Diffusion tensor imaging of mouse brain stem and cervical spinal cord

In vivo diffusion tensor imaging measurements of the mouse brain stem and cervical spinal cord are presented. Utilizing actively decoupled transmit/receive coils, high resolution diffusion images (117 microm x 59 microm x 500 microm) were acquired at 4.7 T within an hour. Both brain stem and cervical spine displayed clear gray-white matter contrast. The cervical spinal cord white matter showed similar tissue characteristics as seen in the thoracic cord. The coherent fiber orientation in the white matter was observed in both the brain stem and the cervical spinal cord. The results may serve as a reference for future inter-lab comparison in mouse brain stem and cervical spine diffusion measurements.     

术中超声在脊髓髓内室管膜瘤和星形细胞瘤外科治疗中的应用

目的探讨术中超声在脊髓髓内室管膜瘤和星形细胞瘤显微外科手术中的应用价值。方法回顾性分析2010年1月至2018年5月华中科技大学同济医学院附属同济医院神经外科收治的78例脊髓髓内室管膜瘤和34例脊髓髓内星形细胞瘤患者的临床资料。根据术中是否使用超声辅助,分别将室管膜瘤和星形细胞瘤患者分为超声组(前者44例,后者18例)和对照组(前者34例,后者16例)。对所有患者行门诊或电话随访,通过影像学复查和改良McCormick量表(MMS)分级评估肿瘤复发和脊髓功能恢复情况。分别比较室管膜瘤和星形细胞瘤两组患者的疗效,并评价术中超声对肿瘤完全切除率的评估准确率。结果两组室管膜瘤和星形细胞瘤患者的性别、年龄、首诊症状、MMS分级及肿瘤累及脊髓节段的差异均无统计学意义(均P>0.05),基线资料均基本一致。室管膜瘤的超声组和对照组患者肿瘤完全切除率[分别为97.7%(43/44)、91.2%(31/34)]、术后并发症发生率[分别为8.8%(3/44)、11.8%(4/34)]及术后3个月脊髓功能恢复良好率[分别为36.4%(16/44)、32.4%(11/34)]的差异均无统计学意义(均P>0.05)。超声组和对照组的星形细胞瘤患者术后并发症发生比例(分别为:0/18、2/16)和术后3个月脊髓功能恢复良好比例(分别为:3/18、2/16)的差异均无统计学意义(均P>0.05);但与对照组比较,超声组的肿瘤完全切除比例高[分别为16/18、9/16,P<0.05]、无进展生存期(PFS)长[中位PFS分别为84.0(67.5~100.5)个月、75.0(52.0~98.0)个月,P<0.05]。以增强MRI为标准,术中超声判断室管膜瘤和星形细胞瘤全切除的准确比率分别为97.7%(42/43)、14/16。结论术中超声有助于实时、准确地判断脊髓髓内室管膜瘤和星形细胞瘤的肿瘤切除程度,且对星形细胞瘤的应用价值较大。     

Simultaneous functional magnetic resonance imaging in the rat spinal cord and brain

Functional magnetic resonance imaging (fMRI) method was developed to investigate the pattern and temporal relationship in neuronal pathways of brain and spinal cord. Signal intensity changes correlating with stimulation patterns were observed simultaneously in the rat spinal cord and brain using fMRI at 9.4 T. Electrical stimulation of the forepaw was used to elicit activity. A quadrature volume RF coil covering both brain and the cervical spinal cord was used. Sets of fast spin echo (FSE) images were acquire simultaneously for both brain and spinal cord fMRI. Experiments were repeated in single animal and across animals. Activities within the dorsal horn of the spinal cord and within the somatosensory cortex were observed consistently within each animal as well as across animals.     

Magnetic resonance imaging of the brain and spinal cord in cerebrotendinous xanthomatosis.

This reports a 40 year old man with cerebrotendinous xanthomatosis who had bilateral cataracts, enlarged Achilles tendons, progressive dementia, gait disturbance and peripheral neuropathy. Electroencephalography, electromyography, and magnetic resonance imaging (MRI) of the brain and spine were performed. Magnetic resonance imaging revealed cerebral, cerebellar and cervical cord atrophy and white matter involvement in the cerebrum and cerebellum correlating well with the clinical findings. To date there has been one previous report of MRI of the brain in cerebrotendinous xanthomatosis and none of the spinal cord.     

Dynamic diffusion tensor imaging of spinal cord contusion: A canine model

This study aimed to explore the dynamic diffusion tensor imaging (DTI) of changes in spinal cord contusion using a canine model of injury involving rostral and caudal levels. In this study, a spinal cord contusion model was established in female dogs using a custom‐made weight‐drop lesion device. DTI was performed on dogs with injured spinal cords (n=7) using a Siemens 3.0T MRI scanner at pre‐contusion and at 3 h, 24 h, 6 weeks and 12 weeks post‐injury. The tissue sections were stained for immunohistochemical analysis. Canine models of spinal cord contusion were created successfully using the weight‐drop lesion device. The fractional anisotropy (FA) value of lesion epicenter decreased, while the apparent diffusion coefficient (ADC), mean diffusivity (MD), and radial diffusivity (RD) values increased, and the extent of the curve was apparent gradually. The site and time affected the DTI parameters significantly in the whole spinal cord, ADC (site, P < 0.001 and time, P = 0.077, respectively); FA (site, P < 0.001 and time, P = 0.002, respectively). Immunohistological analysis of GFAP and NF revealed the pathologic changes of reactive astrocytes and axons, as well as the cavity and glial scars occurring during chronic SCI. DTI is a sensitive and noninvasive imaging tool useful to assess edema, hemorrhage, cavity formation, structural damage and reconstruction of axon, and myelin in dogs. The DTI parameters after contusion vary. However, the curves of ADC, MD, and RD were nearly similar and the FA curve was distinct. All the DTI parameters were affected by distance and time.     

Analysis of high-voltage electrical spinal cord injury using diffusion tensor imaging

The aim of this study was to investigate spinal cord injury (SCI) on the basis of diffusion tensor imaging (DTI) in patients with high-voltage electrical injury. We recruited eight high-voltage electrical injury patients and eight healthy subjects matched for age and sex. DTI and central motor conduction time were acquired in both the patient and control groups. We obtained DTI indices according to the spinal cord levels (from C2 to C7) and cross-section locations (anterior, lateral, and posterior). Fractional anisotrophy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) were compared between the two groups; additionally, they were compared in relation to spinal cord level and cross-section location. In the patient group relative to the control group, the FA value decreased and the MD and RD values increased in all of the regions of interest (ROI) with statistical significance (p < 0.05). In the patient group, particularly in the ROIs of the anterior spinal cord compared with the lateral and posterior spinal cords, the FA value decreased with statistical significance (p < 0.05). The DTI indices did not differ by level. DTI revealed the change of diffusion in the spinal cords of patients with high-voltage electrical injury, and corroborated the pathophysiology, myelinopathy and typical anterior spinal cord location of high-voltage electrical SCI already reported in the literature.     

Magnetic resonance imaging in multiple sclerosis: investigation of brain and spinal cord lesions

Magnetic resonance imaging (MRI) of the brain was performed on forty-five patients with multiple sclerosis (MS), using T1-weighted inversion recovery and T2-weighted spin echo images, and the results were compared with X-ray computed tomography (CT). Some of the 45 MS patients were also examined by neurophysiological studies (visual evoked potentials and auditory brainstem responses) to compare with the brain MRI findings. MRI showed demyelinating plaques of the brain in 20 (74%) of 27 patients with brain symptoms, 11 (61%) of 18 patients without symptoms and 31 (69%) of all 45 patients. In 27 patients with brain symptoms, MRI was able to detect brain lesions in 6 (86%) of 7 acute stage patients and 14 (70%) of 20 non-acute stage patients. Furthermore, MRI was able to detect brain lesions in 21 (70%) of 30 clinically definite MS patients and 10 (67%) of 15 clinically probable MS patients. X-ray CT was performed on all 45 patients and was able to detect brain lesions in 9 (33%) of 27 patients with brain symptoms and 1 (6%) of 18 patients without symptoms. Visual evoked potentials were evaluated in 31 patients, and showed abnormalities in 1 (11%) of 9 patients without symptoms of optic neuritis and 100% of 22 patients with symptoms. Auditory brainstem responses were evaluated in 19 patients, and showed abnormalities in 1 (11%) of 9 patients without brainstem symptoms and 3 (30%) of 10 patients with symptoms. MRI of the brain was markedly superior to X-ray CT, visual evoked potentials and auditory brainstem responses in detecting clinically unsuspected lesions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diagnostic imaging of spinal cord lesions

Magnetic resonance imaging (MRI) has greatly facilitated morphologic evaluation of spinal cord lesions. Eleven cases representative of inflammatory, demyelinating, neoplastic and vascular diseases, are presented which illustrate and summarize important abnormal features in spinal cord imaging, particularly MR findings. Recently, specialised techniques such as MR angiography, fat-inhibiting methods, dynamic MRI and functional imaging have been developed. These methods have facilitated not only lesion diagnosis but also qualitative assessment, and are being used to analyze pathophysiology. Comprehensive diagnoses based on such modalities may be important in determining indications for surgery or defining the extent of surgery or the intensity of other treatments.     

Diffusion-weighted imaging of the spinal cord

Spinal cord DWI may be useful in providing information not available with conventional MR imaging. More work, however, is required to explain what the qualitative and quantitative results actually represent. Computer simulations and detailed radiologic-histologic correlations will therefore be necessary.     

Anesthesia for intraoperative neurophysiologic monitoring of the spinal cord.

Intraoperative neurophysiologic monitoring (INM) using somatosensory and motor evoked potentials (MEPs) has become popular to reduce neural risk and to improve intraoperative surgical decision making. Intraoperative neurophysiologic monitoring is affected by the choice and management of the anesthetic agents chosen. Because inhalational and intravenous anesthetic agents have effects on neural synaptic and axonal functional activities, the anesthetic effect on any given response will depend on the pathway affected and the mechanism of action of the anesthetic agent (i.e., direct inhibition or indirect effects based on changes in the balance of inhibitory or excitatory inputs). In general, responses that are more highly dependent on synaptic function will have more marked reductions in amplitude and increases in latency as a result of the synaptic effects of inhalational anesthetic agents and similar effects at higher doses of intravenous agents. Hence, recording cortical somatosensory evoked potentials and myogenic MEPs requires critical anesthetic choices for INM. The management of the physiologic milieu is also important as central nervous system blood flow, intracranial pressure, blood rheology, temperature, and arterial carbon dioxide partial pressure produce alterations in the responses consistent with the support of neural functioning. Finally, the management of pharmacologic neuromuscular blockade is critical to myogenic MEP recording in which some blockade may be desirable for surgery but excessive blockade may eliminate responses. A close working relationship of the monitoring team, the anesthesiologist, and the surgeon is key to the successful conduct and interpretation of INM.     

Diffusion tensor imaging reveals brain structure changes in dogs after spinal cord injury

Based on the Wallerian degeneration in the spinal cord pathways, the changes in synaptic connections, and the spinal cord-related cellular responses that alter the cellular structure of the brain, we presumed that brain diffusion tensor imaging(DTI) parameters may change after spinal cord injury. However, the dynamic changes in DTI parameters remain unclear. We established a Beagle dog model of T10 spinal cord contusion and performed DTI of the injured spinal cord. We found dynamic changes in DT...     

Magnetization transfer magnetic resonance imaging of the brain, spinal cord, and optic nerve

Magnetic resonance imaging is highly sensitive in revealing CNS abnormalities associated with several neurological conditions, but lacks specificity for their pathological substrates. In addition, MRI does not allow evaluation of the presence and extent of damage in regions that appear normal on conventional MRI sequences and that postmortem studies have shown to be affected by pathology. Quantitative MR-based techniques with increased pathological specificity to the heterogeneous substrates of CNS pathology have the potential to overcome such limitations. Among these techniques, one of the most extensively used for the assessment of CNS disorders is magnetization transfer MRI (MT-MRI). The application of this technique for the assessment of damage in macroscopic lesions, in normal-appearing white and gray matter, and in the spinal cord and optic nerve of patients with several neurological conditions is providing important in vivo information—dramatically improving our understanding of the factors associated with the appearance of clinical symptoms and the accumulation of irreversible disability. MT-MRI also has the potential to contribute to the diagnostic evaluation of several neurological conditions and to improve our ability to monitor treatment efficacy in experimental trials.     

High-resolution single-cell imaging for functional studies in the whole brain and spinal cord and thick tissue blocks using light-emitting diode illumination

Functional studies of neuronal networks require recordings from visually identified neurons in their natural environment preservation of which may demand experimenting with a tissue of a significant depth or the entire brain. Here we describe a new technique of single-cell imaging and visually controlled patch-clamp recordings in both brain slices of unlimited thickness and the whole brain or spinal cord preparations with a cut upper surface. It utilizes an upright microscope and ultra bright light-emitting diodes (LEDs) as a source of oblique illumination. This technique provided high quality images of superficial cells regardless of slice thickness or the presence of opaque structures, like metal plate or bone, below the tissue, when conventional differential interference contrast (DIC) optics became powerless. The technique opens broad possibilities for a single-cell imaging and visually guided recordings from intact neuronal networks in the entire brain or spinal cord.     

Dynamic correlation of diffusion tensor imaging and neurological function scores in beagles with spinal cord injury

Exploring the relationship between different structure of the spinal cord and functional assessment after spinal cord injury is important. Quantitative diffusion tensor imaging can provide information about the microstructure of nerve tissue and can quantify the pathological damage of spinal cord white matter and gray matter. In this study, a custom-designed spinal cord contusion-impactor was used to damage the T_(10) spinal cord of beagles. Diffusion tensor imaging was used to observe changes in the whole spinal cord, white matter, and gray matter, and the Texas Spinal Cord Injury Score was used to assess changes in neurological function at 3 hours, 24 hours, 6 weeks, and 12 weeks after injury. With time, fractional anisotropy values after spinal cord injury showed a downward trend, and the apparent diffusion coefficient, mean diffusivity, and radial diffusivity first decreased and then increased. The apparent diffusion-coefficient value was highly associated with the Texas Spinal Cord Injury Score for the whole spinal cord(R = 0.919, P = 0.027), white matter(R = 0.932, P = 0.021), and gray matter(R = 0.882, P = 0.048). Additionally, the other parameters had almost no correlation with the score(P 0.05). In conclusion, the highest and most significant correlation between diffusion parameters and neurological function was the apparent diffusion-coefficient value for white matter, indicating that it could be used to predict the recovery of neurological function accurately after spinal cord injury.     

Role of intraoperative ultrasound in resection of pediatric brain tumors

Purpose  

In neurosurgery, ultrasound is useful in determination of the tumor location, differentiation between solid tumors and cystic components, as well as definition of the shortest and safest access to the mass. This study aims to evaluate the role of the intraoperative ultrasound in resection of pediatric brain tumors.     

Successful intraoperative spinal cord monitoring during scoliosis surgery using a total intravenous anesthetic regimen including dexmedetomidine

Intraoperative neurophysiological monitoring (IONM) during corrective spinal surgery is widely used. Because of the possible interference with the recording of evoked potentials by inhalational anesthetics, total intravenous anesthetic (TIVA) regimens have been advocated. TIVA regimens may be difficult to use in pediatric populations due to metabolic factors. We report on the results of multimodality IONM during 18 cases in which a TIVA regimen incorporating dexmedetomidine (Precedex, Hespira, Lake Forest, IL) was used. Monitoring techniques included sensory (SSEP) and motor evoked potentials (MEP), as well as pedicle screw stimulation. SSEPs were maintained within an acceptable range of baseline amplitude (50%) and latency (10%), and MEPs remained elicitable throughout each case. We therefore found that the anesthetic regimen did not significantly interfere with any of the monitoring modalities used and conclude that IONM in the presence of dexmedetomidine is feasible under appropriate conditions.     

Diffusion-weighted imaging of the spinal cord and optic nerve

The optic nerve and spinal cord are technically challenging to investigate with any magnetic resonance imaging (MRI) technique due to the effect of the surrounding cerebrospinal fluid and lipid, and the presence of nearby bony structures. Motion and the relatively small cross-section of the structures make diffusion-weighted imaging even harder. With careful choice of pulse sequence and parameters, however, apparent diffusion coefficient (ADC) measurements are now possible in the optic nerve, and both ADC and diffusion tensor imaging (DTI) measurements are becoming available in the spinal cord.