Asymptomatic Hemisphere Research Articles

Thalamic structure and anastomosis in different hemispheres of moyamoya disease.

The progression of the asymptomatic hemisphere of moyamoya disease (MMD) is largely unknown. In this study, we investigated the differences in subcortical gray matter structure and angiographic features between asymptomatic and symptomatic hemispheres in patients with MMD. We retrospectively reviewed patients with MMD in consecutive cases in our center. We compared subcortical gray matter volume and three types of collaterals (lenticulostriate anastomosis, thalamic anastomosis, and choroidal anastomosis) between symptomatic and asymptomatic hemispheres. Symptomatic hemispheres were classified as ischemic hemisphere (i-hemisphere) and hemorrhagic hemisphere (h-hemisphere). Asymptomatic hemispheres were classified as contralateral asymptomatic hemisphere of i-hemisphere (ai-hemisphere), contralateral asymptomatic hemisphere of h-hemisphere (ah-hemisphere), bilateral asymptomatic hemispheres in asymptomatic group (aa-hemisphere). A total of 117 MMD patients were reviewed, and 49 of them met the inclusion criteria, with 98 hemispheres being analyzed. The thalamic volume was found to differ significantly between the i- and ai-hemispheres (P = 0.010), between the i- and ah-hemispheres (P = 0.004), as well as between the h- and ai-hemispheres (P = 0.002), between the h- and ah-hemispheres (P < 0.001). There was a higher incidence of thalamic anastomosis in the ai-hemispheres than i-hemispheres (31.3% vs. 6.3%, P = 0.070), and in the ah-hemispheres than h-hemispheres (29.6% vs. 11.1%, P = 0.088). Additionally, the hemispheres with thalamic anastomosis had a significantly greater volume than those without thalamic anastomosis (P = 0.024). Univariate and multivariate logistic regression analysis showed that thalamic volume was closely associated with thalamic anastomosis. The thalamic volume and the incidence of thalamic anastomosis increase in asymptomatic hemispheres and decrease in symptomatic hemispheres. Combining these two characteristics may be helpful in assessing the risk of stroke in the asymptomatic hemispheres of MMD as well as understanding the pathological evolution of the disease.

Intraplaque CTA characteristics as predictors of symptomatology: a semiautomated volumetric analysis.

Prior studies comparing CT characteristics of carotid plaques to symptomatology have relied on gross morphologic imaging features. This study sought to determine if volumetric measurements of carotid plaque components are associated with ipsilateral neurologic symptoms. CTA images of consecutive patients that underwent a carotid endarterectomy were reviewed with a semiautomated software package. Intraplaque volumes of intraplaque hemorrhage (IPH), lipid-rich necrotic core (LRNC), and matrix were computed, as was the degree of arterial stenosis. Statistics were analyzed on a per cerebral hemisphere basis, and dichotomized into symptomatic and asymptomatic. Clinical and radiological endpoints included transient ischemic attack (TIA), ischemic stroke diagnosed on imaging studies, ophthalmologically diagnosed central or branch retinal artery occlusion (RAO), or amaurosis fugax. One hundred sixty-eight carotid plaques were reviewed. The average age is 70.8years (SD = 8.8); 32/87 (36.8%) were female. Sixty-seven of eighty-seven (77.0%) patients were symptomatic. Sixty-six of one hundred sixty-eight (39.3%) plaques were ipsilateral to the patient's symptoms, while 102/168 (60.7%) were ipsilateral to an asymptomatic hemisphere. Greater intraplaque volumes of IPH (p = 0.03), LRNC (p = 0.008), and matrix (p = 0.0008) were associated with symptoms, as was greater proportion of LRNC in regard to plaque volume (p = 0.04). All but proportion of LRNC remained statistically significant after adjustment for plaque size. More severe luminal stenosis was also associated with ipsilateral neurologic symptoms, both when calculated by smallest diameter or by area (p < 0.0001 for both). Higher volumes of intraplaque IPH, LRNC, matrix, and degree of arterial stenosis are associated with ipsilateral neurologic symptoms. Greater intraplaque proportions of LRNC are also associated with ipsilateral ischemic manifestations, suggesting that larger relative composition of lipids may be particularly predictive of symptomatology.

MR Diffusional Kurtosis Imaging-Based Assessment of Brain Microstructural Changes in Patients with Moyamoya Disease before and after Revascularization.

Conventional imaging examinations are insufficient to accurately assess brain damage in patients with Moyamoya disease. Our aim was to observe brain microstructural changes in patients with Moyamoya disease by diffusional kurtosis imaging and provide support data for application of this technique in individualized assessment of disease severity and surgical outcome among patients with Moyamoya disease. A total of 64 patients with Moyamoya disease and 15 healthy volunteers underwent diffusional kurtosis imaging, and a second scanning was offered to surgical patients 3-4 months after revascularization. The diffusional kurtosis imaging parameter maps were obtained for mean kurtosis, axial kurtosis, radial kurtosis, fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity. The parameter values were measured in sensory pathway-related regions for all subjects. Differences in diffusional kurtosis imaging parameters of these brain regions were examined for healthy volunteers, patients without acroparesthesia, and asymptomatic and symptomatic sides of patients with acroparesthesia. Changes in diffusional kurtosis imaging parameters of patients with Moyamoya disease before and after revascularization were compared. Compared with healthy volunteers, patients with Moyamoya disease showed decreased mean kurtosis, axial kurtosis, radial kurtosis, and fractional anisotropy in the corona radiata. Similarly, mean kurtosis, radial kurtosis, and fractional anisotropy decreased in the posterior limb of the internal capsule, whereas axial kurtosis decreased and radial kurtosis increased in the thalami of patients with Moyamoya disease compared with healthy volunteers. Compared with the asymptomatic contralateral hemisphere, the symptomatic group showed increased mean kurtosis in the contralateral primary somatosensory cortex, increased fractional anisotropy in the contralateral corona radiata and posterior limb of the internal capsule, and decreased axial kurtosis in the contralateral thalamus. Among patients with Moyamoya disease with acroparesthesia, mean kurtosis decreased in the primary somatosensory cortex on the operated side following revascularization. The diffusional kurtosis imaging technique is applicable to patients with Moyamoya disease for detecting brain microstructural changes in white and gray matter before and after revascularization; this feature is useful in the assessment of disease severity and surgical outcome.

Leukoaraiosis May Confound the Interpretation of CT Perfusion in Patients Treated with Mechanical Thrombectomy for Acute Ischemic Stroke.

Leukoaraiosis frequently coexists in patients with acute stroke. We studied whether leukoaraiosis could confound the interpretation of CTP findings in patients treated with mechanical thrombectomy. We analyzed 236 patients with stroke treated with mechanical thrombectomy and studied with CTP, of whom 127 (53.8%) achieved complete reperfusion. Periventricular white matter hyperintensities on MR imaging and hypodensities on NCCT were assessed through the Fazekas score. CTP-predicted nonviable tissue was defined as relative CBF <30%, and final infarct volume was quantified in DWI. We estimated mean MTT, CBV, and CBF in the asymptomatic hemisphere. In patients achieving complete reperfusion, we assessed the accuracy of nonviable tissue to predict final infarct volume using the intraclass correlation coefficient across periventricular hyperintensity/hypodensity Fazekas scores and variable relative CBF cutoffs. MTT was longer (Spearman ρ = 0.279, P < .001) and CBF was lower (ρ = -0.263, P < .001) as the periventricular hyperintensity Fazekas score increased, while CBV was similar across groups (ρ = -0.043, P = .513). In the subgroup of patients achieving complete reperfusion, nonviable tissue-final infarct volume reliability was excellent in patients with periventricular hyperintensity Fazekas score grade 0 (intraclass correlation coefficient, 0.900; 95% CI, 0.805-0.950), fair in patients with periventricular hyperintensity Fazekas scores 1 (intraclass correlation coefficient, 0.569; 95% CI, 0.327-0.741) and 2 (intraclass correlation coefficient, 0.444; 95% CI, 0.165-0.657), and poor in patients with periventricular hyperintensity Fazekas score 3 (intraclass correlation coefficient, 0.310; 95% CI, -0.359-0.769). The most accurate cutoffs were relative CBF <30% for periventricular hyperintensity Fazekas score grades 0 and 1, relative CBF <25% for periventricular hyperintensity Fazekas score 2, and relative CBF <20% for periventricular hyperintensity Fazekas score 3. The reliability analysis according to periventricular hypodensity Fazekas score grades on NCCT was similar to that in follow-up MR imaging. In patients with stroke, the presence of leukoaraiosis confounds the interpretation of CTP despite proper adjustment of CBF thresholds.

Association Between Cerebral Small Vessel Disease and Central Motor Conduction Time in Patients with Vascular Risk

Background and Purpose: Cerebral small vessel disease (CSVD) is related to motor function disturbance. It includes several types: lacunar infarction, white matter hyperintensity, cerebral microbleeds (CMBs), and enlarged perivascular spaces (EPVS). Transcranial magnetic stimulation (TMS) has been successfully used to evaluate the function of the pyramidal tract. Central motor conduction time (CMCT) is one of the indicators of pyramidal tract dysfunction in motor evoked potential (MEP). The aim of this study was to investigate the association between each type of CSVD and CMCT. Methods: We enrolled 350 patients with vascular risk factors or a history of cerebrovascular events, who showed signs of CSVD in magnetic resonance imaging in the prospective registry. Among them, 138 patients agreed to the evaluation of MEP. CMCT, resting motor threshold (RMT), and silent period are indicators of the function of motor pathways in MEP. A total of 276 hemispheres were divided into 45 symptomatic hemispheres with a history of pyramidal tract dysfunction and 231 without it. Correlation between each type of CSVD and CMCT were examined in total, symptomatic, and asymptomatic hemispheres. Results: The mean age was 70.5 ± 10.3 (mean ± SD) years, and 89 (65%) were men. In the symptomatic hemisphere, CMCT and RMT were significantly higher than in the asymptomatic hemisphere. In the symptomatic hemisphere, significant association was observed between the number of EPVS in the white matter and CMCT (R2 = 0.201, p < .01). Conclusions: In the symptomatic hemispheres, CMCT was associated with the number of EPVS in the white matter. The EPVS in the white matter may be involved in the motor disturbance due to CSVD.

Investigating the mechanisms of perioperative ischemic stroke in the Carotid Occlusion Surgery Study

The Carotid Occlusion Surgery Study (COSS) was a large, prospective clinical trial that examined whether superficial temporal artery-middle cerebral artery (STA-MCA) bypass, in addition to best medical therapy, reduced the risk of ipsilateral ischemic stroke in patients with carotid artery occlusion and hemodynamic cerebral ischemia. Despite improved cerebral hemodynamics and excellent bypass graft patency rates, COSS failed to show a benefit for the surgical group with respect to ipsilateral stroke recurrence at 2 years after treatment. This was due to a lower than expected rate of recurrent ipsilateral stroke in the medically treated group and a high rate of perioperative ipsilateral strokes in the surgical group. Critics of the trial have cited surgeon inexperience and technical difficulties related to the performance of the bypass graft as a leading cause of failure of the trial. The authors retrospectively identified all patients from the COSS with an ipsilateral, perioperative (< 30 days) ischemic stroke after STA-MCA cortical branch anastomosis. Study records, operative notes, stroke adjudication forms, and imaging studies were reviewed. Ischemic strokes were characterized as bypass graft related or non-bypass graft related based on clinical and radiographic findings. Fourteen of 93 surgically treated patients experienced an ipsilateral, perioperative ischemic stroke. Postoperatively, the mean oxygen extraction fraction (OEF) ratio between the symptomatic and asymptomatic cerebral hemisphere significantly improved in these patients (1.30 ± 0.18 preoperative vs 1.12 ± 0.11 postoperative; p = 0.02), but did not normalize. In this cohort, total MCA occlusion time during the anastomosis (54.3 ± 23.5 minutes) was no different from the MCA occlusion time in those surgical patients who did not have a perioperative stroke (45.4 ± 24.2 minutes, p = 0.2). Bypass graft patency rates in patients with a perioperative stroke were 92% at 30 days (11 of 12 patients with patency data) and 83% at last follow-up visit (10 of 12 patients with patency data). These patency rates were not significantly different from those achieved at 30 days (100%; 76 of 76 patients with patency data; p = 0.14) and at last follow-up (99%; 71 of 72 patients with patency data; p = 0.052) in patients without a perioperative stroke. Eighty-six percent (12 of 14 patients) of strokes were likely attributable to factors unrelated to the STA-MCA anastomosis. Only 21% of strokes (3 of 14 patients) were in the territory of the recipient vessel and likely related to technical performance of the anastomosis itself. One patient was thought to have dual stroke mechanisms. Only a small minority of ipsilateral, perioperative ischemic strokes in the COSS could be attributed to technical problems of the bypass anastomosis. The majority of ischemic strokes could not be ascribed to this cause and were most likely due to patient hemodynamic fragility and the inability of patients to tolerate surgery.

A comment on “Contralateral cerebral hemodynamic changes after unilateral direct revascularization in patients with moyamoya disease”

A comment on “Contralateral cerebral hemodynamic changes after unilateral direct revascularization in patients with moyamoya disease”

Contralateral cerebral hemodynamic changes after unilateral direct revascularization in patients with moyamoya disease

Direct revascularization has been used successfully to prevent strokes by improving regional cerebral blood flow (rCBF) to the affected hemisphere faster in patients with moyamoya disease (MMD). Since most literatures have focused on the rCBF changes of operative hemisphere, we evaluated the hemodynamics of nonoperative side by xenon-enhanced computed tomography (Xe-CT) and acetazolamide challenge test in patients with MMD during a short time follow-up. Fifteen MMD patients with unilateral ischemic presentations who received direct revascularization on the symptomatic hemispheres with complete hemodynamic evaluations by Xe-CT and acetazolamide challenge test were enrolled. Hemodynamic evaluations were performed 1, 3, and 6 months, postoperatively. The postoperative rCBF and cerebral vascular reserve (CVR) were recorded and correlated with clinical outcome. Angiography was performed if the patient had neurological deterioration or deficits. The average follow-up time was 8.5±3.5 months. Three months after the ipsilateral direct revascularization, the CVR of nonoperative hemispheres (25.8±8.1%) began to decrease significantly (P=0.003). Six months later, the rCBF showed a downward trend in nonoperative hemispheres (47.4±8.0 ml·100 g(-1) min(-1)) than the preoperative status, but the difference was not significant (P=0.053). Three patients presented with decreased rCBF and impaired CVR in the nonoperative hemispheres. Among them, two patients were symptomatic. Unilateral direct revascularization in symptomatic hemisphere for MMD patient could induce CVR impaired in primary asymptomatic hemisphere during the short term after the surgery. Therefore, critical follow-up, especially the hemodynamic follow-up in the asymptomatic hemispheres should be performed in patients with MMD.

1H-MR Spectroscopy Changes in Transient Ischemic Attack Patients and Their Correlation with Perfusion-Weighted Imaging

ABSTRACTPurpose: We investigated whether patients with transient ischemic attack (TIA) have metabolic changes in the brain. Methods: 35 patients with clinically diagnosed TIA were prospectively included in our study. Clinical and neurological data were compiled. 1H-MR spectroscopy and perfusion-weighted imaging were performed in all patients within 3 days of the onset of symptoms. Results: In TIA patients, the N-acetylaspartate (NAA)/choline (Cho) ratio in noninfarcted regions was significantly decreased in the symptomatic hemisphere (1.33 ± 0.38) compared with the asymptomatic hemisphere (1.51 ± 0.41, p < .05). Patients with a history of prior TIA had a significantly decreased NAA/Cho ratio in both the symptomatic (p < .05) and asymptomatic (p < .05) hemispheres compared with TIA patients without a prior TIA. TIA patients with diffusion-weighted imaging lesions had a significantly increased lactate/NAA ratio in both the symptomatic (p < .05) and asymptomatic (p < .05) hemispheres compared with TIA patients without lesions. The relative cerebral blood flow (rCBF) value was directly related to the symptomatic Cho/creatine (Cr) value (r = 0.81, p < .01). The higher the rCBF value, the higher the symptomatic Cho/Cr value. Conclusions: TIA patients have neurological deficits that are transient; however, metabolic damage to the brain is present up to 3 days after the onset of the symptoms. These metabolic changes are not restricted to the symptomatic hemisphere or to areas close to ischemic lesions and the changes are related in the CBF.

Improved cerebrovascular reactivity following low flow EC/IC bypass in patients with occlusive carotid disease

Patients with major cerebral artery occlusive disease can suffer cerebral hypoperfusion and be at an increased risk of future strokes. EC/IC bypass has been shown to reduce this risk. Patients with cerebral hypoperfusion, and who are at risk of haemodynamic ischaemia, can be identified by the use of xenon computerised tomography (XeCT) to demonstrate severe impairment of the cerebrovascular reserve (CVR). We report our series on the effect of low flow EC/IC bypass on CVR in patients with symptomatic cerebral haemodynamic ischaemia. Thirteen patients with clinical and radiological features of cerebral hypoperfusion were assessed with acetazolamide activated XeCT. Pre- and postoperative regional cerebral blood flow (rCBF) and CVR were assessed. The change in CVR from pre- to post surgery was calculated (%CVR). Values were compared using ANOVA and Student's paired t-test. Unless otherwise stated, values are given as mean ± standard error of the mean. Statistical significance was taken at p < 0.05.Pre-operative symptomatic hemisphere CBF was 38 ± 2 mls/100g/min compared to 40 ± 3.2 mls/100 g/min in the asymptomatic hemisphere, with the greatest difference observed in the MCA territory (38.6 ± 2 cf 45.4 ± 3.2 mls/100g/min). Baseline CBF was not significantly improved post EC/IC bypass. However CVR was significantly improved in the symptomatic hemisphere post-operatively (p = 0.015), with the greatest increase (28%) seen in the MCA territory (p = 0.0105). First, 85% of patients had either an improvement in symptoms or no further symptoms. There was a 93% graft patency and no operative mortality. Low flow EC/IC bypass can improve CVR in patients with symptomatic cerebral ischaemia in the presence of occlusive carotid disease. However, therapy must be individualised, with careful patient selection and minimal surgical morbidity.

Efficacy of the revascularization surgery for adult-onset moyamoya disease with the progression of cerebrovascular lesions

Object In moyamoya disease, despite its progressive nature of the occlusive lesions in pediatric patients, the prevalence of the progression in adult patients is undetermined. Furthermore, the optimal timing of the revascularization surgery for progressive cases is controversial. To address these issues, we retrospectively investigate four cases with the adult-onset moyamoya disease manifesting as progression before revascularization surgery. Methods From March 2004 to May 2007, 49 patients with adult-onset moyamoya disease aged from 19 to 62 years old (mean 40.5) underwent superficial temporal artery–middle cerebral artery (STA–MCA) anastomosis on 63 hemispheres. All patients were strictly followed up by magnetic resonance (MR) imaging/angiography postoperatively. Twenty-seven hemispheres of 15 adult patients without surgery were also followed up at outpatient service during the same period. If the patients manifest as the progression of the steno-occlusive lesion on the hemisphere without surgery, they undergo revascularization surgery after the confirmation of hemodynamic compromise. Results During this period, 47 hemispheres including those of outpatient cases were conservatively followed up after initial diagnosis. Among them, six hemispheres (12.8%) of four patients had been proven to show apparent progression of steno-occlusive lesion and were subjected to revascularization surgery. Postoperative courses were uneventful in all four cases, and no patient suffered cerebrovascular event on the operated hemisphere after surgery. Conclusion Adult-onset moyamoya disease, either bilateral or unilateral, has a substantial risk for progression, and careful follow-up is necessary for asymptomatic hemisphere. Once the patient manifests as the progression of cerebrovascular occlusive lesions or ischemic symptoms, we recommend revascularization surgery after the confirmation of the hemodynamic compromise.

Transcranial magnetic stimulation

In this Primer we have been able to give only a snapshot of the basic features and the applications of TMS. Some fundamentals of the use of TMS are falling into place as we learn more about the effects of different combinations of stimulus intensity, frequency, task and behavioural state. We have not had space to cover some important areas, such as studies of depression, language, eye movements and basic motor physiology, but the technique is now used in almost every area of cognitive neuroscience. Areas in which we can expect the next major advances in the use of TMS (and TDCS) include: the combination of TMS with other techniques to investigate causal interactions between cortical areas; the development of new paradigms to change selectively the baseline state of cortical excitation prior to further magnetic stimulation; and the incorporation of TMS into neuro-rehabilitation programmes.

Positron emission tomography in premotor Parkinson's disease

Functional imaging can be used to detect preclinical evidence of dopamine deficiency in people deemed to be at increased risk of Parkinson's disease (PD) based on genetic or environmental risk, or because they have clinical features such as REM sleep behaviour disorder that may be a harbinger of PD. Positron emission tomography (PET) using [11C]dihydrotetrabenazine to label the vesicular monoamine transporter type 2 (VMAT2), a variety of 11C- or 18 F-labeled ligands for the membrane dopamine transporter (DAT), or 6-[18F]fluoro-L-dopa (FD), which assesses uptake and decarboxylation of levodopa as well as vesicular storage of radiolabeled dopamine, can all be used, and all provide comparable, but somewhat different information. DAT binding using either PET or SPECT appears to be the most sensitive marker of dopamine denervation, while FD uptake is subject to compensatory upregulation and its reduction may more closely herald the onset of clinical disease. Alterations in glucose metabolism and in dopamine release also occur in the asymptomatic hemisphere of subjects with unilateral PD. An interesting potential application of PET is the determination of non-dopaminergic abnormalities that correlate with the presence of clinically apparent pre-motor symptoms of PD.

Corticostriatal functional interactions in Parkinson's disease: a rTMS/[11C]raclopride PET study

Several animal studies have shown that striatal dopamine can be released under direct control of glutamatergic corticostriatal efferents. In Parkinson's disease (PD), abnormalities in corticostriatal interactions are believed to play an important role in the pathophysiology of the disease. Previously, we have reported that, in healthy subjects, repetitive transcranial magnetic stimulation (rTMS) of motor cortex (MC) induces focal dopamine release in the ipsilateral putamen. In the present study, using [11C]raclopride PET, we sought to investigate early PD patients with evidence of unilateral motor symptoms. We measured in the putamen changes in extracellular dopamine concentration following rTMS (intensity, 90% of the resting motor threshold; frequency, 10 Hz) of the left and right MC. The main objective was to identify potential differences in corticostriatal dopamine release between the hemisphere associated with clear contralateral motor symptoms (symptomatic hemisphere) and the presymptomatic stage of the other hemisphere (asymptomatic hemisphere). Repetitive TMS of MC caused a binding reduction in the ipsilateral putamen of both hemispheres. In the symptomatic hemisphere, while the amount of TMS-induced dopamine release was, as expected, smaller, the size of the significant cluster of change in [11C]raclopride binding was, instead, 61.4% greater than in the asymptomatic hemisphere. This finding of a spatially enlarged area of dopamine release, following cortical stimulation, may represent a possible in vivo expression of a loss of functional segregation of cortical information to the striatum and an indirect evidence of abnormal corticostriatal transmission in early PD. This has potential implications for models of basal ganglia function in PD.

Cortical motor reorganization after a single clinical attack of multiple sclerosis.

In order to evaluate whether cortical motor reorganization occurs in the earliest phase of multiple sclerosis, we studied patients after a first clinical attack of hemiparesis. From a consecutive series of 70 patients enrolled in a study of patients with clinically isolated syndrome and serial MRI findings indicative of multiple sclerosis, we retrospectively selected 10 patients with hemiparesis as the onset symptom and no further clinical episode [mean age 32 +/- 9 years, disease duration 24 +/- 14 months, median Expanded Disability Status Score (EDSS) 1.25]. Ten age-matched, healthy subjects served as controls. Each subject was submitted to two functional MRI trials (one per hand) using a 1.5 T magnet during a sequential finger-to-thumb opposition task. Image analysis was performed using SPM99 software. Movements of both the 'affected' and the 'unaffected' hand activated significantly larger areas in patients than in controls in both the contralateral and ipsilateral cortical motor areas. Patients activated a greater number of foci than controls during both the right-hand and the left-hand movement. Most of these foci were located in cortical areas which were less or not at all activated in controls, such as the lateral premotor cortex [Brodmann area (BA) 6], the insula and the inferior parietal lobule (BA 40). Between-group analysis of patients versus controls showed significant (P < 0.001) foci in these areas, principally located in the ipsilateral hemisphere during right-hand movement and in both the cerebral hemispheres during left-hand movement. Time since clinical onset showed a significant positive correlation with the extent of activation in the ipsilateral motor areas (P = 0.006) during the right-hand movement and with the extent of activation in both the ipsilateral (P = 0.02) and contralateral (P = 0.006) motor areas during the left-hand movement. The T(1) lesion load along the motor pathway showed a significant positive correlation (P = 0.007) with the extent of activation in the contralateral motor areas during right-hand movement. Our study shows functional adaptive changes that involve both the symptomatic and asymptomatic hemisphere during a simple motor task in patients who had suffered a single clinical attack of hemiparesis. The extent of these changes increased with the time elapsed since disease onset and the severity of brain damage.

Remote Effects of Acute Ischemic Stroke: A Xenon CT Cerebral Blood Flow Study

Objective: The purpose of this study was to verify transhemispheric diaschisis in the early hours after an ischemic event. Methods: XeCT cerebral blood flow (CBF) studies within 8 h of stroke were studied in 23 patients. Mean CBF was evaluated in the ischemic area, contralateral hemisphere and ipsilateral cerebellum. Results: A severe CBF reduction was found in the ischemic area (mean 9 ± 3 ml/100 g/min). The mean CBF in the unaffected hemisphere (33 ± 10 ml/100 g/min) was 35% less compared to the normal mean value. CBF was decreased in the cerebellum ipsilateral to the stroke (mean 31 ± 12 ml/100 g/min) suggesting a blood flow depression of the whole brain. Conclusions: During the initial hours of cerebral ischemia, the asymptomatic hemisphere demonstrated CBF depression that was part of the global flow reduction.

Impaired inhibition in writer's cramp during voluntary muscle activation.

We used paired transcranial magnetic stimulation (TMS) to evaluate inhibitory mechanisms in eight patients with writer's cramp during rest and isometric wrist extension. Both stimuli were 110% of the motor threshold; the interstimulus intervals (ISIs) were 20 to 200 ms in increments of 10 ms. Surface EMG was recorded from wrist extensors. In the symptomatic hemisphere, there was no significant difference in the amplitude of the test (second) motor evoked-potential (MEP) between patients and age-matched controls at rest. However, with voluntary muscle activation, inhibition of the test MEP by the conditioning MEP was significantly less in writer's cramp patients than in controls (p = 0.02). The difference was most prominent at ISIs of 60 to 80 ms in which inhibition is maximum. In the asymptomatic hemisphere, there was no significant difference between patients and controls in both rest and active conditions. The silent period was shorter in patients than controls on the symptomatic side (p = 0.003) but not on the asymptomatic side. We conclude that the inhibitory effects induced by magnetic stimulation are reduced in patients with writer's cramp, but only on the symptomatic side during muscle activation. This may relate to the overflow of muscle activity that characterizes this condition.

Cerebrovascular reserve capacity in patients with occlusive cerebrovascular disease: assessment with dynamic susceptibility contrast-enhanced MR imaging and the acetazolamide stimulation test.

To quantitatively assess cerebrovascular reserve capacity in patients with occlusive cerebrovascular disease. In 21 symptomatic patients with occlusive cerebrovascular disease, magnetic resonance (MR) imaging was performed with a 1.5-T system. Before, during, and after a brief bolus injection of gadopentetate dimeglumine into the antecubital vain, a series of 32 rapid T2*-weighted gradient-echo images of two different sections were acquired simultaneously to measure the concentration-time-curves in the brain tissue and in the brain-feeding arteries. Principles of indicator dilution analysis were applied to compute regional cerebral blood flow (rCBF) and volume. Each patient underwent two examinations, the first before and the second after acetazolamide stimulation. In the asymptomatic hemisphere, a mean increase in rCBF value of 47.1% was observed after acetazolamide stimulation. In the affected areas of the symptomatic hemisphere, a statistically significantly reduced response to acetazolamide stimulation was found, indicating a severely compromised cerebrovascular reserve capacity. MR imaging with the described techniques provides quantitative information about the cerebrovascular reserve capacity in patients with occlusive cerebrovascular disease.

Carotid stenosis and perioperative stroke risk in symptomatic and asymptomatic patients undergoing vascular or coronary surgery.

The management of asymptomatic carotid stenosis found before vascular or coronary surgery is unclear from the literature. We aimed to define the relation of carotid stenosis to perioperative stroke in all patients, symptomatic and asymptomatic, and so determine a policy for the management of asymptomatic carotid stenosis in patients requiring major surgery. We conducted a prospective clinical and Duplex ultrasound study of 358 consecutive noncarotid major vascular or coronary artery bypass operations, with a moratorium on endarterectomy for asymptomatic carotid stenosis. There were 145 vascular and 213 coronary bypass operations. Ten of the 49 cases with prior symptoms of cerebral ischemia (38 carotid, 11 vertebrobasilar) had symptomatic stenosis of 50% or greater or occlusion, and 3 of these (30%) had ipsilateral perioperative cerebral infarction (95% confidence interval, 6.67% to 65.25%). Two of these occurred ipsilateral to symptomatic carotid occlusions, and 1 occurred ipsilateral to an 80% symptomatic stenosis. One symptomatic patient with bilateral 30% stenosis had a perioperative infarct in the asymptomatic hemisphere. Among the 309 asymptomatic patients, 1 perioperative infarct occurred ipsilateral to carotid stenosis of 30%. In all there were 5 (1.4%) perioperative (within 72 hours) and 2 late (after 18 days) strokes. All strokes were hemisphere infarcts confirmed by computed tomography. There were 53 cases with 50% or greater asymptomatic carotid stenosis or occlusion, including 28 with 80% or greater stenosis or occlusion. None had an ipsilateral perioperative stroke (95% confidence interval, 0% to 6.72%). We conclude that the risk of perioperative stroke related to symptomatic carotid stenosis may be high, but for asymptomatic carotid stenosis the risk is low and does not justify preoperative prophylactic carotid endarterectomy.

Reversal of intracerebral steal by STA-MCA anastomosis.

A major factor determining the severity of neurological deficits caused by cerebral ischemia is the ability of the vasculature to provide collateral circulation to the ischemic areas. By establishing a major conduit by means of extracranial-intracranial anastomosis, the increased perfusion pressure through the collateral arterioles may reduce morbidity in these patients. Twenty-seven patients were selected for superficial temporal artery to middle cerebral artery (STA-MCA) anastomosis based on clinical and angiographic evidence of lesions of the internal carotid arterial system. Cerebral blood flows (CBF's) were determined by the xenon-133 inhalation method using 16 symmetrically placed scintillator probes; two-compartment analysis was used to compute a mean flow for the compartment. An average mean flow was computed for each hemisphere, and for four regions with the lowest mean CBF in each hemisphere. The CBF was measured preoperatively and within 8 weeks postoperatively. The average mean flow was 29 ml/100 mg/min in the symptomatic hemisphere, and 30 ml/100 gm/min in the asymptomatic hemisphere. In 11 patients, the mean flow for the symptomatic hemisphere increased by 24% postoperatively, and for the asymptomatic hemisphere by 23%. Regions with lowest CBF showed an increase of 32% in the symptomatic hemisphere, and of 35% in the asymptomatic hemisphere. The low-flow regions differed from the total hemisphere (symptomatic: p less than 0.02; asymptomatic: p less than 0.05). Areas of lowest blood flow preoperatively had the greatest increase in flow postoperatively. Postoperative elevation of CBF in the contralateral hemisphere is consistent with an "intracerebral steal" before surgery. The postoperative elevation of flow in the asymptomatic hemisphere is related to improved perfusion pressure in the symptomatic hemisphere.