Short-term evolution of spinal cord damage in multiple sclerosis: a diffusion tensor MRI study.

INTRODUCTION: The potential of diffusion tensor imaging (DTI) to detect spinal cord abnormalities in patients with multiple sclerosis has already been demonstrated. The objective of this study was to apply DTI techniques to multiple sclerosis patients with a recently diagnosed spinal cord lesion, in order to demonstrate a correlation between variations of DTI parameters and clinical outcome, and to try to identify DTI parameters predictive of outcome. METHODS: A prospective single-centre study of patients with spinal cord relapse treated by intravenous steroid therapy was made. Patients were assessed clinically and by conventional MRI with DTI sequences at baseline and at 3 months. RESULTS: Sixteen patients were recruited. At 3 months, 12 patients were clinically improved. All but one patient had lower fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values than normal subjects in either inflammatory lesions or normal-appearing spinal cord. Patients who improved at 3 months presented a significant reduction in the radial diffusivity (p = 0.05) in lesions during the follow-up period. They also had a significant reduction in the mean ADC (p = 0.002), axial diffusivity (p = 0.02), radial diffusivity (p = 0.02) and a significant increase in FA values (p = 0.02) in normal-appearing spinal cord. Patients in whom the American Spinal Injury Association sensory score improved at 3 months showed a significantly higher FA (p = 0.009) and lower radial diffusivity (p = 0.04) in inflammatory lesion at baseline compared to patients with no improvement. CONCLUSION: DTI MRI detects more extensive abnormalities than conventional T2 MRI. A less marked decrease in FA value and more marked decreased in radial diffusivity inside the inflammatory lesion were associated with better outcome.

Aphasia in border-zone infarcts has a specific initial pattern and good long-term prognosis.

BACKGROUND: While border-zone infarcts (BZI) account for about 10% of strokes, studies on related aphasia are infrequent. The aim of this work was to redefine specifically their early clinical pattern and evolution. METHODS: We prospectively studied consecutive patients referred to our stroke unit within a 2-year period. Cases of aphasia in right-handed patients associated with a MRI confirmed left-sided hemispheric BZI were included. These patients had a standardized language examination in the first 48 h, at discharge from stroke unit and between 6 and 18 months later. RESULTS: Eight patients were included. Three had anterior (MCA/ACA), two posterior (MCA/PCA), two both anterior and posterior, and one bilateral BZI. All our patients initially presented transcortical mixed aphasia, characterized by comprehension and naming difficulties associated with preserved repetition. In all patients, aphasia rapidly improved. It fully recovered within a few days in three patients. Initial improvement was marked, although incomplete in the five remaining patients: their aphasias specifically evolved according to the stroke location toward transcortical motor aphasia for the three patients with anterior BZI and transcortical sensory aphasia for the two patients with posterior BZI. All patients made a full language recovery within 18 months after stroke. CONCLUSIONS: We report a specific aphasic pattern associated with hemispheric BZI, including an excellent long-term outcome. These findings appear relevant to (i) clinically suspect BZI and (ii) plan rehabilitation and inform the patient and his family of likelihood of full language recovery.

Microvascular leakage and contrast enhancement as prognostic factors for recurrence in unfavorable low-grade gliomas.

Perfusion estimates and microvascular leakage (MVL) were recently correlated with glioma angiogenesis and aggressiveness, but their role in predicting outcome of patients (pts) with unfavorable low-grade gliomas (ULGG) is unclear. Their prognostic value was then investigated, versus conventional factors such as age, neurological status, tumor size, and contrast enhancement (CE). Clinical and anatomical magnetic resonance imaging (MRI) criteria of a cohort of ULGG pts were prospectively evaluated. A dynamic T2*-weighted MR sequence was included to detect high-perfusion areas, using the maximal value of the relative cerebral blood volume (rCBV) estimate, and MVL. Conventional and microvascular characteristics were correlated with progression-free survival (PFS). Among the 46 pts included, the following features were present in 61%, 26%, 67%, and 26%, respectively: age >or=40 years, neurological deficits, tumor size >or=6 cm, and CE. High perfusion value was noted in 30% of cases and MVL in 52%. With median follow-up of 22 months (range 4-46 months), median PFS was 32 months [95% confidence interval (CI) 17-45 months]. On univariate analysis, CE, rCBV, and MVL were significantly correlated with PFS. On multivariate analysis, only CE and MVL were unfavorable factors, with hazard ratio of 3.0 and 7.3 and P value of 0.04 and 0.02, respectively. Different prognostic subgroups were identified, with 2-year PFS of 86%, 57%, and 19% for pts with no MVL, MVL without CE, and MVL with CE, respectively. MVL and CE seem to predict short-term outcome in ULGG pts.

[Traumatic cord and nerve root injuries: imaging features at the acute and chronic phases]. / La moelle et les racines traumatiques: imagerie dans la prise en charge aiguë et chronique.

Cord injuries are frequent and severe lesions resulting in significant disability, most frequently in younger subjects. The area of cord injured results in clinical syndromes (Brown-Sequard, motor and/or sensory deficit...). Cord and rootlet injuries are best depicted on MRI. Diffusion tensor imaging with tractography enables depiction of the most severe cord lesions and some prediction of tissue viability which may provide an idea of the potential functional prognosis and patient recovery. MRI is optimal to demonstrate areas of cord hemorrhage or compression, partial or complete cord transsection, nerve root avulsion...

Structural Connectivity and Cortical Thickness Alterations in Transient Global Amnesia.

BACKGROUND AND PURPOSE: Transient global amnesia (TGA) is a sudden onset of anterograde and retrograde amnesia. We aimed to assess differences in terms of cortical thickness and structural brain connectome between patients with TGA (at acute and delayed postrecovery stages) and matched controls. MATERIALS AND METHODS: We report on 18 consecutive patients with TGA who underwent 3T MR imaging, including DTI and MPRAGE sequences, at the acute (mean delay postonset: 44 hours) and delayed post-recovery (mean delay: 35 days) stages. Structural connectome was assessed in patients with TGA and in 18 age- and sex-matched controls by using probabilistic fiber- tracking and segmentation of 164 cortical/subcortical structures ("nodes"). Connectivity graphs were computed and global network metrics were calculated. Network-based statistical analysis (NBS) was applied to compare patients with TGA at each stage with controls. We also compared cortical thickness between patients with TGA and healthy controls. RESULTS: Global network metrics were not altered in patients with TGA. NBS-analysis showed structural connectome alterations in patients with TGA compared with controls, in core regions involving the limbic network, with 113 nodes and 114 connections (33 left intrahemispheric, 31 right intrahemispheric, and 50 interhemispheric connections) showing significantly decreased structural connectivity (P < .05 NBS corrected, t-values ranging from 3.03 to 8.73). Lower cortical thickness compared with controls was associated with these structural alterations in patients with TGA, involving the orbitofrontal, cingulate, and inferior temporal cortices. All the abnormalities were visible at both acute and delayed postrecovery stages. CONCLUSIONS: Our preliminary study suggests there are structural abnormalities of the limbic network in patients with TGA compared with controls, including decreased structural connectivity and cortical thickness.

Assessment of spinal somatosensory systems with diffusion tensor imaging in syringomyelia.

OBJECTIVE: The use of diffusion tensor imaging with three-dimensional fibre tracking (DTI-FT) was tested for the assessment of spinal sensory tract lesions. The relationships between tract lesions quantified with DTI-FT were systematically examined, and somatosensory dysfunction was assessed with quantitative sensory testing (QST) and laser-evoked potentials (LEP), in patients with syringomyelia. METHODS: 28 patients with cervical syringomyelia and thermosensory impairment of the hands, and 19 healthy volunteers, were studied. A DTI-FT of the spinal cord was performed, focusing on the upper segment (C3-C4) of the syrinx. Three-dimensional DTI-FT parameters (fractional anisotropy (FA) and apparent diffusion coefficient (ADC)) of the full, anterior and posterior spinal cord were individually compared with QST (thermal detection thresholds) and LEP (amplitude, latency and spinothalamic tract (STT) conduction time) of the hands. RESULTS: Patients had a significantly lower FA, but not ADC, than healthy subjects. The mean FA of the full section of the spinal cord was correlated both to sensory deficits (ie, increase in warm (rho = -0.63, p<0.010) and cold thresholds (rho = -0.72; p<0.001 of the hands)) and to changes in LEP parameters, in particular STT conduction time (rho = -0.75; p<0.010). Correlations between FA and the clinical and electrophysiological measures were higher in the anterior area (where the spinothalamic tracts are located) than in the posterior area of the spinal cord. CONCLUSIONS: The data indicate that diffusion tensor imaging with 3D-fibre tracking is a new imaging method suitable for the objective and quantitative anatomical assessment of spinal somatosensory system dysfunction.

[Postoperative chest: normal imaging features]. / Imagerie du thorax post-opératoire: les aspects normaux.

Chest radiographs and CT are especially useful for the follow-up of patients after lung resection. The purpose of this paper is to illustrate normal postsurgical imaging findings that differ according to the type of surgery (pneumonectomy, lobectomy, segmentectomy and wedge resection). Anatomic changes induced by surgery affect the remaining lung, pleura and chest wall, mediastinum and diaphragm. After pneumonectomy, there is accumulation of fluid in the post pneumonectomy space, progressive chest retraction with mediastinal shift toward the operated side and elevation of the ipsilateral hemidiaphragm. After lobectomy, there is hyperexpansion of the remaining lung, mediastinal shift and intercostal space narrowing. Theses findings are different according to the delay after surgery. Knowledge of the variable imaging features is necessary to detect complications and to provide appropriate follow-up of the primary disease.

[Feasibility and efficacy of cyberknife radiotherapy for lung cancer: early results]. / Analyse de la toxicité précoce des traitements par Cyberknife des cancers pulmonaires et résultats préliminaires.

PURPOSE: High-dose robotic stereotactic irradiation can be achieved with high precision using the CyberknifeM system equipped with the Synchrony respiratory tracking device. Cyberknife irradiation can overcome some limitations of conventional radiotherapy including errors due to breathing motion and patient setup. High dose levels are of interest for tumours that have shown a dose-response relationship including lung tumours. We reviewed the treatments and outcomes for the first French patients with lung tumours treated at the Cyberknife centre of Nice. PATIENTS AND METHODS: Thirty four patients were treated between November 2006 and November 2007 at the Cyberknife centre of Nice, Centre Lacassagne, France. Thirty had untreated primary lung cancer, 4 had colorectal metastasis to the lung. We evaluated the feasibility and reliability of fiducial placement, toxicity and early outcomes. Objective tumour response was assessed on thoracic CT scan every three months. RESULTS: There was no grade 3-4 toxicity. Toxicity (11%) mainly consisted of grade 1-2 asthenia. Crude overall tumour response rate was 96% for all assessable patients and 91% at 3 and 6 months, respectively. The use of one fiducial ensured minimal toxicity (no grade III pneumothorax) while allowing reliable tumour tracking as shown by the low infield failure rate (no geographic miss). Diagnostic procedure was performed during fiducial placement when required. CONCLUSION: Early toxicity and tumour control rates from this population suggest that the use of a unique fiducial for a Cyberknife treatment was safe and effective for the treatment of selected primary and secondary lung tumours. This strategy is corroborated by similar control rates in the literature. Longer follow-up are awaited.

MR diffusion tensor imaging and fiber tracking in spinal cord arteriovenous malformations: a preliminary study.

BACKGROUND AND PURPOSE: Diffusion tensor imaging (DTI) of the spinal cord in patients harboring spinal arteriovenous malformations (AVMs) was carried out to evaluate the feasibility of this new technique to determine the displacement of the spinal cord tracts and to correlate morphologic and functional DTI data (fractional anisotropy [FA] and apparent diffusion coefficient [ADC]) with the clinical symptoms. MATERIALS AND METHODS: Nine patients with spinal cord AVMs were investigated at 1.5T using a sagittal spin-echo single-shot echo-planar generalized autocalibrating partially parallel acquisition diffusion-weighted imaging sequence. ADC and FA maps were computed in different regions of interest (both above and below the nidus), and tractography was used to visualize the course of the tracts. The data were correlated with the clinical symptoms and compared with 12 healthy control subjects. RESULTS: At the level of the nidus, tracts were normal, shifted, separated, or interrupted but not intermingled with the nidus. Interruption of the tracts was coherent with the clinical symptoms. In patients with severe neurologic deficits, FA values caudal to the nidus showed a reduced anisotropy consistent with loss of white matter tracts. CONCLUSIONS: We demonstrate that AVMs may interrupt, displace, or separate the fiber tracts and that clinical symptoms may be reflected by the quantitative FA results and the morphologic loss of fibers distant to the lesion. DTI with fiber tracking offers a novel approach to image spinal cord AVMs and may open a window to understand the complex pathophysiology of these lesions.

[Diffusion tensor imaging and tractography of the brain and spinal cord]. / Imagerie en tenseur de diffusion et tractographie de l'encéphale et de la moelle.

Diffusion tensor imaging is a magnetic resonance imaging technique that provides details on tissue microstructure and organization well beyond the usual image resolution. With diffusion tensor imaging, diffusion anisotropy can be quantified and subtle white matter changes not normally seen on conventional MRI can be detected. The aim of this article is to review the principles of diffusion tensor imaging and fiber tracking and their applications to the study of the brain, including Alzheimer disease, neuropsychiatric disorders, strokes, multiple sclerosis, brain tumors, and intractable seizures. Emerging applications to spinal cord disorders are also presented.

MR diffusion tensor imaging and fiber tracking in inflammatory diseases of the spinal cord.

PURPOSE: Our aim was to study the fractional anisotropy (FA) variations and the fiber tracking (FT) patterns observed in patients with myelitis. MATERIAL AND METHODS: Fifteen patients with symptomatic myelitis and 11 healthy subjects were prospectively selected. We performed T2-weighted and diffusion tensor imaging on a 1.5T MR scanner. FA and apparent diffusion coefficient maps were computed in both healthy subjects and patients. In each patient, we performed FT to study pathologic aspects on this imaging method. FA data were analyzed by using z-scores. RESULTS: For the healthy subjects, averaged FA values ranged from 0.745 to 0.751. All abnormal areas seen on T2-weighted imaging had a significantly decreased FA value. In 9 patients (60%), FA maps showed decreased FA areas, whereas T2-weighted imaging findings were normal. These areas matched the neurologic deficit in 33%. Eighty percent of patients had multiple decreased FA areas. Five patients (33%) had increased FA values in normal T2-weighted areas. CONCLUSION: We observed specific FA and FT pattern variations in patients with myelitis.

MR diffusion tensor imaging and fiber tracking in 5 spinal cord astrocytomas.

Spinal cord astrocytomas are rare neoplasms that can result in alteration of the spinal cord structural integrity, which can be assessed by using diffusion tensor imaging methods. Our objective was to visualize the deformation of the posterior spinal cord lemniscal and corticospinal tracts in 5 patients with low-grade astrocytomas compared with 10 healthy volunteers by using 3D fiber-tracking reconstructions.

Perfusion-weighted MR imaging studies in brain hypervascular diseases: comparison of arterial input function extractions for perfusion measurement.

BACKGROUND AND PURPOSE: Brain hypervascular diseases are complex and induce hemodynamic disturbances on brain parenchyma, which are difficult to accurately evaluate by using perfusion-weighted (PWI) MR imaging. Our purpose was to test and to assess the best AIF estimation method among 4 patients with brain hypervascular disease and healthy volunteers. METHODS: Thirty-three patients and 10 healthy volunteers underwent brain perfusion studies by using a 1.5T MR imaging scanner with gadolinium-chelate bolus injection. PWI was performed with the indicator dilution method. AIF estimation methods were performed with local, regional, regional scaled, and global estimated arterial input function (AIF), and PWI measurements (cerebral blood volume [CBV] and cerebral blood flow [CBF]) were performed with regions of interest drawn on the thalami and centrum semiovale in all subjects, remote from the brain hypervascular disease nidus. Abnormal PWI results were assessed by using Z Score, and evaluation of the best AIF estimation method was performed by using a no gold standard evaluation method. RESULTS: From 88% to 97% of patients had overall abnormal perfusion areas of hypo- (decreased CBV and CBF) and/or hyperperfusion (increased CBV and CBF) and/or venous congestion (increased CBV, normal or decreased CBF), depending on the AIF estimation method used for PWI computations. No gold standard evaluation of the 4 AIF estimates found the regional and the regional scaled methods to be the most accurate. CONCLUSION: Brain hypervascular disease induces remote brain perfusion abnormalities that can be better detected by using PWI with regional or regional scaled AIF estimation methods.

[Functional MRI in brain tumours]. / IRM fonctionnelle en pathologie cérébrale tumorale.

Functional MRI is a technique of imaging which is developing fast as it allows non-aggressive evaluation of brain functions. Diffusion, perfusion and activation are each used to study brain responsiveness to a given task. As a pretherapeutic routine investigation, in brain tumours, it can be helpful as an additional tool to morphological MRI in evaluating the prognosis of patients.

[Diffusion tensor imaging and tractography of central pontine myelinolysis]. / Suivi évolutif d'une myelinolyse centro-pontique en irm de tenseur de diffusion et de tracking de fibres.

OBJECTIVES: To illustrate the value of diffusion tensor imaging and tractography in the diagnosis and follow-up of central pontine myelinolysis. CASE REPORT: We report a case of central pontine myelinolysis in a 29 year old woman, also anorexic, studied using MR Diffusion Tensor Imaging (DTI) and Fibre Tracking (FT) focused on the pons, and compared with the studies of 5 normal volunteers. Tractography showed a swollen aspect of the right corticospinal fiber tract correlating with mild left lower extremity deficit at clinical evaluation. The pontine fibers were posteriorly displaced but intact. The sensory tracts were also intact. Apparent Diffusion Coefficient values were increased and Fractional Anisotropy was decreased in the lesions. Follow up imaging showed persistent abnormal ADC and FA values in the pons although the left cortico-spinal tract returned to normal, consistent with the clinical outcome. CONCLUSION: Diffusion Tensor Imaging MR and Fiber tractography are a new method to analyse white matter tracts. It can be used to prospectively evaluate the location of white matter tract lesions at the acute phase of central pontine myelinolysis and follow up.

Diffusion-weighted imaging patterns of brain damage associated with cerebral venous thrombosis.

BACKGROUND AND PURPOSE: Apart from cases studies, little is known regarding diffusion-weighted imaging of brain lesions associated with human cerebral venous thrombosis (CVT). Our aim was to describe the initial diffusion-weighted imaging patterns observed in brain areas with MR signal changes associated with CVT and to compare them with those of follow-up imaging. METHODS: The cases of nine patients with brain lesions associated with CVT who underwent CT and diffusion-weighted imaging 3 hours to 4 days after sudden neurologic onset were retrospectively reviewed. The apparent diffusion coefficient (ADC) in abnormal brain was compared with that of contralateral normal regions using z score analysis. MR images obtained during 3 to 6 months of follow-up were available for seven patients. RESULTS: All patients had nonhemorrhagic T2-hyperintense brain regions. These were associated with partially hemorrhagic areas on the CT scans of four patients. In nonhemorrhagic edematous areas, ADC was heterogeneous (coexistence of increased, normal, or decreased ADC) in five patients and homogeneous in four. In the latter four patients, ADC values were within normal range in three, whereas a large homogeneous hyperintensity with decreased ADC values (0.3-0.4 10(-3)mm2/s, <-3 z scores) was observed in one. When available, follow-up images always showed hemorrhagic sequelae in initially hemorrhagic areas. Nonhemorrhagic edematous areas with initially increased ADC values returned to normal. Initially normal or decreased ADC values were predictive of reversibility, although imaging sequelae were rarely observed. CONCLUSION: The diffusion-weighted imaging/ADC pattern of venous stroke is more heterogeneous than previously thought. Large brain regions of reduced ADC values that are not predictive of ultimate infarction in cases of CVT can be observed.

[MRI of the brachial plexus]. / IRM DU PLEXUS BRACHIAL.

Magnetic resonance imaging is the method of choice for the evaluation of brachial plexopathy. Knowledge of the anatomy and normal imaging appearance is required. High-resolution imaging technique is necessary with the use of adequate coils. Evaluation of the brachial plexus requires T1 weighted sequences in three plans, T2 weighted sequences with fat suppression and if necessary the study is completed with gadolinium injection sequences with fat suppression. A CISS sequence is used if a nerve root avulsion is suspected. The spatial resolution must be optimized with the use of adapted parameters. We illustrate a variety of pathologies that can involve the brachial plexus. The pathology includes trauma, primary (neurogenic tumors, lymphomatosis) or secondary tumors, radiation plexopathy or inflammatory polyneuropathy.

[Lyrical and musical auditive mental imagery in functional MRI]. / Imagerie magerie mentale auditive lyrique et musicale en IRM fontionnelle d'activation.

PURPOSE: to explore with functional MRI cerebral areas involved in musical and lyrical sounds signal processing with the mental imagery method. MATERIAL: and METHODS: nine volunteers (mean age: 27 years old) underwent functional MRI with BOLD contrast at 1.5 T. Box-car paradigms of partial recollections of musical or lyrical memories tasks were performed. Statistical correlations mappings were calculated and superimposed on previously realigned anatomical reference imaging to observe activated cerebral areas. RESULTS: all except one subjects had activation areas in primary and secondary auditive cortices in the temporal Heschl gyrus and the Planum Temporale, unilaterally (n=2) or bilaterally (n=6) during both mental tasks. Contralateral activation improvement was observed in 4 cases when the lyrical tasks were performed. Temporal and insular regions involved in language processing were observed in eight of nine subjects. CONCLUSION: auditive mental imagery can show in functional MRI cerebral areas involved in auditive functions and some of the areas involved in language processing.

[Diffusion, perfusion and activation functional MRI studies of brain arteriovenous malformations]. / Explorations des malformations artérioveineuses cérébrales en IRM fonctionnelle de diffusion, de perfusion er d'ativation.

The management of Brain Arteriovenous Malformations continues to be challenged by a lack of understanding and control of pathophysiological processes implied in the clinical symptoms. New data from functional MRI with diffusion-weighted, perfusion-weighted and neuronal activation highlight abnormal brain areas near or remote to the AVM nidus. Moreover, these techniques are able to show hemodynamic and neuronal adaptative phenomena involved in brain plasticity. They reflect the instantaneous hemodynamic brain conditions that may help to correlate the clinical symptoms with the anatomical and functional substratum and to influence any invasive therapy.