Persistent hemodynamic changes in ruptured brain arteriovenous malformations.

BACKGROUND AND PURPOSE: Hemodynamic properties of brain arteriovenous malformations (AVMs) with risk factors for a future hemorrhage are essentially unknown. We hypothesized that AVMs with anatomic properties, which are associated with an increased rupture risk, exhibit different hemodynamic characteristics than those without these properties. METHODS: Seventy-two consecutive patients with AVMs diagnosed by conventional angiography underwent MRI examination, including time-resolved 3-dimensional MR angiography. Signal-intensity curves derived from the time-resolved 3-dimensional MR angiography datasets were used to calculate relative blood flow transit times through the AVM nidus based on the time-to-peak parameter. For identification of characteristics associated with altered transit times, a multiple normal regression model was fitted with stepwise selection of the following regressors: intracranial hemorrhage, deep nidus location, infratentorial location, deep drainage, associated aneurysm, nidus size, draining venous stenosis, and number of draining veins. RESULTS: A previous intracranial hemorrhage is the only characteristic that was associated with a significant alteration of the relative transit time, leading to an increase of 2.4 seconds (95% CI, 1.2-3.6 seconds;, P<0.001) without adjustment and 2.1 seconds (95% CI, 0.6-3.6 seconds; P=0.007) with adjustment for all other regressors considered. The association was independent of the bleeding age. CONCLUSIONS: Hemodynamic parameters do not seem useful for risk assessment of an AVM-related hemorrhage because only a previous AVM rupture leads to a significant and permanent alteration of the hemodynamic situation.

Rigid 3D-3D registration of TOF MRA integrating vessel segmentation for quantification of recurrence volumes after coiling cerebral aneurysm.

INTRODUCTION: A fast and reproducible quantification of the recurrence volume of coiled aneurysms is required to enable a more timely evaluation of new coils. This paper presents two registration schemes for the semi-automatic quantification of aneurysm recurrence volumes based on baseline and follow-up 3D MRA TOF datasets. METHODS: The quantification of shape changes requires a previous definition of corresponding structures in both datasets. For this, two different rigid registration methods have been developed and evaluated. Besides a state-of-the-art rigid registration method, a second approach integrating vessel segmentations is presented. After registration, the aneurysm recurrence volume can be calculated based on the difference image. The computed volumes were compared to manually extracted volumes. RESULTS: An evaluation based on 20 TOF MRA datasets (baseline and follow-up) of ten patients showed that both registration schemes are generally capable of providing sufficient registration results. Regarding the quantification of aneurysm recurrence volumes, the results suggest that the second segmentation-based registration method yields better results, while a reduction of the computation and interaction time is achieved at the same time. CONCLUSION: The proposed registration scheme incorporating vessel segmentation enables an improved quantification of recurrence volumes of coiled aneurysms with reduced computation and interaction time.

Blister-like aneurysms--a diagnostic and therapeutic challenge.

Blister-like internal carotid artery (ICA) aneurysms are known for their fragile and thin-walled morphology associated with a high risk of intraprocedural rupture. Neurosurgical and endovascular options are illustrated on three exemplary cases reviewing the diagnostic and therapeutic implications of these special aneurysms. A 49-year-old woman was admitted with subarachnoid hemorrhage (SAH) in which angiography showed a broad-based, small bulging ectasy of the terminal ICA segment. On the attempt of surgical clipping, the aneurysm ruptured leaving a tear in the ICA. After temporary clipping, the rims of the tear were approximated by sutures. Sufficient closure of the remaining leakage was achieved by circumferential wrapping which was secured by two clips. Postoperative angiography confirmed stenosis of the tightened ICA and patient recovered without neurological deficit. Surgical attempt on a second case with bulging of the C4-segment topped by a small aneurysm was fatal due to extensive laceration of the basal ICA intraoperatively. Endovascular stenting was the choice of treatment in a third SAH patient in which angiography was suspicious of a blister-like ICA aneurysm. Six-month follow-up was uneventful; the patient recovered well and further growth of bulging was not seen. Reviewing the literature, blister-like aneurysms tend to arise at uncommon sites not located at the arterial branches. Small and broad-based bulges with or without true saccular aneurysms have to be assessed as characteristic features of blister-like aneurysms. Rupture of the aneurysm involving the carrying artery has to be considered during therapeutic attempts, in which urgent strategies have to be kept in reserve preventing fatal outcome. Blister-like aneurysms is a hazardous affair for neurosurgeons and neuroradiologists as their fragile structure most likely will lead to intraoperative rupture. If endovascular treatment is not promising, wrapping and revascularization techniques come true to still be an important part of the neurosurgeons toolbox for reconstructing a vessel lumen and preserving a sufficient cerebral blood flow.

Quantification of recurrence volumes after endovascular treatment of cerebral aneurysm as surrogate endpoint for treatment stability.

INTRODUCTION: New coils with unproven clinical benefit enlarge the armamentarium for endovascular aneurysm treatment continuously. Large patient numbers needed to detect benefits of such new techniques prevent timely evaluation of efficacy. We propose measuring the volume of aneurysm recurrences as surrogate endpoint for coil stability. We hypothesize that this method allows detecting effects of new materials with reduced sample sizes in comparison to conventional studies with dichotomous endpoints. METHODS: Institutional review board approval and informed consent were obtained. Fifty-nine patients with decreasing aneurysm size and at least two available follow-up time-of-flight magnetic resonance angiographies (ToF-MRAs) were included. Newly developed software for measuring aneurysm volume differences based on ToF-MRA images was used. Based on the observed recurrence volumes and retreatment rates, the sample size for future studies comparing standard versus "new coils" were calculated. RESULTS: Mean recurrence volume was 38.92 µl (SD110.85 µl). To show a 50% reduction of retreatment rate to control (p = 0.05; power 80%) in a regular study (dichotomous endpoint), the required sample size would be n = 356 compared with n = 78 if using the continuous surrogate endpoint "recurrence volume". When extrapolating our data to data given in the literature, sample sizes could be reduced from n = 948 to n = 74 without loss of statistical power. CONCLUSION: Further studies on new materials using volumetric analysis based on ToF-MRA as surrogate endpoint could substantially decrease sample size and allow a more timely assessment of possible benefit of new materials with a fraction of the cost.

Reference-based linear curve fitting for bolus arrival time estimation in 4D MRA and MR perfusion-weighted image sequences.

The bolus arrival time (BAT) based on an indicator dilution curve is an important hemodynamic parameter. As the direct estimation of this parameter is generally problematic, various parametric models have been proposed that describe typical physiological shapes of indicator dilution curves, but it remains unclear which model describes the real physiological background. This article presents a method that indirectly incorporates physiological information derived from the data available. For this, a patient-specific hemodynamic reference curve is extracted, and the corresponding reference BAT is determined. To estimate a BAT for a given signal curve, the reference curve is fitted linearly to the signal curve. The parameters of the fitting process are then used to transfer the reference BAT to the signal curve. The validation of the method proposed based on Monte Carlo simulations showed that the approach presented is capable of improving the BAT estimation precision compared with standard BAT estimation methods by up to 59% while at the same time reduces the computation time. A major benefit of the method proposed is that no assumption about the underlying distribution of indicator dilution has to be made, as it is implicitly modeled in the reference curve.

Possibilities and limitations in imaging the intracranial arteries in the context of a contrast-enhanced whole-body magnetic resonance angiographic screening protocol at 1.5 versus 3 Tesla.

OBJECTIVE: Evaluation of the diagnostic detectability of the intracranial vasculature on contrast-enhanced whole-body magnetic resonance angiographic (WBMRA) scans at 1.5 versus 3 T. METHODS: Twenty-seven patients with hereditary hyperlipidemia participated. Two experienced neuroradiologists scored the image quality regarding the intracranial arteries applying a 5-point scale. Stenoses and other findings were documented. Weighted κ-statistics were calculated to assess interobserver agreement. RESULTS: Interobserver agreement was very good. Image quality scoring resulted in the following mean values: 3.0 at 1.5 T versus 3.9 at 3 T (P < 0.001). Venous contrast overlay and insufficient anatomic coverage occurred in both groups. Three stenoses were found at both field strengths. CONCLUSIONS: Assessment of the intracranial vasculature on WBMRA data is basically feasible; image quality at 3 T seems superior. Shortcomings appear because of venous contamination and insufficient volume coverage. Therefore, adding a dedicated intracranial MRA to a WBMRA protocol would substantially increase diagnostic certainty.

Endovascular treatment of intracranial aneurysms: long-term stability, risk factors for recurrences, retreatment and follow-up.

It is accepted that endovascular treatment for intracranial aneurysms < 2 cm in diameter is not an alternative option to surgical treatment anymore but has rather gained the place as the first therapeutic option. Still, the long-term efficacy of endovascular aneurysm treatment remains uncertain. This article discusses clinical significance, incidence, risk factors and current management of aneurysm recurrence after endovascular treatment of intracranial aneurysms based on own Hamburg data and review of the literature. It also attempts to address potential solutions and future avenues to improve long-term efficacy of endovascularly treated intracranial aneurysms.

Prevention and treatment of thromboembolism during endovascular aneurysm therapy.

Thromboembolic events with partially or completely persisting neurologic deficits are reported in a substantial number of patients after endovascular aneurysm therapy. The authors discuss the current status of periinterventional coagulation management in endovascular aneurysm therapy. First, some basic aspects of coagulation physiology relevant to neurointerventions are introduced. Second, the most important pharmacological aspects of heparin, protamine sulfate, low-molecular-weight heparin, tissue plasminogen activator, acetylsalicylic acid, clopidogrel, abciximab, tirofiban and eptifibatide for neurointerventions are considered. Third, the use of these drugs in periinterventional coagulation management are discussed with special emphasis on current standards in anticoagulation/antiplatelet strategy and their impact on aneurysm perforation rates. Moreover, treatment of thrombotic complications of endovascular therapy of cerebral aneurysms is discussed.

Abciximab is a safe rescue therapy in thromboembolic events complicating cerebral aneurysm coil embolization: single center experience in 42 cases and review of the literature.

BACKGROUND AND PURPOSE: The purpose of this study was to estimate the safety and efficacy of abciximab treatment in combination with prophylactic heparin, acetylsalicylic acid (ASA), and clopidogrel application in cases of thrombus formation complicating endovascular coil embolization in cerebral aneurysms. METHODS: Thromboembolic incidents during endovascular management of 515 consecutive cerebral aneurysms were observed in 48 cases (9.3%). Eight incidents were observed during embolization of incidental aneurysms (8/174; 4.6%, 95% CI: 2.0 to 8.9%). All patients underwent anticoagulation with heparin and platelet-inhibition with ASA during treatment procedure. In addition, clopidogrel orally was applied 3 days preoperatively in patients with incidental aneurysms. In case of thrombus formation, glycoprotein IIb-IIIa inhibitor abciximab was given in 42 cases. No coagulation-effective rescue treatment was conducted in 5 cases. One patient was treated with r-tPA. End points were infarction on follow-up cranial CT and the rate of intracranial hemorrhages. RESULTS: No infarcts on follow-up CT were observed after treatment with abciximab in 29/42 patients (69.0%, 95% CI: 52.9 to 82.4%). No coagulant rescue therapy was applied in 5 patients because of a small nonocclusive thrombus or good collateral blood supply, showing consecutive infarction on follow-up CT in 3 cases as did the 1 patient treated with r-tPA. No periprocedural bleedings or rebleedings were observed in any case. CONCLUSIONS: Abciximab was safe as rescue treatment in cases of thrombus formation during endovascular aneurysm coiling. In our study the use of Abciximab, in combination with prophylactic anticoagulation and antiaggregation, does not lead to additional intracranial hemorrhages or any extracranial bleeding complications.

Quantitative t2 values predict time from symptom onset in acute stroke patients.

BACKGROUND AND PURPOSE: We hypothesize that in comparison to diffusion-weighted imaging, quantitative T2 values (qT2) are more directly related to water uptake in ischemic tissue, depending on time from symptom onset. We measured the increase of qT2 in the infarct core to quantify the correlation between time from symptom onset and change in qT2. METHODS: Thirty-six patients with acute ischemic stroke in the territory of the proximal middle cerebral artery underwent MRI including diffusion-weighted imaging, fluid-attenuated inversion recovery, and a triple-echo T2 sequence (calculation of T2 maps) within 6 hours after symptom onset. Regions of decreased apparent diffusion coefficient <550 x 10(-9) mm(2)/sec were defined and superimposed onto the corresponding T2 map and the unaffected side in the horizontally flipped maps. Differences of T2/apparent diffusion coefficient values between affected and unaffected side were calculated (differences of T2/differences of apparent diffusion coefficient). Fluid-attenuated inversion recovery images were rated for lesion visibility. RESULTS: Differences of T2 showed a significant correlation with time from symptom onset (R=0.580; P<0.001). T2 values measured in patients with visible fluid-attenuated inversion recovery lesions were significantly higher than in those without visible hyperintensity (P<0.001). The accuracy of qT2 to predict a time from symptom onset <3 hours was 0.794, whereas the corresponding accuracy for visual assessment of fluid-attenuated inversion recovery images was 0.676. CONCLUSIONS: T2 values demonstrated a strong correlation with time from onset, suggesting different pathophysiologic mechanisms than diffusion restriction. Whereas fluid-attenuated inversion recovery only provides binary information on lesion visibility, T2 values correlate well with time from symptom onset, and are free from operator bias, increasing reproducibility to determine time from symptom onset.

Perivascular epitheloid cell tumour (PEComa) of the retroperitoneum - a rare tumor with uncertain malignant behaviour: a case report.

INTRODUCTION: Perivascular epitheloid cell tumours are rare mesenchymal neoplasms characterized by a proliferation of perivascular cells with an epitheloid phenotype and expression of myomelanocytic markers. CASE PRESENTATION: Here we present the case of a cystic perivascular epitheloid cell tumour of the retroperitoneum associated with multifocal lung lesions. A 27-year-old woman underwent laparotomy to remove a 10 x 6 x 4 cm sized retroperitoneal mass. The resected specimen was subjected to frozen and permanent histological sections with conventional and immunohistochemical stains, including antibodies against HMB45. The tumour displayed the typical morphological and immunohistochemical features of a perivascular epitheloid cell tumour. Focal necrosis and a proliferative index of 10% suggested a malignant potential. Moreover, postoperative computed tomography scans demonstrated multiple lung lesions, which were radiologically interpreted as being most likely compatible with lymphangioleiomyomatosis. CONCLUSION: Since lymphangioleiomyomatosis, an otherwise benign condition, belongs to the family of perivascular epitheloid cell tumours, it cannot be excluded that the lung lesions in this case in fact represent metastases from the retroperitoneal perivascular epitheloid cell tumour rather than independent neoplasms. More experience with this new and unusual tumour entity is clearly needed in order to define reliable criteria for benign or malignant behaviour.

Secretory meningiomas: a benign subgroup causing life-threatening complications.

While meningiomas are known as slow-growing extracerebral neoplasms, the subgroup of secretory meningiomas with histologically benign characteristics tend to cause disproportional peritumoral edema, frequently leading to severe medical and neurological complications in postoperative management. Among 1,484 meningiomas that were resected at our institution between 1990 and 2007, 44 (3%) patients were found to have the histological diagnosis of a secretory meningioma. The clinical course, radiological appearance, and histopathological features were retrospectively analyzed to examine the specifics of these benign lesions. Meningiomas were located at the convexity (n = 14), the cranial base (18), and the sphenoid ridge (12). A severe, nearly hemispheric perifocal edema disproportional to tumor size was seen on preoperative MR imaging in 18 (41%) patients. Following surgical resection, the postoperative course was uneventful in 29 patients. In 15 patients, severe peritumoral edema continued or even increased on postoperative CT imaging. Six patients showed midline shift and clinical worsening necessitating respirator-assisted ventilation and intracranial pressure monitoring. An association between the extent of brain edema and number of periodic acid Schiff-positive pseudopsammomas was found (p < 0.02). Further, the size of the edema correlated with the number of immunohistochemically detected cells expressing carcinoembryonic antigen (CEA) and cytokeratin (CK) (p < 0.01). Mean MIB-1 (Ki-67 antigen) proliferation index was 3.0% (range, 0%-17%) and did not correlate with edema or tumor recurrence. Secretory meningiomas are frequently associated with severe peritumoral edema. The extent of edema correlates with immunohistochemically detected expression of CEA and CK. Extended perifocal edema in meningiomas is an unusual finding and should alert the neurosurgeon that surgery may aggravate edema excessively, leading to a life-threatening postoperative situation.

Intravenous administration of acetylsalicylic acid during endovascular treatment of cerebral aneurysms reduces the rate of thromboembolic events.

BACKGROUND AND PURPOSE: The purpose of this study is to analyze the effect of a modified intraoperative anticoagulation strategy including acetylsalicylic acid (ASA) on complication rates during endovascular coil embolization. METHODS: Two hundred and sixty-one cerebral aneurysms were treated in 247 patients by endovascular coil embolization from January 2001 to September 2004. Additional intravenous administration of 250 mg ASA was applied since January 2003. Patients treated before (-ASA; n=102 aneurysms) and after that date (+ASA; n=159 aneurysms) were compared. End points were rates of thromboembolism and severity of hemorrhages after intraoperative aneurysm rupture. RESULTS: Thromboembolic events during the procedure were observed more often in the -ASA group (18/102 aneurysms, 17.6%) in comparison with the +ASA group (14/159 aneurysms, 8.8%; P=0.028; Fisher exact test). Aneurysm perforation events occurring during or immediately after the procedure were observed equally often in the -ASA group (7/102 aneurysms, 6.9%) in comparison with the +ASA group (10/159 aneurysms, 6.3%). CONCLUSIONS: Intravenous application of ASA is feasible and safe during interventional aneurysm embolization. ASA seems to be associated with a significant reduction in the rate of thromboembolic events without increase in the rate or severity of intraoperative bleedings.

Screening for cerebellopontine angle tumors: is a CISS sufficient?

This study attempted to evaluate the reliability of ultra-thin T2-weighted imaging with a constructive interference in steady state (CISS) sequence as a screening method for tumors in the cerebellopontine angle. A retrospective study of 200 CISS examinations was made by five investigators. The examinations were inspected on plain film supported by clinical information. The interobserver agreement in the detection of lesions was analyzed. Fourteen cases (50% of the contrast-enhancing lesions) were rated pathological by all five readers. One case of subarachnoid lymphoma infiltration was overlooked by all five readers. Overall, six pathological lesions (median = 6, range 1-9) were not identified. The interobserver agreement for all pathological lesions was moderate (kappa=0.53; 95% CI, 0.43-0.62). The mean sensitivity was 77.8% (range 72.0-96.3%), and the mean specificity was 97.6% (range 94.8-100%). The median sensitivity for pathological lesions concerning only patients with acute sensorineural hearing loss (n=148, patients with 20 contrast-enhancing cases) was 86.6% (range 80-100%), and median specificity was 95.2% (range 84.4-96.9%) with a moderate interobserver agreement (kappa=0.55; 95% CI, 0.44-0.66). In our opinion the CISS sequence is a valuable addition to the examination of the cerebellopontine angle but lacks sufficient reliability for the detection of tumors of small size or of tumors adjacent to brain parenchyma or the temporal bone.