the exams will be performed according to a standard protocol, whose measurements are mandatory for all participating centers. The advanced protocol is on a voluntary basis and it is optional. It includes, besides the basic one, measurements of blood flow volumes in carotid and vertebral arteries and in jugular and vertebral veins (inflow and outflow), with the definition of the drainage pattern. The ultrasound examination at each clinical site will be followed by a second centralized blinded evaluation. The prevalence of CCSVI in MS will be estimated, with confidence intervals at 95%, and compared with the prevalence in other groups. Moreover, multiple analysis will be done comparing venous hemodynamics in the three different groups.

This contribution summarizes the past and present status of ultrasound-facilitated thrombolysis (sonolysis) with and without the use of microspheres. Different ultrasound techniques are addressed and advantages as well as pitfalls are discussed.

A short introduction is given of how fluid dynamics forces and velocity distribution influence the development of plaque in the carotid bifurcation. The flow parameters are discussed. Flow visualization techniques and also laser-Doppler-anemometer measurements demonstrate the importance of the flow. This will be shown in true-to-scale, physiological accurate models of the carotid arteries. These models have the same compliance as the real blood vessel. Some applications are shown e.g. patches, stents and filters. The most important factors are the flow rate ratio and geometry, unsteady pulsatile flow, wall elasticity and non-Newtonian flow behavior of blood.

Background

Small cerebral vessels respond to variations of cerebral perfusion pressure (CPP) by changes of vessel diameter inducing changes of blood flow resistance and keeping cerebral blood flow constant. This mechanism is called cerebral autoregulation (CA). Recently stronger reactions of CA during pressure increase than during decrease were reported. Aim of this study was to assess the symmetry behavior of CA during spontaneous CPP changes and compare it to cerebrovascular pressure reactivity (CVR).

Methods

In 238 patients with traumatic brain injury or stroke, correlation indices between CPP and cerebral blood flow velocity (CBFV) were calculated during periods of increasing (upMx) and decreasing CPP (downMx). The indices range from −1 to +1, values ≤0 indicating intact, values >0 indicating impaired autoregulation. Similar correlation between arterial blood pressure (ABP) and ICP was calculated during increasing (upPRx) and decreasing ABP (downPRx), negative values indicating intact, positive values indicating impaired CVR. Only recordings with strong pressure changes (CPP/ABP > 10 mmHg) were evaluated.

Results

CA was assessed in 62 patients. On average (mean ± SD) upMx was 0.06 ± 0.52, downMx was 0.15 ± 0.55 (P < 0.005). CVR was assessed in 47 patients. On average upPRx was 0.45 ± 0.43, downPRx was 0.38 ± 0.48 (P < 0.05). In 40 patients both Mx and PRx were calculated. On average upMx was 0.21 ± 0.55 and downMx was 0.27 ± 0.56 (P = 0.05), upPRx was 0.35 ± 0.43 and downPRx was 0.27 ± 0.47 (P < 0.05).

Conclusions

During pressure increase the autoregulatory response was significantly stronger than during decrease, while in contrast the cerebrovascular reactivity was significantly weaker. The reason for this opposed behavior remains unclear and needs further exploration.