Functional MRI of the visual cortex and visual testing in patients with previous optic neuritis

The volume of cortical activation as detected by functional magnetic resonance imaging (fMRI) in the visual cortex has previously been shown to be reduced following optic neuritis (ON). In order to understand the cause of this change, we studied the cortical activation, both the size of the activated area and the signal change following ON, and compared the results with results of neuroophthalmological testing. We studied nine patients with previous acute ON and 10 healthy persons served as controls using fMRI with visual stimulation. In addition to a reduced activated volume, patients showed a reduced blood oxygenation level dependent (BOLD) signal increase and a greater asymmetry in the visual cortex, compared with controls. The volume of visual cortical activation was significantly correlated to the result of the contrast sensitivity test. The BOLD signal increase correlated significantly to both the results of the contrast sensitivity test and to the Snellen visual acuity. Our results indicate that fMRI is a useful method for the study of ON, even in cases where the visual acuity is severely impaired. The reduction in activated volume could be explained as a reduced neuronal input; however, the greater asymmetry might point to a cortical reorganization as a consequence of neuronal damage. Future fMRI studies in ON will add to the understanding of the neural adaptive behaviour following ON.     

Magnetic Resonance Imaging of Multiple Sclerosis

Although conventional magnetic resonance imaging (cMRI) is widely used for diagnosing multiple sclerosis (MS) and monitoring disease activity and evolution, the correlation between cMRI and clinical findings is far from strict. Among the reasons for this "clinical-MRI paradox," a major role has been attributed to the limited specificity of cMRI to the heterogeneous pathological substrates of MS and to its inability to quantify the extent of damage in the normal-appearing tissue. Modern quantitative MRI techniques have the potential to overcome some of the limitations of cMRI. Metrics derived from magnetization transfer and diffusion-weighted MRI enable one to quantify the extent of structural changes occurring within and outside macroscopic MS lesions with increased pathological specificity over cMRI. Magnetic resonance spectroscopy can add information on the biochemical nature of such changes, with the potential to improve significantly our ability to monitor inflammatory demyelination and axonal injury. Finally, functional MRI might provide new insights into the role of cortical adaptive changes in limiting the clinical consequences of white-matter structural damage. This review outlines the major contributions given by MRI-based techniques to the diagnostic work-up of MS patients, to the understanding of the pathobiology of the disease, and to the assessment of the effects of new experimental treatments.     

Magnetic resonance imaging, evoked responses and cerebrospinal fluid findings in a follow-up study of children with optic neuritis

Fourteen patients with previous optic neuritis (ON) in childhood were examined by magnetic resonance (MR) imaging from two months to 14 years after the onset of symptoms. Five patients had a single monosymptomatic course of ON but 7 developed multiple sclerosis (MS); 2 had another demyelinating disease. Eight patients had high signal intensity areas in the T2 weighted images compatible with MS plaques in MR scan; 2 with monosymptomatic ON, 5 with MS and one with another demyelinating disease. The plaques were periventricular or in the optic radiation. The plaques could already be seen during the first symptoms of ON. All 7 MS patients had abnormal visual evoked response, 3/4 abnormal somatosensory evoked response and 5/6 intrathecal immunoglobulin production, when examined at onset of optic neuritis or at follow-up. All patients except one, with lesions in MR, had either oligoclonal CSF antibodies or Dr2 HLA antigen. We suggest that MR is a very sensitive test showing MR abnormalities in children with ON. It is an important tool in the early assessment of MS.     

Visual recovery following acute optic neuritis

Abstract. This study reports the prospective follow–up of a cohort of patients with acute optic neuritis examined with serial visual tests, visual evoked potentials (VEPs), conventional and triple–dose gadolinium (Gd)–enhanced magnetic resonance imaging (MRI) to examine which factors are important in visual recovery. Thirty–three patients were recruited with acute unilateral optic neuritis. A clinical and VEP assessment was performed on each. Optic nerve MRI was performed using fast spin echo (FSE) (on all) and triple-dose Gdenhanced T₁–weighted sequences (n = 28). Optic nerve lesion lengths were measured. Serial assessments were performed on 22 of the patients up to one–year. Serial Gd–enhanced optic nerve imaging was performed on 15 of the patients until enhancement ceased. The final 30–2 Humphrey visual field mean deviation (MD) was 2.55 dB higher in patients in the lowest quartile of initial Gd–enhanced lesion length compared with the other quartiles (p < 0.01) but recovery was not related to the duration of enhancement. The initial recovery of Humphrey MD was 4.60 dB units per day in patients with good eventual recoveries (MD > –6.0 dB) and 0.99 dB per day in poor-recovery patients (p = 0.02).Good–recovery patients had mean central field VEP amplitudes 2.29 µV higher during recovery than poor-recovery patients (p = 0.047). The results suggest that factors which are associated with a better prognosis are: having a short acute lesion on triple–dose gadolinium enhanced imaging, higher VEP amplitudes during recovery and a steep gradient of the initial improvement in vision.     

Differences in Functional Magnetic Resonance Imaging Activation by Category in a Visual Confrontation Naming Task

OBJECTIVE: Cortical processing involved in seemingly similar tasks may differ in important ways. The authors mapped cortical regions engaged in a commonly performed picture naming task, seeking differences by semantic category. Functional magnetic resonance imaging was used during presentation of standardized line drawings in 18 healthy right-handed female participants, comparing living versus nonliving entities. During visual naming, across categories there was strong activation of left frontal (BA45/47), bilateral temporo-occipital junction (BA19), and inferior temporal regions (BA36/37). Activation of right inferior temporal cortex (BA19 and BA37) was greater during naming of living versus nonliving category items. No category differences in activation strength in the left temporal lobe were observed. The authors conclude that visual semantic operations may involve visual association cortex in the right temporal lobe in women.     

脑白质疏松伴认知障碍患者静息态功能磁共振成像研究

目的 研究脑白质疏松（leukoaraiosis,LA）伴发认知障碍患者与健康人静息态脑网络的差异。 方法 分别对根据影像学及临床确诊的40例脑白质疏松伴认知障碍患者及30例年龄、性别、受教育 程度均匹配的健康对照者进行静息态功能磁共振扫描,采用独立成分分析法得到两组被试者的激 活区,对两组数据进行比较,得到两组间的激活差异区。 结果 脑白质疏松伴认知障碍患者默认网络中双侧楔前叶、左侧颞下回、左侧枕颞内侧回、右侧前 扣带回激活较正常对照组减弱,左侧中央旁小叶及右侧楔叶激活程度较正常对照组增强。 结论 脑白质疏松伴认知障碍患者与健康人在脑静息网络激活程度上存在差异。     

帕金森病的功能磁共振成像研究进展

帕金森病（PD）的主要病理改变是黑质多巴胺能神经元变性坏死并引起多巴胺递质减少,通过神经环路可引起包括脑皮质在内广泛的功能及结构改变.功能磁共振成像（fMRI）作为一项功能影像技术能灵敏地检测出这些变化,进而有可能为PD早期诊断提供依据.本文就PD的fMRI研究进展进行综述.     

Clinical Usefulness of Simultaneous Electroencephalography and Functional Magnetic Resonance Imaging in Children With Focal Epilepsy

Background and PurposeThe current study analyzed the interictal epileptiform discharge (IED)-related hemodynamic response and aimed to determine the clinical usefulness of simultaneous electroencephalography and functional magnetic resonance imaging (EEG-fMRI) in defining the epileptogenic zone (EZ) in children with focal epilepsy.MethodsPatients with focal epilepsy showing IEDs on conventional EEG were evaluated using EEG-fMRI. Statistical analyses were performed using the times of spike as events modeled with multiple hemodynamic response functions. The area showing the most significant t-value for blood-oxygen-level-dependent (BOLD) changes was compared with the presumed EZ. Moreover, BOLD responses between -9 and +9 s around the spike times were analyzed to track the hemodynamic response patterns over time.ResultsHalf (n=13) of 26 EEG-fMRI investigations of 19 patients were successful. Two patients showed 2 different types of spikes, resulting in 15 analyses. The maximum BOLD response was concordant with the EZ in 11 (73.3%) of the 15 analyses. In 10 (66.7%) analyses, the BOLD response localized the EZs more specifically. Focal BOLD responses in the EZs occurred before IEDs in 11 analyses and were often widespread after IEDs. Hemodynamic response patterns were consistent in the same epilepsy syndrome or when repeating the investigation in the same patients.ConclusionsEEG-fMRI can provide additional information for localizing the EZ in children with focal epilepsy, and also reveal the pathogenesis of pediatric epilepsy by evaluating the patterns in the hemodynamic response across time windows of IEDs.     

Perivascular Enhancement in a Patient with Neuromyelitis Optica Spectrum Disease during an Optic Neuritis Attack

We present a case with neuromyelitis optica spectrum disease (NMOSD) who had perivascular enhancement during an optic neuritis attack. Cloud‐like enhancement, pencil‐thin enhancement, and leptomeningeal enhancement have been defined as specific enhancement patterns to neuromyelitis optica (NMO). Perivascular enhancement has not been described before in NMO/NMOSD. This finding suggests that perivascular enhancement may also be seen in NMO/NMOSD patients.     

功能磁共振成像在触觉系统研究中的应用进展

血氧水平依赖功能磁共振成像(fMRI)已应用于触觉系统的研究中,并得到了许多重要结果。本文就fMRI在不同触觉刺激模式下激活皮质功能定位中的应用做一综述。     

Magnetic resonance imaging of the brain in patients with acute monosymptomatic optic neuritis

Ophthalmologists and neurologists from a catchment area of 1.5 million people were asked to refer all patients with symptoms and signs of optic neuritis (ON) to our neurological department immediately. A total of 68 consecutive patients were extensively screened for known etiologies of ON. Eleven had definite multiple sclerosis (MS); 7 patients could not participate for various reasons. The cerebrum, cerebellum and brainstem of the remaining 50 untreated patients with monosymptomatic ON were MRI scanned at 1.5 T with 2 sequences (slice thickness 4 mm, voxel size 1.2 x 1.2 x 4 mm3): double spin-echo (TR = 1.8 s, TE = 30 and 90 ms, 12 slices axially) and inversion recovery (TR = 2.45 s, TI = 400 ms, TE = 30 ms, 5 slices sagittaly). Magnetic resonance imaging (MRI) was performed within 3-49 (median 16) days from onset of symptoms. MRI demonstrated multiple asymptomatic central nervous system (CNS) lesions in 62% of patients. The appearance, locations and extents of lesions were consistent with demyelination. A scoring system based on number and size of lesions is proposed. Seven of 50 patients developed definite MS during a median follow-up of 11 months; they all had CNS lesions on the first scan. MRI has thus improved the pathophysiological knowledge of idiopathic ON, which from the very onset is a manifestation of MS in at least two thirds of cases. Patients who have early CNS lesions run a much higher risk of later developing clinically definite MS.     

卒中缺血性半暗带功能磁共振成像评估的研究进展

急性缺血性卒中是导致急性脑组织损伤的重要原因,是中老年人致残、死亡的主要因素,可挽救缺血组织的早期发现是临床及时干预治疗的关键。随着功能磁共振成像技术的发展,临床可从水分子扩散、血流动力学、氧合水平、pH值、代谢及侧支循环等方面全方位评价脑组织的病理改变,为疾病进展及预后评估提供更全面的信息。本文综述急性缺血性卒中缺血性半暗带功能磁共振成像的研究进展,以期为卒中患者的评估和治疗计划提供影像学支撑与指导。