Background and Purpose-In carotid disease, infarcts can occur in the cortical as well as internal watershed (WS), or both.Better understanding the pathophysiology of WS infarcts would guide treatment. Two distinct hypotheses, namely low-flow and micro-embolism, are equally supported by neuropathological and physiological studies. Here we review the evidence regarding the mechanisms for WS stroke in carotid disease and whether they differ between cortical and internal WS infarcts. Summary of Review-After a brief account of the anatomy of the WS and the cerebrovascular physiology in circumstances of low perfusion pressure, the literature concerning the mechanisms of WS infarction in carotid disease is reviewed and discussed with emphasis on imaging and ultrasound studies of the cerebral hemodynamics. Conclusion-The evidence strongly favors a hemodynamic mechanism for internal WS infarction, especially regarding the so-called rosary-like pattern in the centrum semiovale. However, the relationships between cortical WS infarction and hemodynamic compromise appear more complicated. Thus, although severe hemodynamic compromise appears to underlie combined cortical and internal WS infarction, artery-to-artery embolism may play an important role in isolated cortical WS infarcts. Based on the high prevalence of microembolic signals documented by ultrasound in symptomatic carotid disease, a recent hypothesis postulates that embolism and hypoperfusion play a synergetic role, according to which small embolic material prone to lodge in distal field arterioles would be more likely to result in cortical micro-infarcts when chronic hypoperfusion prevails. Future studies combining imaging of brain perfusion, diffusion-weighted imaging, and ultrasound detection of microembolic signals should help resolve these issues. (Stroke. 2005;36:567-577.)

Stroke lesions induce not only loss of local neural function, but disruptions in spatially distributed areas. However, it is unknown whether they affect the synchrony of electrical oscillations in neural networks and if changes in network coherence are associated with neurological deficits. This study assessed these questions in a population of patients with subacute, unilateral, ischemic stroke.Spontaneous cortical oscillations were reconstructed from high-resolution electroencephalograms (EEG) with adaptive spatial filters. Maps of functional connectivity (FC) between brain areas were created and correlated with patient performance in motor and cognitive scores.In comparison to age-matched healthy controls, stroke patients showed a selective disruption of FC in the alpha frequency range. The spatial distribution of alpha band FC reflected the pattern of motor and cognitive deficits of the individual patient: network nodes that participate normally in the affected functions showed local decreases in FC with the rest of the brain. Interregional FC in the alpha band, but not in delta, theta, or beta frequencies, was highly correlated with motor and cognitive performance. In contrast, FC between contralesional areas and the rest of the brain was negatively associated with patient performance.Alpha oscillation synchrony at rest is a unique and specific marker of network function and linearly associated with behavioral performance. Maps of alpha synchrony computed from a single restingstate EEG recording provide a robust and convenient window into the functionality and organization of cortical networks with numerous potential applications.

Objective: Supernumerary phantom limb (SPL) is a rare neurological manifestation where patients with a severe stroke-induced sensorimotor deficit experience the illusory presence of an extra limb that duplicates a real one. The illusion is most often experienced as a somesthetic phantom, but rarer SPLs may be intentionally triggered or seen. Here, we report the case of a left visual, tactile, and intentional SPL caused by right subcortical damage in a nondeluded woman. Methods: Using functional magnetic resonance imaging, we investigated the multimodal nature of this phantom, which the patient claimed to be able see, use, and move intentionally. The patient participated in a series of sensorimotor and motor imagery tasks involving the right, the left plegic, and the SPL's hand. Results: Right premotor and motor regions were engaged when she imagined that she was scratching her left cheek with her left plegic hand, whereas when she performed the same task with the SPL, additional left middle occipital areas were recruited. Moreover, comparison of responses induced by left cheek (subjectively feasible) versus right cheek scratching (reportedly unfeasible movement) with the SPL demonstrated significant activation in right somesthetic areas.Interpretation: These findings demonstrate that intentional movements of a seen and felt SPL activate premotor and motor areas together with visual and sensory cortex, confirming its multimodal dimension and the reliability of the patient's verbal reports. This observation, interpreted for cortical deafferentation/disconnection caused by subcortical brain damage, constitutes a new but theoretically predictable entity among disorders of bodily awareness.Ann Neurol 2009;65:698 -705

Background and Purpose-To determine whether a stratified gray-scale median (GSM) analysis of the carotid plaque combined with color mapping could predict plaque histology better than an overall GSM measurement. Methods-Thirty-one carotid plaques derived from 28 patients undergoing carotid endarterectomy were investigated by ultrasound. GSMs of the whole plaque were used as measurement of echogenicity. A profile of the regional GSM as a function of distance from the plaque surface could be generated. Plaque pixels were further mapped into 3 different colors depending on their GSM value. Results-Plaques with large calcifications presented the highest GSM values, and those with large hemorrhagic areas or with a predominant necrotic core exhibited the lowest. Fibrous plaques had intermediate GSM values. A necrotic core located in a juxtalumenal position was associated with significantly lower GSM values (Pϭ0.009) and with a predominant red color (GSM Ͻ50) at the surface (Pϭ0.0019). With respect to the thickness of the fibrous cap and the position of the necrotic core, the sensitivity and specificity of the predominant red color of the whole plaque was respectively 45% and 67% and 53% and 75%; considering the predominant red color of the surface, the sensitivity and specificity increased to 73% and 67% and 84% and 75%, respectively. Conclusions-The stratified GSM measurement combined with color mapping showed a good correlation with the different histopathological components and further allowed identification with good accuracy of determinants of plaque instability. This approach should be investigated in a prospective, natural history study.

Background and Purpose-To determine whether a stratified gray-scale median (GSM) analysis of the carotid plaque combined with color mapping correlated better with the presence of neurological symptoms and microembolic signals (MES) than a whole plaque measurement. Methods-A total of 131 patients presenting 167 carotid stenoses between 30% and 99% were analyzed by ultrasound.Emboli detection was performed by transcranial Doppler. For each plaque, the GSM values at depth 0 mm (surface) and at one third (30) and one half (50) of the plaque thickness were compared with the values obtained for the whole plaque. The plaque pixels were mapped into 3 colors: red, yellow and green, depending on their GSM value. Results-Mean GSM values were lower among symptomatic plaques, but a statistically significant difference between values of the whole plaque and those of the surface was obtained only for MESϩ stenoses (PϽ0.01). In a proportional odds logistic regression model based on 4 subgroups with an increasing clinical risk (MESϪ/symptomsϪ; MESϪ/ symptomsϩ; MESϩ/symptomsϪ; ϩ; MESϩ/symptomsϩ), low mean GSM values and the predominant red color at the surface were independent factors associated with the presence of symptoms or MES (PϽ0.0005). Furthermore, compared with a whole plaque measurement, analysis of the surface values predicted systematically with a greater sensitivity and specificity (receiver operating characteristic curves) each one of these 4 subgroups. Conclusions-Low mean GSM values and predominance of the red color at the surface correlated with most of the symptomatic or MESϩ stenoses. This combined approach should be further investigated in a longitudinal study.

3D T1 SPACE sequence offers similar information with its 2D counterpart, in a shorter acquisition time and larger coverage area.

Risk index was significantly higher in the presence of symptoms and could therefore be a valuable tool to assess the clinical risk of a carotid plaque.

Aim: The study aims to describe the epidemiology and the neural correlates of peripersonal visuospatial neglect (PVN) in patients admitted to the Geneva Stroke Unit for an acute stroke or a transient ischemic attack (TIA). Methods: Eligible subjects were tested for PVN using both the Ota's discriminative cancellation task and a line bisection task. Brain lesions were identified on diffusion-weighted imaging. A multivariate analysis was performed to identify risk factors of PVN. Results: Ninety-eight consecutive patients (40.8% females) were recruited: 64 cases of ischemic stroke, 9 cases of hemorrhagic stroke and 25 cases of TIAs. The mean age was 61.9 ± 2.86 years. The incidence of PVN was 23.5% (95% CI 15.5-33.1) and was not significantly different between patients with right and left hemisphere stroke. There were 5 cases of ipsilesional neglect. There was no association between PVN and age, sex, stroke severity, handedness, lesion type, lesion volume and time to first examination. Lesions of temporal and parietal lobes were the most frequent in patients with PVN. Conclusion: PVN has a low incidence in the acute stroke settings and there is no particular predictor of its presence. It is most often associated with temporo-parietal lesions.