Bubble Test and Carotid Ultrasound to Guide Indication of Transesophageal Echocardiography in Young Patients With Stroke.

Background And Purpose: Indication of transesophageal echocardiography (TEE) in patients ≤60 years with brain ischemia is uncertain.

Methods: This prospective double-blinded study included patients with cryptogenic acute ischemic stroke or transient ischemic attack (TIA) ≥18 and ≤60 years. After routine diagnostics, all patients underwent patent foramen ovale (PFO) screening by transcranial Doppler (TCD) bubble test, carotid ultrasound for atherosclerosis screening (intima-media-thickness >0.

The course of dynamic cerebral autoregulation during cervical internal carotid artery occlusion.

Objectives: The selection of patients with cervical internal carotid artery occlusion (ICAO) for extracranial-intracranial bypass surgery is based on exhausted cerebrovascular reactivity to vasodilatory stimuli. However, a spontaneous increase in this reactivity can occur with time, questioning the ideal time for bypass surgery. In contrast, the natural course of dynamic cerebral autoregulation is not known in these patients.

Improvement of exhausted cerebral vasoreactivity in carotid occlusion: benefit of statins?

In internal carotid artery occlusion (ICAO), a spontaneous increase of cerebral vasoreactivity (CVR) may occur over time. Statins are known to increase CVR. We analyzed the influence of statin treatment and other cofactors on CVR improvement in patients with ICAO.

Neurovascular coupling and cerebral autoregulation in patients with stenosis of the posterior cerebral artery.

Neurovascular coupling and cerebral autoregulation are two brain intrinsic vasoregulative mechanisms that rapidly adjust local cerebral blood flow. This study examined if stenotic disease affects both mechanisms in the posterior cerebral artery. Ten patients with altogether 13 stenosed (≥50%) posterior cerebral artery (PCA) sides were studied.

Cerebral dysautoregulation and the risk of ischemic events in occlusive carotid artery disease.

Dynamic cerebral autoregulation assessed from blood pressure transients can be considerably impaired in severe internal carotid artery (ICA) obstruction. It is unknown whether impaired autoregulation indicates an increased risk of subsequent ischemic events in this situation. 165 patients with ICA stenosis (> 70 %) or occlusion were prospectively followed until anterior circulation stroke, transient ischemic attack, carotid recanalization without prior event, death or study end.

Oscillatory cerebral hemodynamics--the macro- vs. microvascular level.

The phase shift between oscillations of blood pressure (BP) and Doppler middle cerebral artery flow velocity (MCAFV) reflects continuous cerebral autoregulatory action. It is not known whether a similar phase shift exists for cortical hemodynamics ('microvascular level') assessed by near infrared spectroscopy (NIRS) and what the effects are of pathological conditions. This study investigates the phase relations between oscillations of BP, MCAFV and NIRS parameters in 38 healthy older adults and 28 patients with unilateral severe obstructive carotid disease.

Testing for directed influences among neural signals using partial directed coherence.

One major challenge in neuroscience is the identification of interrelations between signals reflecting neural activity. When applying multivariate time series analysis techniques to neural signals, detection of directed relationships, which can be described in terms of Granger-causality, is of particular interest. Partial directed coherence has been introduced for a frequency domain analysis of linear Granger-causality based on modeling the underlying dynamics by vector autoregressive processes.

Direct or indirect? Graphical models for neural oscillators.

Univariate and bivariate time series analysis techniques have enabled new insights into neural processes. However, these techniques are not feasible to distinguish direct and indirect interrelations in multivariate systems. To this aim multivariate times series techniques are presented and investigated by means of simulated as well as physiological time series.