High spatial resolution and high contrast visualization of brain arteries and veins: impact of blood pool contrast agent and water-selective excitation imaging at 3T.

PURPOSE: To investigate a blood pool contrast agent and water-selective excitation imaging at 3 T for high spatial and high contrast imaging of brain vessels including the veins. METHODS AND RESULTS: 48 clinical patients (47 ± 18 years old) were included. Based on clinical findings, twenty-four patients received a single dose of standard extracellular Gadoterate-meglumine (Dotarem®) and 24 received the blood pool contrast agent Gadofosveset (Vasovist®). After finishing routine MR protocols, all patients were investigated with two high spatial resolution (0.15 mm (3) voxel size) gradient echo sequences in random order in the equilibrium phase (steady-state) as approved by the review board: A standard RF-spoiled gradient-echo sequence (HR-SS, TR/TE 5.1/2.3 msec, FA 30°) and a fat-suppressed gradient-echo sequence with water-selective excitation (HR-FS, 1331 binominal-pulse, TR/TE 8.8/3.8 msec, FA 30°). The images were subjectively assessed (image quality with vessel contrast, artifacts, depiction of lesions) by two investigators and contrast-to-noise ratios (CNR) were compared using the Student's t-test. The image quality and CNR in the HR-FS were significantly superior compared to the HR-SS for both contrast agents (p < 0.05). The CNR was also improved when using the blood pool agent but only to a minor extent while the subjective image quality was similar for both contrast agents. CONCLUSION: The utilized sequence with water-selective excitation improved image quality and CNR properties in high spatial resolution imaging of brain arteries and veins. The used blood pool contrast agent improved the CNR only to a minor extent over the extracellular contrast agent.

Correlation of anatomy and function in medulla oblongata infarction.

BACKGROUND: A presentation of all aspects of the dorsolateral medulla oblongata syndrome is clinically very rare to find. In most cases patients present with fragmentary symptoms, e.g. ipsilateral axial lateropulsion, nystagmus, dysarthria, dysphagia or hemiataxia. However, the clinical presentation and lesion anatomy at the level of the medulla oblongata is still unsatisfactory. The aim of this study was to correlate the functional deficit with structural MRI-data. METHODS: We included thirteen patients (eight male, five female, mean age 65.5) with medulla oblongata infarction with clinically predominant ipsilateral axial lateropulsion and correlated clinical with structural deficits. RESULTS: Magnetic resonance imaging lesion mapping demonstrated ipsilateral axial lateropulsion to result from lesions of the spinocerebellar tract, the inferior cerebellar peduncle or the inferior vestibular nucleus. Nystagmus was associated with lesions of the inferior vestibular nucleus, dissociated sensory loss with the spinothalamic tract and hemiataxia with the spinocerebellar tract. CONCLUSIONS: Correlating dysfunction and lesion anatomy is a promising approach to enhance our knowledge on medulla oblongata topography.

Onyx embolization as a first line treatment for intracranial dural arteriovenous fistulas with cortical venous reflux.

PURPOSE: Our purpose was to present our experience regarding embolization of intracranial dural arteriovenous fistulas (DAVFs) with cortical venous reflux using Onyx, a non-adhesive liquid embolic agent. MATERIALS AND METHODS: From January 2006 to December 2007, 16 patients (12 men and 4 women) with a mean age of 61 years (range 42 - 78) with an intracranial DAVF with cortical venous reflux underwent at least one transarterial embolization using Onyx. According to the Cognard classification, 2 lesions were grade V, 5 were grade IV, 6 were grade III, 2 were grade IIa+b, and 1 was grade IIb. The clinical presentation included 5 hemorrhagic deficits, 10 non-hemorrhagic manifestations, and 1 patient was asymptomatic. RESULTS: Twenty-four embolization sessions were performed in 16 patients with an average of 3 arterial feeders (range 1 - 9) embolized per DAVF. Immediately after embolization, complete occlusion was achieved in 9/16 (56%) patients after the first session. Further postembolization surgical treatment was performed in 3 patients. Partial reperfusion occurred in 1 patient at the time of mean follow-up of 3.7 months (range 0 - 12). Treatment has been completed for 11/16 patients with angiographic cure in 10/11 (91%). An infratentorial bleeding complication related to embolization occurred in one patient with temporary worsening of the patient's gait disturbance. At the time of mean clinical follow-up of 4.5 months (range 0 - 12), no procedure-related permanent morbidity was added to our cohort. CONCLUSION: According to our experience, embolization of intracranial DAVFs with cortical venous drainage using Onyx is feasible with promising results, indicating stability at the time of mid-term follow-up. In very complex DAVFs additional embolization material might be necessary, and in some cases surgery is warranted.

Interrelated neuropsychological and anatomical evidence of hippocampal pathology in the at-risk mental state.

BACKGROUND: Verbal learning and memory deficits are frequent among patients with schizophrenia and correlate with reduced magnetic resonance imaging (MRI) volumes of the hippocampus in these patients. A crucial question is the extent to which interrelated structural-functional deficits of the hippocampus reflect a vulnerability to schizophrenia, as opposed to the disorder per se. METHOD: We combined brain structural measures and the Rey Auditory Verbal Learning Test (RAVLT) to assess hippocampal structure and function in 36 never-medicated individuals suspected to be in early (EPS) or late prodromal states (LPS) of schizophrenia relative to 30 healthy controls. RESULTS: Group comparisons revealed bilaterally reduced MRI hippocampal volumes in both EPS and LPS subjects. In LPS subjects but not in EPS subjects, these reductions were correlated with poorer performance in RAVLT delayed recall. CONCLUSIONS: Our findings suggest progressive and interrelated structural-functional pathology of the hippocampus, as prodromal symptoms and behaviours accumulate, and the level of risk for psychosis increases. Given the inverse correlation of learning and memory deficits with social and vocational functioning in established schizophrenia, our findings substantiate the rationale for developing preventive treatment strategies that maintain cognitive capacities in the at-risk mental state.

Severe inflammatory reaction of the optic system after endovascular treatment of a supraophthalmic aneurysm with bioactive coils.

We report on a patient who, after a symptom-free interval, developed severe vision impairment and whose MR imaging demonstrated extensive edema in the central nervous tissue neighboring the treated aneurysm. To our knowledge, this is an unreported complication of endovascular treatment of aneurysms.

Recovery of the blood pressure - cerebral flow relation after carotid stenting in elderly patients.

BACKGROUND: As a sensitive and convenient means for the cerebral hemodynamic monitoring, dynamic cerebral autoregulation testing could be especially useful in medical conditions where less invasive diagnostics and therapies are preferred. This study analysed the effect of carotid stenting on dynamic autoregulation in elderly patients focussing on the relation between blood pressure and cerebral blood flow velocity. METHODS: We examined 20 patients age 69 +/- 8 years with coexisting cerebrovascular and medical risk factors before and at least six month after stenting of severe carotid stenoses. Data were compared to 24 age-matched healthy controls. Slow spontaneous oscillations were studied in continuous recordings of Transcranial Doppler and beat-to-beat blood pressure. Analysis was based on the "high-pass filter model", which predicts a positive phase relationship between these oscillations. FINDINGS: Whereas phase shift angles were diminished (20.4 +/- 14.1 degrees ) before stenting, after stenting these values were significantly increased to normal (48.1 +/- 16.6 degrees ), to the level of controls (46.7 +/- 15.9 degrees ). Medical conditions such as coronary artery disease, arterial hypertension, and dyslipidemia did not diminish this recovery. The level of increase was inversely correlated with the initial autoregulatory deficit (r = -0.68) which was largest with insufficient collateral blood supply and symptomatic carotid stenoses. CONCLUSIONS: The study showed that an impaired cerebral autoregulation may recover after stent-guided carotid angioplasty even in the elderly with co-existing medical conditions. In this respect to regain vasomotor capability, patients with cerebrovascular risk factors seemed to benefit particularly.

Impact of vertebral artery disease on dynamic cerebral autoregulation.

OBJECTIVES: This study applied dynamic cerebral autoregulation (DCA) testing distally to severe bilateral vertebral artery disease (BVAD). METHODS: Using continuous monitoring of beat-to-beat blood pressure and transcranial Doppler of the posterior cerebral arteries (PCA) were examined in 20 patients with BVAD and 22 controls. DCA testing was based on the 'high-pass filter model', which predicts a positive phase relationship between spontaneous oscillations (M-waves 3-9 cpm and R-waves 9-20 cpm) in blood pressure and cerebral blood flow velocity. RESULTS: In patients with BVAD, DCA testing detected autoregulatory deficits of different degrees. The lowest M-wave phase shift angles were found in the PCA territory distally to intracranial BVAD. CONCLUSION: This study suggests that DCA testing of the PCA could help to quantify the hemodynamic impact of BVAD. It highlights the relevance of functional TCD sonography as a useful diagnostic tool for the hemodynamic evaluation of vertebrobasilar disease.

Treatment of wide-necked aneurysms with balloon-expandable polyurethane-covered stentgrafts: experience in an animal model.

OBJECTIVE: Endovascular treatment of intracranial wide-necked aneurysms employing stentgrafts might constitute a promising alternative to established neurosurgical or endovascular treatment options. However, there is uncertainity concerning long-term vessel patency and biocompatibility of the covering material used for these stentgrafts. The objective of our study was, therefore, to evaluate in an animal model of wide necked aneurysms, which changes within the parent vessel wall are present after stentgraft placement using polyurethane as the covering material. METHODS: Wide-necked aneurysms were created in rabbits by distal ligation and intraluminal incubation of the right common carotid artery with elastase. All 10 animals were treated with polyurethane covered stentgrafts. Angiography and histological analyses were performed including immunohistochemical investigations for estimating the proliferation of the intima and possible inflammatory infiltration of the vessel wall after one (n = 5) and three months (n = 5) observation. RESULTS: Stentgrafts led to a complete and stable aneurysm occlusion in all but one animal in which the stent was initially misplaced. In one animal, the stentgraft was completely occluded as visible both at angiography and on histological examination. Here, old thrombus was found within the stent although the animal was on antiplatelet therapy. The other stentgrafts remained patent and demonstrated only minimal proliferative carrier vessel wall changes and no in-stent stenosis. CONCLUSIONS: In previous animal models using Dacron covered stentgrafts, a poor short term patency rate due to the limited biocompatibility was found. We found, that Polyurethane seemed to have less adverse effects upon the vessel wall. However, a longer follow-up period is necessary to exclude delayed stenosis of the parent vessels. Stentgrafts may, therefore, play a role in broad based aneurysms, dissecting aneurysms or pseudoaneurysms, however, vessel sacrifice using permanent balloon occlusion may be a safer and better established alternative compared to the use of stentgrafts.

Interneuronal systems of the cervical spinal cord assessed with BOLD imaging at 1.5 T.

The purpose of this study was to investigate if functional activity with spinal cord somatosensory stimulation can be visualized using BOLD fMRI. We investigated nine healthy volunteers using a somatosensory stimulus generator. The stimuli were applied in three different runs at the first, third, and fifth finger tip of the right hand, respectively, corresponding to dermatomes c6, c7, and c8. The stimuli gave an increase of BOLD signal (activation) in three different locations of the spinal cord and brain stem. First, activations could be seen in the spinal segment corresponding to the stimulated dermatome in seven out of nine volunteers for c6 stimulation, two out of eight for c7, and three out of eight for c8. These activations were located close to the posterior margin of the spinal cord, presumably reflecting synaptic transmission to dorsal horn interneurons. Second, activation in the medulla oblongata was evident in four subjects, most likely corresponding to the location of the nucleus cuneatus. The third location of activation, which was the strongest and most reliable observed was inside the spinal cord in the c3 and c4 segments. Activation at these spinal levels was almost invariably observed independently of the dermatome stimulated (9/9 for c6, 8/8 for c7, and 7/8 for c8 stimulation). These activations may pertain to an interneuronal system at this spinal level. The results are discussed in relation to neurophysiological studies on cervical spinal interneuronal pathways in animals and humans.

White-matter disease in 18q deletion (18q-) syndrome: magnetic resonance spectroscopy indicates demyelination or increased myelin turnover rather than dysmyelination.

Proton magnetic resonance spectroscopic data ((1)H-MR spectroscopy) of patients with 18q deletion syndrome have not yet been reported. (1)H-MR spectroscopy, performed in an affected 2-year-old girl with markedly delayed neuromotor development and typical supratentorial white-matter disease (WMD), showed an increase of choline and alpha-glutamate concentrations. Eight months later, simultaneously with clinical improvement, alpha-glutamate had normalised whereas choline remained slightly increased. Active demyelination or increased myelin turnover might contribute to the hitherto unexplained WMD of this rare disorder.

[Subperiosteal orbital hemorrhage after heart surgery]. / Subperiostales Hämatom der Orbita nach kardiochirurgischem Eingriff.

We report on a patient who suffered sudden diplopia after heart surgery. Computed tomography of the orbita revealed a subperiosteal hemorrhage as the underlying cause. We discuss possible mechanisms that may have led to the bleeding as well as therapeutic options.

[Cerebral perfusion sonography in comparison with perfusion MRT: a study with healthy volunteers]. / Zerebrale Perfusionssonographie im Vergleich zur Perfusions-MRT: Eine Normalprobandenstudie.

AIM: Perfusion harmonic imaging (PHI) has been used for several years now in neurological as well as other patients. The aim of the study was to compare PHI with perfusion-weighted MR tomography (pMRT) for the evaluation of cerebral parenchymal perfusion. Furthermore, the influence of different trigger intervals on the contrast kinetics in PHI was analysed. METHOD: Fifteen healthy individuals were evaluated with two transtemporal PHI investigations and one pMRT. In PHI, 62 time-triggered images at two different trigger intervals (1 and 0.4 Hz) were recorded after an intravenous bolus of 2 ml of SonoVue(R). pMRT was carried out according to a standard technique using 0.2 mmol/kg Gadolinium-DTPA (Magnevist) and T2*-weighted EPI-sequences. Time-intensity curves of PHI and pMRT-determined data including peak intensity (PI), time-to-peak-intensity (TTP [s]), and area-under-the-curve (AUC) were calculated off-line from 4 regions of interest: ipsi- and contralateral thalamus (i-TH, k-TH), lentiform nucleus (NUC), and white matter (ML). These parameters were compared between the data sets of the two different trigger intervals. Additionally, ratios of the above parameters were calculated to compare the two methods (TH/NUC and TH/ML). RESULTS: Comparison of the two trigger intervals showed significantly lower AUC-values at the higher trigger interval, while the trigger interval had no significant impact on PI- and TTP- values. A good correlation was seen between the trigger intervals for AUC-values and, to a lesser extent, for PI-values. TTP-values did not correlate. TTP was the only depth-independent parameter. There was no significant difference between PHI and pMRT in 10 of 12 parameter ratios analysed. Merely the PI-ratio of i-TH/ML was significantly different at both trigger intervals. CONCLUSION: Regarding the development of adequate set-ups for transcranial PHI, further parameters with impact on contrast agent kinetics (MI, dose of contrast agent) have to be taken into account in addition to the trigger interval. Our findings suggest that, within certain limits, PHI is an imaging technique representing a valuable alternative to MR perfusion imaging, with the TTP representing the most reliable parameter. The AUC is useful for semi-quantitative evaluation of brain perfusion.

Are the configuration and neck morphology of experimental aneurysms predictable? A technical approach.

Aneurysm configuration and neck morphology are important factors in the decision for cerebral aneurysm therapy, i.e., clipping versus coiling. The aim of our study was to create various aneurysm configurations in a predictable and reproducible way in an animal model. In our recently proposed endovascular approach to produce bifurcation aneurysms in the rabbit, the right common carotid artery (CCA) is surgically exposed and distally ligated, and a sheath is advanced retrogradely into the CCA, the base of which is proximally occluded using a Fogarty balloon. Subsequently, elastase is injected via a microcatheter that is placed directly distal to the balloon and allowed to incubate for 20 min. After removal of the sheath, saccular aneurysms begin to form within 2 weeks. For greater variability in aneurysm size and neck morphology, we modified two parameters of this formerly established elastase-induced aneurysm model--the distance between the balloon and sheath and the level of balloon position--before the elastase was endoluminally incubated in 15 rabbits. Three weeks after aneurysm induction, the size and configuration of the aneurysms were controlled using DSA. Our results confirm that balloon occlusion in the brachiocephalic trunk results in broad-based aneurysms, whereas balloon occlusion in the CCA gives rise to circumscribed aneurysm necks. By increasing the distance between the balloon and sheath, the rabbits developed significantly larger aneurysms. The balloon-sheath distance and the level of balloon occlusion proved to be parameters whose modifications result in predictable and reproducible aneurysm variants that can be used for the testing of endovascular devices.

Detection of intracranial aneurysms with multislice CT: comparison with conventional angiography.

We assessed the diagnostic accuracy of multislice CT in detection of intracranial aneurysms in patients presenting with subarachnoid or intracranial haemorrhage. Multislice CT and multiplanar digital subtraction angiography (DSA) images were obtained in 50 consecutive patients presenting with subarachnoid (SAH) and/or intracranial haemorrhage and reviewed by three neuroradiologists for the number, size and site of any aneurysms. The CT data were assessed using multiplanar reformats (MPR), maximum-intensity projections (MIP), surface-shaded display (SSD) and volume-rendering (VRT). In conventional angiography 51 aneurysms were detected in 41 patients. CT angiography (CTA) showed up to 48 aneurysms in 39 patients, depending on the observer. The overall sensitivity of multislice CT was 83.3% for small (< 4 mm), 90.6% for medium-size (5-12 mm) and 100% for large (> 13 mm) aneurysms. The sensitivity of multislice CTA to medium-size and large intracranial aneurysm is within the upper part of the range reported for helical single-slice CT. However, as small aneurysms may not be found, DSA remains the standard technique for investigation of SAH.

Haemorrhagic tracheal necrosis as a lethal complication of an aneurysm model in rabbits via endoluminal incubation with elastase.

BACKGROUND: We describe a lethal complication of an aneurysm model in rabbits for saccular aneurysmal creation via endoluminal incubation with elastase. METHOD: In 24 anaesthetized female New Zealand White rabbits, the right common carotid artery (CCA) was ligated distally to the arteriotomy. A 4F sheath was then placed retrograde into the CCA, and its origin was occluded endoluminally using a 2F Fogarty balloon. Elastase was incubated above the balloon in the separated vessel lumen for the duration of 20 minutes. Two weeks later, digital subtraction angiography was performed for aneurysm control. Two animals were then sacrificed and the aneurysm studied on histology. All animals that died within the experiment were examined post-mortem. FINDINGS: Following this protocol, an aneurysm with a mean size of 7.6 x 3.2 mm could be created in 11 out of 24 animals. 9 out of 13 animals with lethal outcome died from haemorrhagic necrosis of the trachea with subsequent pulmonary complications. DSA releaved an arterial branch originating from the proximal CCA in a near 90 degree-angle aiming at the trachea. INTERPRETATION: The endoluminal incubation with elastase is suitable for aneurysm creation of reproducible size that are suited to test new endovascular devices such as stents and new coils. One should always be aware of an arterial branch of the CCA supplying the trachea. In case of elastase instillation into this branch, lethal haemorrhagic necrosis of the trachea occurs. Bearing this complication in mind, we have experienced a minimal loss of animals in subsequent studies.

M-wave analysis and passive tilt in patients with different degrees of carotid artery disease.

BACKGROUND AND PURPOSE: Carotid artery disease (CAD) is able to critically impair cerebral autoregulation which increases the risk for stroke. As therapeutic strategy largely depends on the degree of CAD, we investigated whether this gradation is also related to significant changes in autoregulatory capacity. We applied cross-spectral analysis (CSA) of spontaneous Mayer-wave (M-wave) oscillations and passive tilting (PT) to test cerebral autoregulation. METHODS: Cerebral autoregulation was tested in 102 patients with carotid stenosis (> or =70%) or occlusion and 14 controls by comparison of continuous transcranial Doppler sonography of the middle cerebral artery and beat-to-beat arterial blood pressure (ABP) during PT to 80 degrees head-up position as well as by CSA of M-waves (3-9 cpm). RESULTS: The orthostatic decrease of cerebral blood flow velocity (CBFV) was not correlated with the degree of CAD and showed a lower sensitivity and specificity than phase angle shifts between M-waves in ABP and CBFV (sensitivity: 75-80%, specificity: 86%). Phase angles were gradually lowered in carotid stenoses > 70%, but apparently, they were only moderately correlated with the degree of CAD (r = -0.35, P < 0.01). An additional influencing factor seemed to be the sufficiency of collateralization. CONCLUSIONS: The results show that CSA of M-waves is more appropriate for testing autoregulation than PT. CSA suggests that the capacity to autoregulate depends to a certain extent on the degree of CAD but is also influenced by the sufficiency of collateral pathways and pre-existing strokes.

Dynamic autoregulation testing in patients with middle cerebral artery stenosis.

BACKGROUND AND PURPOSE: Cross-spectral analysis (CSA) of spontaneous oscillations in cerebral blood flow velocity (CBFV) and arterial blood pressure is considered a sensitive and convenient method for dynamic autoregulation testing. So far, it has been unclear whether CSA can be used to assess stenoses of the intracranial arteries. METHODS: This study for the first time applies CSA to 26 patients with low-, moderate-, and high-degree M1 stenoses and 14 normal control subjects. Using CSA, we studied spontaneous oscillations (M waves, 3 to 9 cpm; B waves, 0.5 to 3 cpm) in continuous recordings of transcranial Doppler of the middle cerebral artery and simultaneously recorded beat-to-beat blood pressure. RESULTS: A gradual decrease in pulsatility indexes confirmed the increasing hemodynamic relevance of the stenoses. Compared with control subjects, M-wave phase shifts between CBFV and blood pressure were gradually reduced with increasing degree of M1 stenosis (control subjects, 44.6+/-21.1 degrees; high-degree stenosis, 16.7+/-19.5 degrees ). The phase relation between B waves in blood pressure and CBFV was shifted to positive values (low-degree stenosis, -9.7+/-108.4 degrees; high-degree stenosis, 50.9+/-43.8 degrees ). CONCLUSIONS: Because B- and M-wave phase shifts seem to characterize the degree of autonomy of CBFV modulation, this study suggests that with increasing degree of M1 stenosis, the arteriolar function is impaired. It shows that CSA is of indicative use for the assessment of intracranial artery stenosis.

Endovascular treatment of experimentally induced aneurysms in rabbits using stents: a feasibility study.

Although Guglielmi detachable coil (GDC) systems have been generally accepted for treatment of intracranial aneurysms, primary stenting of aneurysms using porous stents or implantation of coils after stent placement remains experimental. Testing of these new methods requires an animal model which imitates human aneurysms in size, configuration and neck morphology. We assessed in detail the technical requirements of and steps for transfemoral stent treatment of experimentally induced aneurysms at the top of the brachiocephalic trunk in rabbits. We created aneurysms in ten rabbits by distal ligation and intraluminal digestion of the right common carotid artery with elastase. We treated five animals with porous stents alone, and five with stents plus coiling via the meshes of the stent, which permitted dense packing of coils. No complications related to the procedures occurred. In all animals, even in those treated solely with porous stents, total occlusion of the aneurysm was achieved. Our animal model can be suitable for testing the biocompatibility and occlusion rate of new methods and devices for the treatment of experimental aneurysms.