Perspectives in Medicine最新文献

Background

The hypothesis that cerebral embolism plays no role in late septic encephalopathy and septic shock is based on indirect clinical evidence in the literature. The goal of this study was to prove the hypothesis that cerebral embolism plays no role in the pathophysiology of sepsis by direct evidence.

Methods

To examine this hypothesis, 20 patients with a late septic encephalopathy and septic shock were examined for direct evidence of ongoing cerebral embolism with transcranial Doppler for 30 min. Clinical data analysis included age, gender, cause of sepsis (gram-positive or -negative microorganisms), an index of severity of illness (the APACHE II score) and outcome (survivor/non survivor). Cerebral embolism was quantified by embolus detection software.

Findings

The study revealed no ongoing cerebral embolism during sepsis.

Conclusion

Cerebral micro-embolism plays no role in cerebral dysfunction during sepsis. This negative finding has an important clinical repercussion, because if transcranial Doppler exams should reveal ongoing cerebral embolism in septic shock, the embolism cannot be attributed to the septic shock itself rather it would indicate for a vigorous search for an embolic source.

Sleep is the most conspicuous alteration of cerebral function during the circadian rhythm. It is composed of a cyclic sequence of stages defined on the basis of electrophysiological parameters. The underlying functional activity of the human brain is reflected by sleep correlated changes of cerebral blood flow (CBF), CBF velocity and cerebral metabolism (CM). Transcranial Doppler sonography (TCD) allows to analyze the rapid adaptation processes of cerebral hemodynamics due to TCD capabilities for high temporal resolution and continuous recording during sleep using modern ultrasonic probes with special fixation devices. After the onset of sleep there is a significant progressive reduction of CBF velocity from the waking state to slow wave sleep. The beginning of REM sleep is accompanied by a marked increase in CBF velocity. Furthermore, TCD enables the assessment of perfusion changes in pathological sleep conditions. In sleep apnea syndrome an apnea-associated increase in CBF velocity occurs, which is attributed to apnea-related hypercapnia, whereas a rapid normalization of flow velocity occurs at the end of each apneic episode. TCD is a useful method for long-term and on-line monitoring of dynamic changes in cerebral perfusion during normal sleep and in sleep disorders.

Introduction

Chronic cerebrospinal venous insufficiency (CCSVI) is a newly suggested cause for multiple sclerosis (MS) detected by color-coded Doppler sonography. Our aim was to evaluate the relationship between CCSVI and MS compared to the control group.

Methods

The study was performed on 84 MS patients and 115 healthy subjects. The presence of at least two of the extra- and/or intra-cranial Zamboni's criteria was considered positive for evidence of CCSVI.

Results

Although the total number of MS patients with any detectable CCSVI criterion was significantly higher than the controls (22.6% vs. 10.4%, P = 0.019), only one out of 84 patients fulfilled the Zamboni's criteria (1.2% vs. none, P = 0.422).

Conclusion

Our results do not support the presence of a relationship between MS and CCSVI criteria defined by Zamboni.

Introduction

The ultrasound examination of intracranial venous structures by transcranial color-coded sonography (TCCS) is a validated and standardized application. Similarly some intracranial venous sinuses are known for their relatively low insonation rate, as straight sinus (SRS) and transverse sinus (TS), ranging from 35% to 73%. The relatively high frequency of hypoplasia of TS can partially take account for these data. The aim of this study is to evaluate the feasibility of this approach in a standard TCCS examination, in comparison with magnetic resonance (MR) findings by using the Virtual Navigator system.

Patients and methods

The standardized approach to the TS was a contralateral insonation, starting to the SRS plane and angulating downwards the probe. In this way it is possible to insonate the proximal segment of the contralateral TS. We proposed a new approach with an extreme downwards tilting and a slow opposite angulation of the probe for examining the ispilateral TS. Forty consecutive subjects were chosen among patients who underwent standard TCCS examinations at our lab and had a suitable temporal acoustic window, and a recently performed MR venography. The contralateral TS insonation rate was compared with the ipsilateral one.

Results and discussion

The insonation rate was 61/80 (76.25%) for the contralateral TS and 75/80 (93.75%) for the ipsilateral approach. Two of 5 not detectable TS were aplasic in MR venography and the others were not identified by a poor acoustic window.

Conclusions

The ipsilateral approach could be associated to the contralateral standard study for insonating the TS.

Relation of right-to-left shunt (RLS) with chronic hyperventilation syndrome (CHVS) has not been previously reported. We evaluated the prevalence of RLS in patients with CHVS. Patients with CHVS and 25 healthy controls (CG) were recruited into the study. Vascular RLS was diagnosed using contrast TCD. Of 25 subjects with CHVS, 16 (64%) had RLS vs 3 from CG (12%). TEE confirmed PFO in 10 patients with CHVS (40%) vs 2 from CG (8%). Pulmonary AVM was found in chest CT in 2 patients (10%) with CHVS and none from CG. The prevalence of RLS and PFO in patients with CHVS was significantly higher than in healthy subjects.

The present study aims to validate the technique of in vitro ultrasonography (US) by comparative analysis of premortem intima–media thickness (IMT), postmortem IMT and average wall thickness. In vivo common carotid artery (CCA) IMT was measured bilaterally in 25 patients at 30 mm proximal from the flow divider. After autopsy in vitro US was performed and postmortem IMT was measured at the same level. Snap frozen arterial specimens were processed for average wall thickness determination and for histology. High degree of correlation was found between in vivo IMT, in vitro IMT and average wall thickness. Our results demonstrate: (1) in vitro US is a reliable and reproducible tool for the examination of autopsied arterial specimens to obtain valuable information about vascular wall properties and to identify the optimal vascular segment for tissue sampling; (2) snap freezing and cryosectioning of in toto excised arterial specimens is recommended for comparative histological–US studies.

Cerebral autoregulation is particularly challenged in acute ischemic stroke. In this review we summarize the data of our previous studies on autoregulation regarding the effect of rtPA on autoregulation after stroke. A pooled analysis of two studies (45 patients) has shown a worsening of the autoregulatory index Mx between an early (first 48 h) and late (days 5–7) measurement. This increase was more pronounced on affected sides than on unaffected sides. Poor ipsilateral Mx was associated with a greater volume of MCA infarction at a late measurement and related to poor clinical outcome. Overall, autoregulatory impairment tends to increase mainly in large infarction and generalize to the contralateral side during the first days after ischemic stroke. As a limitation, transcranial Doppler sonography does not allow to detect focal areas of dysautoregulation in smaller strokes. To better understand the temporal and spatial dynamics of dysautoregulation in acute stroke in relation to the type and size of infarction, new bedside hemodynamic monitoring techniques (like multi-channel near-infrared spectroscopy) are needed.

Background

Atherosclerotic stenoses of the intracranial arteries (ICAS) is associated with high risk of stroke after TIA. The prevalence of intracranial stenoses is considered to be low in Caucasians, however population-based data are lacking and only a minority of patients with acute TIA or stroke is evaluated for ICAS.

Methods

We prospectively examined the prevalence of stenoses of the pre- and intracerebral vessels using transcranial colour coded sonography (TCCS) in a population based cohort of all TIA patients in the community of Aarhus, Denmark in the period 1.3.2007–29.2.2008.

Results

The TIA cohort included 203 patients fulfilling the diagnostic criteria for TIA. We examined 195 patients with extra- and intracranial TCCD.

Any stenoses and symptomatic ICAS was found in 12.3% and 8.2%, respectively. The stenoses were located in the intracranial internal carotid artery in 3.6% and 3.1%, anterior cerebral artery in 0.5% and 0%, middle cerebral artery in 4.6% and 2.6%, intracranial vertebral artery in 2.1% and 1.5%, and in the basilar artery in 1.5% and 1.5%, respectively. In comparison, we found any stenoses and symptomatic stenoses in the extracranial carotid artery in 14.4% and 10.8%, and the extracranial vertebral artery in 5.6% and 2.1% of the patients, respectively. Carotid occlusion was found in 3.6%, combined extra- and intracranial stenoses in 4.9%.

Conclusion

The prevalence of ICAS was in this population-based TIA cohort of Caucasians comparable with the prevalence of carotid stenoses. Systematic evaluation for intracranial stenoses should be considered in all patients with acute ischemic cerebrovascular disease.

Background

Carotid angioplasty and stenting (CAS) is increasingly being used as a treatment alternative to endarterectomy (CEA), especially in patients aged <70 years with significant carotid artery stenosis. However, an in-stent restenosis (ISR) might endangering the long-term efficacy of CAS. The aim of this article was to review the current literature regarding incidence and clinical significance as well as predictors of in-stent restenosis.

Methods

We conducted a systematic review of the literature to identify all studies on the abovementioned factors.

Results

3 randomized-controlled trials comparing CAS and CEA and 13 single centre studies fulfilled our inclusion criteria. The occurrence of ISR after CAS ranged from 2.7 to 33% and was detected within the first year in most of the studies. The clinical impact as well as the therapeutic consequence of ISR remains unclear, but many baseline characteristics (age, prior CEA or radiation), procedural (insufficient stent deployment, stent dimensions, inflammatory marker) and follow-up factors (reduced HDL, diabetes mellitus) could be found to identify patients at special risk for ISR. A wide heterogeneity related to the definition and their corresponding ultrasound criteria for ISR was observed.

Conclusions

A close follow-up is suggested especially in those patients with predictors of an ISR. The wide range of ISR ultrasound definitions urges the need for an implementation of generally valid criteria in ISR diagnosis. Against the background of the unknown clinical significance of ISR and a lacking established treatment modality these findings should be taken into account when offering CAS as a treatment alternative to CEA.