Risk factors for the development of secondary intracranial hypertension in acute cerebral venous thrombosis.

PURPOSE: Intracranial hypertension (IH) can complicate cerebral venous thrombosis (CVT), potentially causing permanent visual loss. Current knowledge on risk factors for the development of IH following CVT is scarce. We applied a compound classifier (CSF opening pressure > 25 cmH2O, papilledema, or optic disc protrusion on MRI) as a surrogate for IH and studied the predictive value of thrombus location, the number of thrombosed segments, and thrombus volume. METHODS: We prospectively included 26 patients with acute CVT and complete MRI data. IH was defined by CSF opening pressure > 25 cmH2O, papilledema, or optic disc protrusion on MRI. Using high-resolution contrast-enhanced venography, we determined the thrombus location, number of thrombosed segments, and thrombus volume. We analyzed their association with IH by logistic regression, their predictive power by the area under the receiver operating characteristic curve, and their association with CSF opening pressure by linear regression. RESULTS: IH occurred in 46% of CVT patients and was associated with higher thrombus volume (AUC 0.759, p = 0.025) and superior sagittal sinus thrombosis both alone (OR 2.086, p = 0.049) and combined with transverse sinus thrombosis (OR 2.014, p = 0.028). Effects in patients presenting CSF opening pressure > 25 cm H2O and the compound classifier were consistent. Thrombus volume > 4 ml was the single most important predictor of higher CSF opening pressure (ß = 0.566, p = 0.035), increasing IH risk. CONCLUSION: Larger thrombus volume, dominant transverse sinus occlusion, and extensive superior sagittal combined with transverse sinus thrombosis were associated with IH. Thrombus volumetry might identify patients at risk for IH and direct further clinical evaluation.

[Idiopathic intracranial hypertension]. / Idiopathische intrakranielle Hypertension.

This review describes the clinical findings as well as thes diagnostic and therapeutic options for idiopathic intracranial hypertension (pseudotumor cerebri). Furthermore, the pathophysiological concepts are discussed. Idiopathic intracranial hypertension is characterized by signs and symptoms of raised intracranial pressure with no established pathogenesis. Common symptoms include headaches, visual loss and pulsatile tinnitus. Treatment has two major goals: the alleviation of headaches and the preservation of vision. Weight loss and acetazolamide are the cornerstones in the treatment of the disorder. Drainage of cerebrospinal fluid, optic nerve sheath fenestration and stent angioplasty of a sinus stenosis can be employed in severe cases.

Reliability of cerebral vein volume quantification based on susceptibility-weighted imaging.

INTRODUCTION: Susceptibility-weighted imaging (SWI) visualizes even small cerebral veins and might, therefore, be valuable in monitoring neurological diseases affecting cerebral veins. Since it is generally difficult to evaluate individual results of quantitative MRI measurements, an automatic approach would be highly appreciated to assist the diagnostic process. The aim of this study was to evaluate the rescan and reanalysis reliability using an automatic venous volumetric approach based on SWI in healthy controls. METHODS: SWI was performed in ten healthy controls undergoing MRI examinations using a 32-channel head coil at 3 T five times on five different days. To test for rescan and reanalysis variability, the deep cerebral vein volume was quantified using ANTs and SPM8. RESULTS: Total volumes of cerebral deep veins measured during five MRI scans in ten individuals (n = 50 scans) showed intra-individual volume changes ranging from 0.07 to 1.03 ml (mean variability = 10.2 %). Automatic reanalyses revealed exactly the same results in all scans. CONCLUSION: Automatic SWI-based cerebral vein volumetry shows acceptable rescan-and excellent reanalyses-reliability in healthy volunteers. Therefore, this approach might be beneficial in intra-individual follow-up studies of neurological diseases affecting the cerebral venous system.

Wall shear stress distribution at the carotid bifurcation: influence of eversion carotid endarterectomy.

OBJECTIVES: To test the feasibility of four-dimensional (4D) flow MRI to quantify the systolic wall shear stress (WSSsystole) and oscillatory shear index (OSI) in high-grade internal carotid artery (ICA) stenosis before and after endarterectomy (CEA). METHODS: Twenty patients with ≥60 % ICA stenosis were prospectively and consequently included. Four-dimensional flow MRI was used to measure individual time-resolved 3D blood flow velocities. Segmental WSSsystole and OSI were derived at eight wall segments in analysis planes positioned along the ICA, common (CCA) and external carotid artery (ECA). RESULTS: Regional WSSsystole of all patients decreased after CEA (P < 0.05). Changes were most prominent at the ICA bulb but remained unchanged in the CCA and ECA. OSI was significantly lower after CEA in the lateral vessel walls (P < 0.05). For analysis planes at the stenosis in- and outlet, a reduction of mean WSSsystole by 32 % and 52 % (P < 0.001) and OSI distal to the stenosis (40 %, P = 0.01) was found after CEA. CONCLUSIONS: Our findings show the potential of in vivo 4D flow MRI to quantify haemodynamic changes in wall shear stress even in patients with complex flow conditions.

[Innovations in neuro-monitoring using transcranial ultrasound]. / Innovationen im Neuromonitoring mit Ultraschall.

This review describes transcranial ultrasound-based neuromonitoring by assessing changes of brain structures or cerebral blood flow over time. Some of the presented ultrasound techniques are still experimental. They are advantageous as they provide non-invasive and bed-side imaging. Thus, time, costs and potentially hazardous side effects due to transportation of acutely ill patients to CT or MRI scanners can be avoided. An assessment of increased cerebral pressure can be achieved by repeated determination of individual pulsatility index, cerebral venous blood flow, midline shift and transorbital optic sheath measurements. Moreover, transcranial duplex sonography offers the possibility to detect intracranial haemorrhage and to guide neurosurgical interventions. Finally, the value of measuring cerebral autoregulation and the current state of the art regarding sonothrombolysis in acute intracranial arterial thrombosis is presented.

Acute tick-borne encephalitis during pregnancy - An alarming combination.

We report on a pregnant patient who contracted tick-borne encephalitis (TBE) during her second trimester in an endemic region in Southern Germany. The patient presented with typical symptoms including fever and headache, and TBE infection was confirmed by positive blood and cerebrospinal fluid (CSF) testing. During acute infection there was no evidence of pregnancy complications, and the mother recovered well. We performed a clinical follow-up examination of both mother and child eight months after the diagnosis of TBE, which revealed no signs of sequelae. This case study presents rare evidence of TBE infection during pregnancy and may provide guidance for both physicians as well as mothers-to-be dealing with TBE.

3D blood flow characteristics in the carotid artery bifurcation assessed by flow-sensitive 4D MRI at 3T.

To determine three-dimensional (3D) blood flow patterns in the carotid bifurcation, 10 healthy volunteers and nine patients with internal carotid artery (ICA) stenosis > or =50% were examined by flow-sensitive 4D MRI at 3T. Absolute and mean blood velocities, pulsatility index (PI), and resistance index (RI) were measured in the common carotid arteries (CCAs) by duplex sonography (DS) and compared with flow-sensitive 4D MRI. Furthermore, 3D MRI blood flow patterns in the carotid bifurcation of volunteers and patients before and after recanalization were graded by two independent readers. Blood flow velocities measured by MRI were 31-39% lower than in DS. However, PI and RI differed by only 13-16%. Rating of 3D flow characteristics in the ICA revealed consistent patterns for filling and helical flow in volunteers. In patients with ICA stenosis, 3D blood flow visualization was successfully employed to detect markedly altered filling and helical flow patterns (forward-moving spiral flow) in the ICA bulb and to evaluate the effect of revascularization, which restored filling and helical flow. Our results demonstrate the feasibility of flow-sensitive 4D MRI for the quantification and 3D visualization of physiological and pathological flow patterns in the carotid artery bifurcation.

[Diagnosing stroke aetiologies. Morphologic and functional analysis of the aorta and carotid arteries by MRI]. / Diagnostik von Schlaganfallursachen. Morphologische und funktionelle MRT-Darstellung der Aorta und der Karotiden.

Magnetic resonance imaging allows detailed visualization of the thoracic aorta and is not limited by air artefacts or insonation angles like transoesophageal echocardiography (TEE). Thus the aortic arch can be investigated with higher accuracy, and additional embolic high-risk sources such as complex plaques can be additionally detected by MRI in patients with cryptogenic stroke. Furthermore, MRI provides exact 3D plaque localisation and can be combined with multidirectional 3D MRI velocity mapping. In this way, previously not demonstrable retrograde flow paths originating at complex descending aortic plaques reaching the supra-aortic great arteries can be identified as the probable stroke mechanism in certain patients. The same technique can also be applied to the carotid arteries. This allows analysing the complex 3D helical flow within the internal carotid artery as well as measuring absolute flow velocities and wall shear stress in combination with data on vessel anatomy derived from conventional MR angiography. It is the purpose of this work to describe the state of the art of these modern MR imaging techniques and their potential to identify potential stroke mechanisms, and to analyse the particular role of individual haemodynamic factors on the development of local atherosclerosis.

Reliability of aortic MRI at 3 Tesla in patients with acute cryptogenic stroke.

OBJECTIVES: To evaluate a new three dimensional (3D) MRI protocol for the reliable detection of aortic high risk plaques compared with transoesophageal echocardiography (TOE) and to test the reliability of additional MRI in stroke of undetermined aetiology. METHODS: 74 acute stroke patients were examined by both TOE and MRI at 3 Tesla with special regard to aortic high risk plaques (ie, > OR = 4 mm, superimposed thrombi). ECG synchronised pre- and post-contrast T1 weighted 3D imaging (spatial resolution approximately 1 mm3) covering the thoracic aorta was employed. In plaques > OR = 3 mm, additional two dimensional T2 imaging and time resolved (CINE) imaging sequences were performed. Aetiology of brain ischaemia was classified according to modified TOAST (Trial of Org 10172 in Acute Stroke Treatment) criteria. Aortic high risk embolic sources detected by MRI in patients with cryptogenic stroke were evaluated. RESULTS: Differences in maximum aortic wall thickness for TOE and MRI were not statistically significant for all aortic segments. The overall number of high risk plaques detected by MRI (n = 74) was substantially higher compared with TOE (n = 47). Most noticeably, MRI identified aortic high risk pathologies in 8/26 (30.8%) patients with cryptogenic stroke after standard diagnostics, including TOE (n = 2: dissection or thrombus; n = 6: plaques > OR = 4 mm). CONCLUSIONS: Our results demonstrate the feasibility of this 3D MRI protocol for the reliable detection of aortic high risk plaques in acute stroke patients. Because of improved visualisation of the aortic arch and the detection of additional embolic sources not seen by standard diagnostics, this novel technique may become a valuable tool for future patients with cryptogenic stroke.

Longitudinal Volume Quantification of Deep Medullary Veins in Patients with Cerebral Venous Sinus Thrombosis : Venous Volume Assessment in Cerebral Venous Sinus Thrombosis Using SWI.

PURPOSE: Susceptibility-weighted imaging (SWI) visualizes small cerebral veins with high sensitivity and could, thus, enable quantification of hemodynamics of deep medullary veins. We aimed to evaluate volume changes of deep medullary veins in patients with acute cerebral venous sinus thrombosis (CVST) over time in comparison to healthy controls. METHODS: All magnetic resonance imaging (MRI) experiments were executed at 3 T using a 32-channel head coil. Based on SWI and semiautomatic postprocessing (statistical parametric mapping [SPM8] and ANTs), the volume of deep medullary veins was quantified in 14 patients with acute CVST at baseline and the 6­month follow-up, as well as in 13 healthy controls undergoing repeated MRI examination with an interscan interval of at least 1 month. RESULTS: Deep medullary venous volume change over time was significantly different between healthy controls and patient groups (p < 0.001). Patients with superior sagittal sinus thrombosis (SSST) showed a significant decline from baseline to follow-up measurements (9.8 ± 4.9 ml versus 7.5 ± 4.2 ml; p = 0.02), whereas in patients with transverse sinus thrombosis (TST) and healthy controls no significant volume changes were observable. CONCLUSIONS: Venous volume quantification was feasible and reproducible both in healthy volunteers and in patients. The decrease of venous volume in patients over time represents improvement of venous drainage, reduction of congestion, and normalization of microcirculation due to treatment. Thus, quantification of venous microcirculation could be valuable for estimation of prognosis and guidance of CVST therapy in the future.

[Flow-sensitive in-vivo 4D MR imaging at 3T for the analysis of aortic hemodynamics and derived vessel wall parameters]. / Die Analyse aortaler Hämodynamik und Gefässwandparameter mittels fluss-sensitiver in-vivo 4D-MRT bei 3 Tesla.

Modern phase contrast MR imaging at 3 Tesla allows the depiction of 3D morphology as well as the acquisition of time-resolved blood flow velocities in 3 directions. In combination with state-of-the-art visualization and data processing software, the qualitative and quantitative analysis of hemodynamic changes associated with vascular pathologies is possible. The 4D nature of the acquired data permits free orientation within the vascular system of interest and offers the opportunity to quantify blood flow and derived vessel wall parameters at any desired location within the data volume without being dependent on predefined 2D slices. The technique has the potential of overcoming the limitations of current diagnostic strategies and of implementing new diagnostic parameters. In light of the recent discussions regarding the influence of the wall shear stress and the oscillatory shear index on the genesis of arteriosclerosis and dilatative vascular processes, flow-sensitive 4D MRI may provide the missing diagnostic link. Instead of relying on experience-based parameters such as aneurysm size, new hemodynamic considerations can deepen our understanding of vascular pathologies. This overview reviews the underlying methodology at 3T, the literature on time-resolved 3D MR velocity mapping, and presents case examples. By presenting the pre- and postoperative assessment of hemodynamics in a thoracic aortic aneurysm and the detailed analysis of blood flow in a patient with coarctation we underline the potential of time-resolved 3D phase contrast MR at 3T for hemodynamic assessment of vascular pathologies, especially in the thoracic aorta.

Dynamic cerebral autoregulation in acute ischemic stroke assessed from spontaneous blood pressure fluctuations.

BACKGROUND AND PURPOSE: This study investigates dynamic cerebral autoregulation assessed from spontaneous blood pressure (ABP) and cerebral blood flow velocity (CBFV) fluctuations and its time course in acute ischemic stroke. METHODS: Forty patients admitted with acute ischemic stroke in the territory of the middle cerebral artery (MCA) were enrolled. Admission National Institutes of Health Stroke score was 6+/-4. Study 1 was performed within 22 (+/-11) hours and study 2 was performed within 134 (+/-25) hours of ictus. The final analysis comprised 33 and 29 patients for study 1 and study 2, respectively. Twenty-five age- and sex-matched controls were studied. ABP (Finapres method) and CBFV in both MCAs (transcranial Doppler) were recorded over 10 minutes. Correlations between diastolic and mean ABP and CBFV fluctuations were averaged, yielding the correlation coefficient indices (Dx, Mx). Transfer function analysis was applied to obtain phase shift and gain between ABP and CBFV oscillations. RESULTS: No disturbance of autoregulation was indicated by all parameters at study 1. Separate analyses for clinical severity, stroke side, and size did not reveal significant differences for the various autoregulatory indices at study 1 and 2. At study 2, MCA flow velocity was significantly increased on both sides, the autoregulation index Mx was slightly but significantly (P<0.05) worse on both sides in comparison to study 1, and phase showed a trend toward poorer values on affected sides. No significant differences to controls occurred. Clinical outcome in patients completing both studies was good in all but one patient. CONCLUSIONS: Dynamic cerebral autoregulation assessed from spontaneous blood pressure fluctuations does not seem to be relevantly disturbed in early minor MCA stroke. At the subacute stage, slight autoregulatory disturbance may be present.

Comparison of blood flow velocity quantification by 4D flow MR imaging with ultrasound at the carotid bifurcation.

BACKGROUND AND PURPOSE: 4D flow MR imaging is an emerging technique that allows visualization and quantification of 3D blood flow in vivo. However, representative studies evaluating its accuracy are lacking. Therefore, we compared blood flow quantification by using 4D flow MR imaging with US within the carotid bifurcation. MATERIALS AND METHODS: Thirty-two healthy volunteers (age 25.3 ± 3.4 years) and 20 patients with ≥50% ICA stenosis (age 67.7 ± 7.4 years) were examined preoperatively and postoperatively by use of 4D flow MR imaging, with complete coverage of the left and right carotid bifurcation. Blood flow velocities were assessed with standardized 2D analysis planes distributed along the CCA and the ICA and were compared with US at baseline and postoperatively in patients. In addition, we tested reproducibility and interobserver agreement of 4D MR imaging in 10 volunteers. RESULTS: Overall, 101 CCAs and 79 ICAs were available for comparison. MR imaging underestimated (P < .05) systolic CCA and ICA blood flow velocity by 26% (0.79 ± 0.29 m/s vs 1.06 ± 0.31 m/s) and 19% (0.72 ± 0.21 m/s vs 0.89 ± 0.27 m/s) compared with US. Diastolic blood flow velocities were similar for MR imaging and US (differences, 9% and 3%, respectively; not significant). Reproducibility and interobserver agreement of 4D flow MR imaging was excellent. CONCLUSIONS: 4D flow MR imaging allowed for an accurate measurement of blood flow velocities in the carotid bifurcation of both volunteers and patients with only moderate underestimation compared with US. Thus, 4D flow MR imaging seems promising for a future combination with MRA to comprehensively assess ICA stenosis and related hemodynamic changes.

Do stroke patients with normal carotid arteries require TEE for exclusion of relevant aortic plaques?

OBJECTIVES: This study investigated (a) the hypothesis that stroke patients with aortic atheroma would show comparable atherosclerotic changes in the carotid arteries, which are easily accessible for ultrasound evaluation and (b) the possibility of carotid duplex sonography as a replacement for transoesophageal echocardiography (TEE) for the exclusion or prediction of relevant aortic plaques. METHODS: In 301 consecutive patients (mean age 62 years) with acute cerebral ischaemia, two dimensional ultrasound measurements were taken of common carotid artery intima media thickness (IMT) and maximal plaque area (PA) and the local degree of internal carotid artery (ICA) stenosis were determined. Maximal aortic wall thickness (AWT) was assessed by TEE. RESULTS: An IMT < or =0.9 mm yielded a negative predictive value (NPV) of 95.8% for exclusion of aortic atheromas > or =4 mm and an NPV of 100% for the exclusion of aortic thrombi. However, positive predictive value of IMT >0.9 mm was low (29.6%), increasing only slightly in the presence of carotid plaques (33%). Incidence of aortic thrombi was significantly higher with > or =50% compared with <50% ICA stenosis (11.3% v 3.9%, respectively). IMT and PA correlated moderately with AWT (r = 0.47, r = 0.53, respectively; p<0.001). Systolic blood pressure, coronary heart disease and peripheral artery disease, increased IMT, and ICA stenosis > or =50% were independently related to AWT > or =4 mm. CONCLUSIONS: A high NPV of normal carotid ultrasound does not support routine TEE for the exclusion of complex aortic plaques as a high risk source of cerebral embolism. However, in patients with carotid atherosclerosis, particularly in those with ICA stenosis > or =50%, TEE should be performed to exclude an additional high risk source for stroke.

Fulminant acute disseminated encephalomyelitis mimicking acute bacterial menigoencephalitis.

Most patients with acute disseminated encephalomyelitis (ADEM) recover quickly under corticosteroid treatment and have a favourable long-term prognosis. We report on a young woman with acute onset of an extensive and solitary white-matter lesion in the left hemisphere. Fever, high pleocytosis and elevated protein in cerebrospinal fluid initially suggested bacterial meningoencephalitis. The patient died from brain herniation despite maximal conservative therapy. Histological changes in necropsy were consistent with the diagnosis ADEM. Treatment options of fulminant ADEM are discussed.