Cortical and subcortical changes in resting-state functional connectivity before and during an episode of postoperative delirium.

OBJECTIVE: Delirium is an acute brain failure related to uncertain problems in neural connectivity, including aberrant functional interactions between remote cortical regions. This study aimed to elucidate the underlying neural mechanisms of delirium by clarifying the changes in resting-state functional connectivity induced by postoperative delirium using imaging data scanned before and after surgery. METHOD: Fifty-eight patients with a femoral neck fracture were preoperatively scanned using resting-state functional magnetic resonance imaging. Twenty-five patients developed postoperative delirium, and 14 of those had follow-up scans during delirium. Eighteen patients without delirium completed follow-up scans 5 or 6 days after surgery. We assessed group differences in voxel-based connectivity, in which the seeds were the posterior cingulate cortex, medial prefrontal cortex and 11 subcortical regions. Connections between the subcortical regions were also examined. RESULTS: The results showed four major findings during delirium. Both the posterior cingulate cortex and medial prefrontal cortex were strongly connected to the dorsolateral prefrontal cortex. The posterior cingulate cortex had hyperconnectivity with the inferior parietal lobule, whereas the medial prefrontal cortex had hyperconnectivity with the frontopolar cortex and hypoconnectivity with the superior frontal gyrus. Connectivity of the striatum with the anterior cingulate cortex and insula was increased. Disconnections were found between the lower subcortical regions including the neurotransmitter origins and the striatum/thalamus in the upper level. CONCLUSIONS: Our findings suggest that cortical dysfunction during delirium is characterized by a diminution of the anticorrelation between the default mode network and task-positive regions, excessive internal connections in the posterior default mode network and a complex imbalance of internal connectivity in the anterior default mode network. These dysfunctions can be attributed to the loss of reciprocity between the default mode network and central executive network associated with defective function in the salience network, which might be closely linked to aberrant subcortical neurotransmission-related connectivity and striato-cortical connectivity.

Resting-state fMRI reveals network disintegration during delirium.

Delirium is characterized by inattention and other cognitive deficits, symptoms that have been associated with disturbed interactions between remote brain regions. Recent EEG studies confirm that disturbed global network topology may underlie the syndrome, but lack an anatomical basis. The aim of this study was to increase our understanding of the global organization of functional connectivity during delirium and to localize possible alterations. Resting-state fMRI data from 44 subjects were analyzed, and motion-free data were available in nine delirious patients, seven post delirium patients and thirteen non-delirious clinical controls. We focused on the functional network backbones using the minimum spanning tree, which allows unbiased network comparisons. During delirium a longer diameter (mean (M) = 0.30, standard deviation (SD) = 0.05, P = .024) and a lower leaf fraction (M = 0.32, SD = 0.03, P = .027) was found compared to the control group (M = 0.28, SD = 0.04 respectively M = 0.35, SD = 0.03), suggesting reduced functional network integration and efficiency. Delirium duration was strongly related to loss of network hierarchy (rho = -0.92, P = .001). Connectivity strength was decreased in the post delirium group (M = 0.16, SD = 0.01) compared to the delirium group (M = 0.17, SD = 0.03, P = .024) and the control group (M = 0.19, SD = 0.02, P = .001). Permutation tests revealed a decreased degree of the right posterior cingulate cortex during delirium and complex regional alterations after delirium. These findings indicate that delirium reflects disintegration of functional interactions between remote brain areas and suggest long-term impact after the syndrome resolves.

Neural predisposing factors of postoperative delirium in elderly patients with femoral neck fracture.

Elderly adults are more likely to develop delirium after major surgery, but there is limited knowledge of the vulnerability for postoperative delirium. In this study, we aimed to identify neural predisposing factors for postoperative delirium and develop a prediction model for estimating an individual's probability of postoperative delirium. Among 57 elderly participants with femoral neck fracture, 25 patients developed postoperative delirium and 32 patients did not. We preoperatively obtained data for clinical assessments, anatomical MRI, and resting-state functional MRI. Then we evaluated gray matter (GM) density, fractional anisotropy, and the amplitude of low-frequency fluctuation (ALFF), and conducted a group-level inference. The prediction models were developed to estimate an individual's probability using logistic regression. The group-level analysis revealed that neuroticism score, ALFF in the dorsolateral prefrontal cortex, and GM density in the caudate/suprachiasmatic nucleus were predisposing factors. The prediction model with these factors showed a correct classification rate of 86% using a leave-one-out cross-validation. The predicted probability computed from the logistic model was significantly correlated with delirium severity. These results suggest that the three components are the most important predisposing factors for postoperative delirium, and our prediction model may reflect the core pathophysiology in estimating the probability of postoperative delirium.

Functional connectivity of the circadian clock and neural substrates of sleep-wake disturbance in delirium.

A possible mechanism of disrupted circadian rhythms in delirium was identified using resting-state functional connectivity. Thirty-four delirious patients and 38 non-delirious controls were scanned for resting-state functional MRI. Seed-based connectivity of the suprachiasmatic nucleus was compared between the groups. In delirious patients functional connectivity from the circadian clock was increased to the dorsal anterior cingulate cortex and decreased to the posterior cingulate cortex, parahippocampal gyrus, cerebellum, and thalamus. A dysregulation of the default mode network and mental coordination processing areas by the circadian clock may be the underlying pathophysiology of sleep-wake cycle disturbance and symptom fluctuation in delirium.

What is the impact of child abuse on gray matter abnormalities in individuals with major depressive disorder: a case control study.

BACKGROUND: Patients with major depressive disorder (MDD) present heterogeneous clinical symptoms, and childhood abuse is associated with deepening of psychopathology. The aim of this study was to identify structural brain abnormalities in MDD and to assess further differences in gray matter density (GMD) associated with childhood abuse in MDD. METHODS: Differences in regional GMD between 34 MDD patients and 26 healthy controls were assessed using magnetic resonance imaging and optimized voxel-based morphometry. Within the MDD group, further comparisons were performed focusing on the experience of maltreatment during childhood (23 MDD with child abuse vs 11 MDD without child abuse). RESULTS: Compared with healthy controls, the MDD patient group showed decreased GMD in the bilateral orbitofrontal cortices, right superior frontal gyrus, right posterior cingulate gyrus, bilateral middle occipital gyri, and left cuneus. In addition, the patient group showed increased GMD in bilateral postcentral gyri, parieto-occipital cortices, putamina, thalami, and hippocampi, and left cerebellar declive and tuber of vermis. Within the MDD patient group, the subgroup with abuse showed a tendency of decreased GMD in right orbitofrontal cortex, but showed increased GMD in the left postcentral gyrus compared to the subgroup without abuse. CONCLUSIONS: Our findings suggest a complicated dysfunction of networks between cortical-subcortical circuits in MDD. In addition, increased GMD in postcentral gyrus and a possible reduction of GMD in the orbitofrontal cortex of MDD patients with abuse subgroup may be associated with abnormalities of body perception and emotional dysregulation.

Interobserver and Test-Retest Reproducibility of T1ρ and T2 Measurements of Lumbar Intervertebral Discs by 3T Magnetic Resonance Imaging.

OBJECTIVE: To investigate the interobserver and test-retest reproducibility of T1ρ and T2 measurements of lumbar intervertebral discs using 3T magnetic resonance imaging (MRI). MATERIALS AND METHODS: This study included a total of 51 volunteers (female, 26; male, 25; mean age, 54 ± 16.3 years) who underwent lumbar spine MRI with a 3.0 T scanner. Amongst these subjects, 40 underwent repeat T1ρ and T2 measurement acquisitions with identical image protocol. Two observers independently performed the region of interest measurements in the nuclei pulposi of the discs from L1-2 through L5-S1 levels. Statistical analysis was performed using intraclass correlation coefficient (ICC) with a two-way random model of absolute agreement. Comparison of the ICC values was done after acquisition of ICC values using Z test. Statistical significance was defined as p value < 0.05. RESULTS: The ICCs of interobserver reproducibility were 0.951 and 0.672 for T1ρ and T2 mapping, respectively. The ICCs of test-retest reproducibility (40 subjects) for T1ρ and T2 measurements were 0.922 and 0.617 for observer A and 0.914 and 0.628 for observer B, respectively. In the comparison of the aforementioned ICCs, ICCs of interobserver and test-retest reproducibility for T1ρ mapping were significantly higher than T2 mapping (p < 0.001). CONCLUSION: The interobserver and test-retest reproducibility of T1ρ mapping were significantly higher than those of T2 mapping for the quantitative assessment of nuclei pulposi of lumbar intervertebral discs.

MR imaging features that distinguish spinal cavernous angioma from hemorrhagic ependymoma and serial MRI changes in cavernous angioma.

Cavernous angiomas of the spinal cord exhibit imaging characteristics that may overlap with those of hemorrhagic ependymoma. In the present study, we aimed to identify specific magnetic resonance imaging (MRI) findings that could be used to differentiate cavernous angioma from hemorrhagic ependymoma, and to evaluate serial MRI changes in cases of cavernous angioma. We retrospectively evaluated MR images of spinal cord tumors collected at our hospital from 2007 to 2015. From this cohort of images, 11 pathologically confirmed cavernous angiomas and 14 pathologically confirmed hemorrhagic ependymomas were compared with respect to the size of the tumor, longitudinal location, axial location, enhancement pattern, syrinx, edema, tumor margin, signal intensity of T2WI, signal intensity of T1WI, and longitudinal spreading of the hemorrhage. Serial MR images of seven spinal cavernous angiomas were reviewed. Small size, eccentric axial location, minimal enhancement, and absence of edema were more frequently observed on images of cavernous angioma compared to those of hemorrhagic ependymoma (p < 0.01). Serial MRI changes in cases of cavernous angioma included increased longitudinal spreading of the hemorrhage (6/7, 86 %) and emergence of high signal intensity on T1WI (1/7, 14 %). Small size, eccentric axial location, minimal enhancement, and absence of edema are significant MRI findings that may be used to distinguish Type I and Type II spinal cavernous angiomas from hemorrhagic ependymomas. Furthermore, longitudinal spreading of the hemorrhage may be observed on follow-up MRIs of cavernous angiomas.

Accuracy of Diffusion Tensor Imaging for Diagnosing Cervical Spondylotic Myelopathy in Patients Showing Spinal Cord Compression.

OBJECTIVE: To assess the performance of diffusion tensor imaging (DTI) for the diagnosis of cervical spondylotic myelopathy (CSM) in patients with deformed spinal cord but otherwise unremarkable conventional magnetic resonance imaging (MRI) findings. MATERIALS AND METHODS: A total of 33 patients who underwent MRI of the cervical spine including DTI using two-dimensional single-shot interleaved multi-section inner volume diffusion-weighted echo-planar imaging and whose spinal cords were deformed but showed no signal changes on conventional MRI were the subjects of this study. Mean diffusivity (MD), longitudinal diffusivity (LD), radial diffusivity (RD), and fractional anisotropy (FA) were measured at the most stenotic level. The calculated performance of MD, FA, MD∩FA (considered positive when both the MD and FA results were positive), LD∩FA (considered positive when both the LD and FA results were positive), and RD∩FA (considered positive when both the RD and FA results were positive) in diagnosing CSM were compared with each other based on the estimated cut-off values of MD, LD, RD, and FA from receiver operating characteristic curve analysis with the clinical diagnosis of CSM from medical records as the reference standard. RESULTS: The MD, LD, and RD cut-off values were 1.079 × 10(-3), 1.719 × 10(-3), and 0.749 × 10(-3) mm(2)/sec, respectively, and that of FA was 0.475. Sensitivity, specificity, positive predictive value and negative predictive value were: 100 (4/4), 44.8 (13/29), 20 (4/20), and 100 (13/13) for MD; 100 (4/4), 27.6 (8/29), 16 (4/25), and 100 (8/8) for FA; 100 (4/4), 58.6 (17/29), 25 (4/16), and 100 (17/17) for MD∩FA; 100 (4/4), 68.9 (20/29), 30.8 (4/13), and 100 (20/20) for LD∩FA; and 75 (3/4), 68.9 (20/29), 25 (3/12), and 95.2 (20/21) for RD∩FA in percentage value. Diagnostic performance comparisons revealed significant differences only in specificity between FA and MD∩FA (p = 0.003), FA and LD∩FA (p < 0.001), FA and RD∩FA (p < 0.001), MD and LD∩FA (p = 0.024) and MD and RD∩FA (p = 0.024). CONCLUSION: Fractional anisotropy combined with MD, RD, or LD is expected to be more useful than FA and MD for diagnosing CSM in patients who show deformed spinal cords without signal changes on MRI.

Comparison of Multi-Echo Dixon Methods with Volume Interpolated Breath-Hold Gradient Echo Magnetic Resonance Imaging in Fat-Signal Fraction Quantification of Paravertebral Muscle.

OBJECTIVE: To assess whether multi-echo Dixon magnetic resonance (MR) imaging with simultaneous T2* estimation and correction yields more accurate fat-signal fraction (FF) measurement of the lumbar paravertebral muscles, in comparison with non-T2*-corrected two-echo Dixon or T2*-corrected three-echo Dixon, using the FF measurements from single-voxel MR spectroscopy as the reference standard. MATERIALS AND METHODS: Sixty patients with low back pain underwent MR imaging with a 1.5T scanner. FF mapping images automatically obtained using T2*-corrected Dixon technique with two (non-T2*-corrected), three, and six echoes, were compared with images from single-voxel MR spectroscopy at the paravertebral muscles on levels L4 through L5. FFs were measured directly by two radiologists, who independently drew the region of interest on the mapping images from the three sequences. RESULTS: A total of 117 spectroscopic measurements were performed either bilaterally (57 of 60 subjects) or unilaterally (3 of 60 subjects). The mean spectroscopic FF was 14.3 ± 11.7% (range, 1.9-63.7%). Interobserver agreement was excellent between the two radiologists. Lin's concordance correlation between the spectroscopic findings and all the imaging-based FFs were statistically significant (p < 0.001). FFs obtained from the T2*-corrected six-echo Dixon sequences showed a significantly better concordance with the spectroscopic data, with its concordance correlation coefficient being 0.99 and 0.98 (p < 0.001), as compared with two- or three-echo methods. CONCLUSION: T2*-corrected six-echo Dixon sequence would be a better option than two- or three-echo methods for noninvasive quantification of lumbar muscle fat quantification.

Herniated Lumbar Disks: Real-time MR Imaging Evaluation during Continuous Traction.

PURPOSE: To assess the morphologic changes in herniated lumbar intervertebral disks and surrounding structures during lumbar traction by using real-time magnetic resonance (MR) imaging. MATERIALS AND METHODS: This prospective study was approved by the institutional review board, and written informed consent was obtained from all participants. Forty-eight consecutive patients with lumbar disk herniation (13 men and 35 women) were treated with continuous lumbar traction by using a nonmagnetic traction device. Real-time MR imaging of the lumbar spine was performed before the initiation of traction and at 10-minute intervals during 30 minutes of 30 kg of continuous traction. Sagittal and axial MR images were analyzed to determine qualitative changes during lumbar traction. Quantitative changes caused by traction on the lumbar spine were determined by measurement of lumbar vertebral column elongation and the disk reduction ratio. RESULTS: Continuous traction on herniated lumbar disks and surrounding structures resulted in change in disk shape, disk reduction with opening in the intervertebral disk, reduction of herniated disk volume, separation of the disk and adjoining nerve root, and widening of the facet joint. Both the mean lumbar vertebral column length (elongation of 1.45% after 30 minutes, P < .001) and the mean disk reduction ratio (8.57%, 15.24%, and 17.94% after 10, 20, and 30 minutes of traction, respectively) increased with time of traction. CONCLUSION: The results of this study demonstrated that the real-time effects of continuous traction on herniated lumbar intervertebral disks and their surrounding structures can be visualized by using MR imaging.

Cerebral computed tomography angiography using a 70 kVp protocol: improved vascular enhancement with a reduced volume of contrast medium and radiation dose.

OBJECTIVES: To determine the feasibility of using a 70-kVp protocol compared with a 120-kVp protocol for cerebral CT angiography. An additional target was to investigate a possible reduction in the volume of contrast medium (CM) using the 70-kVp protocol. METHODS: Attenuation value and CNR for iodine were determined at various tube voltage settings using a phantom. Sixty-nine volunteers were randomly assigned to one of three protocols: group A (120-kVp and CM 64 mL), group B (70-kVp and CM 64 mL), or group C (70-kVp and CM 40 mL). The attenuation value, SNR, and CNR of cerebral arteries, subjective image quality, and radiation dose were compared among the groups. RESULTS: The vascular attenuation, SNR, and CNR of group B were significantly higher than those of group A. Group C had a significantly higher vascular attenuation than group A. Groups B and C were significantly better than group A with respect to subjective image quality. An effective dose of 70-kVp was 10 % lower than that of 120-kVp. CONCLUSIONS: Using 70-kVp improved arterial enhancement, SNR, and CNR, and provided better subjective image quality, using a 10 % lower effective dose. Furthermore, the 70-kVp protocol may both reduce volume of CM by 37.5 % and improve arterial enhancement. KEY POINTS: • Cerebral CT angiography at 70-kVp substantially improved vascular enhancement • Subjective image quality was better at 70-kVp, with lower radiation dose • The volume of contrast media can be substantially reduced at 70-kVp.

Differentiation between focal malignant marrow-replacing lesions and benign red marrow deposition of the spine with T2*-corrected fat-signal fraction map using a three-echo volume interpolated breath-hold gradient echo Dixon sequence.

OBJECTIVE: To assess the feasibility of T2*-corrected fat-signal fraction (FF) map by using the three-echo volume interpolated breath-hold gradient echo (VIBE) Dixon sequence to differentiate between malignant marrow-replacing lesions and benign red marrow deposition of vertebrae. MATERIALS AND METHODS: We assessed 32 lesions from 32 patients who underwent magnetic resonance imaging after being referred for assessment of a known or possible vertebral marrow abnormality. The lesions were divided into 21 malignant marrow-replacing lesions and 11 benign red marrow depositions. Three sequences for the parameter measurements were obtained by using a 1.5-T MR imaging scanner as follows: three-echo VIBE Dixon sequence for FF; conventional T1-weighted imaging for the lesion-disc ratio (LDR); pre- and post-gadolinium enhanced fat-suppressed T1-weighted images for the contrast-enhancement ratio (CER). A region of interest was drawn for each lesion for parameter measurements. The areas under the curve (AUC) of the parameters and their sensitivities and specificities at the most ideal cutoff values from receiver operating characteristic curve analysis were obtained. AUC, sensitivity, and specificity were respectively compared between FF and CER. RESULTS: The AUCs of FF, LDR, and CER were 0.96, 0.80, and 0.72, respectively. In the comparison of diagnostic performance between the FF and CER, the FF showed a significantly larger AUC as compared to the CER (p = 0.030), although the difference of sensitivity (p = 0.157) and specificity (p = 0.157) were not significant. CONCLUSION: Fat-signal fraction measurement using T2*-corrected three-echo VIBE Dixon sequence is feasible and has a more accurate diagnostic performance, than the CER, in distinguishing benign red marrow deposition from malignant bone marrow-replacing lesions.

Gadolinium enhanced 3D proton density driven equilibrium MR imaging in the evaluation of cisternal tumor and associated structures: comparison with balanced fast-field-echo sequence.

OBJECTIVES: Although Gadolinium enhanced bFFE is commonly used to evaluate cisternal tumors, banding artifact may interrupt interpretation and adjacent nerve and vessels differentiation is known to be difficult. We analyzed the qualities of Gd enhanced 3D PDDE in the evaluation of cisternal tumors, comparing with bFFE. MATERIAL AND METHODS: Forty five cisternal tumors (33 schwannoma and 12 meningioma) on both bFFE and PDDE were retrospectively reviewed. For quantitative analysis, contrast ratios of CSF to tumor and tumor to parenchyma (CRC/T and CRT/P) on both sequences were compared by paired t-test. For qualitative analysis, the readers gauged the qualities of the two MR sequences with respect to the degree of demarcating cisternal structures (tumor, basilar artery, AICA, trigeminal nerve, facial nerve and vestibulocochlear nerve). RESULTS: In quantitative analysis, CRC/T and CRT/P on 3D PDDE was significantly lower than that of 3D bFFE (p < 0.01). In qualitative analysis, basilar artery, AICA, facial nerve and vestibulocochlear nerves were significantly better demarcated on 3D PDDE than on bFFE (p < 0.01). The degree of demarcation of tumor on 3D PDDE was not significantly different with that on 3D bFFE (p = 0.13). CONCLUSION: Although the contrast between tumor and the surrounding structures are reduced, Gd enhanced 3D PDDE provides better demarcation of cranial nerves and major vessels adjacent to cisternal tumors than Gd enhanced bFFE.

The added value of double dose gadolinium enhanced 3D T2 fluid-attenuated inversion recovery for evaluating small brain metastases.

PURPOSE: Single dose gadolinium (Gd) enhanced fluid-attenuated inversion recovery (FLAIR) is helpful for visualizing superficial parenchymal metastases. However, the usefulness of FLAIR with a higher dose of Gd is uncertain. The aim of our study was two-folds: first, to prove that the signal to noise ratio (SNR) of small brain metastases is higher than large brain metastases on double-dose (DD) enhanced FLAIR and, second, to explore the added value of DD Gd enhanced FLAIR in relation to T1 GRE for evaluating small brain metastases. MATERIALS AND METHODS: For the first purpose, 50 pairs of small (2 mm5 mm) were included. The difference in the SNR and contrast ratio (CR) between small and large metastases on DD Gd-enhanced 3D T2 FLAIR was compared by Wilcoxon signed-rank tests. For the second purpose, a total of 404 small metastases were included. The diagnostic sensitivities between 3D T1 gradient echo (GRE) alone and combined results of 3D T1 GRE and 3D T2 FLAIR were compared with McNemar test. RESULTS: The SNR and CR of small brain metastases were significantly higher than those of large brain metastases (p<0.001). In qualitative analysis, the diagnostic sensitivities for small brain metastases were significantly higher for 3D T1 GRE plus 3D T2 FLAIR than 3D T1 GRE alone regardless of scan time (p<0.001). CONCLUSION: Small brain metastases showed higher signal intensity than large brain metastases on the DD Gd enhanced 3D T2 FLAIR images. DD Gd enhanced 3D T2 FLAIR imaging may have a complementary role to 3D T1 GRE for evaluating small brain metastases.

Validation of compliance zone at cerebral arterial bifurcation using phantom and computational fluid dynamics simulation.

OBJECTIVE: A zone compliant to pulsatile flow (compliance zone) showing evagination and flattening at the apex of the cerebral arterial bifurcation was documented in our previous report using electrocardiogram-gated computed tomographic and magnetic resonance angiography. We aimed to validate the existence of compliance zones and examine their relationship to local thin-elastic walls. METHODS: We examined different bifurcating vascular models: a phantom with a thin elastic region at the apex and computational fluid dynamics models with either an elastic or rigid region at the apex of a bifurcation. RESULTS: In the phantom, the elastic region at the apex of the bifurcation showed evagination and flattening in time with the pulsatile circulating fluids. The size of the evaginations increased when the outlet side was tilted down below the level of the flow-generating pump. Pulsatile evagination could be simulated in the computational fluid dynamics model with an elastic region at the bifurcation apex, and the pressure gradient was highest in the evaginating apex in peak systolic phase. CONCLUSIONS: We were able to demonstrate a compliance zone, which responds to pressure gradients, experimentally, in the form of a thin elastic region at an arterial bifurcation.

Preoperative prediction of the extrathyroidal extension of papillary thyroid carcinoma with ultrasonography versus MRI: a retrospective cohort study.

BACKGROUND: The purpose of this study was to assess the diagnostic performance of preoperative ultrasonography (US) for the prediction of extrathyroidal extension (ETE) in patients with papillary thyroid carcinoma (PTC) and to compare the diagnostic performances of US and magnetic resonance imaging (MRI) for predicting ETE. METHODS: 75 patients with PTC who underwent preoperative US and MRI were retrospectively reviewed in this study. Two radiologists independently evaluated the US and MR findings to assess minimal or extensive ETE of PTC. These results were compared with the histopathologic findings. The diagnostic performances of US and MRI in the evaluation of ETE were compared. RESULTS: US was more accurate than MRI in the prediction of minimal ETE (p < 0.05) and the accuracies were not significantly different between US and MRI in extensive ETE. US showed higher sensitivity, negative predictive value and accuracy than MRI (p < 0.001) in the prediction of overall ETE. CONCLUSION: US provided higher accuracy for assessing overall ETE and higher sensitivity for minimal ETE than MR imaging in preoperative evaluation of ETE of PTC. There was no significant difference in evaluating extensive ETE of PTC between US and MRI.