Occipital lobe infarctions are different

Halvor Naess, Ulrikke Waje-Andreassen, Lars ThomassenDepartment of Neurology, Haukeland University Hospital, University of Bergen, N-5021 Bergen, NorwayObjectives: We hypothesized that occipital lobe infarctions differ from infarctions in other locations as to etiology, risk factors and prognosis among young adults.Methods: Location, etiology, risk factors and long-term outcome were evaluated among all young adults 15–49 years suffering from cerebral infarction in Hordaland County, Norway between 1988 and 1997.Results: The following variables were more frequent among patients with occipital lobe infarction compared with patients with infarctions located elsewhere: younger age (P < 0.001), female sex (P = 0.016), prothrombotic state (P = 0.005) and lack of hypertension (P = 0.001). There was no difference as to long-term mortality or recurrence of cerebral infarction. Conclusion: Occipital lobe infarctions differ from infarctions in other locations among young adults. This may have important etiologic and therapeutical implications that need further studies.Keywords: cerebral infarction, occipital lobe, young adult

Low Frequency AC Transmission - Investigating the Dynamics of an Export Cable for Offshore Wind Power Applications

In the following thesis, the properties of a 16 2/3 Hz, low frequency alternating current (LFAC) export cable was examined in both steady state and dynamic conditions, as part of a simplified offshore transmission system. Simulations were performed for both LFAC and conventional 50 Hz high voltage alternating current (HVAC) systems for comparison purposes. Introductory to the simulations, different cable models were investigated. Using MATLAB/SIMULINK SimPowerSystems, the use of the built-in distributed parameters model (DPM) was considered the best option for simulation, especially when studying the power cable in dynamic situations. For steady state conditions, the utilization of the series pi-model showed satisfying results, e.g. when the effect of voltage rise in a lightly loaded or unloaded transmission system was studied (Ferranti effect). The results revealed a significantly lower voltage increase across the LFAC cable compared to a conventional HVAC cable. Thus, in the case of sudden disconnections or loss of load, the risk of damaging transmission system components can be lower for an LFAC system compared to an HVAC system. Charging currents were observed to be lower and less sensitive to cable length variations for an LFAC cable compared to an HVAC cable. Thus, more active power is allowed to be transmitted in the LFAC cable. During energization of the cable, the LFAC voltages and currents experienced temporary transient distortions of the waveform before stabilizing at steady state, whereas the same distortions were not observed for the HVAC system. Transient distortions were also observed in the fault analysis for different short circuit (SC) events; three phase to ground, double phase to ground and phase to phase faults. The fourth SC event, the single phase to ground fault, showed very little distortion. However, the highest direct current (DC) offset magnitude was observed for the phase to ground voltages posterior to this fault. DC offsets were also observed after clearing the three phase to ground fault and double phase to ground fault, resulting from the lack of grounding in the cable system. The DC offsets were present for a long period of time; up to 100 seconds depending on the type of fault, and the magnitude of the DC offsets was significantly higher for the HVAC system. Connecting the cable's end terminal to ground through a shunt reactor resulted in a far lower DC offset magnitude which was rapidly damped to zero. Similar oscillations were observed for the HVAC system, and the DC offset was damped faster in this case due to higher resistance in the cable. The frequency of the oscillations were 30 Hz for the LFAC system and 44 Hz for the HVAC system, and it should be examined whether such oscillations may contribute to resonance in the power system. Possible measures to increase the damping of the oscillations would be a better optimization of the shunt reactor. Common for the dynamic situations investigated was the presence of harmonic distortion after switching operations or faults/clearing of faults. In the case of switching operations, the problem of transient distortion could possibly be more prominent for LFAC transmission systems compared to HVAC systems. However, further studies should be carried out before making final conclusions on this topic. In summary, the LFAC cable showed promising results in terms of overvoltages under steady and dynamic situations compared to a conventional HVAC system

Early ischemic CT changes before thrombolysis: The influence of age and diabetes mellitus

Lars Thomassen, Ulrike Waje-Andreassen, Halvor NaessDepartment of Neurology, Haukeland University Hospital, Bergen, NorwayObjectives: The significance of early ischemic changes (EIC) on computed tomography (CT) within 3 hours after stroke onset remains controversial. The semi-quantitative Alberta Stroke Program Early CT Score (ASPECTS) is found to have prognostic value in early stroke. This study assesses factors associated with the presence of EIC and the relation between EIC and clinical outcome.Materials and methods: CT scans from 61 consecutive patients receiving thrombolytic therapy were reviewed by 3 experienced stroke neurologists, assessing EIC (ASPECTS) and vascular signs (hyperdense middle cerebral artery stem and/or branches). Short-term outcome was assessed with the National Institute of Health Stroke Scale at 24 hours and long-term outcome with the modified Rankin Scale score after 3 months.Results: The prevalence of EIC was 54% and the agreement between assessors was good (kappa 0.52–0.67). EIC was independently associated with younger age and absence of diabetes mellitus. Neither EIC nor vascular signs were associated with 3-months outcome.Conclusions: ASPECTS is as simple, systematic approach to assessing EIC, and the interobserver agreement is good. Patient age and diabetes mellitus influence the presence of EIC.Keywords: acute stroke, computed tomography, ischemia, thrombolysi

Comparison between Ischemic Stroke Patients <50 Years and ≥50 Years Admitted to a Single Centre: The Bergen Stroke Study

Introduction. Young adults are likely to differ from old patients concerning cerebral infarction. Methods. We compared characteristics of patients aged under and above 50 years, admitted to the Department of Neurology with cerebral infarction between 2006 and 2009, based on prospective registration. Investigation followed one common protocol for both groups. Results and Discussion. One hundred patients (8.2%) were <50 years old, and the proportion of males was higher in this group (72% versus 55.8%, P = .002). Young stroke patients are more often current smokers (44.1% versus 23.6%, P < .001). Common causes for stroke in the young were cervical artery dissection (18% versus 0.6%, P < .001) and cardiac embolism due to disorders other than atrial arrhythmias (18% versus 5.5%, P < .001). Among the old, atrial fibrillation and flutter dominated (29.1% versus 5%, P < .001). Stroke severity and location did not differ. Old patients more often suffered from pneumonia (10.6% versus 2%, P < .003) and urinary tract infection (14.6% versus 2%, P = .001). Conclusions. Males dominate, and current smoking is more common in the young. Cervical artery dissection and nonarrhythmic heart disorders are frequent causes among young patients, while traditional risk factors dominate the old. Stroke severity is similar, but old patients seem more exposed for infectious complications

Low body temperature associated with severe ischemic stroke within 6 hours of onset: The Bergen NORSTROKE Study

Christopher E Kvistad, Lars Thomassen, Ulrike Waje-Andreassen, Halvor NaessDepartment of Neurology, Haukeland University Hospital, University of Bergen, Bergen, NorwayBackground: Hypothermia is considered neuroprotective and a potential treatment in cerebral ischemia. Some studies suggest that hyperthermia may promote clot lysis. We hypothesized that low body temperature would prolong time to spontaneous clot lysis resulting in an association between low body temperature and severe neurological deficits in the early phase of ischemic stroke.Methods: In this prospective study, patients (n = 516) exhibiting ischemic stroke with symptom onset within 6 hours were included. Body temperature and National Institute of Health Stroke Scale (NIHSS) score were registered on admission. Because low body temperature on admission may be secondary to immobilization due to large stroke, separate analyses were performed on patients with cerebral hemorrhage admitted within 6 hours (n = 85).Results: Linear regression showed that low body temperature on admission was independently associated with a high NIHSS score within 6 hours of stroke onset in patients with ischemic stroke (P &amp;lt; 0.001). The association persisted when NIHSS was measured at 24 hours after admission. No such associations were found in patients with cerebral hemorrhage admitted within 6 hours of stroke onset.Conclusion: Our study suggests that low body temperature within 6 hours of symptom onset is associated with severe ischemic stroke. This is in support of our hypothesis, although other contributing mechanisms cannot be excluded.Keywords: body temperature, cerebral infarction, cerebral hemorrhage, clot lysi

Searching for Explanations for Cryptogenic Stroke in the Young : Revealing the Etiology, Triggers, and Outcome (SECRETO): echocardiography performance protocol

Background: The incidence of ischemic stroke in young patients is increasing and associated with unfavorable prognosis due to high risk of recurrent cardiovascular events. In many young patients the cause of stroke remains unknown, referred to as cryptogenic stroke. Neuroimaging frequently suggests a proximal source of embolism in these strokes. We developed a comprehensive step-by-step echocardiography protocol for a prospective study with centralized reading to characterize preclinical cardiac changes associated with cryptogenic stroke. Methods and study design: SECRETO (Searching for Explanations for Cryptogenic Stroke in the Young: Revealing the Etiology, Triggers, and Outcome; NCT01934725) is an ongoing multicenter case-control study enrolling patients (target n = 600) aged 18-49 years hospitalized due to first-ever ischemic stroke of undetermined etiology and age- and sex-matched controls (target n = 600). A comprehensive assessment of cardiovascular risk factors and extensive cardiac imaging with transthoracic and transesophageal echocardiography, electrocardiography and neurovascular imaging is performed. Transthoracic and transesophageal echocardiograms will be centrally read, following an extensive protocol particularly emphasizing the characteristics of left atrium, left atrial appendage and interatrial septum. Conclusions: A detailed assessment of both conventional and unconventional vascular risk factors and cardiac imaging with transthoracic and transesophageal echocardiography are implemented in SECRETO, aiming to establish indirect and direct risk factors and causes for cryptogenic stroke and novel pathophysiological brain-heart pathways. This may ultimately enable more personalized therapeutic options for these patients.Peer reviewe

Admission C – reactive protein after acute ischemic stroke is associated with stroke severity and mortality: The 'Bergen stroke study'

<p>Abstract</p> <p>Background</p> <p>There is growing evidence that inflammation plays an important role in atherogenesis. Previous studies show that C-reactive protein (CRP), an inflammatory marker, is associated with stroke outcomes and future vascular events. It is not clear whether this is due a direct dose-response effect or rather an epiphenomenon. We studied the effect of CRP measured within 24 hours after stroke onset on functional outcome, mortality and future vascular events.</p> <p>Methods</p> <p>We prospectively studied 498 patients with ischemic stroke who were admitted within 24 hours after the onset of symptoms. CRP and NIH stroke scale (NIHSS) were measured at the time of admission. Short-term functional outcome was measured by modified Rankin scale (mRS) and Barthel ADL index (BI) 7 days after admission. Patients were followed for up to 2.5 years for long-term mortality and future vascular events data.</p> <p>Results</p> <p>The median CRP at admission was 3 mg/L. High CRP was associated with high NIHSS (p = 0.01) and high long-term mortality (p < 0.0001). After adjusting for confounding variables, high CRP remained to be associated with high NIHSS (p = 0.02) and high long-term mortality (p = 0.002). High CRP was associated with poor short-term functional outcomes (mRS > 3; BI < 95) (p = 0.01; p = 0.03). However, the association was not significant after adjusting for confounding variables including stroke severity (p = 0.98; p = 0.88). High CRP was not associated with future vascular events (p = 0.98).</p> <p>Conclusion</p> <p>Admission CRP is associated with stroke severity and long-term mortality when measured at least 24 hours after onset. There is a crude association between high CRP and short-term functional outcome which is likely secondary to stroke severity. CRP is an independent predictor of long-term mortality after ischemic stroke.</p

Can the cardiovascular family history reported by our patients be trusted? The Norwegian Stroke in the Young Study

Background and purpose: Family history (FH) is used as a marker for inherited risk. Using FH for this purpose requires the FH to reflect true disease in the family. The aim was to analyse the concordance between young and middle-aged ischaemic stroke patients' reported FH of cardiovascular disease (CVD) with their parents' own reports. Methods: Ischaemic stroke patients aged 15–60 years and their eligible parents were interviewed using a standardized questionnaire. Information of own CVD and FH of CVD was registered. Concordance between patients and parents was tested by kappa statistics, sensitivity, specificity, predictive values and likelihood ratios. Regression analyses were performed to identify patient characteristics associated with non-concordance of replies. Results: There was no difference in response rate between fathers and mothers (P = 0.355). Both parents responded in 57 cases. Concordance between patient and parent reports was good, with kappa values ranging from 0.57 to 0.7. The patient-reported FH yielded positive predictive values of 75% or above and negative predictive values of 90% or higher. The positive likelihood ratios (LR+) were 10 or higher and negative likelihood ratios (LR−) were generally 0.5 or lower. Interpretation regarding peripheral arterial disease was limited due to low parental prevalence. Higher age was associated with impaired concordance between patient and parent reports (odds ratio 1.05; 95% confidence interval 1.01–1.09; P = 0.020). Conclusions: The FH provided by young and middle-aged stroke patients is in good concordance with parental reports. FH is an adequate proxy to assess inherited risk of CVD in young stroke patients

Can the cardiovascular family history reported by our patients be trusted? The Norwegian Stroke in the Young Study

Background and purpose: Family history (FH) is used as a marker for inherited risk. Using FH for this purpose requires the FH to reflect true disease in the family. The aim was to analyse the concordance between young and middle-aged ischaemic stroke patients' reported FH of cardiovascular disease (CVD) with their parents' own reports. Methods: Ischaemic stroke patients aged 15–60 years and their eligible parents were interviewed using a standardized questionnaire. Information of own CVD and FH of CVD was registered. Concordance between patients and parents was tested by kappa statistics, sensitivity, specificity, predictive values and likelihood ratios. Regression analyses were performed to identify patient characteristics associated with non-concordance of replies. Results: There was no difference in response rate between fathers and mothers (P = 0.355). Both parents responded in 57 cases. Concordance between patient and parent reports was good, with kappa values ranging from 0.57 to 0.7. The patient-reported FH yielded positive predictive values of 75% or above and negative predictive values of 90% or higher. The positive likelihood ratios (LR+) were 10 or higher and negative likelihood ratios (LR−) were generally 0.5 or lower. Interpretation regarding peripheral arterial disease was limited due to low parental prevalence. Higher age was associated with impaired concordance between patient and parent reports (odds ratio 1.05; 95% confidence interval 1.01–1.09; P = 0.020). Conclusions: The FH provided by young and middle-aged stroke patients is in good concordance with parental reports. FH is an adequate proxy to assess inherited risk of CVD in young stroke patients.publishedVersio