Neurological imaging of brain damages after radiotherapy and/or chimiotherapy.

Radiotherapy and chemotherapy may induce neurological toxicities with different appearances on CT and MRI scans. While optimized radiotherapy techniques have reduced some complications, new unwanted effects have occurred on account of therapeutic protocols involving the simultaneous use of radiotherapy and chemotherapy. Advances in radio-surgery, innovative anti-angiogenic therapies, as well as prolonged patient survival have led to the emergence of new deleterious side effects. In this report, we describe the early, semi-delayed, and late encephalic complications, while specifying how to identify the morphological lesions depending on the therapeutic protocol.

[Effet blouse blanche résiduel : un outil pertinent en soins premiers?] / Office white-coat effect tail: A useful tool in family practice?

BACKGROUND: White coat effect (WCE) and white coat hypertension (WCH) are hardly both compared in primary care. OBJECTIVE: To assess the usefulness of repeated measures of systolic blood pressure (SBP) to dissociate various forms of white-coat interactions. METHODS: An open cross-sectional study on consecutive patients treated or not for high blood pressure was made in family physicians' offices. SBP was measured 5 times by an electronic device. Measurements were performed before (SBP1) and after (SBP5) the office visit by a lay assistant and at the beginning (SBP2), middle (SBP3) and end (SBP4) of visit, by the family physician. Home BP (HBPM) was measured from 3 consecutive days by the patient. WCE and office WCE tail (OWCET) were defined, respectively, as a 10 mmHg SBP increase or decrease between SBP2-SBP1 or SBP4-SBP2. WCH was considered when HBPM was normal (SBP < 135 mmHg) at home and high during the SBP2 office visit. RESULTS: Two hundred five patients (134 women versus 71 men, ratio 1.9, aged 59.8±15.7 years) were recruited. In categorical terms, there were 51 patients (25%) who presented with WCE, OWCET was seen in 121 patients (62%) and 47 patients (23%) had WCH. Only 36 patients (18%) presented both OWCET and WCE and 32 (16%) had both OWCET and WCH. The receiver operating characteristic curves (ROCs) of OWCET in diagnosing WCE or WCH were respectively 0.67 (p<0.0001) and 0.53 (NS). CONCLUSION: Thus, OWCET was predictive of WCE and not of WCH and it is worthwhile to be measured in the family physician office.

Per-subject characterization of bolus width in pulsed arterial spin labeling using bolus turbo sampling.

Quantification of cerebral blood flow using QUIPSSII pulsed arterial spin labeling requires that the QUIPSS saturation delay TI1 is shorter than the natural temporal bolus width. Yet the duration of the bolus of tagged spins entering the region of interest varies during vasoactive stimuli such as gaseous challenges or across subjects due to differences in blood velocity or vessel geometry. A new technique, bolus turbo sampling, to rapidly measure the duration of the inflowing bolus is presented. It allows to optimize the arterial spin labeling acquisition to ensure reliable quantification of perfusion while maximizing the arterial spin labeling signal by avoiding the use of unnecessarily short label durations. The average bolus width measured in the right and left middle cerebral artery territories using the bolus turbo sampling technique has a repeatability coefficient of 75 ms and correlates significantly with the TI1,max determined from a novel multi-TI1 protocol (R=0.65, P<0.05). The possibility to measure the bolus width under hypercapnia is demonstrated.

Evaluation of dual-source parallel RF excitation technology in MRI of thoraco-lumbar spine at 3.0 T.

High-field 3 T magnetic resonance imaging (MRI) has entered standard clinical practice over the past decade, and its advantages have already been suggested in areas such as neural, musculoskeletal, pelvic and angiographic imaging. However, high-field systems still pose challenges in terms of their specific absorption rate (SAR) and radiofrequency (RF) excitation uniformity. Thus, the aim of the present study was to evaluate the impact, on both these factors, of standard quadrature against parallel RF transmission technology (dual-source parallel RF excitation [DSPE]) in spinal examination at 3 T. The thoracolumbar spine was examined with three different sequences: T1-weighted (T1w); T2-weighted (T2w); and T2w short tau inversion recovery (STIR). Each was acquired with and without DSPE. The manufacturer's implementation of this technology has been associated with optimized handling of patient SAR exposure, resulting in a 38.4% reduction in acquisition time. On comparing sequences with equal repetition times (TRs), the acquisition time reduction was 44.4%. Thus, DSPE allows a reduction in acquisition time. This gain is accompanied by augmentation of the whole-body SAR and diminution of the local SAR. Image quality improvement due to more homogeneous effective transmit B1 was mainly observed at the junction of the thoracolumbar spine.

Functional MRI and neuropsychological evidence for language plasticity before and after surgery in one patient with left temporal lobe epilepsy.

This study explores the language reorganization before and after surgery in a 55-year-old right-handed female patient presenting with left temporal refractory epilepsy. Two aspects of language were explored, phonological and semantic, by using neuropsychological assessments and fMRI protocols. To assess the possible reorganization of language, fMRI results for B.L. were compared with results obtained in a group of healthy control subjects (results not presented in detail). According to our results and compared with healthy subjects, B.L. shows reorganization of temporal regions only. The reorganization had various patterns according to the task. Before surgery, neuropsychological testing in B.L. revealed impairment in phonological abilities and fMRI suggested right temporal involvement (interhemisphere reorganization) during the phonological task; semantic abilities were unaltered and fMRI showed bilateral activation of temporal regions during the semantic task. After surgery, the phonological deficit disappeared and fMRI showed left perilesional location of temporal activation (intrahemispheric reorganization); semantic abilities remain preserved and temporal activation remained located bilaterally but predominantly to the right during the semantic task. Our results suggest that cerebral reorganization of language depends on the language operation tested. Moreover, the results underline the importance of differential assessment of language operations and show functional reorganization after beneficial surgery in an older patient.

[Diffusion-Weighted Imaging infarct volume and neurologic outcomes after ischemic stroke]. / Volumétrie de l'ischémie cérébrale en IRM de diffusion et déficit fonctionnel secondaire après thrombolyse intraveineuse.

BACKGROUND: This study's purpose was to demonstrate a relationship between growth of stroke volume measured on Diffusion-Weighted MRI (DWI) at admission (baseline) and 24 hours later (follow-up) and functional outcome at 90 days evaluated by the modified Rankin Scale (mRS). METHODS: DWI infarct volumes were calculated, using an Analyze Software. Clinical outcomes were assessed at 90 days by the mRS. Univariate regression analysis was performed to assess the relationship between changes in DWI lesion volume and mRS less or equal to 1. RESULTS: Sixty-nine cases had serial DWI scans with a measurable lesion at baseline and follow-up. The median baseline National Institutes of Health Stroke Scale (NIHSS) was 10, 5 and 7 at 24 hours. At 90 days, the proportion of patients with Rankin less or equal to 1 was 51.7%. The average baseline volume was 19.7 cm(3) and average follow-up volume was 46.1 cm(3). For each 10 cm(3) of growth in DWI infarct volume, the odds ratio for a mRS less or equal to 1 was 10,1 (IC 95%, 3-33.9). CONCLUSION: The results of this study provide evidence of a significant inverse relationship between infarct growth measured by DWI and good functional clinical outcome at 90 days.

Impaired cerebral vasoreactivity to CO2 in Alzheimer's disease using BOLD fMRI.

OBJECTIVE: To evaluate the cerebral vasoreactivity using blood oxygenation level dependent functional MRI during carbogen inhalation with 7% CO(2) in Alzheimer's disease and amnestic mild cognitive impairment. PARTICIPANTS AND METHODS: Thirty nine subjects were included to be investigated using blood oxygenation level dependent (BOLD) functional MRI at 1.5T during a block-design carbogen inhalation paradigm, with a high concentration face-mask under physiological monitoring. Basal cerebral perfusion was measured using pulsed arterial spin labeling. Image analyses were conducted using Matlab® and SPM5 with physiological regressors and corrected for partial volume effect. RESULTS: Among selected participants, 12 subjects were excluded because of incomplete protocol, leaving for analysis 27 subjects without significant microangiopathy diagnosed for Alzheimer's disease (n=9), amnestic mild cognitive impairment (n=7), and matched controls (n=11). No adverse reaction related to the CO(2) challenge was reported. Carbogen inhalation induced a whole-brain signal increase, predominant in the gray matter. In patients, signal changes corrected for gray matter partial volume were decreased (0.36±0.13% BOLD/mmHg in Alzheimer's disease, 0.36±0.12 in patients with mild cognitive impairment, 0.62±0.20 in controls). Cerebral vasoreactivity impairments were diffuse but seemed predominant in posterior areas. The basal hypoperfusion in Alzheimer's disease was not significantly different from patients with mild cognitive impairment and controls. Among clinical and biological parameters, no effect of apoE4 genotype was detected. Cerebral vasoreactivity values were correlated with cognitive performances and hippocampal volumes. Among age and hippocampal atrophy, mean CVR was the best predictor of the mini-mental status examination. CONCLUSION: This BOLD functional MRI study on CO(2) challenge shows impaired cerebral vasoreactivity in patients with Alzheimer's disease and amnestic mild cognitive impairment at the individual level. These preliminary findings using a new MRI approach may help to better characterize patients with cognitive disorders in clinical practice and further investigate vaso-protective therapeutics.

Effects of pedunculopontine nucleus area stimulation on gait disorders in Parkinson's disease.

Gait disturbances are frequent and disabling in advanced Parkinson's disease. These symptoms respond poorly to usual medical and surgical treatments but were reported to be improved by stimulation of the pedunculopontine nucleus. We studied the effects of stimulating the pedunculopontine nucleus area in six patients with severe freezing of gait, unresponsive to levodopa and subthalamic nucleus stimulation. Electrodes were implanted bilaterally in the pedunculopontine nucleus area. Electrode placement was checked by postoperative magnetic resonance imaging. The primary outcome measures were a composite gait score, freezing of gait questionnaire score and duration of freezing episodes occurring during a walking protocol at baseline and one-year follow-up. A double-blind cross-over study was carried out from months 4 to 6 after surgery with or without pedunculopontine nucleus area stimulation. At one-year follow-up, the duration of freezing episodes under off-drug condition improved, as well as falls related to freezing. The other primary outcome measures did not significantly change, nor did the results during the double-blind evaluation. Individual results showed major improvement of all gait measures in one patient, moderate improvement of some tests in four patients and global worsening in one patient. Stimulation frequency ranged between 15 and 25 Hz. Oscillopsia and limb myoclonus could hinder voltage increase. No serious adverse events occurred. Although freezing of gait can be improved by low-frequency electrical stimulation of the pedunculopontine nucleus area in some patients with Parkinson's disease our overall results are disappointing compared to the high levels of expectation raised by previous open label studies. Further controlled studies are needed to determine whether optimization of patient selection, targeting and setting of stimulation parameters might improve the outcome to a point that could transform this experimental approach to a treatment with a reasonable risk-benefit ratio.

Prognostic value of perfusion MR imaging in patients with oligodendroglioma: A survival study.

OBJECTIVE: The purpose of this study was to evaluate retrospectively whether cerebral blood volume measurement based on pretreatment perfusion MRI is a prognostic biomarker for survival in patients with oligodendroglioma or mixed oligoastrocytoma. PATIENTS AND METHODS: Between 1998 and 2004, 54 patients (23 females and 31 males), aged 21-73 years, with oligodendroglioma (or mixed tumour) were examined prior to beginning treatment with dynamic susceptibility-weighted contrast (DSC) perfusion MRI during gadolinium first-pass. The relative cerebral blood volume (rCBV) was calculated by dividing the measurement within the tumour by the measurement of the normal-appearing contralateral region. Patients were classified in two groups, grade A and grade B, according to the Saint-Anne Hospital classification and followed-up clinically and by means of MRI until their death or for a minimum of 5 years. Patients were also classified in grade II and grade III-IV, according to the World Health Organisation (WHO) classification, and were analysed with the same methods. Age, sex, treatment, tumour grade, contrast agent uptake, and rCBV were tested using survival curves with Kaplan-Meier's method, and their differences were analysed using the log-rank test. RESULTS: In this population, median survival was 3 years. A rCBV threshold value of 2.2 was validated as a prognostic factor, for survival in these patients with oligodendrogliomas. Age, sex, contrast uptake, and maximum rCBV were found to be prognostic factors in univariate analysis. Multivariate analysis revealed that tumour grade (grade A/grade B), rCBV, age, and sex were prognostic factors independent of the other factors. The tumour grade according to the WHO classification (II versus III-IV) was also detected as an independent prognostic factor. CONCLUSION: Pretreatment rCBV measured by DSC perfusion MRI was found to be a prognostic factor for survival in patients with oligodendroglioma or mixed tumour, by using the Saint-Anne Hospital classification, which separate the IIB from the IIA.

Dynamic susceptibility contrast-enhanced MRI evaluation of cerebral intraventricular tumors: preliminary results.

INTRODUCTION: The aims of the present study were to determine the perfusion characteristics of several types of intraventricular tumors and to evaluate the usefulness of dynamic contrast-enhanced MRI in making the differential diagnosis. METHODS: A total of 28 patients with intraventricular tumors (five meningiomas, five papillomas, three ependymomas, four subependymomas, seven central neurocytomas, two subependymal giant cell astrocytomas and two metastases) underwent conventional and dynamic susceptibility contrast-enhanced MRI. Cerebral blood volume (CBV) maps were obtained and the relative CBV (rCBV) calculated for each tumor. Mean rCBV(max) values were compared across the different types of tumors (ANOVA, P=0.05). RESULTS: Intraventricular tumors presented with three different patterns of vascularization: highly vascularized tumors (mean rCBV(max)>3), including papillomas, meningiomas and renal carcinoma metastases; poorly vascularized tumors (mean rCBV(max)<2), including ependymomas and subependymomas; and intermediately vascularized tumors (mean rCBV(max)>2 but<3), including central neurocytomas and lung metastases. There was a significant difference between the highly vascularized (papillomas, meningiomas) and poorly vascularized (subependymomas) tumors. In cases of suspected meningioma, papilloma or neurocytoma, low rCBV values (<3) point to a diagnosis of neurocytoma rather than either of the other tumor types. CONCLUSION: Susceptibility contrast-enhanced MRI can provide additional information on the vascularization of intraventricular cerebral tumors and may help in making the differential diagnosis.

Perfusion MR imaging and 1H spectroscopy: their role in the diagnosis of microcystic and lipomatous meningiomas.

Microcystic and lipomatous meningiomas represent two of the recognised rare subtypes of meningiomas. We describe the CT and MR findings in one adult case of each subtype with emphasis on the diagnostic benefits of perfusion-weighted MR imaging (PWI) and/or proton magnetic resonance spectroscopy (MRS).

How helical CT helps the surgeon in oculo-orbital trauma.

Whether isolated or associated with craniofacial lesions, traumatic oculo-orbital injuries occur frequently. Radiological evaluation is often necessary to appropriately manage the trauma-related vision loss and oculomotor disturbance. In the emergency setting and after clinical examination, helical CT scanning is the optimal imaging technique for displaying injuries of the orbit and its contents, for determining their severity and for helping the surgeon to choose the best course of treatment. MRI is indicated if the cause of the loss of vision or ocular mobility remain unexplained on CT after ferromagnetic foreign body has been ruled out. Drawing from numerous clinical cases, the purpose of this pictorial review is to demonstrate the wide variety of traumatic lesions of the orbit and eyeball as revealed by helical CT, as well as the limitations of the technique, to provide relevant information for patient care. Helical CT scans remain, in cases of emergency, the optimal imaging technique for the evaluation of oculo-orbital trauma.

[Value of perfusion MRI in the study of pilocytic astrocytoma and hemangioblastoma: preliminary findings]. / Intérêt de l'imagerie de perfusion dans l'étude des astrocytomes pilocytiques et des hémangioblastomes : étude préliminaire.

PURPOSE: Pilocytic astrocytomas (PA) and hemangioblastomas (HB) can present the same morphological characteristics on conventional MRI sequences, most usually in the form of a cerebellar cystic mass with a mural nodule that strongly enhances on post-contrast T1 images. We discuss here the value of perfusion MRI in the differentiation of these two tumors, the diagnoses of which have already been histopathologically established. METHOD: Eleven patients with PA and eight with HB underwent first-pass perfusion MRI. The maximum relative cerebral blood volume (rCBV(max)), defined as the ratio between the CBV(max) in tumor tissue and the CBV in healthy, contralateral white matter, is considered to be indicative of the type of tumor. RESULTS: The difference between the rCBV(max) of PA (rCBV(max)=1.19+/-0.71, range 0.6-3.27) compared with that of HB (rCBV(max)=9.37+/-2.37, range 5.38-13) was significant (P<0.001). The first-pass curve crossed the baseline, corresponding to vascular permeability problems in both PA and HB. CONCLUSION: The first-pass method of perfusion MRI is a quick and useful way to differentiate between PA and HB.

Pyramidal tract side effects induced by deep brain stimulation of the subthalamic nucleus.

OBJECTIVE: To study the pyramidal tract side effects (PTSEs) induced by the spread of current from the subthalamic nucleus (STN) to the pyramidal tract (PT), in patients with parkinsonism undergoing STN stimulation. METHODS: 14 patients bilaterally implanted with tetrapolar electrodes were assessed. For each side separately, the threshold of adverse effects induced by monopolar stimulation delivered by the chronically used contact was detected. The voltage was progressively increased until the patient experienced discomfort. All the PTSEs induced at 130 Hz (high-frequency stimulation (HFS)) and 2 or 3 Hz (low-frequency stimulation (LFS)) were videotaped. By superimposing the preoperative and postoperative MR images, the minimum distance (R) from the centre of the used contact to the medial border of the PT were measured. RESULTS: The progressive increase in voltage at HFS induced tonic motor contractions, mainly located in the face, in 27/28 electrodes. LFS induced synchronous rhythmic myoclonus in the same territory. PTSEs induced at threshold voltage by HFS were observed in the upper face at 13/28 electrodes (bilaterally in six cases) and in the contralateral lower face at five electrodes. A positive correlation was found between the stimulus intensity capable of eliciting motor contractions at HFS and R. CONCLUSIONS: HFS of the STN preferentially activates the corticobulbar tract over the corticospinal tract. Therefore, cranial motor contractions need to be looked for during electrical parameter setting. The positive correlation between the electrical intensity threshold for PTSEs and R reflects the need for millimetre accuracy in electrode positioning.

[MR and CT perfusion imaging of the brain: principles and clinical applications]. / Imagerie de perfusion: principes et applications cliniques.

MR and CT imaging techniques provide both morphological data and functional data. MR and recently CT perfusion have substantially modified the treatment of acute stroke. CT perfusion offers new opportunities to improve the management strategy in vasospasm after subarachnoid hemorrhage. Both are also helpful for the diagnosis of brain tumors and the assessment of treatment effects.

[Perfusion-diffusion 1H spectroscopy: role in the diagnosis and follow-up of supratentorial brain tumours in adults]. / Spectroscopie 1H, perfusion, diffusion: quelle place pour ces techniques lors du diagnostic et du suivi des principales tumeurs cérébrales sus-tentorielles de l'adulte?

INTRODUCTION: In a few years, magnetic resonance imaging (MRI) has evolved from a morphology-based examination to one that encompasses metabolism and function. STATE OF ART: MRI is a well-established tool for the initial evaluation of brain tumors, but conventional MR sequences have some limitations. Conventional MRI is unable to distinguish high-grade glioma from metastasis and abscess, to define precisely the histopathological grade of gliomas, to determine exactly the limits of tumor extension, to characterize meningeal tumors. Differentiation of tumor recurrence from treatment-related changes may be difficult with standard MR imaging because the interpretation is essentially based on volume analysis. PERSPECTIVES: 1H Spectroscopy, diffusion and perfusion imaging become possible with the development of MR imagers and can be routinely performed in clinical settings. They give complementary information about tumor metabolism and vascularity and allow a better analysis of post-treatment modifications. Functional and metabolic explorations should be used to characterize brain tumors.

[Perfusion MR imaging in brain tumors]. / IRM de perfusion des tumeurs cérébrales.

Perfusion MR Imaging is useful for initial diagnosis and follow up of brain tumors. Dynamic susceptibility contrast MR imaging is described. The limitations and advantages of this technique are discussed with respect to quantification and interpretation of results.

[Functional magnetic resonance imaging in clinical practice]. / L'imagerie par résonance magnétique cérébrale fonctionnelle en pratique clinique.

In the last decade, functional MRI (fMRI) has become one of the most widely used functional imaging technique in neurosciences. However, its clinical applications remain limited. Despite methodological and practical issues, fMRI data has been validated by different techniques (magnetoencephalography, Wada test, electrical and magnetic stimulations, and surgical resections). In neurosurgical practice, fMRI can identify eloquent areas involved in motor and language functions, and may evaluate characteristics of postoperative neurological deficit including its occurrence, clinical presentation and duration. This may help to inform patients and to prepare postoperative care. fMRI may also identify epileptic foci. In neurological practice, fMRI may help to determine prognosis of recovery after stroke, appropriate medication, and rehabilitation. fMRI may help to identify patients at risk of developing Alzheimer disease. Finally, cerebrovascular reactivity imaging is an interesting approach that might provide new radiological insights of vascular function.

[Brain perfusion and metabolism imaging techniques]. / Imagerie de la perfusion et du métabolisme cérébral.

Due to recent efforts in improving spatial and temporal resolution in imaging techniques, it is now possible to get relevant information about brain perfusion and metabolism in humans. This information can significantly impact on brain pathophysiology, diagnosis assessment and therapy options, particularly in patients having brain ischemia. Among these imaging and metabolism techniques are dynamic perfusion computed tomography, perfusion MRI, positron emission tomography and NMR spectroscopic imaging. The goal of this article is an overview of these four techniques, with their own technical description, advantages and drawbacks. Details are provided about brain parameters given by each technique and their clinical relevance, the accessibility of the technique in the emergency setting and the optimal window to use it during the patient's evolution.