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.

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.

The identification of vulnerable and unstable carotid atherosclerotic lesions is up-to-date an important topic of research, in order to adopt the adequate strategy for preventing cerebrovascular events. Plaque inflammation, presence of adventitial vasa vasorum, intimal angiogenesis and plaque neovascularization have been identified in histological studies as indicators of the instability of the atheroma of carotid arteries in cerebrovascular patients and of coronary arteries in cardiovascular patents. Consequently, the identification “in vivo” of these pathophysiological aspects has been objective for the development of new imaging techniques. Ultrasound of carotid arteries, with ultrasound contrast agents, is not only able to provide an enhanced visualization of the arterial lumen and plaque morphology, but also allows to directly visualize adventitial vasa-vasorum and carotid plaque neovascularization. This technique and its clinical implications in the unstable plaque identification are discussed in the present paper.

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.

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.

Traumatic brain injury (TBI) is associated with the severest casualties from Operation Iraqi Freedom (OIF) and Operation Enduring Freedom (OEF). From October 1, 2008 the US Army Medical Department initiated a transcranial Doppler (TCD) ultrasound service for TBI patients; included patients were retrospectively evaluated for TCD-determined incidence of posttraumatic cerebral vasospasm and intracranial hypertension after wartime TBI. Ninety patients were investigated with daily TCD studies and comprehensive TCD protocol and published diagnostic criteria for vasospasm and raised intracranial pressure (ICP) were applied. TCD signs of mild, moderate and severe vasospasms were observed in 37%, 22% and 12% of patients, respectively. TCD signs of intracranial hypertension were recorded in 62.2%, five patients (4.5%) underwent transluminal angioplasty for post-traumatic clinical vasospasm treatment and 16 (14.4%) had cranioplasty. These findings demonstrate that cerebral arterial spasm and intracranial hypertension are frequent and significant complications of combat TBI, therefore daily TCD monitoring is recommended for their recognition and subsequent management.

Neurovascular coupling (NVC), analysed by a control system approach, was shown to be unaffected by orthostatic challenge, but data is lacking regarding the mechanism of this interplay and the behaviour of other cerebrovascular reactivity parameters. We investigated the changes in different pressure–velocity models during functional transcranial Doppler (TCD), under different orthostatic conditions.

Thirteen healthy volunteers performed a reading test stimulation task in sitting, supine and head-up tilt (HUT) positions. CBF velocity was monitored with TCD in the posterior cerebral artery, and blood pressure was monitored with Finapres. Cerebrovascular resistance index (CVRi) was compared to a two-parameter model including resistance-area product (RAP) and critical closing pressure (CrCP), in the maximal and in the stable phases of flow response to visual stimulation.

All cerebrovascular resistance parameters decreased with visual stimulation but the magnitude of their variation in each orthostatic condition was not similar. From supine to HUT, CrCP variation decreased (both maximal and stable phase p = 0.001). CVRi variation increased from sitting to HUT positions (maximal p = 0.039; stable phase p = 0.033). RAP variation to visual stimulation did not change between the three positions (maximal p = 0.077; stable phase p = 0.188).

A 2-parameter model of vascular resistance provided better discrimination for the effects of posture on NVC as shown by the adaptive changes in CrCP with orthostatic challenge, in comparison with the classical use of CVRi. These findings suggest that although NVC seemed unaffected by orthostatic challenge, more complex vasoregulative mechanisms are activated in different orthostatic conditions that could potentially be of diagnostic or prognostic value.