Role of multidetector CT in the recognition of hyperdense middle cerebral artery sign (HMCAS) in patients with acute cerebral ischaemia: correlation with DWI-MRI sequences and clinical data.

PURPOSE: The aim of this study was to verify the sensitivity and specificity of the hyperdense middle cerebral artery sign (HMCAS) obtained by multidetector computed tomography (CT) in predicting acute stroke, using diffusion-weighted (DW) magnetic resonance imaging (MRI) as a reference. The location of the HMCAS, the extension of the ischaemic lesion and its prognostic value were also assessed. MATERIALS AND METHODS: The CT examinations of 654 patients with symptoms related to acute cerebral stroke were retrospectively reviewed. DW-MRI confirmed recent stroke in 175 patients. Two expert neuroradiologists analysed the CT examinations of these patients in four phases. Sensitivity, specificity and interobserver reliability was evaluated. Patients were divided into three groups according to the HMCAS site (M1-M2-M3) and the Alberta Stroke Program Early CT Score (ASPECTS) on DW-MRI was calculated. The ASPECTS average score was correlated with the National Institutes of Health Stroke Scale (NIHSS) and modified Rankin scale (mRS) at 3 months. RESULTS: In 41 patients, the presence of HMCAS was confirmed (71 % sensitivity; 100 % specificity; Interobserver reliability k, 84 %). An inverse correlation was found by comparing the ASPECTS and NIHSS scores (Rsq = -0.206). After logistic regression analysis, HMCAS was found to be independently associated with a poor outcome (mRS >2) at 3 months after adjusting for age, NIHSS on admission, risk factors and aetiology of stroke. CONCLUSIONS: Our study demonstrated that HMCAS obtained with multidetector CT can be detected in more than 70 % of patients with large acute ischaemic lesion and it is an unfavourable prognostic sign.

Asymmetric posterior reversible encephalopathy syndrome in patient with hyperplastic anterior choroidal artery.

We describe a case of asymmetric PRES due to the presence of hyperplastic anterior choroidal artery (AChA) in a man affected by sever hypertension. Posterior reversible encephalopathy syndrome (PRES) has become synonymous with a unique pattern of brain vasogenic edema and predominates in the parietal and occipital regions, accompanied by clinical neurological alterations. Sever hypertension is a risk factor that exceeds the limits of brain autoregulation, leading to breakthrough brain edema. In our knowledge this is the first case reported in literature, in which a similar vascular abnormality is linked to a PRES syndrome.

Identification of the pyramidal tract by neuronavigation based on intraoperative magnetic resonance tractography: correlation with subcortical stimulation.

OBJECTIVE: To demonstrate the accuracy of magnetic resonance tractograpghy (MRT) in localizing the cortical spinal tract (CST) close to brain tumours by using intraoperative electric subcortical stimulation. METHODS: Nine patients with intra-axial brain tumours underwent neurosurgery. Planning was based on analysis of the course of streamlines compatible with the CST. After tumour removal, intraoperative MRT was reacquired. Sites at various distance from the CST were repeatedly stimulated to assess whether registered motor evoked potential (MEP) could be elicited. All patients were assessed clinically both pre- and postoperatively. RESULTS: The motor function was preserved in all patients. In all patients intraoperative MRT demonstrated shift of the bundle position caused by the surgical procedure. The distance between the estimated intraoperative CST and the point of elicited MEP was 1 cm or less in all nine patients. At distances greater than 2 cm, no patient reported positive MEP. CONCLUSION: Intraoperative MRT is a reliable technique for localization of CST. In all patients MEP were elicited by direct subcortical electrical stimulation at a distance below 1 cm from the CST as represented by MRT. Brain shifting might impact this evaluation since CST position may change during surgery in the range of 8 mm.

A cervical flexion-extension MRI study in Down syndrome.

OBJECTIVE: To assess what kind of information MR examination in flexed and extended positions provides in Down syndrome subjects with suspected cranio-cervical instability. METHODS: Between 2005 and 2008, 35 subjects with DS were recruited in the study. Ethics committee approval was granted and a signed informed consent was obtained from the parents. All the subjects were affected by hypotonic status and ligament laxity established by clinical evaluation, but were asymptomatic about focal neurological symptoms due to medullar damage caused by cranio-cervical instability. Each patient underwent lateral supine radiographs and MR imaging in the neutral, active flexed and extended positions. For evaluating the atlanto-axial and atlanto-occipital joint stability, multiple measurements were calculated. RESULTS: A significant reduction of anterior subarachnoid space in flexed position was evident in DS subjects compared to healthy controls in neutral and flexed positions. Both, space available for cord and ligamentous thickness showed significant differences between DS subjects and healthy controls. In DS subjects with occipito-cervical instability, the anterior subarachnoidal space reduction was significantly reduced in flexed position. CONCLUSIONS: In DS subjects with asymptomatic cranio-cervical instability, anterior subarachnoidal evaluation and ligamentous status could add new information about the risk of spinal cord damage.

Hemodynamic modifications in patients with symptomatic unilateral stenosis of the internal carotid artery: evaluation with MR imaging perfusion sequences.

BACKGROUND AND PURPOSE: Risk of developing ischemia is higher in patients with reduced cerebrovascular reactivity than in those with preserved cerebrovascular reactivity. Therefore, we assessed cerebral hemodynamic modifications in patients with unilateral stenosis of the internal carotid artery by using perfusion-weighted MR imaging to determine if these modifications underlie or anticipate ischemic signs and symptoms. METHODS: Fifteen patients with unilateral 70-90% carotid artery stenosis were studied with digital subtraction angiography and perfusion-weighted MR imaging. Their findings were compared with those of 15 age- and sex-matched control subjects. Regional cerebral blood volume (rCBV) and mean transit time (MTT) values were calculated in the middle cerebral artery and border zone territories. RESULTS: No significant difference was noted in rCBV and MTT values between the hemispheres in the symptomatic patients. There was a significant difference in MTT values in the border zones between patients and control subjects. MR images in patients and control subjects did not reveal large territorial infarcts and did reveal similar white matter lesion burdens. CONCLUSION: There is adequate compensation of unilateral stenosis when the stenosis is less than 90%. The risk of stroke is higher in patients with stenoses exceeding 70%, mostly because of decreased collateral reserve when confronted with emboli.

Cardiac magnetic resonance evaluation of the impact of interventricular and intraventricular dyssynchrony on cardiac ventricular systolic and diastolic function in patients with isolated left bundle branch block.

Ventricular dyssynchrony significantly impairs cardiac performance. However, the independent role of interventricular dyssynchrony (interVD) and intraventricular dyssynchrony (intraVD) in the development of abnormalities of systolic and diastolic performance is unclear. Cardiac magnetic resonance imaging was performed in 39 patients with left bundle branch block and 13 healthy patients. Structural and functional parameters of the left ventricle and degrees of interVD and intraVD were measured. We found that interVD was inversely correlated with left ventricular (LV) ejection fraction (r = -0.8, p <0.0001) and positively correlated with LV end-diastolic volume (r = 0.4, p <0.01), LV end-systolic volume (r = 0.6, p <0.0001), and LV mass (r = 0.4, p <0.01), thus indicating that interVD significantly affects systolic function and favors ventricular remodeling. Multivariate analysis further confirmed that interVD was an independent predictor of systolic dysfunction. Interestingly, we found that interVD was not associated with abnormalities of diastolic performance. Conversely, we found that intraVD significantly impaired diastolic function, whereas it had no effect on systolic function. IntraVD was inversely correlated with peak filling rate (r = -0.7, p <0.0001) and 1/2 filling fraction (r = 0.4, p = 0.04) and positively correlated with time to peak filling rate (r = 0.6, p <0.0001), validated parameters of diastolic function. Multivariate analysis confirmed that intraVD was an independent predictor of diastolic dysfunction. In conclusion, our study suggests that the 2 components of ventricular dyssynchrony differently affect cardiac performance. If confirmed in prospective studies, our results may help to predict the prognosis of patients with left bundle branch block and different degrees of interVD and intraVD, particularly those subjects undergoing cardiac resynchronization therapy.

Selective white matter involvement in a patient with late onset Krabbe disease: MR, MR spectroscopy, and diffusion tensor study.

The most frequent type of Krabbe disease has an infantile onset. Unusual slowly progressive adult forms have also been described. We described a different involvement of white matter tracts where magnetic resonance signal alterations were evident in a case of a patient affected by late-onset form of disease.

Fiber density index, fractional anisotropy, adc and clinical motor findings in the white matter of patients with glioblastoma.

Whether fractional anisotropy (FA), apparent diffusion coefficient (ADC), and fiber density index (FDi) values differ in the white matter close to glioblastomas of both symptomatic and asymptomatic patients was investigated. Twenty patients with glioblastomas underwent magnetic resonance imaging study. The FDi, FA and ADC values were calculated in areas of white matter in close proximity to the tumor (perWM) and encompassing fibers of cortico-spinal tract and in the contralateral normal-appearing white matter (nWM). The clinical compromise of the cortico-spinal tract was graded using Brunnstrom's criteria. FA and FDi were significantly decreased and ADC increased in perWM compared with the contralateral. Mean FDi, FA, and ADC values comparing perWM and nWM in symptomatic patients showed similar differences. Comparing the perWM of symptomatic and asymptomatic patients, mean FDi and ADC values were lower in symptomatic patients than in asymptomatic ones. A positive correlation was found between the clinical score (CS) and, separately, FDi, FA and ADC per WM values. In a multiple stepwise regression among the same factors, only the ADC of perWM values showed a positive correlation with the CS. An increased ADC plays a major role in reducing the number of fibers (reduced FDi) in symptomatic patients.

Long term evaluation of brain perfusion with magnetic resonance in high flow extracranial-intracranial saphenous graft bypass.

Assessment was made of the cerebral vascular haemodynamic parameters in patients with a high-flow extra-intracranial (EC-IC) bypass performed for therapeutic occlusion of the internal carotid artery (ICA). Sixteen patients with ICA occlusion and EC-IC bypass (time interval from surgery 1-6 years) underwent MRI. Perfusion-weighted magnetic resonance imaging (PW-MRI) sequences were performed without the use of an arterial input function. The relative cerebral blood volume (rCBV), mean transit time (MTT) and relative cerebral blood flow (rCBF) were evaluated in all patients at the level of the basal ganglia, centrum semiovale and cortex in both hemispheres. Statistically significant differences (P<0.005) were observed in the haemodynamic parameters, indicating increased rCBV in the basal ganglia and decreased rCBF and rCBV in the cortex of the hemisphere supplied by the graft with respect to the contralateral. Patients with occlusion of the ICA and high flow EC-IC bypass do have altered vascular haemodynamic status between the hemispheres. In particular, rCBF is impaired in the surgical hemisphere at the level of the cortex. These patients should be followed-up to rule out chronic ischemia.

Migraine with aura, bipolar depression, ACM aneurysm. A case report.

B.D. is a 48-year-old professional woman. She has been suffering for migraine since she was 28, but she did not have serious problems until last year, when headache episodes became more frequent and it was necessary an admission to emergency room. At the beginning, the events were about 6 per month, lasting from 2 to 4 days, beating and of high intensity together with nausea, vomit, photo and phonophobia and visual area. Looking at the anamnesis, we report a psychiatric treatment since about ten years, because of type II bipolar disorder. In spite of the psychopharmacological treatment, as the patient came in our Regional Headache Center, she talked about 7 events with aura (scintillating scotomas, emianopsia) per month, lasting 2-4 days with photo and phonophobia, nausea, crying crisis, anxiety. Although the neurological examination was normal, the sudden aggravation of pain symptomatology and the unresposiveness to usual painkillers, suggested a cerebral CT and CT-angiography. CT and CT-angiography discovered the presence of an aneurysm of the right middle cerebral artery (MCA) of 4 mm diameter, with parietal irregularities. The patient was operated to reduce the hemorrhagic risk, with a positive result. One year after the operation, the patient reports a decrease of headache events with a frequency of 2 per month, lasting only a few hours, which she can now solve with COXIB.

Magnetic resonance imaging in Posterior Reversible Encephalopathy Syndrome: report of three cases and review of literature.

INTRODUCTION: Eclampsia is one of the main causes of Posterior Reversible Encephalopathy Syndrome (PRES) a recent clinico-neuroradiological entity represented by characteristic MR findings of a symmetric bilateral subcortical/cortical hyperintensity in T2-weighted images, more often in parieto-occipital lobes, accompanied by clinical neurological alterations. Neuroradiological and clinical alterations are commonly completely reversible although ischemic evolution has been described. The pathophysiology is still a matter of debate. Specific magnetic resonance (MR) techniques, such as FLAIR (fluid attenuated inversion recovery) and DWI (diffusion weighted images) sequences, have improved the ability to detect subcortical/cortical lesions and helped to clarify the underlying pathophysiological mechanism of cerebrovascular involvement, which results important for an appropriate therapeutic decision. CASE REPORT AND DISCUSSION: We report the MR imaging findings of three patients with eclampsia and PRES as well as a careful review of literature.

Role of contrast-enhanced MR venography in the preoperative evaluation of parasagittal meningiomas.

Parasagittal meningiomas (PSM) may pose a difficult surgical challenge since venous patency and collateral anastomoses have to be clearly defined for correct surgical planning. The aim of this study was to assess the diagnostic value of contrast-enhanced (CE) magnetic resonance venography (MRV) in the preoperative evaluation of venous infiltration and collateral venous anastomoses in patients with PSM. CE-MRV was compared with phase-contrast (PC) magnetic resonance (MR) angiography, conventional angiography (when available), and surgery as a reference. Twenty-three patients undergoing surgery for meningiomas located adjacent to the superior sagittal sinus were prospectively evaluated. All the patients underwent both conventional MR examination and MRV. This was performed by means of PC and CE techniques. Both sets of angiograms (CE and PC) were evaluated by two expert neuroradiologists to assess (1) patency of the sinus (patent/occluded), (2) the extent of occlusion (in centimeters), and (3) the number of collateral anastomoses close to the insertion of the meningioma. Eight patients underwent digital subtraction angiography (DSA). All patients were operated on, and intraoperative findings were taken as the gold standard to evaluate the diagnostic value of MRA techniques. PC-MRV showed a flow void inside the sinus compatible with its occlusion in 15 cases, whereas CE-MRV showed the sinus to be occluded in five cases. CE-MRV data were confirmed by surgery, showing five patients to have an occlusion of the superior sagittal sinus. The PC-MRV sensitivity was thus 100% with a specificity of 50%. In those cases in which both MRV techniques documented occlusion of the sinus, the extent of occlusion was overestimated by PC compared with CE and surgery. CE-MRV depicted 87% of collateral venous anastomoses close to the meningioma as subsequently confirmed by surgery, while PC showed 58%. In the preoperative planning for patients with meningiomas located close to a venous sinus, CE-MRV provides additional and more reliable information concerning venous infiltration and the presence of collateral anastomoses compared with PC sequences.

Cerebrospinal fluid changes after intravenous injection of gadolinium chelate: assessment by FLAIR MR imaging.

Fluid-attenuated inversion recovery (FLAIR) sequence is currently used in clinical practice. Some reports emphasize the possibility that, in pathologic conditions, intravenous injection of gadolinium chelates may lead to an increased signal inside the cerebrospinal fluid (CSF). The aim of this study was to evaluate the presence of CSF signal changes in pathologic conditions causing blood-brain barrier disruption or neovascularization when imaging is performed after intravenous injection of gadolinium. We obtained FLAIR sequences after gadolinium injection from 33 patients affected by different intracranial pathologies and 10 control subjects. Patients were affected by ischemic stroke in the subacute phase, from 2 to 7 days from onset of symptoms (12 patients), meningiomas (8 patients), high-grade gliomas (5 patients), previous surgical procedures for intra-axial neoplasms (5 patients), and multiple sclerosis with active plaques (3 patients). Magnetic resonance imaging was performed in patients and controls using a 1.5-T magnet, using T2- and T1-weighted FLAIR sequences. The FLAIR sequence was acquired before and 1-3 h after injection of a standard dose of gadolinium. In those patients affected by ischemic lesions, FLAIR sequences were repeated the next days and 3-4 days later. The CSF signal was visually evaluated by two readers and scored from 0 to 3 depending by the degree of enhancement. The location of CSF signal changes (close to the lesion, hemispheric, or diffuse) was also considered. The CSF signal was markedly increased after 3 h from intravenous injection of gadolinium in all the patients with stroke, in those with previous surgery, and in those with high-grade gliomas whose neoplasm's surface was in contact with the subarachnoid spaces (SAS) or ventricles; a strong enhancement was also evident inside the necrotic component of the tumor. The CSF changes were more evident close to the pathology and/or in the hemisphere involved by the pathology. Moderate CSF enhancement was observed in the SAS close to meningiomas. No signal changes were evident in all the others. In those patients with stroke imaged in the following days, CSF signal showed to be diffuse to both hemispheres the next day and returned to normal values within 2 days. In patients affected by pathologies with blood-brain barrier breakdown or neovascularization close the SAS or the ventricles, CSF changes, related to gadolinium leakage, are likely when FLAIR sequences are acquired 2-24 h after i.v. injection of the contrast. This pattern should be known in order to differentiate it from that of subarachnoid hemorrhage.

Diffusion-weighted MR imaging in the early diagnosis of periventricular leukomalacia.

Diffusion-weighted imaging (DWI) has been shown to be highly sensitive in detecting acute cerebral infarction, but its use in detecting hypoxic-ischemic encephalopathy (HIE) in neonates is still controversial. Moreover, few reports concern pre-term infants with possible periventricular leukomalacia (PVL). We examined the ability of this technique to detect cerebral changes in the acute phase of PVL. Fifteen MR examinations were performed in 11 pre-term infants (mean age 3.4 days, range 2-6 days). Conventional DWI sequences, apparent diffusion coefficient (ADC) maps, and US obtained in the acute phase were compared. All the neonates underwent US follow-up up to 4 months after delivery; those with suspected PVL also underwent MRI follow-up for up to 2 months. Qualitative and quantitative evaluations were performed to assess the presence of DW changes compatible with PVL. Diffusion-weighted MRI showed signal hyperintensity associated with decreased ADC values in 3 subjects (27%). In these patients conventional MRI sequences were interpreted as normal and US (performed at the same time) as doubtful in 2 and compatible with PVL in 1 subject. The MRI and US follow-up confirmed severe damage in all these patients. In 1 neonate hemorrhages involving the germinative matrix were identified. In 8 neonates MRI was considered normal. In these subjects US follow-up (up to 4 months) confirmed no signs of PVL. Diffusion-weighted imaging may have a higher correlation with later evidence of PVL than does conventional MR imaging and US when performed in the acute phase of the disease.

Diffusion-weighted MR Imaging: clinical applications in neuroradiology.

Among functional magnetic resonance imaging techniques, diffusion-weighted imaging (DWI) plays an important role in the assessment of a wide variety of brain diseases. DWI provides image contrast that depends on the molecular motion of water and it can be easily added to a standard cranial MR examination, with limited increase in time (imaging time ranges from a few seconds to 2 minutes). DWI is particularly sensitive in the detection of acute ischaemic stroke and in monitoring its evolution (also in the light of new therapeutic strategies for early treatment). Diffusion-weighted MR imaging also provides adjunctive information in the differential diagnosis of other brain diseases including neoplasms, intracranial infections, traumatic brain injury and demyelination some of which may manifest with sudden neurological deficits mimicking acute ischaemic stroke.