[Structural and functional neuronal connectivity in Alzheimer's disease: a combined DTI and fMRI study]. / Strukturelle und funktionelle neuronale Konnektivität bei der Alzheimer-Krankheit : Eine kombinierte DTI- und fMRT-Studie.

BACKGROUND: Cognitive performance depends on intact cortical connectivity. Important for memory processing in the human brain is the connection between posterior cingulate cortex and hippocampus, directly as well as indirectly via the parahippocampal gyrus. These brain areas are involved early in Alzheimer's disease (AD). At the same time, they belong to the default mode network (DMN), a functional network showing high functional connectivity under resting state conditions. In AD, this connectivity in specifically compromised, offering the possibility to investigate the structural basis of functional brain connectivity. METHODS: We studied 18 patients with mild to moderate AD, 16 patients with mild cognitive impairment (MCI) and 20 healthy control subjects using diffusion tensor imaging (DTI) and resting state fMRI at 3.0 Tesla. We determined the effect of structural integrity in the posterior cingulate as assessed by DTI on the functional connectivity between posterior cingulate, hippocampus and parahippocampus during resting state in these three groups. RESULTS: Structural integrity was reduced in posterior cingulate fibre tracts in patients with AD in the left hemisphere; however, this effect was partly accounted for by age differences. All three groups showed high functional connectivity between posterior cingulate cortex and hippocampus, via both the direct and the indirect pathways. Determination of effective connectivity yielded a negative fractional anisotropy (FA)-moderated correlation on the direct pathway in AD and MCI for both hemispheres, and in healthy controls for the right hemisphere. The indirect pathway showed a negative FA-moderated correlation in AD for the right hemisphere and in MCI for both hemispheres. Healthy controls showed a positive correlation on the indirect pathway for the left hemisphere. CONCLUSION: Our data suggest that under healthy conditions, effective connectivity in the DMN between posterior cingulate cortex and hippocampus is mainly maintained by the indirect pathway via the parahippocampal gyrus. Patients with AD and patients with MCI show changes in this connectivity with a partial allocation to the direct pathway, most likely reflecting early parahippocampal lesions. The combination of DTI and fMRI broadens our understanding of human brain connectivity and its pathological changes with AD.

Endoleaks after endovascular repair of aortic aneurysm: are they predictable?-initial results.

PURPOSE: To evaluate the predictability of endoleak. MATERIALS AND METHODS: Thirteen women and 60 men (mean age, 69.8 years) underwent transfemoral insertion of endoluminal stent-grafts for treatment of aortic aneurysms. Follow-up included helical computed tomography (CT) at 3-month intervals. In the cases of endoleak, angiography also was performed to document the number of leak sites, their size and position, the feeding artery, the size of the aneurysm, the amount of thrombus, and the visualization of the lumbar arteries and inferior mesenteric artery. These data were correlated (Student t test) with the probability of endoleak. RESULTS: A total of seven (10%) endoleaks were identified at CT in 68 patients. The feeding vessels were lumbar arteries in three cases, the inferior mesenteric artery in three cases, and the median sacral artery in one case. Of all factors, only the number of lumbar arteries visualized preoperatively (P <.005) had a significant correlation with probability of endoleak. In 71% (five of seven patients) of the cases of lumbar endoleak, four lumbar arteries were patent, whereas among the 61 patients with successfully repaired aneurysm, only eight (13%) had four patent lumbar arteries. Endoleaks were never found in the primarily thrombosed sections of an aneurysm. CONCLUSION: Prediction of endoleaks with absolute certainty remains elusive. The single correlating risk factor identified from the data was patency of four or more lumbar arteries visualized preoperatively at CT.

Treatment of leaks after endovascular repair of aortic aneurysms.

PURPOSE: To evaluate leaks after the endovascular repair of aortic aneurysms and treat them with occlusive therapy. MATERIALS AND METHODS: Seventy patients (11 women, 59 men), aged 26-82 years (mean, 69.2 years), underwent transfemoral insertion of endoluminal stent-grafts for treatment of aortic aneurysms. Indications were traumatic pseudoaneurysms (n = 5) or arteriosclerotic aneurysms (n = 65). Aneurysms were thoracic (n = 5) or infrarenal (n = 65). To exclude the possibility of leaks, spiral computed tomography (CT) was performed at 3-month intervals. Patients with leaks that persisted unchanged longer than 3 months were referred for angiography and occlusive therapy. RESULTS: At CT, 21 leaks were identified in 17 of 70 patients (24%). Only 11 of those 17 patients (65%) had leaks identified with conventional aortography. Selective angiography, however, depicted all of these. Eighteen of 21 leaks proved amenable to occlusive treatment: surgery (n = 1), further stent implantation (n = 4), or embolization (n = 13). In one leak, spontaneous occlusion occurred after 3 months. Two leaks in either the iliolumbar or the median sacral artery were inaccessible; one remained untreated, and the other was unsuccessfully treated. Mean follow-up of occlusive therapy was 6.8 months (range, 2-14 months). CONCLUSION: Successful occlusion of perigraft leaks is feasible in most cases and can be performed without major complications.

Endovascular repair of aortic aneurysms: treatment of complications.

PURPOSE: To evaluate the use of interventional procedures for treating complications following endovascular repair of aortic aneurysms. METHODS: Fifty-five patients (49 men; mean age 67.5 years) underwent endoluminal stent-graft repair of traumatic (n = 4) or arteriosclerotic (n = 51) aortic aneurysms in the thoracic (n = 3) or infrarenal (n = 52) aorta. Follow-up of therapeutic success included periodic clinical examination, angiography, and spiral computed tomography. RESULTS: Discounting the 25 (45%) cases of postimplantation syndrome that did not require treatment, there were 22 complications observed in 20 (36%) patients over a mean 10-month follow-up (range 1 to 27). There were 2 transrenal endograft maldeployments, 1 case of twisted graft limbs, 2 access site problems (1 patient), 12 endoleaks (11 patients), 1 late graft limb thrombosis, 1 symptomatic internal iliac artery occlusion, 2 myocardial infarctions, and 1 transient psychosis. Seven (13%) patients did not undergo specific therapy, while 4 (7%) required operation (2 crossover bypass grafts, 1 suture revision, and 1 graft replacement). Among 9 (16%) patients treated with interventional techniques, 7 underwent percutaneous coil embolization for 8 endoleaks (7 successfully resolved). One late stent-graft disconnection required an additional stent-graft, and 1 of the 2 malpositioned endografts was repositioned. All patients remain alive with no increase in the diameter of the aneurysm in any patient. CONCLUSIONS: Technical problems resulting from the endovascular repair of aortic aneurysms often respond to interventional treatment.

Bilateral renal cell carcinoma in a horseshoe kidney: preoperative assessment with MRI and digital subtraction angiography.

Renal cell carcinoma in a horseshoe kidney is an unusual entity. To our knowledge, only 123 cases have been published to date. We report the first bilateral case of two clear-cell carcinomas in an asymmetrically fused kidney. Optimum preservation of renal function after radical tumor removal requires accurate preoperative imaging. Since the vascular supply in fusion anomalies is extremely variable, angiography is mandatory. Magnetic resonance imaging was most suitable to predict the tumor extent and localization, because it simultaneously gave the most comprehensive anatomical overview of the malformation.

[Radiation exposure of the ocular lens and thyroid gland in digital subtraction angiography of brain-supplying arteries]. / Strahlenexposition der Augenlinse und der Schilddrüse bei der Digitalen Subtraktionsangiographie der hirnversorgenden Arterien.

PURPOSE: To find out the individual level of radiation exposure of the ocular lens and thyroid gland during DSA of arteries supplying the brain, considering the indication. MATERIAL AND METHOD: The study was conducted on 72 patients during aortic arch and cerebral artery angiographies using thermoluminescent dosimetry. RESULTS: During 20 aortic arch angiographies the measured values were within non-critical limits, whereas during carotid, vertebral or cerebral four-vessel angiography of the left ocular lens exposure values of more than 500 mGy (max. 782 mGy) were stated in two of 52 cases. The highest measured exposure relating to the right ocular lens was 126 mGy, to the thyroid gland 88 mGy. However, in 51 of 52 cases thyroid gland doses of below 51 mGy were measured. In 71 of 72 cases there was a lateral difference between right and left lens exposure up to twice the measured dose for the right ocular lens during aortic arch angiographies and up to sixteen-fold in respect of the left lens during cerebral angiographies. CONCLUSION: In addition to the fluoroscopic time, number of images, fade-in and zoom some other dose-influencing factors, radiation geometry is especially decisive for organ exposure. The risk of cataracts or thyroid gland carcinomas/hypothyrosis can be neglected with median values of 40 and 70 mGy relating to the ocular lens and 17 mGy for the thyroid gland during cerebral angiographies.

Immediate sealing of arterial puncture site following femoropopliteal angioplasty: a prospective randomized trial.

PURPOSE: A new hemostatic puncture closure device (HPCD) was evaluated following femoropopliteal angioplasty. Efficacy in hemostasis and complications were compared between manual compression and the new system. METHODS: One hundred patients undergoing percutaneous interventional procedures were randomly assigned to receive either manual compression or HPCD. The time to complete hemostasis (when a compression bandage was applied) was noted as well as complications such as hematoma or arterial stenosis at the puncture site. Follow-up was by clinical examination and color-coded duplex sonography (CCDS). RESULTS: With the HPCD, immediate hemostasis was achieved in 22 patients (44%). Discrete oozing without the necessity of external compression or further consequences was observed in 11 patients. Mean manual compression time was 25 (+/- 20) min including application of the pressure bandage. Eleven patients needed additional manual compression and technical failures were observed in 6 patients (12%). The compression time in these 17 cases was 27 (+/- 12) min. Subcutaneous hematomata with a diameter of more than 5 cm developed in 15 of 48 patients in the HPCD group and in 14 of 48 patients in the manual compression group. No surgical or percutaneous intervention was necessary. The complication rate was comparably low in the experimental and control groups. CONCLUSION: Compared with manual compression HPCD is faster and more accurate for sealing the arterial puncture defect following angioplasty. After an initial learning curve, it is easy to handle and time-saving as well as convenient for the patient. Furthermore, immediate and full anticoagulation is possible and arterial inflow is not compromised. A drawback is the necessity of an 8 Fr sheath. Nevertheless, the complication rate is comparably low for both methods.

[The reduction of the extent of vascular lesions during angioplasty by the use of a sheath]. / Reduktion des Ausmasses von Gefässläsionen im Rahmen der Angioplastie bei Gebrauch einer Schleuse.

PURPOSE: To document the protection of the vessel using an introducer sheath. MATERIAL AND METHODS: In eleven in situ specimens we compared in the inguinal vessel the macroscopic and histologic trauma to the vascular wall during antegrade percutaneous balloon dilatation either without or with a sheath. RESULTS: Significant differences we observed regarding both the puncture site configuration and the puncture hole border, which were evaluated macroscopically. During the histological assessment we found only small intimal trauma in the puncture track in the group where a sheath had been used. Severe intimal damages and the media showed tears if no sheath had been used (100/36% vs. 0/64%). CONCLUSION: It is evident that using a sheath during angioplasty reduces the risk of intimal damage and, consequently, of complications such as recurrent haematoma, stenosis at the puncture site or formation of aneurysms due to the puncture.