**1. Introduction**

258 Neuroimaging for Clinicians – Combining Research and Practice

Shepherd, R. B., & Carr, J. A. (2005). New aspects for the physiotherapy of pushing

Talairach, J., Tournoux, P. (1988). Co-planar stereotaxic atlas of the human brain. Thieme

Ticini, L. F., Klose, U., Nagele, T., & Karnath, H. O. (2009). Perfusion imaging in Pusher

Trousselard, M., Barraud, P. A., Nougier, V., Raphel, C., & Cian, C. (2004). Contribution of

Tyson, S. F., Hanley, M., Chillala, J., Selley, A., & Tallis, R. C. (2006). Balance disability after

Van der Werf, Y. D., Witter, M. P., Uylings, H. B., & Jolles, J. (2000). Neuropsychology of infarctions in the thalamus: a review. Neuropsychologia, 38(5), 613-627. Wilde EA, McCauley SR, Kelly TM, Levin, H.S., Pedroza, C., Clifton, G.L., Valadka, A.B.,

for Traumatic Brain Injury (NOS-TBI) in adults. J Neurotrauma. 27, 975-981. Wityk, R.J., Pessin, M.S., Kaplan, R.F., & Caplan, L.R. (1994). Serial assessment of acute

Wulf, G., Hoss, M., & Prinz, W. (1998). Instructions for Motor Learning: Differential Effects of Internal Versus External Focus of Attention. J Mot Behav, 30(2), 169-179. Zazulia, A.R., Diringer, M.N., Derdeyn, C.P., & Powers, W.J. (1999). Progression of

mass effect after intracerebral hemorrhage. Stroke, 30, 1167-1173.

stroke using the NIH Stroke Scale. Stroke, 25, 362-365.

NeuroRehabilitation, 20(4), 343-345.

Medical Publishers, New York.

position. PLoS One, 4(5), e5737.

Cogn Brain Res, 20(3), 355-362.

stroke. Phys Ther, 86(1), 30-38.

behaviour, D. Broetz and H.-O. Karnath, Neurorehabilitation 20 (2005), 133-138.

syndrome to investigate the neural substrates involved in controlling upright body

tactile and interoceptive cues to the perception of the direction of gravity. Brain Res

Robertson, C.S., & Moretti, P. (2010). Feasibility of the Neurological Outcome Scale

Stroke is a condition with an high mortality rate and a relevant burden of disability and social costs. Indeed it is the third cause of death and the first cause of disability in western countries. About 80% of strokes is ischemic and due to the occlusion of a large or small cerebral artery. Therefore the rationale of thrombolysis is the reopening of the occluded vessel within a short time window from symptoms onset, mainly by using iv rtPA but also by using local delivery of rtPA and/or mechanical disruption of the thrombus. The basic assumption is simple and clear: a large vessel was abruptly occluded and the corresponding brain territory was deprived of oxygenated blood and nutrients. The brain metabolism during ischemia is flow- and time-dependent; there are precise perfusional thresholds for maintaining membrane pump activity; therefore the cell integrity and the duration of neuronal life is related to the time from the vessel occlusion, in a variable combination of individual ischemic tolerance and activation of the collateral circulation. The irreversibly damaged brain tissue is known as ischemic core and the suffering, but still viable, tissue is known as penumbra. The penumbra to core ratio is affected by several factors, but it is widely recognized that both occlusive pattern and time from symptoms onset are strong predictors of the presence of as much viable tissue as needed for the success of the reperfusion treatment. The clinical data and the neurological severity scales, as NIHSS (National Institute of Health Stroke Scale), do not reliably predict if there is a large vessel occlusion and for which extent in single cases. The clinical presentation can be the same for a very proximal large arterial occlusion and for a small perforating artery involvement, but the recanalization rate is strictly dependent on the occlusive pattern. Therefore, because the recanalization is a strong predictor of a good outcome, the prognosis depends on it and it can be early inferred by the diagnosis of the occlusive pattern.

All efforts should be made to achieve the diagnosis of vessel occlusion ad brain perfusion condition as early as possible, in order not only to predict the prognosis but also to tailor the treatment.

In acute stroke time is brain, and therefore the diagnostic steps should be reliable, fast and not time consuming. Ultrasound techniques have these features for other body districts, also for extracranial vessels, but their use for the examination of the intracranial circulation has been hampered for many years, because of the attenuation effect of the skull. In the last twenty years this limitation has been demonstrated to be passed by neurosonological

Neurosonological Evaluation of the Acute Stroke Patients 261

techniques, in the setting of acute stroke, and the main target of these studies was the intracranial disease. Therefore we are somewhat obliged to translate the reliability data of the non acute phase to the acute phase. This process is make easier by the high accuracy of neurosonological grading of carotid stenosis in a symptomatic patient (Chapell F et al., 2009;

The overall accuracy of ultrasound examination of the internal carotid artery versus neuroradiological techniques was the subject of several studies and the following figure (from Wardlaw et al. 2006, modified) shows the results of a meta-analysis of them for the 70-

Fig. 1. Sensitivity and specificity for the diagnosis of a severe carotid stenosis (ultrasound versus neuroradiological techniques) of non-invasive diagnostic techniques compared to

In the acute setting, even more than in a post-acute management, the main objective is the diagnosis or the exclusion of carotid lesion amenable to surgical or endovascular treatment, according to the current guidelines. Therefore it is relevant to assess the reliability of ultrasound techniques for 70-99% stenosis. In the above cited meta-analysis 41 studies (2541 patients, 4876 arteries) from 1980 to 2004 were included, comparing non-invasive imaging with intra-arterial angiography. The conclusion of this meta-analysis agrees with the common clinical practice of using first-line non-invasive tests, as DUS, for diagnosing 70– 99% stenosis. For lesser degrees of stenosis (50–69%) the accuracy of non-invasive techniques is not so high, but again, if surgical indication is well documented for symptomatic carotid stenosis > 70%, the benefit is discussed and very narrow, also for high risk patients, for lesser degrees of stenosis. This categorization is internationally made using the angiographic NASCET grading system (NASCET coll. 1991) and non-invasive imaging techniques should have validated their diagnostic and grading criteria versus the NASCET

The ultrasound grading criteria were stated in the Consensus Conference of American Academy of Radiology in 2003 (Grant et al. 2003), but neuroradiological techniques have less shared criteria, based on caliper measurements and ratios, rather than the subjective visual impression. Unfortunately, an implementation of their use in the clinical practice, outside the clinical trials and the evaluation of a central reader, is needed, because the visual impression could be useful only for excluding very tight stenosis, but not for achieving a

Wardlaw et al. 2006).

DUS: Doppler UltraSound

DSA

system.

99% range with the NASCET system.

CTA: Computed Tomography Angiography MRA: Magnetic Resonance Angiography

precise grading (U-King-Im et a. 2007).

CEMRA: Contrast Enhanced Magnetic Resonance Angiography

techniques, Transcranial Doppler (TCD) and Transcranial Colour Coded Duplex Sonography (TCCS). Both these tools are safe, reliable, bedside executable, fast, not expensive and repeatable. Because of these advantages, neurosonology represents an ideal tool to diagnose patients with a focal neurological deficit of suspected vascular origin, particularly in an emergency setting. Furthermore the repeatability and the safety make transcranial Doppler the most suitable tool for monitoring the recanalization, both during a thrombolytic treatment and spontaneously.

In the following sections mainly TCCS will be mentioned and discussed, first because of the undeniable advantage of the B-mode visualization of the brain structures and vascular landmarks, and second because the expertise of our group with this technique and the related literature contributes. In a similar manner our attention will be focused on the anterior circulation stroke.
