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.
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.
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).
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.
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.
Purpose
Complex claustral connection network was widely demonstrated both in humans and animals. Moreover, several studies have suggested that claustral connections directly involve also the ...contralateral hemisphere. Detection of contralateral cortico-claustral and inter-claustral connections was reported mainly in animals and only partially in humans. The main purpose of this study was to provide more robust tractography-driven support of the existence of inter-hemispheric claustral connections in humans, by means of a dedicated optimized tractographic protocol.
Methods
Fifteen healthy subjects were examined by means of an advanced magnetic resonance imaging-based probabilistic constrained spherical deconvolution tractographic protocol. Moreover, quantitative diffusion parameters were extracted by each reconstructed pathway.
Results
In this study, further imaging-based support on the possible existence in humans of contralateral cortico-claustral and inter-claustral connections was provided. These connections were found to involve almost all the superior portion of each claustrum, showing a topographical organization. Moreover, the detection of inter-claustral connections passing through the anterior commissure was reported, for the first time, in humans.
Conclusions
The possible existence of inter-claustral and cortico-claustral contralateral pathways might provide the morphological basis for the complex functional phenomena observed in previous studies. Furthermore, these connections might have several important clinical implications, since they might explain how the inter-hemispheric coordination governed by the claustrum, as well as the functional recovery subsequent to damages involving one claustrum, takes place.
Resistance to thyroid hormone (RTH) describes a rare syndrome in which serum levels of thyroid hormones are elevated but serum levels of thyroid stimulating hormone (TSH) are unsuppressed. The ...importance of thyroid hormones for the normal function of the adult brain is corroborated by the frequent association of thyroid dysfunctions with neurological and psychiatric symptoms. In this study we investigated whether adult thyroid hormone resistance affects cortical excitability and modulates inhibitory and excitatory intracortical circuitries by using transcranial magnetic stimulation. Cortical excitability was probed with transcranial magnetic stimulation in 4 patients with thyroid hormone resistance, 10 patients affected by overt hypothyroidism (OH) and 10 age-matched healthy controls. We tested motor thresholds, motor evoked potential recruitment curve, cortical silent period (CSP), short interval intracortical inhibition (SICI) and intracortical facilitation. In both OH and RTH patients, the inhibitory cortical circuits were affected compared with euthyroid controls, but in opposite ways. In OH patients, CSP was prolonged and SICI was decreased. On the contrary, in RTH patients CSP was shortened and SICI was increased. Thyroid hormones may influence cortical excitability and cortical inhibitory circuits.
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 seems to be lost in dystonia. To explore if sensory information is abnormally processed and integrated in focal dystonia and if surround inhibition phenomena are operating during sensory-motor plasticity and sensory-motor integration in normal humans and in patients with focal hand dystonia. We looked at motor evoked potential (MEP) facilitation, in the APB and ADM muscles, obtained after 5Hz repetitive paired associative stimulation, stimulating median (PAS M), ulnar (PAS U) and median+ulnar nerve (PAS MU) in 8 normal subjects and 8 dystonic patients. We evaluated the ratio MU/(M+U)×100. Moreover, we tested the spatial and temporal somatosensory integration recording SEPs evoked by a dual nerve input. Our data confirmed that in dystonic patients the amount of facilitation was larger than normal subjects and the spatial specificity was lost. The MU/(M+U)×100 ratio was similar in healthy subjects and in dystonic patients and the somatosensory integration was normal in this subset of patients. These data suggest that lateral surround inhibition phenomena during sensory-motor plasticity are normal in focal hand dystonia.
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.
Cone-rod dystrophies (CORDs) are a heterogeneous group of inherited retinopathies (IRDs) with more than 30 already known disease-causing genes. Uncertain phenotypes and extended range of intra- and ...interfamilial heterogenicity make still difficult to determine a precise genotype-phenotype correlation. Here, we used a next-generation sequencing approach to study a Sicilian family with a suspected form of CORD. Affected family members underwent ophthalmological examinations and a proband, blind from 50 years, underwent whole genome and exome sequencing. Variant analysis was enriched by pathway analysis and relevant variants were, then, investigated in other family members and in 100 healthy controls from Messina. CORD diagnosis with an intricate pattern of symptoms was confirmed by ophthalmological examinations. A total of about 50,000 variants were identified in both proband's genome and exome. All affected family members presented specific genotypes mainly determined by mutated GUCY2D gene, and different phenotypical traits, mainly related to focus and color perception. Thus, we looked for possible modifier genes. According to relationship with GUCY2D, predicted functional effects, eye localization, and ocular disease affinity, only 9 variants, carried by 6 genes (CACNG8, PAX2, RXRG, CCDC175, PDE4DIP and LTF), survived the filtering. These genes encode key proteins involved in cone development and survival, and retina neurotransmission. Among analyzed variants, CACNG8c.*6819A>T and the new CCDC175 c.76C>T showed extremely low frequency in the control group, suggesting a key role on disease phenotypes. Such discovery could enforce the role of modifier genes into CORD onset/progression, contributing to improve diagnostic test towards a better personalized medicine.
Several techniques and protocols of non-invasive transcranial brain stimulation (NIBS), including transcranial magnetic and electrical stimuli, have been developed in the past decades. These ...techniques can induce long lasting changes in cortical excitability by promoting synaptic plasticity and thus may represent a therapeutic option in neuropsychiatric disorders. On the other hand, despite these techniques have become popular, the fragility and variability of the after effects are the major challenges that non-invasive transcranial brain stimulation currentlyfaces. Several factors may account for such a variability such as biological variations, measurement reproducibility, and the neuronal state of the stimulated area. One possible strategy, to reduce this variability is to monitor the neuronal state in real time using EEG and trigger TMS pulses only at pre-defined state. In addition, another strategy under study is to use the spaced application of multiple NIBS protocols within a session to improve the reliability and extend the duration of NIBS effects. Further studies, although time consuming, are required for improving the so far limited effect sizes of NIBS protocols for treatment of neurological or psychiatric disorders.
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.
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