Diffusion-weighted MRI in patients with non-diagnostic CT in the post-acute phase of cerebral ischemia.

BACKGROUND: Unenhanced computed tomography (CT) is the imaging technique used in acute stroke. In some cases it is unable to detect damage even 24-48 h after symptom onset. The aim of our work was to evaluate the diagnostic value of diffusion-weighted imaging (DWI) in the post-acute phase of cerebral ischemia in patients in whom CT did not yield a definitive diagnosis. METHODS: We retrospectively evaluated DWI findings in 214 patients, out of a series of 1,680 patients admitted to our hospital following the acute onset of focal neurological symptoms, in whom non-contrast CT, performed within 30 h of symptom onset, was normal (123), incongruous, i.e. a marked hypodensity indicative of an old infarct or a slight hypodensity not consistent with the clinical findings (66), or leukoaraiotic, i.e. diffuse chronic hypodensities in the periventricular white matter (25). RESULTS: DWI showed signs of recent brain ischemia in 125/214 (58%) patients: 64/123 (52%) with a normal CT, 41/66 (62%) with an incongruous CT, and 20/25 (80%) with leukoaraiosis (p=0.027). Multiple lesions were detected in 16/125 (16%) patients, while single lesions were

Embolism to the brain during carotid stenting and surgery.

UNLABELLED: The aim of this study was to assess the prevalence and clinical relevance of microembolism in one hundred unselected patients submitted to 50 carotid endarterectomy (CEA) and 50 carotid stenting (CAS) procedures from January 2005 to January 2006 for hemodynamic lesions of the carotid bifurcation (> 70% stenosis). MATERIAL AND METHODS: High-resolution Colour-Flow Mapping (CFM), Transcranial Doppler (TCD), cerebral computed tomography (CT) or magnetic resonance (MR) and four psychometric tests (Mini mental state, Beck depression inventory, Zung anxiety inventory, SF-12) were carried out in the preoperative evaluation in all the patients. In the CEAs loco-regional anesthesia (100%), patch angioplasty (84%) and Pruitt- Inahara shunt (4%) were employed; in the CASs local anesthesia (100%), three different carotid stents (Precise-Cordis, Acculink-Guidant and Carotid Wallstent-Boston Scientific) and three temporary distal filter protection devices (Angioguard-Cordis, Accunet-Guidant, Filterwire-EZ- Boston Scientific), without pre-dilatation, were employed. TCD monitoring was used intra-operatively and 12 hours post-operatively to evaluate the presence and the number of microembolic events (ME's) and to investigate the efficiency of neuroprotective filter devices. The efficacy of the in situ opened filter was judged evaluating the decrease of mean blood velocity in ipsilateral middle cerebral artery and the reduction rate of microembolic events (number of microemboli detected during the entire procedure/number of microemboli detected during the filter positioning). Diffusion-weighted magnetic resonance imaging (DWI) of the brain was obtained within 24 to 48 hours after the procedures to detect new ischemic brain lesions. Psychometric tests were repeated at the discharge of the patient and after two months to evaluate cognitive faculties. RESULTS: During postoperative period (30 days) and follow-up, no procedure-related death and three regressive minor strokes occurred : 1 in CEA (2%) and 2 in CASs (4%) ; a cranial nerve lesion occurred in CEA (2%). TCD monitoring showed ME's (a mean of five events) in 37 CEAs (74%) and in 50 CASs (100%) (a mean of 60 ME's). In five patients submitted to CAS repeated microemboli occurred during one hour postoperative TCD control (10%). A 10-30% decrease of mean blood velocity basal value was recorded in the ipsilateral middle cerebral artery when the filter device was opened. A mean 70% reduction of ME's was obtained with a cerebral protection system deployed. Postoperative DWI detected new focal ischemic lesions in 24 patients [22 after CAS (44%) (a mean of 5 new ipsi and contra-lateral lesions) , and 2 after CEA (4%). Cognitive capability worsened in 20 patients [18 after CAS (36%) e 2 after CEA (4%)]. CONCLUSIONS: Mortality and morbidity rates of patients submitted to CAS are comparable to the results obtained by CEA. A great number of ME's are recorded by TCD during endovascular procedures, more than during open surgery. ME's due to CAS are reduced by filter protection devices, but the cognitive faculties in a great number of "asymptomatic" patients are decreased after CAS.

Hemorrhagic transformation of ischemic brain tissue: asymptomatic or symptomatic?

BACKGROUND AND PURPOSE: The term symptomatic hemorrhage secondary to ischemic stroke implies a clear causal relationship between clinical deterioration and hemorrhagic transformation (HT) regardless of the type of HT. The aim of this study was to assess which type of HT independently affects clinical outcome. METHODS: We used the data set of the European Cooperative Acute Stroke Study (ECASS) II for a post hoc analysis. All patients had a control CT scan after 24 to 96 hours or earlier in case of rapid and severe clinical deterioration. HT was categorized according to radiological criteria: hemorrhagic infarction type 1 and type 2 and parenchymal hematoma type 1 and type 2. The clinical course was prospectively documented with the National Institutes of Health Stroke Scale and the modified Rankin Scale: The independent risk of each type of HT was calculated for clinical deterioration at 24 hours and disability and death at 3 months after stroke onset and adjusted for possible confounding factors such as age, severity of stroke syndrome at baseline, and extent of the ischemic lesion on the initial CT. RESULTS: Compared with absence of HT, only parenchymal hematoma type 2 was associated with an increased risk for deterioration at 24 hours after stroke onset (adjusted odds ratio, 18; 95% CI, 6 to 56) and for death at 3 months (adjusted odds ratio, 11; 95% CI, 3.7 to 36). All other types of HT did not independently increase the risk of late deterioration. CONCLUSIONS: Only parenchymal hematoma type 2 independently causes clinical deterioration and impairs prognosis. It has a distinct radiological feature: it is a dense homogeneous hematoma >30% of the ischemic lesion volume with significant space-occupying effect.

Serial study of gadolinium-DTPA MRI enhancement in multiple sclerosis.

We performed serial baseline and gadolinium (Gd)-DTPA-enhanced MRI in 4 patients with definite multiple sclerosis. Studies were performed every month for a total of 4 scans. We obtained short TR/short TE sequences at 10 and 60 minutes after Gd-DTPA injection. All patients had multiple hyperintense lesions seen on baseline MRI with long TR/short and long TE. There was Gd-DTPA enhancement in new, enlarging, and preexisting lesions that were unchanged in size. The enhancing lesions were always seen on T2-weighted images. There was no difference in enhancement between the 10- and 60-minute studies. Six of 85 preexisting lesions enhanced whereas all new or enlarging lesions enhanced. Enhancement persisted in only 1/3 of the new or enlarging lesions, suggesting that MR enhancement is a transient phenomenon due to local temporary blood-brain barrier breakdown. Our data indicate that Gd-DTPA enhancement monitoring is more sensitive than unenhanced MRI for detecting disease activity in MS.

Internal borderzone infarction following acute middle cerebral artery occlusion.

In 36 patients suffering acute middle cerebral artery (MCA) occlusion, we studied the angiographic findings within 6 hours of the ictus and the chronic CT results at 3 months. Seven patients suffering distal pial MCA branch occlusion developed a pattern of internal borderzone infarction on follow-up CT. Carotid artery or carotid siphon stenosis or occlusion was absent in all seven. Proximal MCA branch occlusions, prior to the origin of the lenticulostriate arteries, were associated with extensive cortical and deep infarction in the entire MCA territory in 14 patients. There was proximal carotid artery or siphon stenosis or occlusion in 12 of these 14 patients. The remaining 15 patients showed a mixture of proximal and distal MCA occlusions and patchy ischemic damage in the MCA territory. There were no cases of superficial cortical watershed infarction. These data show that internal borderzone infarctions may result from intracranial MCA branch occlusions alone and need not be associated with hemodynamic alterations due to large vessel extracranial disease.

Transcranial Doppler in acute hemispheric brain infarction.

We studied cerebrovascular anatomy using intra-arterial digital angiography, and blood flow velocity in the middle cerebral artery (MCA) using transcranial Doppler (TCD) ultrasonography in 42 patients with acute hemispheric ischemic brain infarction. We compared angiography with TCD and the clinical findings within 6 hours of the onset of symptoms. The location and extent of the chronic ischemic brain damage was assessed by CT performed 1 to 3 months after the ictus. Abnormal TCD, as manifested by either an unobtainable MCA flow signal or a significantly depressed MCA flow velocity, was highly associated with proximal MCA occlusions demonstrated by angiography. Abnormal TCD predicted both larger chronic CT lesions and more extensive ischemic change within the MCA territory. These data demonstrate that early TCD conveys useful information concerning cerebral tissue prognosis following hemispheric ischemia.

Effect of steroids on Gd-enhancing lesions before and during recombinant beta interferon 1a treatment in relapsing remitting multiple sclerosis.

The aim of this study was to investigate whether a concomitant treatment with recombinant interferon beta 1a (rIFN beta-1a) modifies the effect of steroids on the blood-brain barrier (BBB) in relapsing remitting MS patients, as evaluated by enhanced MRI of the brain. We evaluated 19 patients with a clinical relapse treated only with intravenous methylprednisolone (IVMP; 1 g daily for 6 days), and 10 patients who experienced a clinical relapse and were treated with IVMP (1 g daily for 6 days) during an rIFN beta-1a treatment period. The number and volume of enhancing lesions were analyzed on four serial MR images obtained at monthly intervals (one scan before and three scans after IVMP treatment). A significant reduction in the mean number and volume of enhancing lesions was seen in the first scan after IVMP treatment in all patients. However, while persistently low enhancement was seen in the follow-up scans of patients treated with rIFN beta-1a, a rebound effect (i.e., increase in the number and volume of gadolinium-enhancing lesions) was observed in the other patients during the follow-up. These data suggest that rIFN beta-1a prolongs the beneficial effect of steroids on the BBB.

Hemorrhagic transformation of brain infarct: predictability in the first 5 hours from stroke onset and influence on clinical outcome.

OBJECTIVE: To identify, in the first 5 hours of acute brain infarct, clinical and radiologic predictors of subsequent hemorrhagic transformation (HT), and to evaluate its influence on the clinical course. BACKGROUND: The identification of early predictors of HT might be important to plan antithrombotic or thrombolytic treatments. PATIENTS: One hundred fifty consecutive patients with cerebral anterior circulation infarct systematically underwent a first CT within 5 hours of onset. During the first week after stroke, we performed a repeat CT or autopsy to look for HT. Outcome measures were early neurologic deterioration within the first week of onset and 30-day case fatality rate and disability. RESULTS: HT was observed in 65 patients (43%): 58 (89%) had a petechial HT and seven (11%) a hematoma. Among initial clinical an CT findings, the only independent predictor of HT was early focal hypodensity. Its presence was associated with subsequent HT in 77% of cases (95% CI, 68 to 86%), whereas its absence predicted the absence of subsequent HT in 94% of cases (95% CI, 89 to 99%). No baseline clinical or CT characteristic differentiated patients with petechial HT from those with hematoma. Antithrombotic and antiplatelet agents did not influence the occurrence of either type of HT. The frequency of early neurologic deterioration and of 30-day death or disability in HT patients was twice as high as in those without HT. However, a large-sized infarct and the presence of mass effect at the repeat CT or autopsy were the only factors independently linked to both the outcome events, irrespective of the development of HT. Clinical evolution of HT patients given antithrombotics was comparable with that of HT patients not receiving these drugs. CONCLUSIONS: HT of a brain infarct is a common event that occurs independently of anticoagulation and can be reliably predicted as early as 5 hours from stroke onset by the presence of focal hypodensity at CT. Apart from the infrequent cases of massive hematoma, HT does not influence prognosis, whereas a poor outcome in HT patients is correlated with a higher frequency of large edematous infarcts in this subgroup. The clinical course and final outcome of HT in anticoagulated patients does not differ from that of non-anticoagulated HT patients.

fMRI/EEG in paroxysmal activity elicited by elimination of central vision and fixation.

Using functional MRI (fMRI) with concurrent EEG monitoring the authors studied cortical activation associated with epileptiform discharges in three patients with fixation-off sensitivity. The EEG paroxysmal activity elicited by eliminating central vision correlated significantly with an increased blood oxygen level-dependent signal in the extrastriate cortex (Brodmann areas 19 and 37). fMRI provides a unique opportunity for localizing precisely the cortical areas generating paroxysmal activity in patients with fixation-off sensitivity.

Presurgical integrated MRI/SPECT localization of the sensorimotor cortex in a patient with a low-grade astrocytoma in the rolandic area.

We describe the case of a young man who, despite the presence of a tumour in the left sensorimotor cortex, exhibited no motor deficit. Integrated MRI/SPECT-CBF study during motor activation was aimed at determining which cerebral areas were involved in movement execution in this patient and their relationship with the tumour. CBF changes during motor activation were located in two motor areas: anteriorly and medially to the tumour in the left frontal lobe (+29%) and in the right medial frontal cortex (+43%). Integrated MRI/SPECT images provided both an anatomical and functional definition of the motor areas in a patient with a rolandic tumour and could prove useful in determining preoperatively an appropriate surgical strategy.

Ischaemic supratentorial stroke: angiographic findings in patients examined in the very early phase.

Eighty patients were studied by angiography within 6 h of an ischaemic stroke. Angiography was carried out with digital equipment and was usually limited to the vascular territory responsible for the neurological deficits. In 12 of 19 patients with internal carotid occlusion, the contralateral side was also studied. The angiographic abnormalities were classified as extracranial, intracranial, and combined extra and intracranial. The data show a high incidence (66%) of occlusive pathology of intracranial arteries, either isolated or associated with a significant presence of a potential embolic source (85%), and a high incidence of carotid occlusions located at the cervical segment (8 of 19). These observations suggest that most strokes are occlusive in origin.

Quantitative magnetic resonance analysis in vascular dementia.

The potential role of magnetic resonance imaging (MRI) in differentiating between specific causes of cognitive decline in patients with vascular dementia (VD) has not yet been fully established. We therefore decided to assess the supratentorial cerebral contents in 24 patients with a diagnosis of probable VD and in 24 normal subjects, matched for age and education level, using MRI volumetric parameters obtained by means of a quantitative method. The volumes of subarachnoid and ventricular spaces, cerebral tissue, and hyperintense areas on T2-weighted images were calculated. In order to reduce interindividual variability caused by differences in intracranial size, each absolute measurement was normalized to the relative size of the intracranial volume. In addition, we calculated the ratio between the areas of the corpus callosum (CC) and supratentorial brain at the same level on the T1-weighted image midsagittal plane. The MRI data were correlated with the deterioration of cognitive functions. Patients with VD showed significantly lower cerebral tissue volume and CC area, and higher ventricular space volume than normal subjects. Furthermore, the total volume of the T2 signal alterations was higher in VD patients than in normal subjects. In VD patients, this volume was found to be proportional to the increase in the volume of the ventricular space. On the other hand, no correlation was found between the volume of the T2 signal alterations and the area of the CC. The degree of global cognitive dysfunction and the score of each neuropsychological test did not show any correlation with the MRI data. Our results suggest that ventricular enlargement in VD patients is correlated with the increase in volume of the T2 signal abnormalities, but that the degree of global cognitive dysfunction is not influenced by the volume of these T2 signal abnormalities. Furthermore, the CC atrophy does not influence the score of any neuropsychological test or the degree of global cognitive dysfunction.

Correlation of angiographic and sequential CT findings in patients with evolving cerebral infarction.

The usefulness of CT and angiography for predicting the final ischemic brain damage resulting from supratentorial ischemic stroke was evaluated in 36 patients. CT was performed within 4 hr and angiography within 6 hr after the onset of symptoms. CT was used to assess the site and size of parenchymal brain damage and angiography was used to evaluate the cerebral circulation. A 3-month follow-up CT study was used to determine the site and size of final ischemic damage. Angiography was normal in six patients and showed complete occlusion in 30. Angiographic findings in patients with arterial occlusion were classified as either internal carotid artery occlusion or middle cerebral artery (MCA) occlusion. MCA occlusions were subdivided into occlusion before the origin of internal lenticulostriate arteries (type 1), occlusion beyond the origin of these branches (type 2), occlusion at the bifurcation of the main trunk (type 3), and occlusion of the peripheral branches (type 4). Collateral blood supply was also studied. Early CT findings were positive in 25 of 36 patients; the lentiform nucleus alone, the lentiform nucleus and the cortex, or only the cortex were involved. In all patients with positive early CT findings, angiography showed an arterial occlusion, often located in the main trunk of the MCA. Involvement of the lentiform nucleus on early CT was always seen in patients with internal carotid artery or type 1 MCA occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhanced and unenhanced MR with magnetization transfer in multiple sclerosis.

PURPOSE: To evaluate the use of magnetization transfer and the apparent enhancement of lesions on contrast-enhanced MR images in patients with multiple sclerosis. METHODS: Contrast-enhanced T1-weighted spin-echo MR images obtained in 20 patients with relapsing-remitting multiple sclerosis, with and without magnetization transfer, were evaluated to determine the number of enhancing plaques. Comparison was made with unenhanced T1-weighted magnetization transfer images. Contrast-to-noise ratios were obtained for these lesions on both the enhanced and unenhanced magnetization transfer T1-weighted spin-echo MR images. RESULTS: Ten plaques were considered enhancing only when the enhanced magnetization transfer T1-weighted images (11% or more) were used; however, they were all hyperintense on unenhanced T1-weighted magnetization transfer images. The contrast-to-noise ratios of these lesions were 16.52 for the enhanced images and 15.65 for the unenhanced images. The two values were not statistically different. CONCLUSIONS: In patients with multiple sclerosis, examination with contrast-enhanced magnetization transfer MR images alone may overestimate the number of enhancing plaques.

Early angiographic and CT findings in patients with hemorrhagic infarction in the distribution of the middle cerebral artery.

Hemorrhagic infarction subsequent to ischemic brain damage, even if small, slight, or marbled, can be detected by CT. The mechanisms that give rise to this transformation in humans are not well elucidated. Previous reports indicate that hemorrhagic infarction is most common in embolic stroke and large infarcts, and can worsen the clinical state of ischemic patients. We examined 36 patients with supratentorial ischemic signs and symptoms within the first hours after onset. CT was used to judge if hypodensity on early CT studies might predict the development of hemorrhagic infarction. Angiography was used to observe the site of arterial occlusion, the state of collateral circulation, and the mechanisms of late reperfusion. Hemorrhagic infarction was present in 18 of our 36 patients. Angiography revealed occlusion of the middle cerebral artery or internal carotid artery (three cases) in all patients. Hypodensity was present on early CT studies in all of the 18 patients who developed hemorrhagic infarction. The finding of hypodensity on CT studies performed soon after embolic ischemic stroke is strongly predictive of hemorrhagic transformation.

Relationship between vascular enhancement, cerebral hemodynamics, and MR angiography in cases of acute stroke.

BACKGROUND AND PURPOSE: The use of MR angiography and contrast-enhanced T1-weighted MR imaging in cases of acute cerebral ischemia may be helpful in the evaluation of middle cerebral artery (MCA) occlusion and leptomeningeal collaterals, respectively. The aim of our work was to investigate the relationship between MCA occlusion, T1-weighted vascular contrast enhancement, hemodynamic alterations, and tissue damage in cases of acute ischemic stroke. METHODS: We studied the MCA territory in 15 patients with acute ischemic stroke within 8 hr of symptom onset. The first MR imaging study (<8 hr after onset) comprised diffusion-weighted imaging, MR angiography, perfusion-weighted imaging, and contrast-enhanced T1-weighted MR imaging sequences. Follow-up MR imaging, performed 1 week later, consisted of MR angiography and T2-weighted fluid-attenuated inversion recovery MR imaging. RESULTS: Early MR angiography showed MCA stem occlusion in nine of 15 patients. Patients with MCA occlusion had significantly larger areas of abnormality on early diffusion-weighted images, significantly larger areas of altered hemodynamics, larger final lesion volumes, and poorer clinical outcome. Among the nine patients with MCA stem occlusion, vascular enhancement was marked in seven and absent in two who had complete MCA infarcts and poor clinical outcome. Among patients with MCA patency, vascular enhancement was marked in only one, mild in four, and absent in one. Patients with marked vascular enhancement had significantly larger regions of altered hemodynamics and significantly higher asymmetries in both regional cerebral blood volume and mean transit time because of increased values in the affected hemisphere. CONCLUSION: Among patients with stroke with MCA occlusion, marked vascular enhancement and increased blood volume indicate efficient leptomeningeal collaterals and compensatory hemodynamic mechanisms.

Cerebral hemodynamics on MR perfusion images before and after bypass surgery in patients with giant intracranial aneurysms.

BACKGROUND AND PURPOSE: Preoperative assessment of the anatomy and dynamics of cerebral circulation for patients with giant intracranial aneurysm can improve both outcome prediction and therapeutic approach. The aim of our study was to use perfusion MR imaging to evaluate cerebral hemodynamics in such patients before and after extraintracranial high-flow bypass surgery. METHODS: Five patients with a giant aneurysm of the intracranial internal carotid artery underwent MR studies before, 1 week after, and 1 month after high-flow bypass surgery. We performed MR and digital subtraction angiography, and conventional and functional MR sequences (diffusion and perfusion). Surgery consisted of middle cerebral artery (MCA)-internal carotid artery bypass with saphenous vein grafts (n = 4) or MCA-external carotid artery bypass (n = 1). RESULTS: In four patients, MR perfusion study showed impaired hemodynamics in the vascular territory supplied by the MCA of the aneurysm side, characterized by significantly reduced mean cerebral blood flow (CBF), whereas mean transit time (MTT) and regional cerebral blood volume (rCBV) were either preserved, reduced, or increased. After surgery, angiography showed good canalization of the bypass graft. MR perfusion data obtained after surgery showed improved cerebral hemodynamics in all cases, with a return of CBF index (CBFi), MTT, and rCBV to nearly normal values. CONCLUSION: Increased MTT with increased or preserved rCBV can be interpreted as a compensatory vasodilatory response to reduced perfusion pressure, presumably from compression and disturbed flow in the giant aneurysmal sac. When maximal vasodilation has occurred, however, the brain can no longer compensate for diminished perfusion by vasodilation, and rCBV and CBFi diminish. Bypass surgery improves hemodynamics, increasing perfusion pressure and, thus, CBFi. Perfusion MR imaging can be used to evaluate cerebral hemodynamics in patients with intracranial giant aneurysm.

Fast spin-echo and fast fluid-attenuated inversion-recovery versus conventional spin-echo sequences for MR quantification of multiple sclerosis lesions.

PURPOSE: To compare fast spin-echo (FSE) and fast fluid-attenuated inversion recovery (FLAIR) sequences with conventional spin-echo (CSE) MR imaging in the quantification of the number and volume of multiple sclerosis lesions. METHODS: In 30 patients with relapsing-remitting multiple sclerosis, we calculated the total number and volume of lesions detected with each of the three sequences using a semiautomated program. RESULTS: On CSE sequences, we calculated a total of 2,583 lesions with a global volume of 836.3 cm3. With FSE sequences, we observed a 16% relative reduction in the number of lesions detected and a 25% relative reduction in global volume as compared with CSE. With fast FLAIR sequences, we detected a significantly lower number and volume of infratentorial lesions, whereas at the cortical/subcortical level the lesions were both more numerous and bulkier than on CSE sequences. Finally, we observed a higher lesion/white matter contrast, a significant reduction in time required for the quantification of lesion load, and a very low interobserver variability in favor of fast FLAIR sequences. CONCLUSION: Despite its limitations in the detection of infratentorial lesions, the fast FLAIR sequence in conjunction with a semiautomated quantification program provides a reliable means to evaluate the total lesion burden in patients with MS.

Clinical and instrumental evaluation of patients with ischemic stroke within the first six hours.

The development of fibrinolytic agents such as streptokinase and recombinant tissue type plasminogen activator (r-TPA) and other modalities of treatment in acute ischemic stroke, has raised the need for a more precise knowledge of the pathophysiology of the acute phases of ischemic stroke as it pertains to prediction of clinical outcome. In a prospective analysis, 80 patients were studied within less than 6 h from the onset of symptoms by means of a detailed protocol including clinical evaluation, cerebral computed tomography, digital angiography and ultrasound transcranial Doppler sonography. Early angiography revealed a complete arterial occlusion in 76% of cases, the majority of which were intracranial (66%). Seventy percent of the occlusions that were retested were removed within 1 week. Potential embolic sources were found in more than 80% of cases. Patients with documented intracranial occlusion and scarce or absent collateral filling at early angiography, had the worst clinical outcome (P less than 0.05), based on mortality data and the Canadian Neurological Scale. The 30-day mortality rate was 25%. Survival was significantly better (P less than 0.01) in patients with a Canadian Neurological Score on entry of greater than or equal to 6.5 than in patients with a less than 6.5 value. Our data indicate that early pathophysiological studies augment the clinical information and should be taken into account in the design and analysis of therapeutic trials of acute ischemic stroke.

Relationship between corpus callosum atrophy and cerebral metabolic asymmetries in multiple sclerosis.

Corpus callosum (CC) atrophy by magnetic resonance imaging (MRI) is a common finding in multiple sclerosis (MS). In order to examine the relationship between CC atrophy and cortical brain metabolism, we compared the cerebral metabolic rates for glucose (CMRglc), measured by positron emission tomography (PET), of 8 MS patients with evidence of CC atrophy on midsagittal MRI, 8 MS patients without CC atrophy and 10 healthy controls. Results showed no significant differences in supratentorial CMRglc absolute values between the three groups, although a slight metabolic reduction was observed in both MS groups compared with normal controls. By contrast, only patients with CC atrophy showed greater directional metabolic asymmetry than normals, the left frontal, temporal and parietal association cortices being significantly lower than the right. Predominant left hemispheric metabolic reductions were not accompanied by a corresponding left-sided predominance in the extent of MRI-detected demyelinating lesions. Therefore our data suggest that CC atrophy interfers more with left than with right metabolic function.