Can Apparent Diffusion Coefficient (ADC) maps replace Diffusion Tensor Imaging (DTI) maps to predict the volumetric response of meningiomas to Gamma Knife Radiosurgery?

PURPOSE: Noninvasive methods are desired to predict the treatment response to Stereotactic Radiosurgery (SRS) to improve individual tumor management. In a previous study, we demonstrated that Diffusion Tensor Imaging (DTI)-derived parameter maps significantly correlate to SRS response. This study aimed to analyze and compare the predictive value of intratumoral ADC and DTI parameters in patients with meningiomas undergoing radiosurgery. METHODS: MR images of 70 patients treated with Gamma Knife SRS for WHO grade I meningiomas were retrospectively reviewed. MR acquisition included pre- and post-treatment DWI and DTI sequences, and subtractions were calculated to assess for radiation-induced changes in the parameter values. RESULTS: After a mean follow-up period (FUP) of 52.7 months, 69 of 70 meningiomas were controlled, with a mean volume reduction of 34.9%. Whereas fractional anisotropy (FA) values of the initial exam showed the highest correlation to tumor volume change at the last FU (CC = - 0.607), followed by the differences between first and second FU values of FA (CC = - 0.404) and the first longitudinal diffusivity (LD) value (CC = - 0.375), the correlation coefficients of all ADC values were comparably low. Nevertheless, all these correlations, except for ADC measured at the first follow-up, reached significance. CONCLUSION: For the first time, the prognostic value of ADC maps measured in meningiomas before and at first follow-up after Gamma Knife SRS, was compared to simultaneously acquired DTI parameter maps. Quantities assessed from ADC maps present significant correlations to the volumetric meningioma response but are less effective than correlations with DTI parameters.

MRI radiomics in the prediction of the volumetric response in meningiomas after gamma knife radiosurgery.

PURPOSE: This report presents the first investigation of the radiomics value in predicting the meningioma volumetric response to gamma knife radiosurgery (GKRS). METHODS: The retrospective study included 93 meningioma patients imaged by three Tesla MRI. Tumor morphology was quantified by calculating 337 shape, first- and second-order radiomic features from MRI obtained before GKRS. Analysis was performed on original 3D MR images and after their laplacian of gaussian (LoG), logarithm and exponential filtering. The prediction performance was evaluated by Pearson correlation, linear regression and ROC analysis, with meningioma volume change per month as the outcome. RESULTS: Sixty calculated features significantly correlated with the outcome. The feature selection based on LASSO and multivariate regression started from all available 337 radiomic and 12 non-radiomic features. It selected LoG-sigma-1-0-mm-3D_firstorder_InterquartileRange and logarithm_ngtdm_Busyness as the predictively most robust and non-redundant features. The radiomic score based on these two features produced an AUC = 0.81. Adding the non-radiomic karnofsky performance status (KPS) to the score has increased the AUC to 0.88. Low values of the radiomic score defined a homogeneous subgroup of 50 patients with consistent absence (0%) of tumor progression. CONCLUSION: This is the first report of a strong association between MRI radiomic features and volumetric meningioma response to radiosurgery. The clinical importance of the early and reliable prediction of meningioma responsiveness to radiosurgery is based on its potential to aid individualized therapy decision making.

Adaptation of visual cortex to damage of visual pathways in suprasellar tumors before and after gamma knife radiosurgery.

PURPOSE: To demonstrate that lesions of the visual pathways due to suprasellar tumors are accompanied by alterations of the visual cortex and to see if these alterations are reversible after treatment of tumors by gamma knife radiosurgery. MATERIALS AND METHODS: In 36 patients with peri-optic tumors and defects of their visual fields and in an age-matched control group, magnetic resonance imaging was performed before and after treatment. T1 weighted images were evaluated by voxel-based morphometry and correlated to the degree of visual field defects. RESULTS: In patients, grey matter density and cortical thickness were reduced in all parts of the occipital cortex, reaching significance (p < 0.05) in the left superior and middle occipital gyri, with correlation to visual field defects. Follow-up scans showed further reduction in all occipital areas. CONCLUSION: As in other peripheral lesions of the optic system, damage of the optic pathways affects the visual cortex. A prospective follow-up study is needed to determine if these alterations are reversible after successful tumor treatment.

Atrophy, focal spinal cord lesions and alterations of diffusion tensor imaging (DTI) parameters in asymptomatic virus carriers and patients suffering from human T-lymphotrophic virus type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP).

In tropical spastic paraparesis, spinal cord atrophy is a well-known finding in magnetic resonance imaging. But in contrast to histological reports, focal lesions of the spinal cord have only been described in imaging reports in exceptional acute cases. Here, we looked for such focal lesions and for alterations of diffusion tensor imaging parameters of the long fibre tracts in the usual case of a long-standing and slowly progressive disease. We examined 10 symptomatic patients, 11 seropositive, but asymptomatic human T-lymphotrophic virus type 1 carriers and 18 seronegative volunteers as controls. Sagittal and transversal T2-weighted images were visually assessed for atrophy and focal cord lesions. The spinal cord cross-sectional areas and the segmental cord volumes were measured at all levels. High-resolution diffusion tensor imaging was performed in sagittal planes from the bregma down to the cervical spine. For tractography and calculation of fractional anisotropy and mean diffusivity, we used manufacturer-provided software. Two-thirds of patients showed focal lesions affecting the antero-lateral columns and in two cases also the dorsal columns. Compared to carriers and volunteers, patients presented a significant spinal cord atrophy and a reduction of fractional anisotropy (p < 0.05), correlating more to duration of symptoms than to clinical impairment. Because our carriers did not show a significant atrophy, focal lesions or a change of diffusion tensor imaging parameters, we need further long-term studies to see if these parameters at some stage may be used as early indicators of spinal cord affection in virus carriers.

Missense PANK2 mutation without "eye of the tiger" sign: MR findings in a large group of patients with pantothenate kinase-associated neurodegeneration (PKAN).

PURPOSE: To present some unusual MR findings in a group of patients from the south-west of the Dominican Republic suffering from Pantothenate Kinase Associated Neurodegeneration (PKAN). MATERIALS AND METHODS: Twenty patients and one preclinical case homozygous for the PANK2 mutation, 13 heterozygous gene carriers and 14 healthy volunteers were scanned prospectively using a 3 Tesla system. RESULTS: All patients showed the typical signal reduction within the globus pallidus and the substantia nigra. A surprising finding was the absence of the bright spot ("tiger's eye") in the medial part of the pallidum in 6 patients, but not in the preclinical case. Both fractional anisotropy (FA) and mean diffusivity (MD) were increased with high significance in the globus pallidus, whereas a reduction of FA in the anterior parts of the internal capsule was accompanied by an elevation of MD. CONCLUSION: Our findings support the hypothesis that the absence of the "tiger's eye" in PKAN might be secondary, probably caused by an increased accumulation of iron. This could artificially increase FA and MD values and change fiber tracking results. Except for the fronto-basal tracts, white matter was preserved well. This encouraging finding might support efforts to develop further therapeutic strategies in this devastating dystonia.

White matter abnormalities and their impact on attentional performance in adult attention-deficit/hyperactivity disorder.

Inattention is the most important behavioral feature of adult patients with attention-deficit/hyperactivity disorder (ADHD). Neuroimaging studies in ADHD have demonstrated abnormalities primarily in the frontostriatal circuitry and were mostly conducted in children. We investigated white matter (WM) integrity in adult ADHD patients and the correlation of WM microstructure and neuropsychological parameters in 37 (21 men) never-medicated adult ADHD patients and 34 age- and gender-matched healthy controls. All subjects underwent clinical interviews, rating scales, and neuropsychological tests of attentional performance. Diffusion tensor imaging (DTI) was acquired, and 12 WM regions-of-interest (ROIs) within the attentional network were chosen. Group differences of mean fractional anisotropy (FA) and mean diffusivity (MD) values were calculated for each ROI, and patients' DTI measures were then correlated with measures of attentional performance. FA values in ADHD patients were significantly reduced in the left inferior longitudinal fasciculus (ILF), while MD values were significantly increased in ADHD patients in the frontal portion of the left frontooccipital fasciculus (IFO). In ADHD patients, MD values were negatively correlated with attentional performance in the left ILF. Our findings provide further support for disturbed frontostriatal structural connectivity and also point to an involvement of the left temporal white matter with an impact on attentional performance.

Broad disruption of brain white matter microstructure and relationship with neuropsychological performance in male patients with severe alcohol dependence.

AIMS: In the last years, refined magnetic resonance diffusion tensor imaging (DTI) methods have become available to study microstructural alterations in the human brain. We investigated to what extent white matter tissue abnormalities are present in male patients after chronic, excessive alcohol consumption and if these alterations are correlated with measures of alcohol consumption and neuropsychological performance. METHODS: Twenty-four detoxified adult male patients with severe alcohol dependence and 23 healthy male control subjects were included in the study. Neuropsychological tests were assessed for executive function, attention, memory and visuospatial function. DTI was acquired and preprocessing of the data was performed using tract-based spatial statistics. Group differences of fractional anisotropy (FA) as well as correlation analyses with neuropsychological measures and drinking history were calculated. RESULTS: Performance in alcoholic patients was significantly poorer in tests of non-verbal reasoning and attention. In detoxified alcoholic patients, lower FA was primarily found in the body of the corpus callosum, but these findings did not correlate directly with behavioral measures. However, executive and psychomotor performance (Trail-Making Test) correlated significantly with FA in right anterior cingulate and left motor areas. CONCLUSION: These findings provide further evidence for reduced integrity of interhemispheric connections in male patients with severe alcohol dependence, and neurocognitive performance was in part correlated with FA.

Development of the Arterial Supply of the Spinal Cord Tissue Based on Radioanatomical and Histological Studies in Cattle.

PURPOSE: Angiographic techniques have gained increasing importance in suspected vascular disease of the spinal cord. This demands an advanced understanding of spinal cord blood vessel anatomy and its embryologically founded broad spectrum of variations. The aim of this study was to improve knowledge on contentious issues concerning the development of spinal cord arterial supply in higher mammals and to offer visual information of high didactic value. METHODS: The prenatal development was examined in cattle, using multiplanar high-resolution microangiography of injected specimens and microscopic sections. The gestational ages of the 15 specimens were between the late embryonic and the early fetal period (5-11 weeks). Microangiography of the human spinal cord from an earlier published study were used to envisage an adult arterial vascularization pattern in higher mammals. RESULTS: Establishment of the unpaired anterior spinal artery (ASA) goes through two procedures of reconfiguration until achieving its final design. Regression of the primarily established anteromedian tract is observed in cattle fetuses of 9-10 weeks. Return to the ontogenetic disposition of bilateral symmetry and a burst of vascularization from all parts of the spinal meninges follow and include the anterior median fissure as a preferred vascular pathway. Large sulcal/central arteries longitudinally anastomosing between each other emerge on both sides of the midline. The embryological pattern of exclusive peripheral medullary supply must have been converted into a combined system of predominant central (centrifugal) supply of the enlargements before a final unpaired ASA can be reconstructed. CONCLUSION: Previous investigators focused on the early embryonic development of spinal cord arteries and missed the profound remodeling of the vascular architecture in the early fetal period.

Cerebral and cerebellar white matter tract alterations in patients with Pantothenate Kinase-Associated Neurodegeneration (PKAN).

BACKGROUND: To examine structural connectivity of white matter tracts in patients with Pantothenate Kinase-Associated Neurodegeneration (PKAN) dystonia and identify those ones which correlate negatively to severity of symptoms. METHODS: In a group of 41 patients suffering from PKAN dystonia and an age- and gender-matched control group, white matter tractography was carried out, based on diffusion tensor imaging magnetic resonance data. Postprocessing included assessment of Quantitative Anisotropy (QA) using q-space diffeomorphic reconstruction in order to reduce influence of iron accumulation in globus pallidus of patients. RESULTS: Whole brain tractography presented significantly reduced QA values in patients (0.282 ± 0.056, as compared to controls (0.325 ± 0.046, p < 0.001). 9 fiber clusters of tracts correlated negatively to the dystonia score of patients: the middle cerebellar peduncle and the tracts of both cerebellar hemispheres as well as corpus callosum, forceps minor, the superior cortico-striate tracts and the superior thalamic radiations of both cerebral hemispheres (False Discovery Rate FDR = 0.041). CONCLUSION: The finding of a reduced global structural connectivity within the white matter and of negative correlation of motor system-related tracts, mainly those between the basal ganglia, cortical areas and the cerebellum, fits well to the concept of a general functional disturbance of the motor system in PKAN.

Anatomical correlate of impaired covert visual attentional processes in patients with cerebellar lesions.

In the past years, claims of cognitive and attentional function of the cerebellum have first been raised but were later refuted. One reason for this controversy might be that attentional deficits only occur when specific cerebellar structures are affected. To further elucidate this matter and to determine which cerebellar regions might be involved in deficits of covert visual attention, we used new brain imaging tools of lesion mapping that allow a direct comparison with control patients. A total of 26 patients with unilateral right-sided cerebellar infarcts were tested on a covert visual attention task. Eight (31%) patients showed markedly slowed responses, especially in trials in which an invalid cue necessitated reorienting of the focus of attention for target detection. Compared with the 18 patients who performed within the range of healthy control subjects, only the impaired patients had lesions of cerebellar vermal structures such as the pyramid. We suggest that these midcerebellar regions are indirectly involved in covert visual attention via oculomotor control mechanisms. Thus, specific cerebellar structures do influence attentional orienting, whereas others do not.

Voxel-based morphometry depicts central compensation after vestibular neuritis.

OBJECTIVE: Patients who have had vestibular neuritis (VN) show a remarkable clinical improvement especially in gait and posture >6 months after disease onset. METHODS: Voxel-based morphometry was used to detect the VN-induced changes in gray and white matter by means of structural magnetic resonance imaging. Twenty-two patients were compared an average 2.5 years after onset of VN to a healthy sex-and age-matched control group. RESULTS: Our analysis revealed that all patients had signal intensity increases for gray matter in the medial vestibular nuclei and the right gracile nucleus and for white matter in the area of the pontine commissural vestibular fibers. A relative atrophy was observed in the left posterior hippocampus and the right superior temporal gyrus. Patients with a residual canal paresis also showed an increase of gray matter in middle temporal (MT)/V5 bilaterally. INTERPRETATION: These findings indicate that the processes of central compensation after VN seem to occur in 3 different sensory systems. First of all, the vestibular system itself showed a white matter increase in the commissural fibers as a direct consequence of an increased internuclei vestibular crosstalk of the medial vestibular nuclei. Second, to regain postural stability, there was a shift to the somatosensory system due to an elevated processing of proprioceptive information in the right gracile nucleus. Third, there was a bilateral increase in the area of MT/V5 in VN patients with a residual peripheral vestibular hypofunction. This seems to be the result of an increased importance of visual motion processing.

Functional implications of hippocampal degeneration in early Alzheimer's disease: a combined DTI and PET study.

PURPOSE: Hypometabolism of the posterior cingulate cortex (PCC) in early Alzheimer's disease (AD) is thought to arise in part due to AD-specific neuronal damage to the hippocampal formation. Here, we explored the association between microstructural alterations within the hippocampus and whole-brain glucose metabolism in subjects with AD, also in relation to episodic memory impairment. METHODS: Twenty patients with early AD (Mini-Mental State Examination 25.7 ± 1.7) were studied with [(18)F]fluorodeoxyglucose (FDG) positron emission tomography and diffusion tensor imaging. Episodic memory performance was assessed using the free delayed verbal recall task (DVR). Voxel-wise relative FDG uptake was correlated to diffusivity indices of the hippocampus, followed by extraction of FDG uptake values from significant clusters. Linear regression analysis was performed to test for unique contributions of diffusivity and metabolic indices in the prediction of memory function. RESULTS: Diffusivity in the left anterior hippocampus negatively correlated with FDG uptake primarily in the left anterior hippocampus, parahippocampal gyrus and the PCC (p < 0.005). The same correlation pattern was found for right hippocampal diffusivity (p < 0.05). In linear regression analysis, left anterior hippocampal diffusivity and FDG uptake from the PCC cluster were the only significant predictors for performance on DVR, together explaining 60.6% of the variance. We found an inverse association between anterior hippocampal diffusivity and PCC glucose metabolism, which was in turn strongly related to episodic memory performance in subjects with early AD. CONCLUSION: These findings support the diaschisis hypothesis of AD and implicate a dysfunction of structures along the hippocampal output pathways as a significant contributor to the genesis of episodic memory impairment.

Performing real-time interactive fiber tracking.

Fiber tracking is a technique that, based on a diffusion tensor magnetic resonance imaging dataset, locates the fiber bundles in the human brain. Because it is a computationally expensive process, the interactivity of current fiber tracking tools is limited. We propose a new approach, which we termed real-time interactive fiber tracking, which aims at providing a rich and intuitive environment for the neuroradiologist. In this approach, fiber tracking is executed automatically every time the user acts upon the application. Particularly, when the volume of interest from which fiber trajectories are calculated is moved on the screen, fiber tracking is executed, even while it is being moved. We present our fiber tracking tool, which implements the real-time fiber tracking concept by using the video card's graphics processing units to execute the fiber tracking algorithm. Results show that real-time interactive fiber tracking is feasible on computers equipped with common, low-cost video cards.

Changes in Cerebral Gray and White Matter in Patients with Pantothenate Kinase-Associated Neurodegeneration: A Long-Term Magnetic Resonance Imaging Follow-Up Study.

OBJECTIVE: To determine the volume changes in gray and white matter during a long-term follow-up in patients suffering from pantothenate kinase-associated neurodegeneration (PKAN). METHODS: Magnetic resonance imaging was repeated in 13 patients and 14 age-matched controls after a mean interval of more than 7 years. T1-weighted sequences were evaluated by fully automated atlas-based volumetry, compared between groups and correlated with disease progression. RESULTS: The patients did not show generalized cerebral atrophy but did show a significantly faster volume reduction in the globus pallidus during follow-up (between -0.96% and -1.02% per year, p < 0.05 adjusted for false discovery rate) than controls, which was significantly related to the progression in their dystonia scores (p = 0.032). CONCLUSION: The volume loss in the globus pallidus over time-together with the accumulation of iron known as the "tiger's eye"-supports the pathophysiologic concept of this nucleus as a center of inhibition and its severe malfunction in PKAN.

Functional connectivity of the motor system in dystonia due to PKAN.

PURPOSE: To demonstrate deviations of functional connectivity within the motor system in dystonic patients suffering from Pantothenate Kinase Associated Neurodegeneration, a genetic and metabolic disease, which is characterized by a primary lesion in the globus pallidus. MATERIAL AND METHODS: Functional Magnetic Resonance Imaging data were measured during resting state in 12 patients suffering from a confirmed mutation of the PANK2 gene. In this region-of-interest based analysis, data were evaluated in respect to correlation of signal time course between basal ganglia, motor-related cortical regions and cerebellum, were related to clinical data and were compared to a control group of 20 healthy volunteers. RESULTS: During resting state, correlation coefficients within the motor system were significantly lower in patients than in controls (0.025 vs. 0.133, p < 0.05). Network analysis by Network Based Statistics showed that these differences mainly affected the connectivity between a sub-network consisting of the basal ganglia and another one, the motor system-related cortical areas (p < 0.05). 6 out of 12 connections, which correlated significantly to duration of disease, were connections between both sub-networks. CONCLUSION: The finding of a reduced functional connectivity within the motor network, between the basal ganglia and cortical motor-related areas, fits well into the concept of a general functional disturbance of the motor system in PKAN.

Occurence and clinical predictors of spasticity after ischemic stroke.

BACKGROUND AND PURPOSE: There is currently no consensus on (1) the percentage of patients who develop spasticity after ischemic stroke, (2) the relation between spasticity and initial clinical findings after acute stroke, and (3) the impact of spasticity on activities of daily living and health-related quality of life. METHODS: In a prospective cohort study, 301 consecutive patients with clinical signs of central paresis due to a first-ever ischemic stroke were examined in the acute stage and 6 months later. At both times, the degree and pattern of paresis and muscle tone, the Barthel Index, and the EQ-5D score, a standardized instrument of health-related quality of life, were evaluated. Spasticity was assessed on the Modified Ashworth Scale and defined as Modified Ashworth Scale >1 in any of the examined joints. RESULTS: Two hundred eleven patients (70.1%) were reassessed after 6 months. Of these, 42.6% (n=90) had developed spasticity. A more severe degree of spasticity (Modified Ashworth Scale >or=3) was observed in 15.6% of all patients. The prevalence of spasticity did not differ between upper and lower limbs, but in the upper limb muscles, higher degrees of spasticity (Modified Ashworth Scale >or=3) were more frequently (18.9%) observed than in the lower limbs (5.5%). Regression analysis used to test the differences between upper and lower limbs showed that patients with more severe paresis in the proximal and distal limb muscles had a higher risk for developing spasticity (P

Multiple somatotopic representations of heat and mechanical pain in the operculo-insular cortex: a high-resolution fMRI study.

Whereas studies of somatotopic representation of touch have been useful to distinguish multiple somatosensory areas within primary (SI) and secondary (SII) somatosensory cortex regions, no such analysis exists for the representation of pain across nociceptive modalities. Here we investigated somatotopy in the operculo-insular cortex with noxious heat and pinprick stimuli in 11 healthy subjects using high-resolution (2 × 2 × 4 mm) 3T functional magnetic resonance imaging (fMRI). Heat stimuli (delivered using a laser) and pinprick stimuli (delivered using a punctate probe) were directed to the dorsum of the right hand and foot in a balanced design. Locations of the peak fMRI responses were compared between stimulation sites (hand vs. foot) and modalities (heat vs. pinprick) within four bilateral regions of interest: anterior and posterior insula and frontal and parietal operculum. Importantly, all analyses were performed on individual, non-normalized fMRI images. For heat stimuli, we found hand-foot somatotopy in the contralateral anterior and posterior insula [hand, 9 ± 10 (SD) mm anterior to foot, P < 0.05] and in the contralateral parietal operculum (SII; hand, 7 ± 10 mm lateral to foot, P < 0.05). For pinprick stimuli, we also found somatotopy in the contralateral posterior insula (hand, 9 ± 10 mm anterior to foot, P < 0.05). Furthermore, the response to heat stimulation of the hand was 11 ± 12 mm anterior to the response to pinprick stimulation of the hand in the contralateral (left) anterior insula (P < 0.05). These results indicate the existence of multiple somatotopic representations for pain within the operculo-insular region in humans, possibly reflecting its importance as a sensory-integration site that directs emotional responses and behavior appropriately depending on the body site being injured.

Disturbed structural connectivity is related to inattention and impulsivity in adult attention deficit hyperactivity disorder.

Inattention and impulsivity are the most prominent clinical features of attention deficit hyperactivity disorder (ADHD) in adulthood. Structural and functional neuroimaging studies of subjects with ADHD have demonstrated abnormalities in several brain areas, including fronto-striatal and fronto-cerebellar networks. Mostly, these studies were based on volumetric measurements and have been conducted in children. We investigated white matter (WM) integrity and correlation with measures of attention and impulsivity in adult patients with ADHD adopting diffusion tensor imaging (DTI). N = 37 (21 males) never-medicated adult patients with ADHD combined subtype and N = 34 (16 males) healthy controls were investigated. ADHD diagnosis (DSM-IV) was assessed with clinical interviews and rating scales, subjects also underwent a large neuropsychological test battery including tests of attention and impulsivity. DTI was acquired, and group differences of fractional anisotropy (FA) and mean diffusivity (MD) as well as correlation analyses with measures of attentional performance and impulsivity were calculated using voxel-based analyses. In adult patients with ADHD, we found reduced FA as well as higher MD bilaterally in orbitomedial prefrontal WM and in the right anterior cingulate bundle, while elevated FA was present bilaterally in temporal WM structures. Measures of attention were correlated with DTI parameters in the right superior longitudinal fasciculus, whereas measures of impulsivity were correlated with FA in right orbitofrontal fibre tracts. This is the first DTI study demonstrating disturbed structural connectivity of the frontal-striatal circuitry in adult patients with ADHD. Moreover, a direct correlation between WM integrity and measures of attention and impulsivity is shown.

Cerebral blood flow in dystonia due to pantothenate kinase-associated neurodegeneration.

BACKGROUND AND PURPOSE: The aim of this study was to look for deviations of cerebral perfusion in patients suffering from pantothenate kinase-associated neurodegeneration, where the globus pallidus is affected by severe accumulation of iron. MATERIAL AND METHODS: Under resting conditions, cerebral blood flow was measured by the magnetic resonance imaging technique of arterial spin labelling in cortical areas and basal ganglia in eight pantothenate kinase-associated neurodegeneration patients and 14 healthy age-matched control subjects and correlated to T2* time of these areas and - in patients - to clinical parameters. RESULTS: Despite highly significant differences of T2* time of the globus pallidus (20 vs 39 ms, p < 0.001), perfusion values of this nucleus were nearly identical in both groups (32 ± 3.3 vs 31 ± 4.0 ml/min/100 g) as well as in total brain gray matter (both 62 ± 6.7 resp. ±10.3 ml/min/100 g), putamen (41 ± 5.4 vs 40 ± 6.1 ml/min/100 g), in selected cortical regions, and the cerebellum. Correlations between perfusion and T2* time to clinical data did not reach significance (p > 0.05). CONCLUSION: The absence of any obvious deviations of perfusion in the group of patients during a resting condition does not support the view that (non-functional) vascular pathology is a major pathogenic factor in pantothenate kinase-associated neurodegeneration in the younger age group. The findings underline the value of the arterial spin technique to measure cerebral blood flow in areas of disturbed susceptibility.

Correlation of brain white matter diffusion anisotropy and mean diffusivity with reaction time in an oddball task.

BACKGROUND: Reaction time (RT) is a frequently used measure of information processing speed, but the underlying physiological and anatomical conditions are not yet fully understood. A correlation between measures of white matter (WM) ultrastructural properties and RT is expected--particularly for those WM tracts that are involved in the attentional system of the brain. METHODS: Diffusion tensor imaging data were acquired in 43 unrelated healthy subjects (age: 22.7 +/- 1.8 years), and RT was measured during an attention-requiring visual oddball task in the same scanning session. Voxel-by-voxel and region of interest analyses were performed for the large association tracts. A linear regression model was used to correlate fractional anisotropy (FA) and mean diffusivity (MD) values with mean RT. RESULTS: Our analyses revealed significant positive correlations between RT and MD in several WM association tracts, predominantly in the right hemisphere. To a lesser extent, significant negative correlations were found between RT and FA in right temporal WM. CONCLUSION: These findings suggest that subcortical ultrastructural properties of the dorsal and ventral visual stream are relevant with regard to information processing speed. Furthermore, MD appears to be more sensitive than FA in detecting functionally relevant ultrastructural variations in WM tracts.