Functional

Microstructure of the Default Mode Network in Preterm Infants

Editor’s Choice

A cohort of 44 preterm infants underwent T1WI, resting-state fMRI, and DTI at 3T, including 21 infants with brain injuries and 23 infants with normal-appearing structural imaging as controls. Neurodevelopment was evaluated with the Bayley Scales of Infant Development at 12 months’ adjusted age. Results showed decreased fractional anisotropy and elevated radial diffusivity values of the cingula in the preterm infants with brain injuries compared with controls. The Bayley Scales of Infant Development cognitive scores were significantly associated with cingulate fractional anisotropy. The authors suggest that the microstructural properties of interconnecting axonal pathways within the default mode network are of critical importance in the early neurocognitive development of infants.

Improved Leakage Correction for Single-Echo Dynamic Susceptibility Contrast Perfusion MRI Estimates of Relative Cerebral Blood Volume in High-Grade Gliomas by Accounting for Bidirectional Contrast Agent Exchange

Editor’s Choice

The authors’ hypothesis is that incorporating bidirectional contrast agent transport into the DSC MR imaging signal model will improve rCBV estimates in brain tumors. A unidirectional contrast agent extravasation model (Boxerman-Weisskoff) was compared with a bidirectional contrast agent exchange model. For both models, they compared the goodness of fit with the parent leakage-contaminated relaxation rate curves and the difference between modeled interstitial relaxation rate curves and dynamic contrast-enhanced MR imaging in 21 patients with glioblastoma. The authors conclude that the bidirectional model more accurately corrects for the T1 or T2* enhancement arising from contrast agent extravasation due to blood-brain barrier disruption in high-grade gliomas by incorporating interstitial washout rates into the DSC MR imaging relaxation rate model.

Interrogating the Functional Correlates of Collateralization in Patients with Intracranial Stenosis Using Multimodal Hemodynamic Imaging

Editor’s Choice

The authors assessed correlations among baseline perfusion and arterial transit time artifacts, cerebrovascular reactivity, and the presence of collateral vessels on digital subtraction angiography. Arterial spin-labeling MRI and DSA were compared with BOLD MR imaging measures of hypercapnic cerebrovascular reactivity in 18 patients with symptomatic intracranial stenosis. In regions with normal-to-high signal on ASL, collateral vessel presence on DSA strongly correlated with declines in cerebrovascular reactivity (as measured on BOLD MRI). These data support the use of ASL MR imaging rather than invasive DSA to assess the presence of collateralization, even for patients with internal carotid stenosis from nonatherosclerotic etiologies. Also, collaterals identified on ASL with arterial transit artifacts correlated with decreased CVR compared with regions not perfused via collaterals.

Abstract

A, Arterial transit artifacts (arrow) at the ganglionic level on ASL MR imaging in the M3 region (ASPECTS designation criteria) representing leptomeningeal collateralization. B, A similar distribution is shown in an early venous phase anteroposterior right ICA angiogram showing leptomeningeal collaterals (arrows) arriving at the periphery of the ischemic site.
A, Arterial transit artifacts (arrow) at the ganglionic level on ASL MR imaging in the M3 region (ASPECTS designation criteria) representing leptomeningeal collateralization. B, A similar distribution is shown in an early venous phase anteroposterior right ICA angiogram showing leptomeningeal collaterals (arrows) arriving at the periphery of the ischemic site.

BACKGROUND AND PURPOSE

The importance of collateralization for maintaining adequate cerebral perfusion is increasingly recognized. However, measuring collateral flow noninvasively has proved elusive. The aim of this study was to assess correlations among baseline perfusion and arterial transit time artifacts, cerebrovascular reactivity, and the presence of collateral vessels on digital subtraction angiography.

MATERIALS AND METHODS

The relationship between the presence of collateral vessels on arterial spin-labeling MR imaging and DSA was compared with blood oxygen level–dependent MR imaging measures of hypercapnic cerebrovascular reactivity in patients with symptomatic intracranial stenosis (n = 18). DSA maps were reviewed by a neuroradiologist and assigned the following scores: 1, collaterals to the periphery of the ischemic site; 2, complete irrigation of the ischemic bed via collateral flow; and 3, normal

Presurgical Assessment of the Sensorimotor Cortex Using Resting-State fMRI

Editor’s Choice

Editor’s Comment

Task-based approaches to functional localization of the motor cortex have limitations such as long scanning times and exclusion of patients with severe functional or neurologic disabilities and children. Resting-state fMRI may avoid these difficulties because patients do not perform any goal-directed tasks. Nineteen patients were prospectively evaluated by using task-based and resting-state fMRI to localize sensorimotor function. Independent component analyses were performed to generate spatial independent components reflecting functional brain networks or noise. The motor cortex was successfully and consistently identified by using resting-state fMRI. Hand, foot, and face regions were defined in a comparable fashion with task-based fMRI.

Abstract

Figure from Schneider et al -- Editor's choice
Illustration of expected findings by using rs-fMRI (light gray) and tb-fMRI (dark gray). rs-fMRI is presumed to show the whole motor cortex (possibly bilaterally), whereas a single motor cortex representation (face, hand, or foot) would be obtained by using tb-fMRI.

BACKGROUND AND PURPOSE

The functional characterization of the motor cortex is an important issue in the presurgical evaluation of brain lesions. fMRI noninvasively identifies motor areas while patients are asked to move different body parts. This task-based approach has some drawbacks in clinical settings: long scanning times and exclusion of patients with severe functional or neurologic disabilities and children. Resting-state fMRI can avoid these difficulties because patients do not perform any goal-directed tasks.

MATERIALS AND METHODS

Nineteen patients with diverse brain pathologies were prospectively evaluated by using task-based and resting-state fMRI to localize sensorimotor function. Independent component analyses were performed to generate spatial independent components reflecting functional brain networks or noise. Three radiologists identified the motor components and 3 portions of the motor cortex corresponding to the hand, foot, and face representations. Selected motor independent components were compared with task-based fMRI activation maps resulting from movements of the corresponding body parts.

RESULTS

The motor cortex was …

The Contribution of Common Surgically Implanted Hardware to Functional MR Imaging Artifacts

Editor’s Choice

Editor’s Comment

The authors calculated the BOLD-dependent MR imaging artifact impact arising from surgically implanted hardware through a retrospective analysis of fMRIs acquired from 2006–2014. Mean artifact volume associated with intracranial hardware was 4.3 cubic centimeters. The mean artifact volume from extracranial hardware in patients with cerebrovascular disease was 28.4 cubic centimeters. Artifacts had no-to-mild effects on clinical interpretability in all patients with intracranial implants. Extracranial hardware artifacts had no-to-moderate impact on clinical interpretability. The exceptions to interpretability in the face of hardware were ventriculoperitoneal shunts, particularly those with programmable valves and siphon gauges, and large numbers of KLS-Martin maxDrive screws.

Abstract

A representative patient (patient 3) with an intracranial implant. Signal drop-out from a left MCA Pharos Vitesse stent (Codman Neurovascular) is apparent on the magnitude BOLD fMRI image (A, white arrow), resulting in a total artifact volume of 2.1 cm3, which only mildly affected clinical interpretation of the examination. The patient was evaluated 2 years following implantation of the Pharos Vitesse stent in a stenosed left MCA. DSA (B) shows in-stent restenosis (black arrow), with corresponding decreased cerebrovascular reactivity (normalized CVR: voxel CVR normalized to cerebellar CVR) in the left MCA territory (C). In contrast, there is relative symmetry of the temporal signal-to-noise ratio (tSNR) map (D), suggesting that the asymmetric hemodynamic findings are not attributable to artifacts.
A representative patient (patient 3) with an intracranial implant. Signal drop-out from a left MCA Pharos Vitesse stent (Codman Neurovascular) is apparent on the magnitude BOLD fMRI image (A, white arrow), resulting in a total artifact volume of 2.1 cm3, which only mildly affected clinical interpretation of the examination. The patient was evaluated 2 years following implantation of the Pharos Vitesse stent in a stenosed left MCA. DSA (B) shows in-stent restenosis (black arrow), with corresponding decreased cerebrovascular reactivity (normalized CVR: voxel CVR normalized to cerebellar CVR) in the left MCA territory (C). In contrast, there is relative symmetry of the temporal signal-to-noise ratio (tSNR) map (D), suggesting that the asymmetric hemodynamic findings are not attributable to artifacts.

BACKGROUND AND PURPOSE

Blood oxygenation level–dependent MR imaging is increasingly used clinically to noninvasively assess cerebrovascular reactivity and/or language and motor function. However, many patients have metallic implants, which will induce susceptibility artifacts, rendering the functional information uninformative. Here, we calculate and interpret blood oxygenation level–dependent MR imaging artifact impact arising from surgically implanted hardware.

MATERIALS AND METHODS

A retrospective analysis of all blood oxygenation level–dependent MRIs (n = 343; B0 = 3T; TE = 35 ms; gradient …

Seizure Frequency Can Alter Brain Connectivity: Evidence from Resting-State fMRI

Editor’s Choice

Editor’s Comments

Resting-state fMRI data from 36 patients with hot-water epilepsy (18 with infrequent seizures) and 18 healthy age- and sex-matched controls were analyzed for seed-to-voxel connectivity. Patients in the frequent-seizure group had increased connectivity within the medial temporal structures and widespread areas of poor connectivity, including the default mode network. Seizure frequency can alter functional brain connectivity, which can be visualized by resting-state fMRI.

Abstract

Whole-brain cluster-correlation maps of seed-to-voxel–based resting-state functional connectivity for the PCC seed region (FDR-corrected P < .001). Shown is DMN connectivity using PCC seed at 3 different axial levels: at the level of ventricles in the top row, midbrain in the middle row, and the cerebellum in the bottom row for healthy controls (A), the infrequent-seizure group (B), the frequent-seizure group (C), the infrequent-seizure group versus healthy controls (D), the frequent-seizure group versus healthy controls (E), and the infrequent-seizure group versus the frequent-seizure group (F). The colors represent the significance of connectivity; red indicates an increase in connectivity, and blue indicates a decrease in connectivity.
Whole-brain cluster-correlation maps of seed-to-voxel–based resting-state functional connectivity for the PCC seed region (FDR-corrected P < .001). Shown is DMN connectivity using PCC seed at 3 different axial levels: at the level of ventricles in the top row, midbrain in the middle row, and the cerebellum in the bottom row for healthy controls (A), the infrequent-seizure group (B), the frequent-seizure group (C), the infrequent-seizure group versus healthy controls (D), the frequent-seizure group versus healthy controls (E), and the infrequent-seizure group versus the frequent-seizure group (F). The colors represent the significance of connectivity; red indicates an increase in connectivity, and blue indicates a decrease in connectivity.

BACKGROUND AND PURPOSE

The frequency of seizures is an important factor that can alter functional brain connectivity. Analysis of this factor in patients with epilepsy is complex because of disease- and medication-induced confounders. Because patients with hot-water epilepsy generally are not on long-term drug therapy, we used seed-based connectivity analysis in these patients to assess connectivity changes associated with seizure frequency without confounding from antiepileptic drugs.

MATERIALS AND METHODS

Resting-state fMRI data from 36 patients with hot-water epilepsy (18 with frequent seizures [>2 per month] and 18 with infrequent seizures [≤2 per month]) and 18 healthy age- and sex-matched controls were analyzed for seed-to-voxel connectivity by using 106 seeds. Voxel wise paired t-test analysis (P < .005, corrected for false-discovery rate) was used to identify

Challenges in Identifying the Foot Motor Region in Patients with Brain Tumor on Routine MRI: Advantages of fMRI

Fellows’ Journal Club

Editor’s Comment

Thirty-five attending-level raters evaluated 14 brain tumors involving the frontoparietal convexity. Raters identified the location of the foot motor homunculus and determined whether the tumor involved the foot motor area and/or motor cortex by using anatomic MR imaging. Seventy-seven percent of the time raters correctly identified whether the tumor was in the foot motor cortex. Raters with fMRI experience were significantly better than raters without experience at foot motor fMRI centroid predictions.

Abstract

Axial T1-weighted without (A) or with (B) coregistered functional MR images obtained during a bilateral finger-tapping and foot motor paradigm. The raters were asked to identify the foot motor homunculus solely on the basis of the anatomic images (A) without the benefit of fMRI (B). fMRI places the extra-axial lesion just posterior to the primary motor gyrus, including the foot motor portion of the motor homunculus. Edema extends to involve both the precentral and postcentral gyri. The average arrow placement from the foot motor center was 16 mm in those with fMRI experience and 23 mm in those without it. A higher percentage of raters with fMRI experience than those without it placed the arrow in the motor gyrus (65% versus 50%). Eighteen percent of raters with fMRI experience correctly identified the tumor as not being located in the foot motor cortex, while 33% of raters without fMRI experience did so. Last, 35% and 39% of raters with and without fMRI experience, respectively, correctly identified the tumor as not being located in the motor gyrus. Most of the incorrect arrow placements were due to the arrow being placed in a gyrus posterior to the motor gyrus.
Axial T1-weighted without (A) or with (B) coregistered functional MR images obtained during a bilateral finger-tapping and foot motor paradigm. The raters were asked to identify the foot motor homunculus solely on the basis of the anatomic images (A) without the benefit of fMRI (B). fMRI places the extra-axial lesion just posterior to the primary motor gyrus, including the foot motor portion of the motor homunculus. Edema extends to involve both the precentral and postcentral gyri. The average arrow placement from the foot motor center was 16 mm in those with fMRI experience and 23 mm in those without it. A higher percentage of raters with fMRI experience than those without it placed the arrow in the motor gyrus (65% versus 50%). Eighteen percent of raters with fMRI experience correctly identified the tumor as not being located in the foot motor cortex, while 33% of raters without fMRI experience did so. Last, 35% and 39% of raters with and without fMRI experience, respectively, correctly identified the tumor as not being located in the motor gyrus. Most of the incorrect arrow placements were due to the arrow being placed in a gyrus posterior to the motor gyrus.

Background and Purpose

Accurate localization of the foot/leg motor homunculus is essential because iatrogenic damage can render a …

Brain Structure and Function in Patients after Metal-on-Metal Hip Resurfacing

Editor’s Choice

September 2014

(2 of 3)

Malfunction of metal-on-metal hip prostheses may produce visual, hearing, and motor deficits. These authors compared brain volumes, metal deposition, and gray matter attenuation in 2 groups of patients 8 years after surgery. Whole blood cobalt and chromium levels were higher in patients with metal-on-metal prostheses and associated with subtle structural changes in the visual pathways and basal ganglia.

EIC signature

Abstract

BACKGROUND AND PURPOSE
Hip prostheses that use a metal-on-metal articulation expose the brain to elevated metal concentrations that, in acute excess due to prosthesis malfunction, is associated with neurologic damage, including visual and hearing loss and motor deficits. Here, we examined whether chronic exposure to lower elevated metal levels, typical of well-functioning prostheses, also affects brain structure and function.

MATERIALS AND METHODS
We compared brain volumes, metal deposition, and gray matter attenuation by MR imaging and clinical neurologic function in patients 8 years after receiving a metal-on-metal hip resurfacing versus a matched group of patients with the same duration exposure to a conventional hip prosthesis.

RESULTS
Twenty-nine patients (25 men; mean, age 59 ± 7 years) after metal-on-metal hip resurfacing and 29 patients (25 men; 59 ± 8 years) after total hip arthroplasty were compared. Whole blood cobalt and chromium concentrations were 5–10 times higher in the metal-on-metal hip resurfacing group (P < .0001). Occipital cortex gray matter attenuation tended to be lower (P < .005 uncorrected, P > .05 corrected), and the optic chiasm area tended to be lower (mean difference, −2.7 mm2; P = .076) in the metal-on-metal hip resurfacing group. Subgroup analyses in 34 patients (17 per group), after exclusion of primary ocular pathology, showed the same trend in gray matter attenuation in the occipital cortex and basal ganglia and a smaller optic chiasm in the metal-on-metal

Crossed Cerebellar Diaschisis

CCD1

CCD2

A 41-year-old female with history of migraine presented to the ED with acute onset of aphasia. In addition to the aphasia, there was numbness and tingling in the right arm and face. Patient demonstrated expressive aphasia and was not able to answer questions posed in the ED. Gadolinium MR perfusion images demonstrated decreased relative cerebral blood flow (top) in the left parietal/occipital lobes and increased time-to-peak (bottom) in the contralateral cerebellar hemisphere. Although crossed cerebellar diaschisis (CCD) is seen mostly on radiotracer studies (hypometabolism on PET studies), it was nicely demonstrated in our patient. CCD occurs more often after supratentorial infarctions but has been reported in the setting of migraine. This phenomenon occurs immediately after brain injury due to the large number of functional connections between cerebrum and cerebellum. In reverse CCD, the brain abnormality is due to injury of the cerebellum. Because of the limited number of slices on perfusion MR studies, particularly when using ASL techniques, it is important to keep in mind that the cerebellum may be involved in several supratentorial abnormalities and needs to be included in the study.  I would be interested in finding out if anyone else has seen this type of migraine-associated CCD.…

Mass in Septum Pellucidum

imag191 imag19a1
imag202 imag20a1

Does anyone know what this mass could be? It was biopsied 2 years ago and pathology reported it as  “normal brain tissue”.

As you can see, the lesion is hyperintense on T2, hypointense on T1 and does not enhance.  No calcifications are present and no there is no restricted diffusion .

The patient is 25  year old and has loss of short term memory and seizures.

Any input into the nature of the mass is welcome.…