Evaluation of electrode position in deep brain stimulation by image fusion (MRI and CT).

INTRODUCTION: Imaging has an essential role in the evaluation of correct positioning of electrodes implanted for deep brain stimulation (DBS). Although MRI offers superior anatomic visualization of target sites, there are safety concerns in patients with implanted material; imaging guidelines are inconsistent and vary. The fusion of postoperative CT with preoperative MRI images can be an alternative for the assessment of electrode positioning. The purpose of this study was to assess the accuracy of measurements realized on fused images (acquired without a stereotactic frame) using a manufacturer-provided software. METHODS: Data from 23 Parkinson's disease patients who underwent bilateral electrode placement for subthalamic nucleus (STN) DBS were acquired. Preoperative high-resolution T2-weighted sequences at 3 T, and postoperative CT series were fused using a commercially available software. Electrode tip position was measured on the obtained images in three directions (in relation to the midline, the AC-PC line and an AC-PC line orthogonal, respectively) and assessed in relation to measures realized on postoperative 3D T1 images acquired at 1.5 T. RESULTS: Mean differences between measures carried out on fused images and on postoperative MRI lay between 0.17 and 0.97 mm. CONCLUSION: Fusion of CT and MRI images provides a safe and fast technique for postoperative assessment of electrode position in DBS.

[Radioinduced brain cyst: case report]. / Kyste radioinduit du cerveau: case report.

We present a case of intraparenchymal radioinduced cyst of the brain observed in our department. It is a rare and relatively benign pathology which is usually treated conservatively or by surgery. We emphasize long-term imaging follow up in patients treated by radiosurgery, which can lead to the demonstration of multiple adverse events such as tumefactive cyst formation.

Systemic cytokines related to memory function 6-9 months and 12-15 months after SARS-CoV-2 infection.

Cognitive symptoms persisting beyond the acute phase of COVID-19 infection are commonly described for up to 2 years after infection. The relationship between cognitive performance, in particular episodic memory processes observed chronically after infection, and cytokine levels in the acute phase of COVID-19 has not yet been identified in humans. To determine whether the levels of cytokines IL1ß, IL-6 and TNFα secreted in the acute phase of SARS-CoV-2 infection are associated and predict verbal and visuospatial episodic memory performance in humans 6 to 9 months and 12 to 15 months post-infection. The associations and predictive value of the concentration of cytokines measured in acute phase (IL-1ß, IL-6, TNFα) from plasma samples of N = 33 hospitalized COVID-19 patients (mean age 61 years, 39-78, 65% in intensive care) in relation to their verbal and visuospatial episodic memory performance measured at 6-9 months and 12-15 months post-infection were analyzed. To do this, we used Spearman correlations and generalised linear mixed models. IL-1ß levels were associated with verbal episodic memory total recall scores 6-9 months post-infection. At 12-15 months post-infection IL-6 predicted verbal episodic memory score. This study demonstrated that the severity of inflammatory reaction at acute phase of SARS-CoV-2 infection predicts verbal episodic memory performance in the long-term post-infection.

Differentiation between Parkinson disease and other forms of Parkinsonism using support vector machine analysis of susceptibility-weighted imaging (SWI): initial results.

OBJECTIVES: To diagnose Parkinson disease (PD) at the individual level using pattern recognition of brain susceptibility-weighted imaging (SWI). METHODS: We analysed brain SWI in 36 consecutive patients with Parkinsonism suggestive of PD who had (1) SWI at 3 T, (2) brain (123)I-ioflupane SPECT and (3) extensive neurological testing including follow-up (16 PD, 67.4 ± 6.2 years, 11 female; 20 OTHER, a heterogeneous group of atypical Parkinsonism syndromes 65.2 ± 12.5 years, 6 female). Analysis included group-level comparison of SWI values and individual-level support vector machine (SVM) analysis. RESULTS: At the group level, simple visual analysis yielded no differences between groups. However, the group-level analyses demonstrated increased SWI in the bilateral thalamus and left substantia nigra in PD patients versus other Parkinsonism. The inverse comparison yielded no supra-threshold clusters. At the individual level, SVM correctly classified PD patients with an accuracy above 86 %. CONCLUSIONS: SVM pattern recognition of SWI data provides accurate discrimination of PD among patients with various forms of Parkinsonism at an individual level, despite the absence of visually detectable alterations. This pilot study warrants further confirmation in a larger cohort of PD patients and with different MR machines and MR parameters.

Evaluation of whole-body MR to CT deformable image registration.

Multimodality image registration plays a crucial role in various clinical and research applications. The aim of this study is to present an optimized MR to CT whole-body deformable image registration algorithm and its validation using clinical studies. A 3D intermodality registration technique based on B-spline transformation was performed using optimized parameters of the elastix package based on the Insight Toolkit (ITK) framework. Twenty-eight (17 male and 11 female) clinical studies were used in this work. The registration was evaluated using anatomical landmarks and segmented organs. In addition to 16 anatomical landmarks, three key organs (brain, lungs, and kidneys) and the entire body volume were segmented for evaluation. Several parameters--such as the Euclidean distance between anatomical landmarks, target overlap, Dice and Jaccard coefficients, false positives and false negatives, volume similarity, distance error, and Hausdorff distance--were calculated to quantify the quality of the registration algorithm. Dice coefficients for the majority of patients (> 75%) were in the 0.8-1 range for the whole body, brain, and lungs, which satisfies the criteria to achieve excellent alignment. On the other hand, for kidneys, Dice coefficients for volumes of 25% of the patients meet excellent volume agreement requirement, while the majority of patients satisfy good agreement criteria (> 0.6). For all patients, the distance error was in 0-10 mm range for all segmented organs. In summary, we optimized and evaluated the accuracy of an MR to CT deformable registration algorithm. The registered images constitute a useful 3D whole-body MR-CT atlas suitable for the development and evaluation of novel MR-guided attenuation correction procedures on hybrid PET-MR systems.

Frequency of Abnormally Low Neuropsychological Scores in Post-COVID-19 Syndrome: the Geneva COVID-COG Cohort.

OBJECTIVE: Several studies have reported poor long-term neuropsychological performances in patients following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, but none has yet considered the effect of administering multiple intercorrelated neuropsychological tests and assessed the frequency of cognitive deficits in a normative population. Our aim was therefore to assess the presence of cumulative neuropsychological deficits in an actual post-coronavirus disease of 2019 (COVID-19) comparison group versus one simulated using Monte-Carlo methods. METHOD: Validated neuropsychological Monte-Carlo simulation methods were applied to scores from a battery of neuropsychological tests (memory, executive, attentional, perceptual, logical reasoning, language, and ideomotor praxis) administered to 121 patients who had had mild, moderate, or severe COVID-19 (mean age: 56.70 years; 32% women), 222 ± 43 days post-infection. The cumulative percentages of the three severity subgroups were compared with the results of a false discovery rate-corrected probability analysis based on normative data. RESULTS: The cumulative percentages of deficits in memory and executive functions among the severe and moderate patients were significantly higher than those estimated for the normative population. Moderate patients also had significantly more deficits in perception and logical reasoning. In contrast, the mild group did not have significantly more cumulative deficits. CONCLUSIONS: Moderate and severe forms of COVID-19 cause greater long-term neuropsychological deficits than those that would be found in a normative population, reinforcing the hypothesis of long-term effects of SARS-CoV-2 on cognitive function, independent of the severity of the initial infection.

Acute TNFα levels predict cognitive impairment 6-9 months after COVID-19 infection.

BACKGROUND: A neurocognitive phenotype of post-COVID-19 infection has recently been described that is characterized by a lack of awareness of memory impairment (i.e., anosognosia), altered functional connectivity in the brain's default mode and limbic networks, and an elevated monocyte count. However, the relationship between these cognitive and brain functional connectivity alterations in the chronic phase with the level of cytokines during the acute phase has yet to be identified. AIM: Determine whether acute cytokine type and levels is associated with anosognosia and functional patterns of brain connectivity 6-9 months after infection. METHODS: We analyzed the predictive value of the concentration of acute cytokines (IL-1RA, IL-1ß, IL-6, IL-8, IFNγ, G-CSF, GM-CSF) (cytokine panel by multiplex immunoassay) in the plasma of 39 patients (mean age 59 yrs, 38-78) in relation to their anosognosia scores for memory deficits via stepwise linear regression. Then, associations between the different cytokines and brain functional connectivity patterns were analyzed by MRI and multivariate partial least squares correlations for the whole group. RESULTS: Stepwise regression modeling allowed us to show that acute TNFα levels predicted (R2 = 0.145; ß = -0.38; p = .017) and were associated (r = -0.587; p < .001) with scores of anosognosia for memory deficits observed 6-9 months post-infection. Finally, high TNFα levels were associated with hippocampal, temporal pole, accumbens nucleus, amygdala, and cerebellum connectivity. CONCLUSION: Increased plasma TNFα levels in the acute phase of COVID-19 predict the presence of long-term anosognosia scores and changes in limbic system functional connectivity.

Creutzfeldt-Jakob disease revealed by a logopenic variant of primary progressive aphasia.

Logopenic aphasia, mainly characterized by word anomia, sentence and phrase comprehension difficulties secondary to phonological loop deficits but relatively preserved single word comprehension and no agrammatism, is one of the 3 main variants of primary progressive aphasia (PPA). We describe the first case of PPA that fulfilled clinical criteria of logopenic aphasia but showed abnormal DWI hyperintensities that were predominant on the left hemisphere and compatible with Creutzfeldt-Jakob disease (CJD). After abnormally long isolated language deficits, the patient rapidly worsened and died. Autopsy performed 18 months after onset of language difficulties confirmed the diagnosis. We therefore advocate performing DWI sequences in any suspicion of PPA in order to rule out CJD.

Longitudinal analysis of cognitive performances and structural brain changes in late-life bipolar disorder.

OBJECTIVES: Cross-sectional studies in bipolar disorder (BD) suggested the presence of cognitive deficits and subtle magnetic resonance imaging (MRI) changes in limbic areas that may persist at euthymic stages. Whether or not cognitive and MRI changes represent stable attributes of BD or evolve with time is still matter of debate. To address this issue, we performed a 2-year longitudinal study including detailed neuropsychological and magnetic resonance imaging (MRI) analyses of 15 euthymic older BD patients and 15 controls. METHODS: Neuropsychological evaluation concerned working memory, episodic memory, processing speed, and executive functions. MRI analyses included voxel-based morphometry (VBM) analysis of gray matter including region of interest (ROI) analysis and tract-based spatial statistics (TBSS) analysis of white matter of diffusion tensor imaging derived fractional anisotropy (FA). RESULTS: BD patients displayed significantly lower performances in processing speed and episodic memory but not in working memory and executive functions compared to controls. However, BD patients did not differ from controls in the mean trajectory of cognitive changes during the 2 years follow-up. In the same line, longitudinal gray matter (VBM, ROI) and white matter (TBSS FA) changes did not differ between BD patients and controls. CONCLUSION: The lack of distinction between BD patients and controls in respect to the 2-year changes in cognition and MRI findings supports the notion that this disorder does not have a significant adverse impact on cognitive and brain aging. From this point of view, the present results convey a message of hope for patients suffering from BD.

ADC mapping of chronic cerebral hypoperfusion induced by carotid artery stenosis.

BACKGROUND: Carotid artery stenosis is associated with the occurrence of acute and chronic ischemic lesions that increase with age in the elderly population. Diffusion Imaging and ADC mapping may be an appropriate method to investigate patients with chronic hypoperfusion consecutive to carotid stenosis. This non-invasive technique allows to investigate brain integrity and structure, in particular hypoperfusion induced by carotid stenosis diseases. The aim of this study was to evaluate the impact of a carotid stenosis on the parenchyma using ADC mapping. METHODS: Fifty-nine patients with symptomatic (33) and asymptomatic (26) carotid stenosis were recruited from our multidisciplinary consultation. Both groups demonstrated a similar degree of stenosis. All patients underwent MRI of the brain including diffusion-weighted MR imaging with ADC mapping. Regions of interest were defined in the anterior and posterior paraventricular regions both ipsilateral and contralateral to the stenosis (anterior circulation). The same analysis was performed for the thalamic and occipital regions (posterior circulation). RESULTS: ADC values of the affected vascular territory were significantly higher on the side of the stenosis in the periventricular anterior (P<0.001) and posterior (P<0.01) area. There was no difference between ipsilateral and contralateral ADC values in the thalamic and occipital regions. CONCLUSIONS: We have shown that carotid stenosis is associated with significantly higher ADC values in the anterior circulation, probably reflecting an impact of chronic hypoperfusion on the brain parenchyma in symptomatic and asymptomatic patients. This is consistent with previous data in the literature.

Interictal arterial spin-labeling MRI perfusion in intractable epilepsy.

INTRODUCTION: Magnetic resonance imaging (MRI) is required for the investigation of surgically intractable epilepsy. In addition to the standard MRI techniques, perfusion sequences can be added to improve visualization of underlying pathological changes. Arterial spin-labeling (ASL) MRI perfusion does not require contrast administration and, for this reason, may have advantages in these patients. METHODS: We report here on 16 patients with epilepsy who underwent MRI of the brain with ASL and positron emission tomography (PET). RESULTS: Despite a slightly reduced resolution with ASL, we found a correlation between ASL, PET and electrophysiological data, with hypoperfusion on ASL that corresponded with hypoperfusion on interictal PET. CONCLUSION: Given the correlation between ASL and PET and electrophysiology, perfusion with ASL could become part of the standard work-up in patients with epilepsy.

Arterial spin-labeling MRI perfusion in tuberous sclerosis: correlation with PET.

Neuroimaging using magnetic resonance imaging (MRI) is required for the investigation of surgically intractable epilepsy. In addition to the standard MRI techniques, perfusion sequences can be added to improve visualization of the underlying pathological changes. Also, as arterial spin-labeling (ASL) MRI perfusion does not require contrast administration, it may even be advantageous in these patients. We report here on three patients with epilepsy and tuberous sclerosis who underwent brain MRI with ASL and positron emission tomography (PET), both of which were found to correlate with each other and with electrophysiological data.

Resting-State Brain Activity for Early Prediction Outcome in Postanoxic Patients in a Coma with Indeterminate Clinical Prognosis.

BACKGROUND AND PURPOSE: Early outcome prediction of postanoxic patients in a coma after cardiac arrest proves challenging. Current prognostication relies on multimodal testing, using clinical examination, electrophysiologic testing, biomarkers, and structural MR imaging. While this multimodal prognostication is accurate for predicting poor outcome (ie, death), it is not sensitive enough to identify good outcome (ie, consciousness recovery), thus leaving many patients with indeterminate prognosis. We specifically assessed whether resting-state fMRI provides prognostic information, notably in postanoxic patients in a coma with indeterminate prognosis early after cardiac arrest, specifically for good outcome. MATERIALS AND METHODS: We used resting-state fMRI in a prospective study to compare whole-brain functional connectivity between patients with good and poor outcomes, implementing support vector machine learning. Then, we automatically predicted coma outcome using resting-state fMRI and also compared the prediction based on resting-state fMRI with the outcome prediction based on DWI. RESULTS: Of 17 eligible patients who completed the study procedure (among 351 patients screened), 9 regained consciousness and 8 remained comatose. We found higher functional connectivity in patients recovering consciousness, with greater changes occurring within and between the occipitoparietal and temporofrontal regions. Coma outcome prognostication based on resting-state fMRI machine learning was very accurate, notably for identifying patients with good outcome (accuracy, 94.4%; area under the receiver operating curve, 0.94). Outcome predictors using resting-state fMRI performed significantly better (P < .05) than DWI (accuracy, 60.0%; area under the receiver operating curve, 0.63). CONCLUSIONS: Indeterminate prognosis might lead to major clinical uncertainty and significant variations in life-sustaining treatments. Resting-state fMRI might bridge the gap left in early prognostication of postanoxic patients in a coma by identifying those with both good and poor outcomes.

Large Neck and Strong Ostium Inflow as the Potential Causes for Delayed Occlusion of Unruptured Sidewall Intracranial Aneurysms Treated by Flow Diverter.

BACKGROUND AND PURPOSE: Flow diverter-induced hemodynamic change plays an important role in the mechanism of intracranial aneurysm occlusion. Our aim was to explore the relationship between aneurysm features and flow-diverter treatment of unruptured sidewall intracranial aneurysms. MATERIALS AND METHODS: MR imaging, 4D phase-contrast, was prospectively performed before flow diverter implantation in each patient with unruptured intracranial aneurysm. Two postprocedure follow-ups were scheduled at 6 and 12 months. Responses were grouped according to whether the aneurysms were occluded or remnant. Preprocedural aneurysm geometries and ostium hemodynamics in 38 patients were compared between the 2 groups at 6 and 12 months. Receiver operating characteristic curve analyses were performed for significant geometric and hemodynamic continuous parameters. RESULTS: After the 6-month assessment, 21 of 41 intracranial aneurysms were occluded, and 9 additional aneurysms were occluded at 12 months. Geometrically, the ostium maximum diameter was significantly larger in the remnant group at 6 and 12 months (both P < .001). Hemodynamically, the proximal inflow zone was more frequently observed in the remnant group at 6 months. Several preprocedural ostium hemodynamic parameters were significantly higher in the remnant group. As a prediction for occlusion, the areas under the curve of the ostium maximum diameter (for 6 and 12 months), systolic inflow rate ratio (for 6 months), and systolic inflow area (for 12 months) reached 0.843, 0.883, 0.855, and 0.860, respectively. CONCLUSIONS: Intracranial aneurysms with a large ostium and strong ostium inflow may need a longer time for occlusion. Preprocedural 4D flow MR imaging can well illustrate ostium hemodynamics and characterize aneurysm treatment responses.

Arterial spin labeling shows cortical collateral flow in the endovascular treatment of vasospasm after post-traumatic subarachnoid hemorrhage.

We report here on the case of a patient who, 10 days prior to his admission to hospital, had suffered a bicycle accident. He presented with signs of minor dysphasia. A brain CT-scan revealed slight subarachnoid hemorrhage (SAH) in the left sylvian fissure as well as narrowing of the distal M1 segment of the left middle cerebral artery (MCA) on CT-angiography. MRI showed diffusion abnormalities and hypoperfusion in the left MCA territory with cortical hyperperfusion on arterial spin labeling (ASL). Arteriography confirmed the vasospasm, but showed no sign of aneurysm. Angioplasty of the narrowed MCA was successful, and follow-up MRI showed reperfusion of the MCA territory.

Evaluation of perfusion CT and TIBI grade in acute stroke for predicting thrombolysis benefit and clinical outcome.

OBJECTIVE: To evaluate the prognostic accuracy of combining perfusion CT (PCT) and thrombolysis in brain ischemia (TIBI) ultrasonographic grade in the triage of stroke patients who will benefit from thrombolysis and in predicting the clinical outcome. METHODS: We conducted a prospective study of all consecutive stroke patients admitted to our hospital from March 2003 to July 2007, presenting with signs of acute stroke within the therapeutic window, who had undergone either intravenous or combined intravenous and intra-arterial thrombolysis. All patients were evaluated by a complete stroke CT protocol, transcranial color-coded duplex sonographic monitoring, follow-up imaging (CT or MRI) and clinical outcome at 3 months, as assessed by the modified Rankin scale (mRS). RESULTS: A total of 34 patients were included with a mean NIHSS on admission of 14.2. This study revealed that PCT had 95% sensitivity and 71% specificity in the evaluation of therapy benefit as well as 75% sensitivity and 39% specificity in predicting clinical outcome. The extent of ischemic tissue according to PCT and TIBI grade were significantly correlated (p<0.05). Using the MTT-TTP approach was an alternative to the classical MTT-CBV approach for determining tissue at risk. The clinical outcome assessed by the mRS was considered favorable (mRS 0-2) in 16 patients and unfavorable (mRS>2) in 18 patients. CONCLUSION: PCT was the most accurate predictor of both thrombolytic therapy benefit and clinical outcome. The TIBI score was useful for determining whether or not to perform intravenous therapy alone or as a combined therapy.

[Carotid stenting: an alternative to surgery?]. / Stenting de la carotide: une alternative à la chirurgie?

A stenosis of the internal carotid artery may cause 10-20% of all ischemic strokes. In symptomatic patients, carotid revascularization is indicated in the presence of a stenosis 50%. in asymptomatic patients, the indication for revascularization based on randomized trials is given at > or = 60% stenosis, as long as the estimated perioperative death or stroke risk is < 3%. In clinical practice however, asymptomatic stenoses are usually treated only if luminal narrowing exceeds 70-80%. The choice of the revascularization strategy (endarterectomy versus stenting) should be based on the surgical risk profile of the patient and on the locally available expertise. Carotid artery stenting is particularly beneficial in patients at high risk for surgery.

How Flow Reduction Influences the Intracranial Aneurysm Occlusion: A Prospective 4D Phase-Contrast MRI Study.

BACKGROUND AND PURPOSE: Flow-diverter stents are widely used for the treatment of wide-neck intracranial aneurysms. Various parameters may influence intracranial aneurysm thrombosis, including the flow reduction induced by flow-diverter stent implantation, which is assumed to play a leading role. However, its actual impact remains unclear due to the lack of detailed intra-aneurysmal flow measurements. This study aimed to clarify this relationship by quantitatively measuring the intra-aneurysmal flow using 4D phase-contrast MR imaging. MATERIALS AND METHODS: We acquired prospective pre- and post-stent implantation 4D phase-contrast MR imaging data of a consecutive series of 23 patients treated with flow-diverter stents. Velocity field data were combined with the intraprocedural 3D angiogram vessel geometries for precise intracranial aneurysm extraction and partial volume correction. Intra-aneurysmal hemodynamic modifications were compared with occlusion outcomes at 6 and 12 months. RESULTS: The averaged velocities at systole were lower after flow-diverter stent implantation for all patients and ranged from 21.7 ± 7.1 cm/s before to 7.2 ± 2.9 cm/s after stent placement. The velocity reduction was more important for the group of patients with aneurysm thrombosis at 6 months (68.8%) and decreased gradually from 66.2% to 55% for 12-month thrombosis and no thrombosis, respectively (P = .08). CONCLUSIONS: We propose an innovative approach to measure intracranial flow changes after flow-diverter stent implantation. We identified a trend between flow reduction and thrombosis outcome that brings a new insight into current understanding of the flow-diversion treatment response.