New insights into cortico-basal-cerebellar connectome: clinical and physiological considerations

The current model of the basal ganglia system based on the 'direct', 'indirect' and 'hyperdirect' pathways provides striking predictions about basal ganglia function that have been used to develop deep brain stimulation approaches for Parkinson's disease and dystonia. The aim of this review is to challenge this scheme in light of new tract tracing information that has recently become available from the human brain using MRI-based tractography, thus providing a novel perspective on the basal ganglia system. We also explore the implications of additional direct pathways running from cortex to basal ganglia and between basal ganglia and cerebellum in the pathophysiology of movement disorders

MRI Tractography of Corticospinal Tract and Arcuate Fasciculus in High-Grade Gliomas Performed by Constrained Spherical Deconvolution: Qualitative and Quantitative Analysis

BACKGROUND AND PURPOSE: MR imaging tractography is increasingly used to perform noninvasive presurgical planning for brain gliomas. Recently, constrained spherical deconvolution tractography was shown to overcome several limitations of commonly used DTI tractography. The purpose of our study was to evaluate WM tract alterations of both the corticospinal tract and arcuate fasciculus in patients with high-grade gliomas, through qualitative and quantitative analysis of probabilistic constrained spherical deconvolution tractography, to perform reliable presurgical planning. MATERIALS AND METHODS: Twenty patients with frontoparietal high-grade gliomas were recruited and evaluated by using a 3T MR imaging scanner with both morphologic and diffusion sequences (60 diffusion directions). We performed probabilistic constrained spherical deconvolution tractography and tract quantification following diffusion tensor parameters: fractional anisotropy; mean diffusivity; linear, planar, and spherical coefficients. RESULTS: In all patients, we obtained tractographic reconstructions of the medial and lateral portions of the corticospinal tract and arcuate fasciculus, both on the glioma-affected and nonaffected sides of the brain. The affected lateral corticospinal tract and the arcuate fasciculus showed decreased fractional anisotropy ( z = 2.51, n = 20, P = .006; z = 2.52, n = 20, P = .006) and linear coefficient ( z = 2.51, n = 20, P = .006; z = 2.52, n = 20, P = .006) along with increased spherical coefficient ( z = −2.51, n = 20, P = .006; z = −2.52, n = 20, P = .006). Mean diffusivity values were increased only in the lateral corticospinal tract ( z = −2.53, n = 20, P = .006). CONCLUSIONS: In this study, we demonstrated that probabilistic constrained spherical deconvolution can provide essential qualitative and quantitative information in presurgical planning, which was not otherwise achievable with DTI. These findings can have important implications for the surgical approach and postoperative outcome in patients with glioma

Cognitive processess and cognitive reserve in multiple sclerosis

Multiple Sclerosis (MS) is characterized by motor, cognitive, and neuropsychiatric symptoms, which can occur independently. While MS is traditionally considered an inflammatory disease of the white matter, degeneration of gray matter is increasingly recognized as an important contributor to the progressive cognitive decline. A protective factor against the progression of cognitive dysfunction in MS could be the cognitive reserve, defined as resistance to brain dysfunction. Aim of the present study is to evaluate the role of cognitive reserve for different aspects of cognitive dysfunction of patients with MS. We found that patients with MS and lower cognitive reserve have poorer neuropsychological performance and slower information speed processing. These findings support the notion that intellectual reserve may protect some aspects of cognitive function in patients with MS

Spatial Integration of Somatosensory Inputs during Sensory-Motor Plasticity Phenomena Is Normal in Focal Hand Dystonia.

Background: Surround inhibition is a system that sharpens sensation by creating an inhibitory zone around the central core of activation. In the motor system, this mechanism probably contributes to the selection of voluntary movements, and it seems to be lost in dystonia. Objectives. To explore if sensory information is abnormally processed and integrated in focal hand dystonia (FHD) and if surround inhibition phenomena are operating during sensory-motor plasticity and somatosensory integration in normal humans and in patients with FHD. Methods. We looked at the MEP facilitation obtained after 5 Hz repetitive paired associative stimulation of median (PAS M), ulnar (PAS U), and median + ulnar nerve (PAS MU) stimulation in 8 normal subjects and 8 FHD. We evaluated the ratio MU/(M + U) ∗ 100 and the spatial and temporal somatosensory integration recording the somatosensory evoked potentials (SEPs) evoked by a dual nerve input. Results: FHD had two main abnormalities: first, the amount of facilitation was larger than normal subjects; second, the spatial specificity was lost. The MU/(M + U) ∗ 100 ratio was similar in healthy subjects and in FHD patients, and the somatosensory integration was normal in this subset of patients. Conclusions. The inhibitory integration of somatosensory inputs and the somatosensory inhibition are normal in patients with focal dystonia as well as lateral surrounding inhibition phenomena during sensory-motor plasticity in FHD

The Limbic and Sensorimotor Pathways of the Human Amygdala: A Structural Connectivity Study

The amygdala plays a key role in gathering social cues to context-appropriate responses that require refined motor behavior, involving either direct or indirect connections with sensorimotor-related areas. Although, several studies investigated the structural and functional limbic connectivity of the amygdala both in animals and in humans, less is known about the limbic modulation on sensorimotor-related areas. However, recent evidences suggest the amygdala as a possible cornerstone in the limbic–motor interface. Herein, we used high-resolution diffusion data of the Massachusetts General Hospital–University of Southern California (MGH–USC) Adult Diffusion Dataset, constrained spherical deconvolution-based signal modeling and probabilistic tractography aimed at identifying and reconstructing the connectivity patterns linking the amygdala to the limbic- and sensorimotor-related areas. As regards the limbic network, our results showed that the amygdala has high probability to be connected with the fusiform gyrus and the lateral orbitofrontal cortex. On the other hand, our connectomic analysis revealed a close interplay between the amygdala and the inferior parietal lobule, followed by the postcentral gyrus, the precentral gyrus and the paracentral lobule. The findings of the present study are in line with previous literature and reinforce the idea of the existence of a limbic–motor interface, which is likely to be involved in the emotional modulation of complex functions such as spatial perception and movement computation. Considering that these pathways may play an important role, not on in physiological conditions, but also in pathological context, further studies should be fostered in order to confirm the existence of a limbic–motor interface and its precise functional meaning

The cortico-rubral and cerebello-rubral pathways are topographically organized within the human red nucleus

The Red Nucleus (RN) is a large nucleus located in the ventral midbrain: it is subdivided into a small caudal magnocellular part (mRN) and a large rostral parvocellular part (pRN). These distinct structural regions are part of functionally different networks and show distinctive connectivity features: the mRN is connected to the interposed nucleus, whilst the pRN is mainly connected to dentate nucleus, cortex and inferior olivary complex. Despite functional neuroimaging studies suggest RN involvement in complex motor and higher order functions, the pRN and mRN cannot be distinguished using conventional MRI. Herein, we employ high-quality structural and diffusion MRI data of 100 individuals from the Human Connectome Project repository and constrained spherical deconvolution tractography to perform connectivity-based segmentation of the human RN. In particular, we tracked connections of RN with the inferior olivary complex, the interposed nucleus, the dentate nucleus and the cerebral cortex. We found that the RN can be subdivided according to its connectivity into two clusters: a large ventrolateral one, mainly connected with the cerebral cortex and the inferior olivary complex, and a smaller dorsomedial one, mainly connected with the interposed nucleus. This structural topography strongly reflects the connectivity patterns of pRN and mRN respectively. Structural connectivity-based segmentation could represent a useful tool for the identification of distinct subregions of the human red nucleus on 3T MRI thus allowing a better evaluation of this subcortical structure in healthy and pathological conditions

MRI Tractography of Corticospinal Tract and Arcuate Fasciculus in High-Grade Gliomas Performed by Constrained Spherical Deconvolution: Qualitative and Quantitative Analysis

BACKGROUND AND PURPOSE: MR imaging tractography is increasingly used to perform noninvasive presurgical planning for brain gliomas. Recently, constrained spherical deconvolution tractography was shown to overcome several limitations of commonly used DTI tractography. The purpose of our study was to evaluate WM tract alterations of both the corticospinal tract and arcuate fasciculus in patients with high-grade gliomas, through qualitative and quantitative analysis of probabilistic constrained spherical deconvolution tractography, to perform reliable presurgical planning. MATERIALS AND METHODS: Twenty patients with frontoparietal high-grade gliomas were recruited and evaluated by using a 3T MR imaging scanner with both morphologic and diffusion sequences (60 diffusion directions). We performed probabilistic constrained spherical deconvolution tractography and tract quantification following diffusion tensor parameters: fractional anisotropy; mean diffusivity; linear, planar, and spherical coefficients. RESULTS: In all patients, we obtained tractographic reconstructions of the medial and lateral portions of the corticospinal tract and arcuate fasciculus, both on the glioma-affected and nonaffected sides of the brain. The affected lateral corticospinal tract and the arcuate fasciculus showed decreased fractional anisotropy ( z = 2.51, n = 20, P = .006; z = 2.52, n = 20, P = .006) and linear coefficient ( z = 2.51, n = 20, P = .006; z = 2.52, n = 20, P = .006) along with increased spherical coefficient ( z = −2.51, n = 20, P = .006; z = −2.52, n = 20, P = .006). Mean diffusivity values were increased only in the lateral corticospinal tract ( z = −2.53, n = 20, P = .006). CONCLUSIONS: In this study, we demonstrated that probabilistic constrained spherical deconvolution can provide essential qualitative and quantitative information in presurgical planning, which was not otherwise achievable with DTI. These findings can have important implications for the surgical approach and postoperative outcome in patients with glioma

MRI patient selection for endovascular thrombectomy in acute ischemic stroke: correlation between pretreatment diffusion weighted imaging and outcome scores

Introduction: Eligibility for endovascular treatment (EVT) in patients with acute ischemic stroke (AIS) depends, amongst other factors, on CT- or MR-based scores. The aim of this study was to investigate the role of Alberta Stroke Program Early CT score based on diffusion weighted imaging (MR-ASPECT) in the assessment of brain damage pre-EVT, patient selection for EVT and outcome. Materials and methods: We included in this study patients with National Institute of Health stroke score (NIHSS) at admission ≥ 8, MR-ASPECT ≥ 5 and anterior AIS, who were treated with EVT in our hospital. All patients were clinically evaluated at admission, post-EVT, discharge and at 3-month follow-up. We used MR-ASPECT to establish infarct core extension at admission. We evaluated ASPECT score at admission (CT-ASPECT-IN), 24 h after EVT and at discharge, NIHSS, modified Ranking Scale (mRS), Thrombolysis in Cerebral Infarction scale (TICI), onset-to-intervention-delay (OTID) and Collateral Circulation Score (CCS). Results: 68 patients (mean age 78 ± 11.9 years) were included in this study. 54.4 and 64.7% of patients had strong clinical improvement after 24 h from EVT and at discharge, respectively. NIHSS evaluated 24 h after EVT correlated with CCS, TICI and OTID. We observed a favourable outcome (mRS 0–2) in 52.9% of patients at 3-month follow-up. MR-ASPECT score correlated with post-EVT outcome better than CT-ASPECT-IN scores. Conclusion: MR-ASPECT score based on diffusion weighted imaging is useful for the selection of patients with AIS that can have a favourable outcome from EVT. A prompt EVT has huge impact on patient outcome