Large Neck and Strong Ostium Inflow as the Potential Causes for Delayed Occlusion of Unruptured Sidewall Intracranial Aneurysms Treated by Flow Diverter

BACKGROUND AND PURPOSE

Flow diverter-induced hemodynamic change plays an important role in the mechanism of intracranial aneurysm occlusion. Our aim was to explore the relationship between aneurysm features and flow-diverter treatment of unruptured sidewall intracranial aneurysms.

MATERIALS AND METHODS

MR imaging, 4D phase-contrast, was prospectively performed before flow diverter implantation in each patient with unruptured intracranial aneurysm. Two postprocedure follow-ups were scheduled at 6 and 12 months. Responses were grouped according to whether the aneurysms were occluded or remnant. Preprocedural aneurysm geometries and ostium hemodynamics in 38 patients were compared between the 2 groups at 6 and 12 months. Receiver operating characteristic curve analyses were performed for significant geometric and hemodynamic continuous parameters.

RESULTS

After the 6-month assessment, 21 of 41 intracranial aneurysms were occluded, and 9 additional aneurysms were occluded at 12 months. Geometrically, the ostium maximum diameter was significantly larger in the remnant group at 6 and 12 months (both P < .001). Hemodynamically, the proximal inflow zone was more frequently observed in the remnant group at 6 months. Several preprocedural ostium hemodynamic parameters were significantly higher in the remnant group. As a prediction for occlusion, the areas under the curve of the ostium maximum diameter (for 6 and 12 months), systolic inflow rate ratio (for 6 months), and systolic inflow area (for 12 months) reached 0.843, 0.883, 0.855, and 0.860, respectively.

CONCLUSIONS

Intracranial aneurysms with a large ostium and strong ostium inflow may need a longer time for occlusion. Preprocedural 4D flow MR imaging can well illustrate ostium hemodynamics and characterize aneurysm treatment responses.

Clinicoradiologic Correlations of Cerebral Microbleeds in Advanced Age

BACKGROUND AND PURPOSE

The presence of cerebral microbleeds has been associated with dementia and cognitive decline, although studies report conflicting results. Our aim was to determine the potential role of the presence and location of cerebral microbleeds in early stages of cognitive decline.

MATERIALS AND METHODS

Baseline 3T MR imaging examinations including SWI sequences of 328 cognitively intact community-dwelling controls and 72 subjects with mild cognitive impairment were analyzed with respect to the presence and distribution of cerebral microbleeds. A neuropsychological follow-up of controls was performed at 18 months post inclusion and identified cases with subtle cognitive deficits were referred to as controls with a deteriorating condition. Group differences in radiologic parameters were studied by using nonparametric tests, 1-way analysis of variance, and Spearman correlation coefficients.

RESULTS

Cerebral microbleed prevalence was similar in subjects with mild cognitive impairment and controls with stable and cognitively deteriorating conditions (25%-31.9%). In all diagnostic groups, lobar cerebral microbleeds were more common. They occurred in 20.1% of all cases compared with 6.5% of cases with deep cerebral microbleeds. None of the investigated variables (age, sex, microbleed number, location and depth, baseline Mini-Mental State Examination score, and the Fazekas score) were significantly associated with cognitive deterioration with the exception of education of >12 years showing a slight but significant protective effect (OR, 0.44; 95% CI, 0.22-0.92; P = .028). The Mini-Mental State Examination and the Buschke total score were correlated with neither the total number nor lobar-versus-deep location of cerebral microbleeds.

CONCLUSIONS

Cerebral microbleed presence, location, and severity are not related to the early stages of cognitive decline in advanced age.

Evaluation of whole-body MR to CT deformable image registration

Multimodality image registration plays a crucial role in various clinical and research applications. The aim of this study is to present an optimized MR to CT whole‐body deformable image registration algorithm and its validation using clinical studies. A 3D intermodality registration technique based on B‐spline transformation was performed using optimized parameters of the elastix package based on the Insight Toolkit (ITK) framework. Twenty‐eight (17 male and 11 female) clinical studies were used in this work. The registration was evaluated using anatomical landmarks and segmented organs. In addition to 16 anatomical landmarks, three key organs (brain, lungs, and kidneys) and the entire body volume were segmented for evaluation. Several parameters — such as the Euclidean distance between anatomical landmarks, target overlap, Dice and Jaccard coefficients, false positives and false negatives, volume similarity, distance error, and Hausdorff distance — were calculated to quantify the quality of the registration algorithm. Dice coefficients for the majority of patients (>75%) were in the 0.8–1 range for the whole body, brain, and lungs, which satisfies the criteria to achieve excellent alignment. On the other hand, for kidneys, Dice coefficients for volumes of 25% of the patients meet excellent volume agreement requirement, while the majority of patients satisfy good agreement criteria (>0.6). For all patients, the distance error was in 0–10 mm range for all segmented organs. In summary, we optimized and evaluated the accuracy of an MR to CT deformable registration algorithm. The registered images constitute a useful 3D whole‐body MR‐CT atlas suitable for the development and evaluation of novel MR‐guided attenuation correction procedures on hybrid PET‐MR systems.

PACS number: 07.05.Pj

Penumbra system: a novel mechanical thrombectomy device for large-vessel occlusions in acute stroke

BACKGROUND AND PURPOSE

Large IC artery occlusion is often resistant to recanalization. We present our initial experience with the PS.

MATERIALS AND METHODS

Presenting with a severe acute ischemic stroke, the first 27 consecutive patients were considered for thromboaspiration therapy and retrospective data base analysis. All patients received standard thrombectomy treatment as monotherapy or in combination with thrombolysis or IC stent placement. The primary end point was revascularization of the target vessel to grade 2 or 3 on the TICI scale. Secondary end points were improvement of >4 points on the NIHSS score at discharge and favorable outcome, and improvement in overall mortality at 3 months and in sICH- and procedure-related adverse events.

RESULTS

At baseline, the mean age was 66 +/- 14 years and the mean NIHSS score was 14 +/- 7. The anterior circulation was affected in 23 patients, and there were 4 basilar artery occlusions. Intracranial stent placement was performed in 4 patients. A recanalization to TICI 2 or 3 was achieved in 25 patients (93%). None of the patients developed sICH. At hospital discharge, 15 patients (56%) had an NIHSS improvement of >4 and 13 patients (48%) had an mRS score of <2 at 3 months. There was a significant correlation between complete vessel recanalization and favorable outcome. The all-cause mortality at 3 months was 11%.

CONCLUSIONS

The PS showed a high potential for recanalization of acute thromboembolic occlusions of the large cerebral arteries. Complete recanalization was strongly correlated with good clinical outcome.

Contribution of the apparent diffusion coefficient in perilesional edema for the assessment of brain tumors

OBJECTIVES

Diffusion-weighted MRI is sensitive to molecular motion and has been applied to the diagnosis of stroke. Our intention was to investigate its usefulness in patients with brain tumor and, in particular, in the perilesional edema.

METHODS

We performed MRI of the brain, including diffusion-weighted imaging and mapping of the apparent diffusion coefficient (ADC), in 16 patients with brain tumors (glioblastomas, low-grade gliomas and metastases). ADC values were determined by the use of regions of interest positioned in areas of high signal intensities as seen on T2-weighted images and ADC maps. Measurements were taken in the tumor itself, in the area of perilesional edema and in the healthy contralateral brain.

RESULTS

ADC mapping showed higher values of peritumoral edema in patients with glioblastoma (1.75 x 10(-3)mm(2)/s) and metastatic lesions (1.61 x 10(-3)mm(2)/s) compared with those who had low-grade glioma (1.40 x10(-3)mm(2)/s). The higher ADC values in the peritumoral zone were associated with lower ADC values in the tumor itself.

CONCLUSIONS

The higher ADC values in the more malignant tumors probably reflect vasogenic edema, thereby allowing their differentiation from other lesions.

Neuro-imaging of cerebral ischemic stroke

Major progress has recently been made in the neuro-imaging of stroke as a result of improvements in imaging hardware and software. Imaging may be based on either magnetic resonance imaging (MRI) or computed tomography (CT) techniques. Imaging should provide information on the entire vascular cervical and intracranial network, from the aortic arch to the circle of Willis. Equally, it should also give information on the viability of brain tissue and brain hemodynamics. CT has the advantage in the detection of acute hemorrhage whereas MRI offers more accurate pathophysiological information in the follow-up of patients.

[Male sexual function after stroke]

Stroke represents the third leading cause of death, ranking behind heart disease and cancer and it is the major cause of worldwide long-term disability after the age of 65. Stroke has an important psychological and emotional impact on the patient and his environment. Some trials show the substantial lowering of libido, of the frequency of sexual intercourse, the presence of erectile dysfunction and reduced sexual satisfaction. After stroke it is important to evaluate the relational and sexual aspects of the patient and his sexual partner. A specialized consultation should be proposed when necessary to optimise the patient's post-stroke rehabilitation.

Line-scan diffusion tensor imaging of the posttraumatic brain stem: changes with neuropathologic correlation

Following trauma, imaging of brain stem lesions is often inconclusive. In a man who suffered a lethal accident, postmortem MR diffusion tensor (DT) imaging of the brain and neuropathologic examination were performed. DT imaging showed a disorganization of fibers in the brain stem that was not found in 2 controls and corresponded to changes on neuropathologic correlation. Diffusion tensor imaging provides an insight into the organization of myelinated structures of the CNS, potentially allowing diagnosis of traumatic fiber tract rupture.

Degeneration of the cervical disc: histology compared with radiography and magnetic resonance imaging

Decisions about the treatment of neck pain are largely made on the basis of information gained from plain X-rays and magnetic resonance imaging (MRI), which are used routinely as part of preliminary investigation. We performed a descriptive cadaveric study to compare histology with radiography and MRI. We correlated plain radiography, disc height [Farfan index (FI)] and MRI findings with histology to assess the ability of radiology to detect significant pathologic lesions. The study included 52 motion segments from nine subjects over the age of 50, who underwent routine hospital autopsy. Disc degeneration was assessed by histology, radiography, disc height (FI: anterior disc height plus posterior disc height divided by anterioposterior diameter) and MRI using established grading systems. Most of the discs were classified radiologically as grade 1 (19/52), grade 2 (13/52), grade 3 (9/52) or grade 4 (3/52). Eight of the discs were graded as normal. The distribution of MRI grades was grade 0 (9/36), grade 1 (9/36), grade 2 (7/36), grade 3 (8/36) and grade 4 (3/36). Half of the discs (26/52) showed advanced (grade 4) degeneration histologically. FI correlated with histological grade (P = 0.013), MRI grade (P = 0.02) and radiological grade (P < 0.001) of degeneration. Radiological and histological grade of degeneration showed a weak correlation (r = 0.3, P = 0.033). MRI correlated with overall histological grade (r = 0.41, P = 0.015, n = 34). Histological features (e.g., tears, rim lesions, prolapse of nucleus material) were poorly recognised by MRI, which had a sensitivity for disc material prolapse and annulus tears of less than 40%. Our study showed that discs from patients over 50 years are histologically severely degenerated; however, these changes may not be detected by conventional radiography and MRI.

ADC mapping of the aging frontal lobes in mild cognitive impairment

Normal aging, leukoaraiosis (LA) and vascular disease particularly involve the human frontal lobes. We decided to investigate a population of elderly patients referred for neuroimaging because of progressive minor cognitive deficits but no dementia. They underwent conventional Magnetic resonance imaging (MRI) using axial T1 and T2-weighted imaging as well as coronal FLAIR sequences in addition to the axial diffusion-weighted MRI. MRI allowed us to differentiate patients with leukoaraïosis (LA+) from those without it (LA-) and mapping of the apparent diffusion coefficient (ADC) to investigate local tissular water motion. We observed an increase in the ADC in all investigated patients with increasing age (r=0.326, p=0.002). This increase was observed in both patients groups (LA+ and LA-). In addition, the LA+ group had significant higher ADC values than the LA- group after controlling for age (p<0.0001).

Diffusion-weighted MRI in cortical ischaemia

We carried out MRI on 16 male and three female comatose patients, aged 2 days to 79 years, with suspected cortical ischaemia referred from our intensive care units. Using a head coil, and following standard imaging, including coronal fluid-attenuated inversion-recovery images, we performed diffusion-weighted imaging (DWI) using a whole-brain multislice single-shot echo-planar sequence with b 0 and 1000 s/mm2: 5-mm slices covering the whole brain, TR 7000 TE 106 ms, 128 x 128 pixels, field of view 250 mm, one excitation. Maps of apparent diffusion coefficients (ADC) were generated automatically. DWI showed cortical, basal ganglia and watershed-area high signal in all cases, associated with a decrease in ADC to 60- 80% of normal. DWI showed lesions not seen (40%) or underestimated (40%) on conventional T2-weighted imaging. Within 24 h of the onset of symptoms, DWI showed changes not readily detectable on T2-weighted images. The cortical high signal on DWI and the ADC changes, suggesting severe ischaemia rather than oedema, was found in areas known to be affected by cortical laminar necrosis. Extension to the brain stem and white matter was associated with a higher likelihood of death.

Diffusion-weighted MRI in acute spinal cord ischaemia

Acute spinal cord ischaemia is often undetectable with conventional MRI. Diffusion-weighted MRI (DWI) has been difficult to use in the spine because of susceptibility artefacts. We assessed the diagnostic value of echoplanar DWI for early confirmation of spinal cord ischaemia. We performed conventional MRI and DWI in two men and three women, aged 54-75 years with clinically suspected acute spinal cord ischaemia. Imaging was performed 9-46 h after the onset of symptoms, and 2-9 days later to assess the extent of ischaemic signal change. Spatial resolution of DWI within the spine using standard equipment was poor, but in all patients, early DWI revealed areas of high signal indicating decreased diffusion, confirmed by measurement of apparent diffusion coefficients. Follow-up MRI showed high signal on T2-weighted images and contrast enhancement at the expected levels. Neurological deficits corresponded with radiological findings in four patients: various syndromes, including isolated bilateral weakness or sensory change and combined deficits, were found. Echoplanar DWI may be helpful for confirmation of spinal cord ischaemia in the acute stage, but follow-up T2-weighted images have superior spatial resolution and correlation with clinical findings and lesion extent.

Isotropic apparent diffusion coefficient mapping of postnatal cerebral development

Diffusion-weighted imaging (DWI) allows us to image the motion of tissue water. This has been used to demonstrate acute ischaemia. Diffusion imaging is also sensitive to water movement along neuronal tracts. Our objective was to map brain maturation in vivo using maps of apparent diffusion coefficient (ADC). We studied 22 children without neurological disease aged between 2 and 720 days. MRI was performed at 1.5 tesla. Multislice single-shot echoplanar DWI was performed at b 0 and 1000 s/mm(2). ADC maps were generated automatically and measurements were performed in the basal ganglia, frontal and temporal white matter and the pons. There was a decrease over time in water diffusion in the areas examined, most marked in the frontal (0.887-1.898 x 10(-3) mm(2)/s) and temporal (1.077-1.748 x 10(-3) mm(2)/s)lobes. There was little change, after an initial decrease, in the basal ganglia (0.690-1.336 x 10(-3) mm(2)/s). There was a difference in water diffusion between the anterior (0.687-1.581 x 10(-3) mm(2)/s) and posterior (0.533-1.393 x 10(-3) mm(2)/s) pons. These changes correlate well with those observed in progressive myelination: the increased water content probably reflects incomplete myelination and the decrease with time in water motion reflects the increase in myelinated brain.

Changes on diffusion-weighted MRI with focal motor status epilepticus: case report

Transient imaging abnormalities, including changes on diffusion-weighted imaging (DWI), may be seen in focal status epilepticus. The changes on DWI provide am insight into the pathophysiology. We report a 53-year-old man with focal motor status epilepticus involving the left hand, arm and face with focal slowing on EEG. The apparent diffusion coefficients (ADC) were higher in the affected hemisphere than on the other side. At 10 days and 6 weeks after the end of the seizures, we saw normal ADCs and atrophy of the affected hemisphere. We conclude that the MRI findings indicate both cytotoxic and vasogenic oedema during seizure activity and subsequent loss of brain parenchyma.

Apparent diffusion coefficient mapping of infarcted tissue and the ischaemic penumbra in acute stroke

MRI assessment of diffusion changes in acute cerebral ischaemia necessitates analysis of the apparent diffusion coefficient (ADC). We used the concept of relative weighted mean ADC (rwmADC) to obtain an accurate estimate of the extent of infarcted tissue. We studied ten patient with of acute ischaemic stroke, using diffusion- and perfusion- weighted MRI. The rwmADC was used to calculate a corrected ADC-lesion volume (DLVR), which was compared with the diffusion-lesion volume (DLV), initial perfusion lesion volumes and the follow-up infarct volume on T2-weighted images. We looked at correlations between the MRI and clinical findings. DLVR was closest to the final infarct size and had the best clinicoradiological correlation (r=0.77). Weighting the mean ADC within the ischaemic and normal parenchyma can give a more correct estimate of the volume of infarcted brain parenchyma, thus improving the definition of the penumbra.

Magnetic resonance angiography with ultrashort echo times reduces the artefact of aneurysm clips

We evaluated the ability of an ultrashort echo time (TE) three-dimensional (3D) time-of-flight (TOF) magnetic resonance angiography (MRA) sequence to reduce the metal artefact of intracranial aneurysm clips and to display adjacent cerebral arteries. In five patients (aged 8-72 years) treated with Elgiloy or Phynox aneurysm clips we prospectively performed a conventional (TE 6.0 ms) and a new ultrashort TE (TE 2.4 ms) 3D TOF MRA. We compared the diameter of the clip-induced susceptibility artefact and the detectability of flow in adjacent vessels. The mean artefact diameter was 22.3+/-6.4 mm (range 14-38 mm) with the ultrashort TE and 27.7+/-6.4 mm (range 19-45 mm) with the conventional MRA ( P<0.0001). This corresponded to a diameter reduction of 19.5+/-9.2%. More parts of adjacent vessels were detected, but with less intense flow signal. The aneurysm dome and neck remained within the area of signal loss and were therefore not displayed. Ultrashort TE MRA is a noninvasive and fast method for improving detection of vessels adjacent to clipped intracranial aneurysms, by reducing clip-induced susceptibility artefact. The method cannot, however, be used to show remnants of the aneurysm neck or sac as a result of imperfect clipping.

Diffusion and perfusion MRI for the localisation of epileptogenic foci in drug-resistant epilepsy

Drug-resistant epilepsy is an important clinical challenge, both diagnostically and therapeutically. More and more surgical options are being considered, but precise presurgical assessment is necessary. We prospectively studied eight patients with drug-resistant epilepsy, who underwent clinical examination, single photon emission computed tomography (SPECT) and interictal MRI, including diffusion- and perfusion-weighted echoplanar sequences. Lesions suspected on SPECT of being epileptogenic showed mild hypoperfusion, while the diffusion-weighted MRI (DWI) revealed increased apparent diffusion coefficients relative to the other side. However, these abnormalities were not visible on the corresponding maps. We showed that DWI and perfusion-weighted MRI could be used confirm the characteristics and site of an epileptogenic area in patients with drug-resistant epilepsy.

Focal status epilepticus: follow-up by perfusion- and diffusion MRI

Diffusion-weighted MRI demonstrated bright right temporoparietal cortex, right hippocampus, and left cerebellum in a 63-year-old female suffering a focal convulsive status epilepticus. Hyperperfusion was noted in the right temporoparietal region. Two days later, a tendency to normalization of most of the diffusion and perfusion changes was noted, apart from the right hippocampus which became brighter on diffusion- and T2-weighted images. On the tenth day the apparent diffusion coefficient was slightly elevated, getting brighter on T2-weighted images with suspected mild post-contrast enhancement. We postulate that the discharging right hippocampus suffered cytotoxic edema, which later progressed to cell damage.

Anterior spinal artery stroke demonstrated by echo-planar DWI

Diffusion-weighted MR (DWI) is becoming an established method for the investigation of cerebral ischemia. Its value in spinal ischemia has to be demonstrated. We report on a patient presenting with postoperative paraparesis who underwent emergency MRI of the spine with echo-planar diffusion-weighted imaging which showed an area of hyperintensity corresponding to a decrease of diffusion as measured by the apparent diffusion coefficient. On follow-up imaging spinal stroke was confirmed. In conclusion, spinal echo-planar MR imaging can demonstrate ischemic changes despite strong echo-planar artifacts. It could become an important adjunct to the management of patients with suspected spinal ischemia.

Whole-brain functional magnetic resonance imaging of cerebral arteriovenous malformations involving the motor pathways

To investigate cortical, basal ganglia and cerebellar activation in patients with arteriovenous malformations (AVMs) involving the motor pathways, we studied ten patients (six male, four female, mean age 30.3 years, range 7.4-44.1) by whole-brain functional magnetic resonance imaging (fMRI) in a 1.5-T scanner with the EPI-BOLD-technique. In seven cases multiple fMRI studies were available, acquired in the course of the multi-session endovascular interventional treatment. Self-paced right- and left-handed finger-tapping tasks were used to invoke activation. In six patients a super-selective amytal test (Wada test) was performed during diagnostic pre-interventional angiography studies. Abnormal cortical activation patterns, with activation of the primary sensorimotor area, the supplementary motor area and/or the cerebellum shifted to unphysiological locations, were found in four patients. In all cases, localization of the AVM could account for the changes from the normal. After endovascular procedures, fMRI demonstrated shifts in the activation pattern in three patients. In the six patients that had undergone fMRI studies and the Wada test, both methods yielded comparable results. The fact that AVMs are structural anomalies for which the brain can partly compensate ('plasticity') was underlined by these results. fMRI is a valuable tool in the pre-therapeutic evaluation and post-interventional follow-up of patients with cerebral AVMs in whom an operation or an endovascular procedure is planned.

Damage to the parietal lobe impairs bimanual coordination

Moving the upper limbs at a common tempo according to a mirror or parallel mode represents elementary coordination dynamics. Previously, the role of the medial wall areas have been emphasized for successful production of these bimanual patterns. The involvement of the parietal lobe is less clear despite its importance for the representation of motor skill and sensorimotor integration. The objective of this study was to investigate temporal control in patients with parietal pathology when performing isofrequency configurations. As compared to control subjects, these patients showed desynchronization of movement trajectories that was most apparent during parallel patterns. These observations suggest the significant role of the parietal lobe for bimanual coordination which becomes increasingly relevant as a function of task complexity.

Diffusion-weighted mr in cerebral venous thrombosis

The diagnosis of cerebral venous thrombosis is often difficult both clinically and radiologically and until now there is no method available to predict if brain lesions, detected clinically and using conventional brain imaging methods, may lead to full recovery, as expected in vasogenic edema or ischemic infarcts and even a hematoma. New fast neuroimaging techniques such as diffusion-weighted imaging (DWI) are sensitive to different reasons of changes in local tissular water concentration thus giving further insight into the pathophysiological mechanism as well as prognosis of cerebral venous thrombosis. We report the cases of 18 consecutive patients with a diagnosis of cerebral venous thrombosis based on clinical and imaging criteria. All patients underwent magnetic resonance imaging (MRI) of the brain, which comprised isotropic diffusion-weighted MR. Diffusion-weighted MRI showed positive findings in 17/18 cases. In 7 cases the clot could be directly visualized as an area of hyperintensity in the affected vein on DWI. In 7 cases DWI showed areas of signal loss corresponding to hematomas. In 6 cases DWI showed changes in signal intensity that were more subtle. In 4 cases of superficial venous thrombosis, there were areas of decreased ADC values (0.65-0.79 x 10(-3) mm(2)/s) whereas in 2 cases of deep venous thrombosis, increased DWI intensities could be found that corresponded to both an increase and a decrease in ADC, corresponding to a coexistence of cytotoxic and vasogenic edemas. Diffusion-weighted MRI can demonstrate directly the presence of an intravenous clot in a select number of patients. It can also demonstrate early ischemic changes, and can differentiate conventional T2-weighted MR areas of cytotoxic from vasogenic edema.

Reperfusion demonstrated by apparent diffusion coefficient mapping after local intra-arterial thrombolysis for ischaemic stroke

Diffusion-weighted MRI (DWI) is becoming important for diagnosis and investigation of acute cerebral ischaemia. It has been reported that apparent diffusion coefficient (ADC) maps could be an indicator of reperfusion. Our aim was to use echo-planar technology to investigate this phenomenon. We report 19 patients treated by local intra-arterial thrombolysis for middle cerebral artery stroke within 6 h of the onset of symptoms, in whom we performed follow-up DWI. ADC were found to be higher in the patients with angiographically proven reperfusion.

Diffusion-weighted MRI of middle cerebral artery stroke in a newborn

Diffusion-weighted MRI of the brain is becoming clinically available as a tool to investigate cerebral ischaemia. We report a newborn girl presenting with seizures in whom diffusion-weighted MRI showed a large hyperintensity in the area perfused by the left middle cerebral artery. Short-term neurological follow-up before discharge was uneventful and the patient was discharged without sequelae. On follow-up clinical examination, right-sided spastic signs were noted which disappeared with time.

Relation between directly detected patent foramen ovale and ischemic brain lesions in sport divers

BACKGROUND

In divers, the significance of a patent foramen ovale and its potential relation to paradoxical gas emboli remain uncertain.

OBJECTIVE

To assess the prevalence of symptoms of decompression illness and ischemic brain lesions in divers with regard to the presence of a patent foramen ovale.

DESIGN

Retrospective cohort study.

SETTING

University hospital and three diving clubs in Switzerland.

PARTICIPANTS

52 sport divers and 52 nondiving controls.

MEASUREMENTS

Prevalence of self-reported decompression events, patent foramen ovale on contrast transesophageal echocardiography, and ischemic brain lesions on magnetic resonance imaging.

RESULTS

The risk for decompression illness events was 4.5-fold greater in divers with patent foramen ovale than in divers without patent foramen ovale (risk ratio, 4.5 [95% CI, 1.2 to 18.0]; P = 0.03). Among divers, 1.23 +/- 2.0 and 0.64 +/- 1.22 ischemic brain lesions per person (mean +/- SD) were detected in those with and those without patent foramen ovale, respectively. Among controls, 0.22 +/- 0.44 and 0.12 +/- 0.63 lesion per person were detected (P < 0.001 for all groups).

CONCLUSIONS

Regardless of whether a diver has a patent foramen ovale, diving is associated with ischemic brain lesions.

CT and MRI in acute hemorrhagic stroke

We report the case of a woman presenting with an acute onset of hemiplegia. MRI was performed and showed a hyperintense mass on diffusion-weighted imaging, with areas of high signal intensity on T2* imaging and T2/PD imaging. T1-weighted imaging showed a more inhomogeneous lesion with a central isointense part corresponding to the acute clot, as well as a peripheral crescent of hypointense plasma; since another mass lesion could not be acutely excluded, computed tomography was performed immediately afterwards, showing a hyperdense hematoma. The patient was taken to the neurosurgical operating theater, where she underwent decompressive craniotomy and evacuation of the hematoma.

Clinical correlations of diffusion and perfusion lesion volumes in acute ischemic stroke

The aim of this study was to describe the clinico-radiological correlations of magnetic resonance (MR) perfusion and diffusion-weighted imaging (DWI) abnormalities in ischemic stroke. Eighteen patients had undergone MR imaging and clinical evaluation within 24 h of symptom onset and at or after 7 days. During the first 24 h the volume of perfusion abnormality (measured on the relative mean transit time map) was larger than the DWI lesion in 12/18 patients. In 6/18 patients the DWI lesion volume was larger. Acutely (<24 h) all lesion volumes showed a significant correlation with acute clinical severity measured by the National Institutes of Health Stroke Scale score. The correlations of the hypoperfusion volume (rho = 0.86, p = 0.0001) and the volume 'tissue at risk' (larger than the DWI and perfusion lesion volumes, rho = 0.86, p = 0. 0001) with acute clinical severity were slightly higher than for the DWI lesion volume (rho = 0.76, p = 0.0001). The difference between the volume of tissue at risk (acutely) and the infarct on follow-up T(2)-weighted imaging correlated significantly with change in clinical severity from acute to chronic time points (rho = 0.72, p = 0.001). Such clinico-radiological relationships may support the use of DWI and perfusion MR in decisions concerning the administration and evaluation of stroke therapies.

Endovascular treatment of acute and subacute hemorrhage in the head and neck

OBJECTIVE

Acute and subacute hemorrhage in the head and neck often represent a life-threatening situation. The goal of this study is to evaluate the indications for and contributions of endovascular techniques in the diagnosis and management of such severe cases.

DESIGN

Seventy-two patients with acute or subacute intractable hemorrhage of the head and neck were treated over a period of 5 years: 2 patients had experienced trauma; in 6 cases the cause of bleeding was iatrogenic; and in 2 patients intraosseous arteriovenous malformations were manifested. Fifteen patients had tumors, 9 of whom had prior radiotherapy. Forty-seven patients presented with epistaxis (41 idiopathic and 6 during anticoagulation therapy). The endovascular therapy was performed using polyvinyl alcohol particles, fibered platinum or electrolytically detachable coils (Guglielmi detachable coils; Target Therapeutics, Fremont, Calif), a stent, glue (Ethibloc; Ethicon GmbH, Norderstedt, Germany, and Histoacryl; B. Braun Melsungen AG, Melsungen, Germany), or with a combination of these different embolic materials.

RESULTS

The acute bleeding was successfully controlled in all cases. Fourteen patients (7 with epistaxis, 5 with tumors, and 2 with arteriovenous malformations) had to be embolized more than once before the bleeding could be controlled. The idiopathic, traumatic, iatrogenic, and remaining tumoral cases were treated only once. The long-term morbidity was 1.9%.

CONCLUSIONS

Owing to the recent continuous advances in interventional radiologic techniques, it is possible to treat both acute and subacute life-threatening head and neck hemorrhage most efficiently. In many cases the endovascular therapy complements surgery.

Diffusion-weighted MRI suggests the coexistence of cytotoxic and vasogenic oedema in a case of deep cerebral venous thrombosis

We report a 20-year-old woman who suffered headaches before presenting with a state of fluctuating vigilance. MRI showed diffuse high signal in the basal ganglia bilaterally on diffusion- and T2-weighted images, which had areas of both low and high apparent diffusion coefficient, presumed to correspond to cytotoxic and vasogenic oedema. MR venography showed no flow in the deep cerebral veins or straight sinus. Heparin was given, with clinical recovery. On follow-up MRI, the appearances became normal.

Abnormal myelination in a patient with deletion 14q11.2q13.1

A male carrying an interstitial deletion of chromosome 14, presumably del(14)(q11.2q13), and presenting with abnormal myelination on magnetic resonance imaging is described. The abnormal myelination was evidenced as a high-signal intensity on T(2)-weighted magnetic resonance imaging. The patient had severe neurologic signs, various dysmorphic features, and a marked microcephaly. To our knowledge, this case is the first patient reported with abnormal myelination and a deletion of chromosome 14.

Silent cerebral ischemia detected by diffusion-weighted MRI after carotid endarterectomy

BACKGROUND AND PURPOSE

Small emboli arising from a friable plaque during carotid endarterectomy (CEA) constitute an important risk of perioperative ischemic complications. To evaluate the incidence and significance of silent cerebral ischemic lesions of embolic origin after CEA, we prospectively examined a series of surgical patients with high-grade carotid stenosis by using diffusion-weighted MRI (DWI). We also tried to correlate postoperative ischemic lesions with the occurrence of sonographic cerebral embolic signals, the presence of plaque ulcerations, and the use of intraoperative shunting.

METHODS

Of a consecutive series of 53 patients undergoing elective CEA for high-grade carotid stenosis, 48 patients with unchanged postoperative neurological status were prospectively studied with DWI of the brain the day before and the day after the operation. The magnetic resonance images were analyzed by 2 neuroradiologists blinded to the clinical result of the operation. Any new hyperintense signal was interpreted as a postoperative ischemic lesion.

RESULTS

Forty-six (95.8%) of 48 patients had unchanged postoperative brain DWI. In 2 patients (4.2%), a new single asymptomatic hyperintense signal was observed on the side of the operation. Both lesions were small and presumably of embolic origin. They were not related to sonographic embolic signals, plaque ulcerations, or intraoperative shunting.

CONCLUSIONS

These results suggest that the incidence of silent ischemic brain lesions of embolic origin after CEA is low and does not correlate with the occurrence of intraoperative sonographic microemboli. They confirm that CEA is a safe procedure that carries a low risk of postoperative cerebral events.

Imaging the rat brain on a 1.5 T clinical MR-scanner

Magnetic resonance imaging (MRI) offers a noninvasive technique for studying neurodegenerative events in the rat brain, however, most of the studies are performed on small bore purpose dedicated MR scanners of limited availability and at high cost. The present study explored the feasibility of using a clinical whole body MR-scanner to perform imaging in rat brain and specifically in models of Parkinson's (PD) and Huntington's disease (HD). For that purpose rats were placed into a specially designed PVC device equipped with a flexible surface coil-and T2-weighted spin echo sequences were acquired on a Siemens Magnetom Vision at 1.5 T. In the experimental protocols of PD and HD, animals underwent 6-hydroxydopamine (6-OHDA) and quinolinic acid (QA) injections, respectively and were subsequently grafted with fetal tissue. T2-weighted images showed a small hyperintense area at the 6-OHDA lesion site and a diffuse hyperintensity in the striata with QA lesions. Transplants were seen as a hypointense area surrounded by a hyperintense rim on T1-weighted images. Moreover, disturbances of the blood-brain-barrier and its time of restoration could be monitored. In conclusion, high-resolution in vivo imaging of small animals is feasible with clinical MR-scanners and hence allows the study of various experimental protocols.

Multiple acute stroke syndrome: marker of embolic disease?

OBJECTIVE

To determine the frequency and etiologic significance of multiple acute ischemic lesions in stroke.

BACKGROUND

Although patients may have more than one stroke during the course of their lives, acute ischemic stroke is usually thought of as a single event. Using diffusion-weighted imaging (DWI), an MRI technique that detects ischemic injury within minutes after onset, we have often observed multiple acute ischemic lesions.

METHODS

The MRI scans of 59 consecutively studied patients were reviewed to determine the frequency and etiologic significance of multiple acute ischemic lesions on DWI.

RESULTS

Multiple acute ischemic lesions were present in 10 (17%) of 59 patients. The lesions usually occurred within one major circulation (anterior or posterior), but in two patients (3%), lesions occurred in both cerebral hemispheres or in the anterior and the posterior circulations. The lesions often were small and resulted from presumed multiple emboli or the break-up of an embolus. Two patients had internal carotid artery occlusive disease and four had a cardiac or aortic source. In the other four patients the source was not determined. Lesions larger than 1 cm in diameter progressed to infarction, but some smaller lesions were not seen on follow-up T2-weighted imaging.

CONCLUSIONS

Multiple acute stroke lesions on DWI are common and could be caused by multiple emboli or the breakup of an embolus. In some cases it might become possible to make early inferences concerning the stroke mechanism that could be of use for immediately directing the clinical work-up and treatment of the patient.

Diffusion-weighted MRI for monitoring neurovascular interventions

Carotid stenting is increasingly considered as treatment for carotid artery disease. A reliable noninvasive method is desirable for assessing the safety of the procedure. Diffusion-weighted MRI (DWI) is sensitive to early brain ischaemia which becoming widely available and might therefore serve this purpose. We prospectively studied 19 patients referred for investigation of carotid artery disease by echo-planar whole-brain DWI before and within 24 h of stenting. The images obtained at a high b value were examined by two independent blinded reviewers for new high-signal areas consistent with ischaemia. We found that 15 patients had no new changes after stenting. One patient showed enlargement of a posterior watershed lesion after the procedure, which correlated with an increase in neurological deficit. Three other patients had presumed small embolic infarcts on DWI; two were asymptomatic and one had weakness at the hand that corresponded to an embolic infarct with a lesion on DWI in the hand notch. There were no false- positive or -negative results on DWI, when compared to clinical findings. DWI is thus a new method that can demonstrate neurologically silent or asymptomatic infants. It can be used to help to assess the safety and efficacy of neurovascular intervention.

Diffusion-weighted magnetic resonance imaging in brain death

BACKGROUND; Traditionally the diagnosis of brain death is established on the basis of a combination of clinical signs and paraclinical methods. Diffusion-weighted MRI is a new method sensitive to cerebral ischemia. Its value in brain death has not been demonstrated until now.

CASE DESCRIPTION

A patient was referred to MRI with suspicion of a brain stem stroke. Echo-planar whole-brain, multislice, diffusion-weighted MRI was performed in addition to conventional sequences and MR angiography sequences. In addition to the extensive bilateral hyperintensities observed on T2-weighted images, diffusion-weighted MRI showed diffuse hyperintensities involving both hemispheres as well as a severe drop in the apparent diffusion coefficient in both affected hemispheres. There was also transtentorial herniation with compression of the brain stem as well as absence of flow voids on the T2-weighted images and absence of intracranial vessels on MR angiography. On the basis of the clinical and imaging findings, it was concluded that the patient was in a state of brain death. The patient died the same day.

CONCLUSIONS

With the use of new fast techniques such as diffusion-weighted imaging, now MRI can not only display anatomic changes associated with severe brain suffering but can also demonstrate ultrastructural changes secondary to brain death and differentiate them from edematous changes seen on T2-weighted images.

[Aphasia research and speech localization in the brain]

Aphasia research has become an acknowledged branch of modern cognitive neuropsychology research whose aim is to explore more fully the structures of knowledge and of cerebral processes which might both be affected in patients with aphasia. Up to the second half of this century, a model based on a specific cerebral localisation of language processes had emerged based on brain localisation research by Broca and Wernicke (among others). New modern neuroimaging techniques, however, such as computed tomography and magnetic resonance imaging (MRI), but also functional imaging modalities such as positron emission tomography or functional MRI, have modified these concepts. It emerges that in comprehension as well as in production of language, not only a few well defined centres are responsible for the activity, but there is a synchronised activity in large neuronal networks connecting various regions located both in the cortex and in the deep subcortical structures; today, this activity can be demonstrated best in a non-invasive and reproducible way with functional MRI.

Silent functional magnetic resonance imaging demonstrates focal activation in rapid eye movement sleep

Functional imaging of human sleep has been performed with nuclear medicine methods, but MRI has been difficult to implement, in part because of the noise associated with echo-planar imaging as well as the difficulty in reading physiologic signals in the MRI environment. We describe a silent MR sequence that can record brain activation over many hours with simultaneous acquisition of an EEG. This shows activation of occipital cortex and deactivation of frontal cortex during REM sleep, in agreement with previous studies using other techniques. MRI-Sleep-REM sleep.

Clinical single-shot diffusion-weighted MRI of the human brain on a short-bore medium-field imager

Diffusion-weighted MRI (DWI) is becoming important for assessment of acute stroke. Until recently single-shot DWI required expensive technology such as echoplanar imaging (EPI) available only at some research sites. A new medium-field (1.0 T) short-bore MR imager has been developed with which DWI data sets can be acquired. We prospectively studied 169 patients on this 1.0 T commercial system. After conventional imaging, DWI was performed with a single-shot multi-slice sequence with b values 0 an 900 s/mm2, and with the gradients switched in three directions. The apparent diffusion coefficients were calculated with online calculation software. There were 50 patients with totally normal MRI, and 17 had strokes, these strokes were detected as areas of high signal on the images at a maximal b value. There was a drop in the ADC in ischaemic regions: in sub-acute infarcts, the values were between 0.41 and 0.531 x 10(-3) mm2/s. In old infarcts the ADC was 1.15 x 10(-3) mm2/s. Cerebrospinal fluid (CSF) gave low signal whereas areas in the brain had more intermediate intensities (CSF: 3.00; deep white matter: 0.75, cortical grey matter: 0.80, basal ganglia (thalamus): 0.70 and cerebellar white matter: 0.65 x 10(-3) mm2/s. Anisotropy was detected as areas of restricted diffusion along the tracts. These preliminary data show that DWI can be acquired successfully on a medium-field short-bore system. This should allow the technique to be implemented at more sites, therefore facilitating the diagnosis of acute stroke and rendering early intervention feasible.

The ischemic penumbra: operationally defined by diffusion and perfusion MRI

BACKGROUND

Identifying tissue at risk for infarction is important in deciding which patients would benefit most from potentially harmful therapies and provides a way to evaluate newer therapies with regard to the amount of ischemic tissue salvaged.

OBJECTIVE

To operationally define and characterize cerebral tissue at risk for stroke progression.

METHODS

We retrospectively selected 25 patients with an acute onset of a hemispheric stroke from our database who had undergone a combination of two diffusion-weighted MRI studies and a perfusion-weighted MRI study. We applied a logistic regression model using maps of the relative mean transit time and relative cerebral blood flow (rCBF) as well as three different maps of the relative cerebral blood volume (rCBV) to predict an operationally defined penumbra (region of mismatch between the diffusion lesion on day 1 and its extension 24 to 72 hours later).

RESULTS

Maps of the rCBF and initial rCBV were significant predictors for identifying penumbral tissue. Our operationally defined penumbral region was characterized by a reduction in the initial rCBV (47% of contralateral control region [CCR]), an increase (163% of CCR) in the total rCBV, and a reduction (37% of CCR) in the rCBF, whereas the operationally defined ischemic core showed a more severe reduction in the rCBF (12% of CCR) and in the initial rCBV (19% of CCR).

CONCLUSION

These MR indexes may allow the identification and quantification of viable but ischemically threatened cerebral tissue amenable to therapeutic interventions in the hyperacute care of stroke patients.

Striatal grafts in a rat model of Huntington's disease: time course comparison of MRI and histology

Survival and integration into the host brain of grafted tissue are crucial factors in neurotransplantation approaches. The present study explored the feasibility of using a clinical MR scanner to study striatal graft development in a rat model of Huntington's disease. Rat fetal lateral ganglionic eminences grown as free-floating roller-tube cultures were grafted into the quinolinic acid-lesioned striatum, and T1- and T2-weighted sequences were acquired at 2, 7, 21, and 99 days posttransplantation. MR images were then compared with images of corresponding histological sections. The lesion-induced striatal degeneration caused a progressive ventricle enlargement, which was significantly different from controls at 21 days posttransplantation. Seven days posttransplantation, T1-weighted images revealed a defined liquid-isointense signal surrounded by a hyperintense rim at the site of graft placement, which was found unaltered for the first 21 days posttransplantation, whereas a hypointense graft signal was detected at 99 days posttransplantation. At 2 days posttransplantation, T2-weighted images showed the graft region as a hyperintense area surrounded by a rim of low signal intensity but at later time-points graft location could not be further verified. Measures for graft size and ventricle size obtained from MR images highly correlated with measures obtained from histologically processed sections (R = 0.8, P < 0.001). In conclusion, the present study shows that fetal rat lateral ganglionic eminences grown as free-floating roller-tube cultures can be successfully grafted in a rat Huntington model and that a clinical MR scanner offers a useful noninvasive tool for studying striatal graft development.

Local intra-arterial thrombolysis in acute ischemic stroke

BACKGROUND AND PURPOSE

We performed a retrospective analysis of the prognostic factors in patients treated with local intra-arterial thrombolysis (LIT). The purpose of this study was to evaluate the safety and efficacy of LIT using urokinase in patients with acute ischemic stroke of the anterior or posterior circulation and to determine the influence of clinical and radiological parameters on outcome.

METHODS

Forty-three patients were treated with LIT using urokinase (median dose, 0.75x10(6) IU). The median National Institutes of Health Stroke Scale (NIHSS) score at hospital admission was 18 (range, 9 to 36). Nine patients had occlusions of the internal carotid artery (ICA), 23 of the middle cerebral artery (MCA), 1 of the anterior cerebral artery, and 10 of the basilar artery (BA). Outcome was assessed after 3 months and classified as good for Rankin Scale (RS) scores of 0 to 3 and poor for RS scores of 4 or 5 and death.

RESULTS

Nine patients (21%) recovered to RS scores 0 or 1, 17 (40%) to scores of 2 or 3, and 7 (16%) to scores of 4 or 5. Ten patients (23%) died. Outcome was good in 17 patients (80%) with MCA occlusions, in 3 patients (33%) with ICA, and in 5 patients (50%) with BA occlusions. Good outcome was associated with an initial NIHSS score of <20 (P<0.001), improvement by 4 or more points on NIHSS score within 24 hours (P=0.001), and vessel recanalization (P=0.02). Recanalization was more likely if LIT was started within 4 hours (P=0.01). Symptomatic cerebral hemorrhage occurred in 2 patients (4.7%).

CONCLUSIONS

LIT was most efficacious in patients with MCA and BA occlusions when the initial NIHSS score was less than 20 and when treated within 4 hours. It is of limited value in patients with distal ICA occlusions.

[Diffusion-weighted imaging in acute stroke]

Magnetic resonance imaging represents today the most important tool in neuroradiology for both clinical practice and research. MRI allows imaging of the human body in 2 or 3 dimensions with variable tissue contrast. The natural diffusion of tissue protons can now be used as a supplementary contrast mechanism. Different MRI techniques can be used to obtain clinically useful diffusion-weighted images. These techniques all require the use of strong gradient pulses in order to obtain the diffusion contrast. In the current article, the most important physical principles of diffusion measurement are presented. After a short introduction into the basic physical principles, we will present the prerequisites and limitations of clinically relevant applications today. Finally a few select examples of clinical use of these techniques in the acute diagnosis of stroke will be presented.