Analyte capture in an array of functionalized droplets for a regenerable biosensor

We describe in this work an advanced microfluidic chip for the capture of bioanalyte on the surface of droplets arranged in a dense array. We show the procedure for generating, functionalizing, and arranging the droplets inside the device for capturing a specific bioanalyte. Then, we demonstrate the capacity of the array to capture analyte from a cross-flowing liquid, using a biotin/streptavidin model. The paper also proposes to use the droplets array, after integration with acoustic detection, as a regenerable detection interface for bioanalyte sensing. We model the arrangement of droplet in dense array and show that they present a larger effective capture surface and shorter capture distance than standard flat surface biosensor of the same footprint. As the droplets can be easily evacuated and replaced inside the device analysis chamber, the proposed biosensor would allow biointerface regeneration and chain measurement without dismounting the device.

Serotonin Selective Reuptake Inhibitors (SSRIs) and Stroke

PURPOSE OF REVIEW

The interest in SSRIs after stroke has increased in the past few years, with better knowledge of post-stroke depression and with the demonstrated capacity of some SSRIs to act on the functional recovery of non-depressed subjects.

RECENT FINDINGS

Arguments for the action of SSRIs in favour of post-stroke neurological function recovery have improved through new elements: basic science and preclinical data, positive clinical trials and repeated series of stroke patient meta-analysis, and confirmation of favourable safety conditions in post-stroke patients. Global coherence is appearing, showing that SSRIs improve stroke recovery in non-depressed patients when given for 3 months after the stroke, with highly favourable safety conditions and a favourable benefit/risk ratio. Large series are still needed.

Cortical superficial siderosis and acute convexity subarachnoid hemorrhage in cerebral amyloid angiopathy

BACKGROUND AND PURPOSE

Acute convexity subarachnoid hemorrhage (cSAH) and cortical superficial siderosis (cSS) are neuroimaging markers of cerebral amyloid angiopathy (CAA) that may arise through similar mechanisms. The prevalence of cSS in patients with CAA presenting with acute cSAH versus lobar intracerebral hemorrhage (ICH) was compared and the physiopathology of cSS was explored by examining neuroimaging associations.

METHODS

Data from 116 consecutive patients with probable CAA (mean age, 77.4 ± 7.3 years) presenting with acute cSAH (n = 45) or acute lobar ICH (n = 71) were retrospectively analyzed. Magnetic resonance imaging scans were analyzed for cSS and other imaging markers. The two groups' clinical and imaging data were compared and the associations between cSAH and cSS were explored.

RESULTS

Patients with cSAH presented mostly with transient focal neurological episodes. The prevalence of cSS was higher amongst cSAH patients than amongst ICH patients (88.9% vs. 57.7%; P < 0.001). In multivariable logistic regression analysis, focal [odds ratio (OR) 6.73; 95% confidence interval (CI) 1.75-25.81; P = 0.005] and disseminated (OR 11.68; 95% CI 3.55-38.35; P < 0.001) cSS were independently associated with acute cSAH, whereas older age (OR 0.93; 95% CI 0.87-0.99; P = 0.025) and chronic lobar ICH count (OR 0.45; 95% CI 0.25-0.80; P = 0.007) were associated with acute lobar ICH.

CONCLUSIONS

Amongst patients with CAA, cSS is independently associated with acute cSAH. These findings suggest that cSAH may be involved in the pathogenesis of the cSS observed in CAA. Longitudinal studies are warranted to assess this potential causal relationship.

Comparison between PET template-based method and MRI-based method for cortical quantification of florbetapir (AV-45) uptake in vivo

PURPOSE

Florbetapir (AV-45) has been shown to be a reliable tool for assessing in vivo amyloid load in patients with Alzheimer's disease from the early stages. However, nonspecific white matter binding has been reported in healthy subjects as well as in patients with Alzheimer's disease. To avoid this issue, cortical quantification might increase the reliability of AV-45 PET analyses. In this study, we compared two quantification methods for AV-45 binding, a classical method relying on PET template registration (route 1), and a MRI-based method (route 2) for cortical quantification.

METHODS

We recruited 22 patients at the prodromal stage of Alzheimer's disease and 17 matched controls. AV-45 binding was assessed using both methods, and target-to-cerebellum mean global standard uptake values (SUVr) were obtained for each of them, together with SUVr in specific regions of interest. Quantification using the two routes was compared between the clinical groups (intragroup comparison), and between groups for each route (intergroup comparison). Discriminant analysis was performed.

RESULTS

In the intragroup comparison, differences in uptake values were observed between route 1 and route 2 in both groups. In the intergroup comparison, AV-45 uptake was higher in patients than controls in all regions of interest using both methods, but the effect size of this difference was larger using route 2. In the discriminant analysis, route 2 showed a higher specificity (94.1 % versus 70.6 %), despite a lower sensitivity (77.3 % versus 86.4 %), and D-prime values were higher for route 2.

CONCLUSION

These findings suggest that, although both quantification methods enabled patients at early stages of Alzheimer's disease to be well discriminated from controls, PET template-based quantification seems adequate for clinical use, while the MRI-based cortical quantification method led to greater intergroup differences and may be more suitable for use in current clinical research.

Use of antidepressant medications to improve outcomes after stroke

Interest in the use of antidepressants after stroke has been renewed by better knowledge of poststroke depression, but mainly by the capacity of some of them to promote functional recovery of nondepressed subjects. Recombinant tissue plasminogen activator thrombolysis within the first few hours after the stroke is currently the only validated treatment able to improve the spontaneous--and most of the time incomplete--recovery of neurological functions after stroke. However, we have learned from research over the last decade, in part based on the considerable improvement of neuroimaging techniques, that spontaneous recovery of neurological functions is associated with a large intracerebral reorganization of the damaged human brain. The question of whether lesioned-brain plasticity can be modulated by external factors such as pharmacological antidepressant agents is now being addressed with the aim of improving recovery and reducing the final disability of patients. Poststroke depression is known to be frequent and deleterious for patient outcome. We review the interest in the use of antidepressants after stroke in classic but often neglected poststroke depression and we strongly underline the action of some antidepressants in promoting functional recovery of nondepressed patients after stroke.

[Early diagnosis of Alzheimer's disease]

INTRODUCTION

Diagnosis of Alzheimer's disease (AD) remains difficult to establish, and can only be considered as certain thanks to anatomopathological evidence, or genetic mutations. Current diagnostic criteria rely on innovative imaging and biological tools, in order to detect pathological cues from very early stages, and with best sensibility and sensitivity.

STATE OF ART

Advances in neuro-imaging enabled the development of different tools to help establishing the diagnosis, such as cerebral atrophy assessment on magnetic resonance imaging (MRI), and cerebral metabolism study on positron emission tomography (PET). Besides, the increasing use of in vivo biological markers, combined to clinical criteria, enables to discriminate patients from healthy controls at even earlier stages. This includes studies on tau and beta-amyloid proteins concentrations in the cerebrosinal fluid, and amyloid-specific radioligands uptake. Familial forms of Alzheimer represent a great model for studying early or even pre-symptomatic AD, as genetic analyses constitute a diagnosis of certainty, even though they usually evolve earlier and faster.

PERSPECTIVES, CONCLUSION

Diagnostic tools are more and more numerous and performant. According to patients' clinical heterogeneity, it appears essential to associate different method to investigate, in order to make a diagnosis as early and as reliable as possible.

[Iatrogenic venous cerebral air embolism without pulmonary manifestation: A retrograde mechanism?]

INTRODUCTION

Air embolism is a rare complication of various invasive medical procedures. Venous cerebral air embolism is usually the consequence of paradoxical embolism. We report a case of isolated cerebral air embolism resulting from a non-paradoxical mechanism.

CASE REPORT

A few minutes after his central venous catheter had been accidentally disconnected, a 63-year-old man developed left-sided rhythmic jerking movements followed by left hemiplegia. There were no associated cardiologic or pulmonary signs. Brain CT showed air bubbles in the right frontal cortical sulci. The brain MRI DWI and FLAIR sequences showed a high intensity right frontal cortical lesion without reduction in ADC. Transesophageal echocardiogram did not find a patent foramen ovale.

CONCLUSIONS

In this case of venous cerebral air embolism, the lack of any cardiopulmonary manifestation, the lack of a patent foramen ovale and the neuroradiological findings are not in favor of the hypothesis of paradoxical embolism. The hypothesis of retrograde venous cerebral air embolism is discussed.

Wakefulness and loss of awareness: brain and brainstem interaction in the vegetative state

OBJECTIVE

The ascending reticular activating system (ARAS) modulates circadian wakefulness, which is preserved in a persistent vegetative state (PVS). Its metabolism is preserved. Impairment of metabolism in the polymodal associative cortices (i.e., precuneus) is characteristic of PVS where awareness is abolished. Because the interaction of these 2 structures allows conscious sensory perception, our hypothesis was that an impaired functional connectivity between them participates in the loss of conscious perception.

METHODS

(15)O-radiolabeled water PET measurement of regional cerebral blood flow (rCBF) was performed at rest and during a proprioceptive stimulation. Ten patients in PVS and 10 controls were compared in a cross-sectional study. The functional connectivity from the primary sensorimotor cortex (S1M1) and the ARAS in both groups was also investigated.

RESULTS

Compared with controls, patients showed significantly less rCBF in posterior medial cortices (precuneus) and higher rCBF in ARAS at rest. During stimulation, bilateral Brodmann area 40 was less activated and not functionally correlated to S1M1 in PVS as it was in controls. Precuneus showed a lesser degree of deactivation in patients. Finally, ARAS whose activity was functionally correlated to that of the precuneus in controls was not in PVS.

CONCLUSIONS

Global neuronal workspace theory predicts that damage to long-distance white matter tracts should impair access to conscious perception. During persistent vegetative state, we identified a hypermetabolism in the ascending reticular activating system (ARAS) and impaired functional connectivity between the ARAS and the precuneus. This result emphasizes the functional link between cortices and brainstem in the genesis of perceptual awareness and strengthens the hypothesis that consciousness is based on a widespread neural network.

Posterior Cerebral Hypoperfusion in Migraine Without Aura

In cerebral blood flow studies, migraine aura is characterized by a posterior cortical hypoperfusion. In contrast, only rare and mild changes in brain perfusion have been demonstrated in migraine without aura, suggesting two different haemodynamic patterns in migraine with and without aura. Our aim was to study hypoperfusion with positron emission tomography (PET) as early as possible during spontaneous migraine without aura attacks. We used H215O PET to investigate seven patients (six female, one male) with migraine without aura (International Classification of Headache Diseases-II code 1.1) in three situations: during the headache phase, after headache relief following sumatriptan injection, and during an attack-free interval. Statistical analysis was performed with SPM2. Within 4 h after the attack onset, significant relative bilateral posterior cortical hypoperfusion was found and persisted after headache relief following sumatriptan injection. A posterior cortical hypoperfusion demonstrated in migraine without aura could suggest a common pathogenesis in migraine with and without aura. The significance of relative posterior hypoperfusion in migraine without aura is discussed according to the current knowledge of migraine pathogenesis.

The functional anatomy of recovery from brain injury

The functional neuroanatomical basis for recovery from ischaemic brain injury is not known. We have used positron emission tomography (PET) to study changes in the functional organization of the brain in patients recovering from striatocapsular motor strokes. Significant changes in regional cerebral blood flow (rCBF) were found during repetitive sequential opposition movements of the fingers in normal subjects and in patients with recovery from motor deficits. There was a difference in the pattern of cerebral activation when patients performed the motor task with the unaffected hand (when the activation was lateralized to contralateral sensorimotor and premotor cortex and ipsilateral cerebellum) and when the task was performed with the recovered, previously plegic hand (when the activation was bilateral and involved novel areas of cortex, especially area 40). Comparisons of rCBF maps at rest in the patient group and in normal subjects showed areas with significantly decreased rCBF in the patients (contralateral to the plegic hand in the basal ganglia, thalamus, insular cortex, brainstem and ipsilateral cerebellum), which reflected the distribution of dysfunction caused by the ischaemic lesions. A significantly increased activation over and above that in normal subjects was found in patients during movement of the recovered fingers in ipsilateral premotor cortex and bilateral frontal opercular/insular regions and area 40, the ipsilateral basal ganglia (the ischaemic lesion lying contralaterally) and the contralateral cerebellum. We postulate that these findings may be explained by the generation of movements by pathways that are different from those that normal subjects use to perform what are ordinarily fairly simple, automated tasks. We suggest that this is a direct demonstration of cerebral plasticity resulting in the resolution of acquired motor deficits.

Neural Correlates of Proprioceptive Integration in the Contralesional Hemisphere of Very Impaired Patients Shortly After a Subcortical Stroke: An fMRI Study

Background. The effects of physiotherapy are difficult to assess in very impaired early stroke patients. Objective. The aim of the study was to characterize the impact of 4 weeks of passive proprioceptive training of the wrist on brain sensorimotor activation after stroke. Methods. Patients with a subcortical ischemic lesion of the pyramidal tract were randomly assigned to a control or a wrist-training group. All patients had a single pure motor hemiplegia with severe motor deficit. The control group (6 patients) underwent standard Bobath rehabilitation. The second, “trained,” group (7 patients) received Bobath rehabilitation plus 4 weeks of proprioceptive training with daily passive calibrated wrist extension. Before and after the training period, patients were examined with validated clinical scales and functional MRI (fMRI) while executing a passive movement versus rest. The effect of standard rehabilitation on sensorimotor activation was assessed in the control group on the wrist, and the effect of standard rehabilitation plus proprioceptive training was assessed in the trained group. The effect of 4-week proprioceptive training alone was statistically evaluated by difference between groups. Results. Standard rehabilitation along with natural recovery mainly led to increases in ipsilesional activation and decreases in contralesional activation. On the contrary, standard rehabilitation and paretic wrist proprioceptive training increased contralesional activation. Proprioceptive training produced change in the supplementary motor area (SMA), prefrontal cortex, and a contralesional network including inferior parietal cortex (lower part of BA 40), secondary sensory cortex, and ventral premotor cortex (PMv). Conclusion. We have demonstrated that purely passive proprioceptive training applied for 4 weeks is able to modify brain sensorimotor activity after a stroke. This training revealed fMRI change in the ventral premotor and parietal cortices of the contralesional hemisphere, which are secondary sensorimotor areas. Recent studies have demonstrated the crucial role of these areas in severely impaired patients. We propose that increased contralesional activity in secondary sensorimotor areas likely facilitates control of recovered motor function by simple proprioceptive integration in those patients with poor recovery.

Carotidynia: a new case for an old controversy

Whereas International Headache society (IHS) criteria of carotidynia were defined in 1988, its validity as a distinct nosological entity has recently been questioned, leading this entity to be removed from the second IHS classification in 2004. We report the case of a 30-year-old woman who developed a pain located at the left carotid bulb, associated with typical findings on ultrasonography and MRI. We discuss new criteria and denomination of this clinical entity.

Évaluation à 4 ans de la filière « Urgences AVC » de l’Hôpital Purpan (Toulouse) et analyse de 69 patients consécutifs traités par rt-PA intra-veineux

INTRODUCTION

After the 2002 European agreement on the use of rt-PA for fibrinolysis within less than 3 hours after ischemic stroke, we designed a specific patient management scheme for patients referred to our center.

METHODS

We report the activity of the "stroke emergency" pathway in the Purpan Hospital (Toulouse) for 4 years. We wanted to evaluate our daily practice and to confirm that the results obtained in the randomized clinical trials with rt-PA can be reproduced in routine practice.

RESULTS

Among all stroke patients treated in the Neurology Department, 10.2 per cent were managed via this new pathway, in order to receive a fibrinolytic treatment. Amongst these, 25.6 per cent were treated with rt-PA (2.6 per cent of all ischemic and hemorrhagic strokes, with an average NIHSS score of 15.8 at admission [5; 25]. In 90 per cent of the cases, potential patients for thrombolysis were selected by CT-scan. Time from onset to treatment averaged 2 h 25 min, whilst door-to-treatment time averaged 40 minutes. Two patients (3 percent) showed a symptomatic intra-cerebral hemorrhage. Death rate was 18.8 per cent. After 3 months, 53.5 per cent of patients were regarded as functionally "independent" (Rankin scale<3).

CONCLUSION

These results in our unit confirm the feasibility, reproducibility, efficacy and safety of the rt-PA fibrinolytic treatment for ischemic stroke of less than 3 hours. A "Stroke emergency" pathway appears to be a helpful option to treat as many patients as possible with the shortest possible lead times.

Chronic administration of selective serotonin reuptake inhibitor (SSRI) paroxetine modulates human motor cortex excitability in healthy subjects

The aim of the study was to investigate the effect of chronic administration of paroxetine (selective serotonin reuptake inhibitor: SSRI) on motor cortex excitability in healthy subjects by means of transcranial magnetic stimulation (TMS), functional magnetic resonance imaging (fMRI) and behavioral motor tests. In a randomized, double-blind, crossover study, twenty-one right-handed subjects received 20 mg daily of either paroxetine or a placebo over a period of 30 days separated by a period of 3 months wash-out. The TMS study is presented here correlated with some results of the motor behavior study (finger tapping test) and the fMRI study (primary sensorimotor cortex (S1M1) volume of activation). TMS was used to test motor threshold (MT), motor evoked potential recruitment curve (RC), cortical silent period (CSP) and paired-pulse intracortical inhibition and facilitation (ICI, ICF). Chronic administration of paroxetine did not modulate ICI or CSP but induced a significant enhancement of mean ICF (ANOVA P=0.04), which significantly correlated with increase of speed in a finger tapping test (P=0.02). This suggests a modulation of cortical interneuronal excitatory pathways without changes in the excitability of cortical inhibitory GABAergic interneurons. A decrease of RC (ANOVA P=0.05) was also observed after 30 days intake of paroxetine in comparison with placebo and was associated with changes of fMRI activation intensity (left S1M1 hypoactivation, ), without changes of S1M1 activation volume. Finally, the different modulation of RC and ICF after chronic administration of paroxetine compared to single dose (opposite effects) emphasizes the different pharmacological action of the drug at cortical level depending on its acute or long-term administration.

Tomographie par émission de positons dans la migraine

Due to technical constraints and randomness of migraine attacks, studies using PET are scarce. Nevertheless, these studies have given new insights into migraine pathogenesis. One of the main facts revealed by PET studies is that posterior cerebral hypoperfusion accompanying migraine auras could also be present in migraine attacks without aura. This hypoperfusion is probably due to an increase of intrinsic vasoconstrictive tone in the cerebral circulation. Using PET within 6 hours after the onset of a spontaneous migraine attack, significant activations of brainstem (midbrain and pons) and of hypothalamus, persisting after headache relief by sumatriptan have been shown. These structures could play the role of migraine attack generators, modulating intrinsic vascular tone and central pain transmission.

[Risk of recurrent stroke in adults aged under 45 years following a first ischemic stroke: a five-year study of 95 patients]

Few data are available concerning the risk of recurrence of cerebral ischemic infarction in young adults (less than 45-years-old) after a first episode of ischemic stroke. From 1992 to 1996, 95 patients less than 45 years old were enrolled in a prospective study in order to define the etiology of their ischemic infarction with systematic and exhaustive explorations. They were recalled five years later (mean follow-up of 67,07 +/- 25,6 months) to determine the risk of stroke recurrence, the rate of cardiac and vascular events and the mortality. At 5 years, 4 patients had a recurrence of ischemic stroke (4.7 p. cent). Seven patients had a coronary event (4 myocardial infarction and 4 angina). Eleven patients died (6 during the acute period). No recurrence of stroke was noticed in patients with stroke of undetermined cause or with minor cardiopathy (abnormalities of the atrial septum). The risk of recurrence of ischemic stroke in young adults appears to be very low.

Fluoxetine modulates motor performance and cerebral activation of patients recovering from stroke

In order to determine the influence of a single dose of fluoxetine on the cerebral motor activation of lacunar stroke patients in the early phase of recovery, we conducted a prospective, double-blind, crossover, placebo-controlled study on 8 patients with pure motor hemiparesia. Each patient underwent two functional magnetic resonance imaging (fMRI) examinations: one under fluoxetine and one under placebo. The first was performed 2 weeks after stroke onset and the second a week later. During the two fMRI examinations, patients performed an active controlled motor task with the affected hand and a passive one conducted by the examiner with the same hand. Motor performance was evaluated by motor tests under placebo and under fluoxetine immediately before the examinations to investigate the effect of fluoxetine on motor function. Under fluoxetine, during the active motor task, hyperactivation in the ipsilesional primary motor cortex was found. Moreover, fluoxetine significantly improved motor skills of the affected side. We found that a single dose of fluoxetine was enough to modulate cerebral sensory-motor activation in patients. This redistribution of activation toward the motor cortex output activation was associated with an enhancement of motor performance.

EFNS Task Force on Teaching of Neuroimaging in Neurology Curricula in Europe: present status and recommendations for the future

A Task Force on 'Teaching of Neuroimaging in Neurology Curricula in Europe' was appointed in September 1998 by the education committee of the European Federation of Neurological Societies (EFNS) in order to: (1) examine the present status of teaching of neuroimaging in the training of neurology in European countries, and, in particular, to assess the strengths and weaknesses of the various countries; (2) give recommendations for global improvement and harmonization of such training. A questionnaire was completed in February 1999 and sent to 35 delegates of national neurological societies. Completed questionnaires were received from 21 countries: Albania, Austria, Croatia, Czech Republic, Denmark, Estonia, Finland, Germany, Greece, Hungary, Israel, Italy, Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Switzerland, Turkey and UK. The questionnaire revealed that the situation in Europe is highly heterogeneous, both as regards the training in neurology in general and, more specifically, the teaching of neuroimaging during the training. Some recommendations to make the teaching of neuroimaging more homogeneous across European countries and to improve it are provided.

Perimetric visual field and functional MRI correlation: implications for image-guided surgery in occipital brain tumours

OBJECTIVE

To compare the results of visual functional MRI with those of perimetric evaluation in patients with visual field defects and retrochiasmastic tumours and in normal subjects without visual field defect. The potential clinical usefulness of visual functional MRI data during resective surgery was evaluated in patients with occipital lobe tumours.

METHODS

Eleven patients with various tumours and visual field defects and 12 normal subjects were studied by fMRI using bimonocular or monocular repetitive photic stimulation (8 Hz). The data obtained were analyzed with the statistical parametric maps software (p<10(-8)) and were compared with the results of Goldmann visual field perimetric evaluation. In patients with occipital brain tumours undergoing surgery, the functional data were registered in a frameless stereotactic device and the images fused into anatomical three standard planes and three dimensional reconstructions of the brain surface.

RESULTS

Two studies of patients were discarded, one because of head motion and the other because of badly followed instructions. On the remaining patients the functional activations found in the visual cortex were consistent with the results of perimetric evaluation in all but one of the patients and all the normal subjects although the results of fMRI were highly dependent on the choices of the analysis thresholds. Visual functional MRI image guided data were used in five patients with occipital brain tumours. No added postoperative functional field defect was detected.

CONCLUSIONS

There was a good correspondence between fMRI data and the results of perimetric evaluation although dependent on the analysis thresholds. Visual fMRI data registered into a frameless stereotactic device may be useful in surgical planning and tumour removal.

Pharmacologic modulation of human cerebral activity: contribution of functional neuroimaging

This article highlights the following: (1) How the tools of functional neuroimaging analyze the effect of drug therapy on the central nervous system; (2) how the interactions between the drugs and the cortical neuronal networks have illustrated new aspects of the concepts of cerebral neuroplasticity; and (3) how functional neuroimaging has proved to be a valuable tool in understanding the mechanisms that govern the therapeutic activity of experimental drugs.

Within-session and between-session reproducibility of cerebral sensorimotor activation: a test--retest effect evidenced with functional magnetic resonance imaging

The aim of the current study was to assess the reproducibility of functional magnetic resonance imaging (fMRI) brain activation signals in a sensorimotor task in healthy subjects. Because random or systematic changes are likely to happen when movements are repeated over time, the authors searched for time-dependent changes in the fMRI signal intensity and the extent of activation within and between sessions. Reproducibility was studied on a sensorimotor task called "the active task" that includes a motor output and a sensory feedback, and also on a sensory stimulation called "the passive task" that assessed the sensory input alone. The active task consisted of flexion and extension of the right hand. The subjects had performed it several times before fMRI scanning so that it was well learned. The passive task consisted of a calibrated passive flexion and extension of the right wrist. Tasks were 1 Hz-paced. The control state was rest. Subjects naïve to the MRI environment and non--MRI-naïve subjects were studied. Twelve MRI-naïve subjects underwent 3 fMRI sessions separated by 5 hours and 49 days, respectively. During MRI scanning, they performed the active task. Six MRI-naïve subjects underwent 2 fMRI sessions with the passive task 1 month apart. Three non--MRI-naïve subjects performed twice an active 2-Hz self-paced task. The data were analyzed with SPM96 software. For within-session comparison, for active or passive tasks, good reproducibility of fMRI signal activation was found within a session (intra-and interrun reproducibility) whether it was the first, second, or third session. Therefore, no within-session habituation was found with a passive or a well-learned active task. For between-session comparison, for MRI-naïve or non--MRI-naïve subjects, and with the active or the passive task, activation was increased in the contralateral premotor cortex and in ispsilateral anterior cerebellar cortex but was decreased in the primary sensorimotor cortex, parietal cortex, and posterior supplementary motor area at the second session. The lower cortical signal was characterized by reduced activated areas with no change in maximum peak intensity in most cases. Changes were partially reversed at the third session. Part of the test-retest effect may come from habituation of the MRI experiment context. Less attention and stress at the second and third sessions may be components of the inhibition of cortical activity. Because the changes became reversed, the authors suggest that, beyond the habituation process, a learning process occurred that had nothing to do with procedural learning, because the tasks were well learned or passive. A long-term memory representation of the sensorimotor task, not only with its characteristics (for example, amplitude, frequency) but also with its context (fMRI), can become integrated into the motor system along the sessions. Furthermore, the pattern observed in the fMRI signal changes might evoke a consolidation process.

[Anomalties of the interatrial septum and latent atrial vulnerability in unexplained ischemic stroke in young adults]

Seventy-four consecutive patients (18 to 55 years) underwent programmed atrial stimulation in the investigation of unexplained ischaemic stroke after a full work-up including transoesophageal echocardiography to exclude abnormalities of the interatrial septum (patent foramen ovale and/or atrial septal aneurysm). The parameters recorded during atrial electrophysiological investigation were: the effective atrial refractory period, loco-regional intra-atrial conduction, the index of latent atrial vulnerability and the inducibility by the extrastimulus technique. Seventy five per cent of patients with a patent foramen ovale and/or an atrial septal aneurysm were inducible compared with only 38% of patients with normal interatrial septa on transoesophageal echocardiography (p = 0.001). Fifty two per cent of patients with an anomaly of the atrial septum had latent atrial vulnerability compared with 26% of those with normal transoesophageal echocardiography (p = 0.02). These results confirm the relationship between atrial septal anomalies and latent atrial vulnerability in unexplained ischaemic stroke of young adults.

[Acute blood pressure elevations]

Blood pressure (BP) elevations may correspond to different clinical situations. Hypertensives emergencies are situations that require immediate reduction in BP because of acute or rapidly progressing target organ damage: accelerated malignant hypertension, hypertensive encephalopathy, acute myocardial infarction, acute aortic dissection, acute left ventricular failure, and eclampsia. Hypertensive urgencies are those with marked elevated BP in which it is desirable to reduce BP progressively within few hours, such as severe hypertension, progressive target organ damage, perioperative hypertension. Cerebrovascular accidents have to be individualized. In most patients in the immediate post-stroke period, BP should not be lowered. Caution is advised in lowering BP in these patients because excessive falls may precipitate cerebral ischemia. In situations without symptoms or progressive target organ it is necessary to exclude proximate causes of elevated BP such as pain and elevated BP alone rarely requires antihypertensive treatment. Among parenteral antihypertensive (AH) drugs labetalol, nicardipine, urapidil, and nitroprussiate are generally used, and the choice of AH drug depends on the clinical situation. It is not required to normalize BP immediately but to reduce mean BP no more than 25%, then toward 160/100 mmHg as recommended by JNC VI, in order to avoid an impairment of renal, cerebral or coronary ischemia. Oral long-acting dihydropyridines are often subsequently administrated, except in myocardial ischemia. Therapeutic attitudes vary considerably according to the clinical situation: abstention, immediate decrease or progressive decrease in BP have to be decided.

Functional MRI and intraoperative brain mapping to evaluate brain plasticity in patients with brain tumours and hemiparesis

OBJECTIVE

To support the hypothesis about the potential compensatory role of ipsilateral corticofugal pathways when the contralateral pathways are impaired by brain tumours.

METHODS

Retrospective analysis was carried out on the results of functional MRI (fMRI) of a selected group of five paretic patients with Rolandic brain tumours who exhibited an abnormally high ipsilateral/contralateral ratio of activation-that is, movements of the paretic hand activated predominately the ipsilateral cortex. Brain activation was achieved with a flexion extension of the fingers. Statistical parametric activation was obtained using a t test and a threshold of p<0.001. These patients, candidates for tumour resection, also underwent cortical intraoperative stimulation that was correlated to the fMRI spatial data using three dimensional reconstructions of the brain. Three patients also had postoperative control fMRI.

RESULTS

The absence of fMRI activation of the primary sensorimotor cortex normally innervating the paretic hand for the threshold chosen, was correlated with completely negative cortical responses of the cortical hand area during the operation. The preoperative fMRI activation of these patients predominantly found in the ipsilateral frontal and primary sensorimotor cortices could be related to the residual ipsilateral hand function. Postoperatively, the fMRI activation returned to more classic patterns of activation, reflecting the consequences of therapy.

CONCLUSION

In paretic patients with brain tumours, ipsilateral control could be implicated in the residual hand function, when the normal primary pathways are impaired. The possibility that functional tissue still remains in the peritumorous sensorimotor cortex even when the preoperative fMRI and the cortical intraoperative stimulations are negative, should be taken into account when planning the tumour resection and during the operation.

Serum lipids in young patients with ischaemic stroke: a case-control study

OBJECTIVES

The relation between serum lipids and ischaemic stroke remains controversial. Studies of lipid related risk factors in cerebrovascular disease have varied greatly in their findings and also in their definition of the cerebrovascular end points. Serum lipids are thought to interact with the pathogenesis of stroke through an atherosclerosis mechanism. Stroke in young patients have been shown to be related to non-atherosclerotic causes most of the time. The aim was to determine the serum lipid profile and the vascular risk factors for ischaemic stroke in a series of patients under 45 with an ischaemic stroke and to compare them with a series of controls of the same age.

METHODS

Ninety four consecutive patients with ischaemic stroke were compared with 111 controls of the same age recruited from a regional electoral list. Vascular risk factors were recorded and serum lipid profile was determined in all of them.

RESULTS

Multivariate analyses showed that low HDL cholesterol, male sex, smoking, hypertension, and oral contraceptives were risk factors for intracerebral arterial occlusion.

CONCLUSION

Low HDL cholesterol was the only serum lipid index to be associated to an increased risk of stroke in this population. Low HDL cholesterol must be considered in the care management of young patients regardless of the detectable presence of atherosclerosis.