Search PubMed⌕ Search

Biomedical subjects

Andrea Rocco

Publications and source records attributed to Andrea Rocco.

6 recordsLinked to original sources

Update on stroke.

PURPOSE OF REVIEW: This review highlights the progress achieved in stroke during the last year, and emphasizes recent controversies concerning its pathophysiology, therapy and secondary complications. RECENT FINDINGS: Studies published in 2004 provided new insights into the therapeutic window and ischemic penumbra, thrombolysis therapy, uncommon risk factors for stroke, and neuropsychological post-stroke complications. Despite the diffusion-perfusion mismatch remaining the most widely used technique to identify thresholds for ischemic penumbra and irreversible brain tissue damage, new imaging such as arterial spin-labeling perfusion and computed tomographic perfusion may define this impaired tissue more accurately. New studies assessed the relation of the interval from stroke onset to start intravenous thrombolysis treatment (tissue plasminogen activator) on favorable 3-month outcome, and on the occurrence of clinically relevant parenchymal hemorrhage: the benefit of tissue plasminogen activator could extend beyond 3 h, but with a few risks. Systemic inflammations and infections have been found to be associated with a substantial increase in the risk of developing vascular events, supporting the concept that systemic inflammation itself alters the probability of stroke occurrence. Recent literature concerning neuropsychological post-stroke complications focused mainly on the concept of mixed dementia and confirmed that mood disorders are common after stroke, and interfere with its long-term outcome. SUMMARY: Significant advances have been made during the last year in determining more accurately the therapeutic window, using new strategies and clinical markers. Moreover, new light has been thrown on less common stroke risk factors, and neuropsychological post-stroke complications.

Journal Article↗

Streamer branching rationalized by conformal mapping techniques.

Spontaneous branching of discharge channels is frequently observed, but not well understood. We recently proposed a new branching mechanism based on simulations of a simple continuous discharge model in high fields. We here present analytical results for such streamers in the Lozansky-Firsov limit where they can be modeled as moving equipotential ionization fronts. This model can be analyzed by conformal mapping techniques which allow the reduction of the dynamical problem to finite sets of nonlinear ordinary differential equations. Our solutions illustrate that branching is generic for the intricate head dynamics of streamers in the Lozansky-Firsov limit.

Journal Article↗

Branching of negative streamers in free flight.

We have recently shown that a negative streamer in a sufficiently high homogeneous field can branch spontaneously due to a Laplacian instability, rather than approach a stationary mode of propagation with fixed radius. In our previous simulations, the streamer started from a wide initial ionization seed on the cathode. We here demonstrate, in improved simulations, that a streamer emerging from a single electron branches in the same way. In fact, though the evolving streamer is much more narrow, it branches after an even shorter propagation distance.

Journal Article↗

Diffusion coefficient of propagating fronts with multiplicative noise.

Recent studies have shown that in the presence of noise, both fronts propagating into a metastable state and so-called pushed fronts propagating into an unstable state, exhibit diffusive wandering about the average position. In this paper, we derive an expression for the effective diffusion coefficient of such fronts, which was motivated before on the basis of a multiple scale ansatz. Our systematic derivation is based on the decomposition of the fluctuating front into a suitably positioned average profile plus fluctuating eigenmodes of the stability operator. While the fluctuations of the front position in this particular decomposition are a Wiener process on all time scales, the fluctuations about the time-averaged front profile relax exponentially.

Journal Article↗

Stroke beyond the first hours: the role of monitoring.

It is now recognized that a specialized multidisciplinary team, focusing on the care of stroke patients, leads to lower mortality and better outcomes. The positive effect of stroke units in regard to the outcome of stroke patients seems to be related to the careful monitoring of clinical parameters and clinical emergencies. The monitoring of physiological parameters in the acute phase of stroke can be considered an important management tool that can improve significantly the quality of care provided. It allows timely detection and correction of complications and consequently has a beneficial effect on outcome.

Acute Disease↗

Functional neuroimaging in acute stroke.

To the present day, the first and most widespread diagnostic approach in the assessment of acute stroke remains CT scan. Its sensitivity is very high (nearly 100%) in detecting intracerebral hemorrhage in the acute period, but its capability of revealing ischemic injury in the very first hours from symptom onset is relatively poor. Since the efficacy of thrombolytic treatment in acute stroke has been suggested by the ECASS and NINDS rt-PA trials, functional neuroimaging able to distinguish potentially salvageable tissue from irreversibly injured areas has acquired primary importance. The possibility to correctly identify the tissue of the ischemic penumbra within the first hours from symptom onset is essential for correct patient selection for thrombolitic treatment. Different imaging strategies are available for the definition of perfusion deficits within the acute time window; among these are positron emission tomography (PET), single photon emission computed tomography (SPECT), Xenon CT (XeCT), dynamic CT perfusion imaging (CTP), diffusion weighted magnetic resonance imaging (DW-MRI), and perfusion weighted magnetic resonance imaging (PW-MRI). Though each technique has its advantages and limitations to present day functional MRI remains the most widespread imaging technique in the assessment of acute stroke being more accessible than both SPECT and PET, and capable of giving information on both perfusion and tissue functional status in a single imaging session. In this paper we discuss the role of functional neuroimaging in acute stroke.

Brain Ischemia↗