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Patrik Michel - Top 30 Publications

Prevalence of Imaging Biomarkers to Guide the Planning of Acute Stroke Reperfusion Trials.

Imaging biomarkers are increasingly used as selection criteria for stroke clinical trials. The goal of our study was to determine the prevalence of commonly studied imaging biomarkers in different time windows after acute ischemic stroke onset to better facilitate the design of stroke clinical trials using such biomarkers for patient selection.

Prestroke CHA2DS2-VASc Score and Severity of Acute Stroke in Patients with Atrial Fibrillation: Findings from RAF Study.

The aim of this study was to investigate for a possible association between both prestroke CHA2DS2-VASc score and the severity of stroke at presentation, as well as disability and mortality at 90 days, in patients with acute stroke and atrial fibrillation (AF).

Prediction of Early Recurrent Thromboembolic Event and Major Bleeding in Patients With Acute Stroke and Atrial Fibrillation by a Risk Stratification Schema: The ALESSA Score Study.

This study was designed to derive and validate a score to predict early ischemic events and major bleedings after an acute ischemic stroke in patients with atrial fibrillation.

Sex Differences and Functional Outcome After Intravenous Thrombolysis.

Women have a worse outcome after stroke compared with men, although in intravenous thrombolysis (IVT)-treated patients, women seem to benefit more. Besides sex differences, age has also a possible effect on functional outcome. The interaction of sex on the functional outcome in IVT-treated patients in relation to age remains complex. The purpose of this study was to compare outcome after IVT between women and men with regard to age in a large multicenter European cohort reflecting daily clinical practice of acute stroke care.

Prehospital Scales for Large Vessel Occlusion: Closing in on a Moving Target.

Number needed to screen for acute revascularization trials in stroke: Prognostic and predictive imaging biomarkers.

Objective To systematically assess imaging biomarkers on CT-based multimodal imaging for their being predictive versus prognostic biomarkers for intravenous and endovascular (IA) revascularization therapy, and for their prevalence. Methods Our retrospective study included patients suspected of acute ischemic stroke with admission work-up including a non-contrast head CT, perfusion CT, and CT angiography. Modified Rankin scores at 90 days were used as outcomes. For each imaging biomarker, the effect size of the test of interaction between the presence of the biomarker and the treatment effect was calculated, allowing the inference of a total sample size. The total sample size required was combined with the prevalence of the biomarker to determine the number needed to screen. Results In the 0-4.5-h time window, the two predictive biomarkers associated with the smallest number needed to screen were perfusion CT penumbra ≥ 20% (404 NNS) and CT angiography collateral score ≥ 2 (581 NNS). In the 3-9-h time window, the four predictive biomarkers associated with the smallest number needed to screen were clot burden score (CBS) on CT angiography (1181 NNS), clot length ≥ 10 mm (1924 NNS), CBS and clot length ≥ 10 mm (1132 NNS), and CBS and perfusion CT penumbra ≥ 100% (1374 NNS). Perfusion CT ischemic core was a prognostic biomarker in both time windows. Interpretation Predictive biomarkers need to be differentiated from prognostic biomarkers when being considered to select patients for a trial, and their prevalence should be assessed to determine the number needed to screen and overall feasibility of the trials.

No Impact of Body Mass Index on Outcome in Stroke Patients Treated with IV Thrombolysis BMI and IV Thrombolysis Outcome.

The impact of excess body weight on prognosis after stroke is controversial. Many studies report higher survival rates in obese patients ("obesity paradox"). Recently, obesity has been linked to worse outcomes after intravenous (IV) thrombolysis, but the number and sample size of these studies were small. Here, we aimed to assess the relationship between body weight and stroke outcome after IV thrombolysis in a large cohort study.

CT-angiography source images indicate less fatal outcome despite coma of patients in the Basilar Artery International Cooperation Study.

Background Coma is associated with poor outcome in patients with basilar artery occlusion. Aims We sought to assess whether the posterior circulation Acute Stroke Prognosis Early CT Score and the Pons-Midbrain Index applied to CT angiography source images predict the outcome of comatose patients in the Basilar Artery International Cooperation Study. Methods Basilar Artery International Cooperation Study was a prospective, observational registry of patients with acute basilar artery occlusion with 48 recruiting centers worldwide. We applied posterior circulation Acute Stroke Prognosis Early CT Score and Pons-Midbrain Index to CT angiography source images of Basilar Artery International Cooperation Study patients who presented with coma. We calculated adjusted risk ratios to assess the association of dichotomized posterior circulation Acute Stroke Prognosis Early CT Score (≥8 vs. <8) and Pons-Midbrain Index (<3 vs. ≥3) with mortality and favourable outcome (modified Rankin Scale score 0-3) at one month. Results Of 619 patients in the Basilar Artery International Cooperation Study registry, CT angiography source images were available for review in 158 patients. Among these, 78 patients (49%) presented with coma. Compared to non-comatose patients, comatose patients were more likely to die (risk ratios 2.34; CI 95% 1.56-3.52) and less likely to have a favourable outcome (risk ratios 0.44; CI 95% 0.24-0.80). Among comatose patients, a Pons-Midbrain Index < 3 was related to reduced mortality (adjusted RR 0.66; 95% CI 0.46-0.96), but not to favourable outcome (adjusted RR 1.19; 95% CI 0.39-3.62). Posterior circulation Acute Stroke Prognosis Early CT Score dichotomized at ≥ 8 vs. <8 was not significantly associated with death (adjusted RR 0.70; 95% CI 0.46-1.05). Conclusion In comatose patients with basilar artery occlusion, the extent of brainstem ischemia appears to be related to mortality but not to favourable outcome.

Embolic Stroke of Undetermined Source and Detection of Atrial Fibrillation on Follow-Up: How Much Causality Is There?

There is increasing debate whether atrial fibrillation (AF) episodes during follow-up in patients with embolic stroke of undetermined source (ESUS) are causally associated with the event. AF-related strokes are more severe than strokes of other etiologies. In this context, we aimed to compare stroke severity between ESUS patients diagnosed with AF during follow-up and those who were not. We hypothesized that, if AF episodes detected during follow-up are indeed causally associated with the index event, stroke severity in the AF group should be higher than the non-AF group.

Sinking flap syndrome with abdominal pain: an atypical presentation.

A 53-year-old man developed significant mass effect secondary to an ischaemic stroke and was treated with decompressive craniectomy. During the first few days postsurgery he developed orthostatic vertigo with nausea. After a month, with increasing mobilisation and rehabilitation, he started reporting of severe abdominal pain. No aetiology could be found despite extensive local work up and the symptoms were resistant to any symptomatic treatment. Within days postcranioplasty there was a complete resolution of all the symptoms.

Intravenous Thrombolysis and Passes of Thrombectomy as Predictors for Endovascular Revascularization in Ischemic Stroke.

Patient selection for endovascular revascularization treatment (ERT) in acute ischemic stroke depends on the expected benefit-risk ratio. As rapid revascularization is a major determinant of good functional outcome, we aimed to identify its predictors after ERT.

Complete lingual palsy from bilateral Dejerine syndrome (bilateral medial medullary stroke).

Fatal subarachnoid hemorrhage following ischemia in vertebrobasilar dolichoectasia.

Vertebrobasilar dolichoectasia (VBD) is a chronic disorder with various cerebrovascular and compressive manifestations, involving subarachnoid hemorrhage (SAH). Occurrence of SAH shortly after worsening of clinical VBD symptoms has occasionally been reported. The goal of the study was to examine this association, in particular its pathophysiology, clinical precursor signs, time course, and outcome.To this end, in a retrospective multicenter study, we analyzed 20 patients with VBD and SAH in regard to preceding clinical symptoms, presence of vertebrobasilar thrombosis and ischemia, outcome and neuropathological correlates.Median age of the 7 female and 13 male patients was 70 years (interquartile range [IQR] 18.3 years). Fourteen patients (70%) presented with new or acutely worsening posterior fossa signs at a median of 3 days prior to SAH (IQR 2, range 0.5-14). A thrombus within the VBD was detected in 12 patients (60%). Thrombus formation was associated with clinical deterioration (χ = 4.38, P = 0.04) and ponto-cerebellar ischemia (χ = 8.09, P = 0.005). During follow-up after SAH, 13 patients (65%) died, after a median survival time of 24 hours (IQR 66.2, range 2-264 hours), with a significant association between proven ponto-cerebellar ischemia and case fatality (χ = 6.24, P = 0.01).The data establish an association between clinical deterioration in patients with VBD, vertebrobasilar ischemia, and subsequent SAH. Antithrombotic treatment after deterioration appears controversial and SAH outcome is frequently fatal. Our data also indicate a short window of 3 days that may allow for evaluating interventional treatment, preferably within randomized trials.

Repeated Intravenous Thrombolysis for Early Recurrent Stroke: Challenging the Exclusion Criterion.

Intravenous thrombolysis (IVT) within 4.5 hours from symptom onset improves functional outcome in patients with acute ischemic stroke. Its use in patients with previous stroke within the preceding 3 months is contraindicated because of the assumed higher risk of intracranial hemorrhage. In addition, tissue-type plasminogen activator may itself promote neurotoxicity and blood-brain barrier disruption. However, safety and effectiveness of repeated IVT is essentially unknown in patients with early (<3 months) recurrent stroke (ERS), because they were excluded from thrombolysis trials. This article reports the largest case series of repeated IVT in ERS.

Hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu syndrome): clinical manifestations and multidisciplinary management.

Hereditary hemorrhagic telangiectasia (HHT), or Osler- Weber-Rendu syndrome, is a rare genetic disorder with autosomal dominant inheritance, characterized by recurrent epistaxis, mucocutaneous telangiectasia and visceral arteriovenous malformations (AVMs), which may lead to severe complications. The diagnosis of HHT is often delayed due to the rarity of the disease, and the variety of clinical manifestations. The management of HHT includes systematic screening for visceral AVMs at regular intervals, preventive interventions to reduce the risk of complications, and symptomatic measures. A multidisciplinary standardized program in specialised centers may improve the management of patients with HHT.

Eligibility and Predictors for Acute Revascularization Procedures in a Stroke Center.

Endovascular treatment (EVT) is a new standard of care for selected, large vessel occlusive strokes. We aimed to determine frequency of potentially eligible patients for intravenous thrombolysis (IVT) and EVT in comprehensive stroke centers. In addition, predictors of EVT eligibility were derived.

Large arterial occlusive strokes as a medical emergency: need to accurately predict clot location.

Endovascular treatment for acute ischemic stroke with a large intracranial occlusion was recently shown to be effective. Timely knowledge of the presence, site, and extent of arterial occlusions in the ischemic territory has the potential to influence patient selection for endovascular treatment. We aimed to find predictors of large vessel occlusive strokes, on the basis of available demographic, clinical, radiological, and laboratory data in the emergency setting.

Prediction of Large Vessel Occlusions in Acute Stroke: National Institute of Health Stroke Scale Is Hard to Beat.

Endovascular treatment for acute ischemic stroke with a large vessel occlusion was recently shown to be effective. We aimed to develop a score capable of predicting large vessel occlusion eligible for endovascular treatment in the early hospital management.


In 2015, cerebral stimulation becomes increasingly established in the treatment of pharmacoresistant epilepsy. Efficacy of endovascular treatment has been demonstrated for acute ischemic stroke. Deep brain stimulation at low frequency improves dysphagia and freezing of gait in Parkinson patients. Bimagrumab seems to increase muscular volume and force in patients with inclusion body myositis. In cluster-type headache, a transcutaneous vagal nerve stimulator is efficient in stopping acute attacks and also reducing their frequency. Initial steps have been undertaken towards modulating memory by stimulation of the proximal fornix. Teriflunomide is the first oral immunomodulatory drug for which efficacy has been shown in preventing conversion from clinical isolated syndrome to multiple sclerosis.

Intravenous Thrombolysis in Patients Dependent on the Daily Help of Others Before Stroke.

We compared outcome and complications in patients with stroke treated with intravenous thrombolysis (IVT) who could not live alone without help of another person before stroke (dependent patients) versus independent ones.

Beauty parlor stroke revisited: An 11-year single-center consecutive series.

Hairdresser-related ischemic cerebrovascular events (HICE) are attributed to compression of vertebral arteries or cervical artery dissections. We determined their frequency, mechanisms, localization and outcome in a pre-specified study.

Mechanical thrombectomy in acute ischemic stroke: Consensus statement by ESO-Karolinska Stroke Update 2014/2015, supported by ESO, ESMINT, ESNR and EAN.

The original version of this consensus statement on mechanical thrombectomy was approved at the European Stroke Organisation (ESO)-Karolinska Stroke Update conference in Stockholm, 16-18 November 2014. The statement has later, during 2015, been updated with new clinical trials data in accordance with a decision made at the conference. Revisions have been made at a face-to-face meeting during the ESO Winter School in Berne in February, through email exchanges and the final version has then been approved by each society. The recommendations are identical to the original version with evidence level upgraded by 20 February 2015 and confirmed by 15 May 2015. The purpose of the ESO-Karolinska Stroke Update meetings is to provide updates on recent stroke therapy research and to discuss how the results may be implemented into clinical routine. Selected topics are discussed at consensus sessions, for which a consensus statement is prepared and discussed by the participants at the meeting. The statements are advisory to the ESO guidelines committee. This consensus statement includes recommendations on mechanical thrombectomy after acute stroke. The statement is supported by ESO, European Society of Minimally Invasive Neurological Therapy (ESMINT), European Society of Neuroradiology (ESNR), and European Academy of Neurology (EAN).

Cognitive improvement in patients with carotid stenosis is independent of treatment type.

Treatment of carotid artery stenosis decreases the long-term risk of stroke and may enhance cerebral blood flow. It is therefore expected to have the potential to prevent cognitive decline or even improve cognition over the long-term. However, intervention itself can cause peri-interventional cerebral infarcts, possibly resulting in a decline of cognitive performance, at least for a short time. We investigated the long-term effects of three treatment methods on cognition and the emotional state one year after intervention. In this prospective observational cohort study, 58 patients with extracranial carotid artery stenosis (≥ 70%) underwent magnetic resonance imaging and assessment of cognition, mood and motor speed before carotid endarterectomy (n = 20), carotid stenting (n = 10) or best medical treatment (n = 28) (i.e., time-point 1 [TP1]), and at one-year follow-up (TP2). Gain scores, reflecting cognitive change after treatment, were built according to performance as (TP2 -TP1)/TP1. Independent of the treatment type, significant improvement in frontal lobe functions, visual memory and motor speed was found. Performance level, motor speed and mood at TP1 were negatively correlated with gain scores, with greater improvement in patients with low performance before treatment. Active therapy, whether conservative or interventional, produces significant improvement of frontal lobe functions and memory in patients with carotid artery disease, independent of treatment type. This effect was particularly pronounced in patients with low cognitive performance prior to treatment.

Prediction of Early Arterial Recanalization and Tissue Fate in the Selection of Patients With the Greatest Potential to Benefit From Intravenous Tissue-Type Plasminogen Activator.

Our objective is to determine the performance of the combination of likelihood of arterial recanalization and tissue fate to predict functional clinical outcome in patients with acute stroke.

Stroke: two steps forward, one step sideward.

Lifestyle modification for stroke prevention: facts and fiction.

The purpose is to summarize recent evidence on lifestyle modifications and first or recurrent stroke risk.

Erratum to: Risk factors, aetiology and outcome of ischaemic stroke in young adults: the Swiss Young Stroke Study (SYSS).

Prognostic value of trans-thoracic echocardiography in patients with acute stroke and atrial fibrillation: findings from the RAF study.

Anticoagulant therapy is recommended for the secondary prevention of stroke in patients with atrial fibrillation (AF). T he identification of patients at high risk for early recurrence, which are potential candidates to prompt anticoagulation, is crucial to justify the risk of bleeding associated with early anticoagulant treatment. The aim of this study was to evaluate in patients with acute ischemic stroke and AF the association between findings at trans-thoracic echocardiography (TTE) and 90 days recurrence. In consecutive patients with acute ischemic stroke and AF, TTE was performed within 7 days from hospital admission. Study outcomes were recurrent ischemic cerebrovascular events (stroke or TIA) and systemic embolism. 854 patients (mean age 76.3 ± 9.5 years) underwent a TTE evaluation; 63 patients (7.4%) had at least a study outcome event. Left atrial thrombosis was present in 11 patients (1.3%) among whom 1 had recurrent ischemic event. Left atrial enlargement was present in 548 patients (64.2%) among whom 51 (9.3%) had recurrent ischemic events. The recurrence rate in the 197 patients with severe left atrial enlargement was 11.7%. On multivariate analysis, the presence of atrial enlargement (OR 2.13; 95% CI 1.06-4.29, p = 0.033) and CHA2DS2-VASc score (OR 1.22; 95% CI 1.04-1.45, p = 0.018, for each point increase) were correlated with ischemic recurrences. In patients with AF-associated acute stroke, left atrial enlargement is an independent marker of recurrent stroke and systemic embolism. The risk of recurrence is accounted for by severe atrial enlargement. TTE-detected left atrial thrombosis is relatively uncommon.

Final infarct volume discriminates outcome in mild strokes.

Knowledge of whether final infarct volume (FIV) predicts disability after mild stroke is limited. We sought to determine if FIV could differentiate good versus poor outcome after mild stroke.

External Validation of the Prestroke Independence, Sex, Age, National Institutes of Health Stroke Scale (ISAN) Score for Predicting Stroke-Associated Pneumonia in the Athens Stroke Registry.

The Prestroke Independence, Sex, Age, National Institutes of Health Stroke Scale (ISAN) score was developed recently for predicting stroke-associated pneumonia (SAP), one of the most common complications after stroke. The aim of the present study was to externally validate the ISAN score.