Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Structural MRI”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed2001

Local Lyapunov exponents detect epileptic zones in spike-less interictal MEG recordings.

OBJECTIVE: In terms of dynamical system theory the rapid alteration of electromagnetic brain signal properties observed with transition from interictal into ictal epileptic activity implies an alteration between at least two dynamical states (attractors). We explored whether such a multistability is reflected also in the dynamical characteristics of the interictal signal. METHODS: A combined method consisting of structural MRI, multichannel magnetoencephalography (MEG) and the non-linear dynamics was applied for the detection of subthreshold interictal activity in temporal lobe epilepsy. Employing multichannel MEG we calculated local Lyapunov exponents (ILE) as a measure of the probability of state transitions in patients with mesiotemporal and extra-mesiotemporal focal epilepsy. RESULTS: The spatial distribution of the variability of ILE was found to be correlated to the side of the epileptic focus, thus, providing a reliable estimate of its localization. CONCLUSION: Our results demonstrate that interictal epileptic activity is characterized by an increase of the number of transitions between different attractors.

Adult↗
PubMed1998

Parieto-occipital cortex activation during self-generated eye movements in the dark.

A number of extrastriate visual areas in the parieto-occipital cortex are known from single-cell recordings of the macaque monkey to be involved in the coding of eye-position signals in the brain. These are important for the accurate location of visual objects in extrapersonal space. It can be predicted that these areas will show increased activation during the performance of eye movements at high frequency. In the present study PET and measurements of the regional distribution of cerebral blood flow (rCBF) were used as indirect measures of neural activity. Two independent groups of normal volunteers performed large-amplitude self-generated eye movements in complete darkness, thus removing the confounding effects of visual stimulation on parieto-occipital activation. The first group (group A; n = 5) served as a hypothesis-generating group and the second group (group B; n = 4) served as a hypothesis-testing group. The data were analysed using statistical parametric mapping at a significance level corrected for multiple comparisons (group A, Z > 4.08; group B, Z > 4.04). Significant rCBF increases were found for both groups in the frontal eye fields, supplementary eye fields, cerebellar vermis and putamina/thalami. Additionally, activation was found in the cunei in the posterior bank of the parieto-occipital sulcus. Also, the extraocular muscles were activated and, as a consequence of the partial volume effect, projected to the orbitofrontal cortices. At a less conservative threshold, activation was found close to the intraparietal sulci on the left side (Z = 3.91, P = 0.09) and right side (Z = 3.33, P = 0.42). The locations of these areas were confirmed in group B with reference to high-resolution structural MRI scans. The activation of the parieto-occipital cortex without overt visual stimuli is interpreted as the result of neural activity related to the reception of efferent copies of motor commands and/or the activation of neurons coding for eye position relative to the orbits. These are important constituents for the location and remapping of visual stimuli in space.

Adult↗
PubMed1998

Left planum temporale surface correlates with functional dominance during story listening.

The relationship between anatomical asymmetry of the planum temporale (PT) and functional lateralization for language comprehension was studied in 14 normal volunteers, including five left-handers (LH). PT surfaces and asymmetry were measured in each subject using structural MRI, while functional lateralization was assessed on individual regional cerebral blood flow (rCBF) difference images of a PET-H2(15)O activation protocol in which a story listening condition was contrasted with a control state. Significant positive correlations were found between the left PT surface and the amount of NrCBF increase during the story listening in the left superior temporal gyrus as well as with the left-right activation index in the superior temporal and the temporal pole. Functional imaging data were correlated neither with the right PT surface nor with the right-left PT surface asymmetry index. However the latter index was correlated with handedness scores. The present results indicate that the size of the left PT is the relevant anatomical landmark for language dominance, and demonstrate that anatomical asymmetries are part of the functional variability for language.

Adult↗
PubMed2000

Lateralization of movement-related potentials and the size of corpus callosum.

Using structural MRI and whole-head EEG recordings, we analyzed the correlations between the anatomical parameters of the corpus callosum and the hemispheric distribution of the cortical movement-related potentials during right finger and shoulder movements in nine right-handed men. Statistically significant correlation was found only in finger movements. A relatively large genu and the anterior part of the truncus of the corpus callosum correlated with enhanced pre-movement EEG potential over the ipsilateral M1/S1 area. The lateralization of the movement-related potentials correlates with the size of those callosal regions which connect the homologous areas of the primary sensorimotor and frontal cortices.

Adult↗
PubMed2000

A lesion of cortical area V2 selectively impairs the perception of the direction of first-order visual motion.

Lesions of area MT/V5 in monkeys and its presumed homologue, the motion area, in humans impair motion perception, including the discrimination of the direction of global motion in random dot kinematograms. Here we report the results of similar tests on patient TF, who has a discrete and very small, unilateral infarct in the medial superior part of the right occipital cortex. Structural MRI, co-registered in software with a standardized human brain atlas, reveals that the lesion involves area V2. The patient was impaired in his retinotopically corresponding left lower quadrant on several motion tasks including discrimination in random dot kinematograms of direction, speed and motion-defined discontinuity. He was also impaired on tasks selectively involving first-order motion based on luminance contrast but not on second-order motion based on texture contrast. The results show that even though area MT/V5 is intact, motion perception is abnormal and, in particular, his perception of first-order motion is impaired.

Cerebral Infarction↗
PubMed2001

Voxel-based morphometric analyses of the brain in children and adolescents prenatally exposed to alcohol.

Children of mothers who abuse alcohol during pregnancy can suffer varying degrees of neurological abnormality, cognitive impairment, and behavioral problems, and in the worst case, are diagnosed with fetal alcohol syndrome (FAS). The purpose of the present study was to localize brain abnormalities in a group of children and adolescents prenatally exposed to alcohol using high resolution, 3D structural MRI data and whole-brain voxel-based morphometry (VBM). Data were collected for 21 children and adolescents with histories of prenatal alcohol exposure (ALC) and 21 normally developing individuals. Statistical parametric maps revealed abnormalities most prominent in the left hemisphere perisylvian cortices of the temporal and parietal lobes where the ALC patients tended to have too much gray matter and not enough white matter. These results provide further support for dysmorphology in temporo-parietal cortices above and beyond the overall microcephaly that results from severe prenatal alcohol exposure.

Adolescent↗
PubMed1998

Coordinated expression in chronically unconscious persons.

The clinically described 'persistent vegetative state' (PVS), consists of wakefulness unaccompanied by any evidence of the subject's awareness of self or environment. Past studies from our own and other laboratories have used positron emission tomography (PET) to study brain metabolism in approximately 20 such patients during wakeful periods. All those efforts identified global cerebral glucose metabolism at or below levels encountered during deep barbiturate anaesthesia. Nevertheless, the clinical literature includes rare reports of relatively isolated cognitive functions expressed by PVS patients late in their course. The observation raises the question of whether such activity reflects awareness or unconscious automatic behaviour. We employed magnetometry (MEG), PET scanning, MR imaging and 24-hour EEG recordings to evaluate three patients clinically vegetative between six months and 20 years after onset. Neither meticulous clinical examinations nor 24-hour EEG and video monitoring provided any hint of cognitive interaction in any subject. Nevertheless, patient 1 uttered single words once every 48 hours or more; patient 2 frequently expressed coordinated, non-purposeful, non-dystonic movements in arms and/or legs; and, patient 3 expressed strong emotional negativity without motor responses to noxious stimuli with occasional quieting in response to prosodic stimuli. All patients had whole-brain averaged global metabolism levels below 50% of normal. Patient 1, however, demonstrated preserved islands of increased metabolism in the posterior frontal and posterior temporal lobes, as well as MEG activations of Heschl's gyrus all located in the left hemisphere. In patient 2, selected increased metabolism was confined to the frontal poles and related subcortical structures. MRI in patient 3 demonstrated severe, bilateral post-traumatic cerebral atrophy. PET metabolism was diffusely reduced to 40% of normal but MEG evoked potentials indicated early and late sensory processing with abnormal later evoked components. The correlation of fragmentary behaviour with preserved metabolic and physiologic activity in cortical and subcortical regions known to support specific modular functions is novel. The finding demonstrates the capacity of severely damaged brains to partially express surviving modular functions without evidence of integrative processes that would be necessary to produce consciousness. We conclude that the mere expression of isolated neuropsychologic activity by isolated modules is insufficient to generate consciousness in overwhelmingly damaged brains.

Adult↗
PubMed2000

From healthy aging to early Alzheimer's disease: in vivo detection of entorhinal cortex atrophy.

Using quantitative structural MRI protocols, we examined the effects of age on alterations in entorhinal cortex (EC) volume. The left EC was found to be smaller than the right in both young and healthy aged subjects. More importantly, the right EC, but not the left, was significantly smaller in elderly participants compared to young controls. In an attempt to determine the earliest sites of involvement in mild and incipient Alzheimer's disease (AD), we compared entorhinal and hippocampal volume in (1) healthy elderly controls, (2) patients with very mild AD, and (3) elderly patients who were evaluated for cognitive complaints, but did not meet criteria for dementia. Both patient groups differed from controls in EC volume, but not from each other. In contrast, the two patient groups differed in hippocampal volume from controls, as well as from each other, with the mild AD cases showing the greatest atrophy. These results suggest that degeneration of the EC and hippocampal formation occurs before the onset of overt dementia. In fact, follow-up clinical evaluations available on 23 of 28 nondemented patients indicated that 12 of 23 had converted to AD. Converters could be best differentiated from nonconverters on the basis of entorhinal volume.

Aging↗
PubMed1998

Intracranial chondrosarcoma: review of the literature and report of 15 cases.

The available data in the literature (177 cases), two current clinical patients, and cases which occurred in The Netherlands (13) were reviewed concerning the clinical presentation, pathological features, radiological data, and treatment options of chondrosarcoma of the cranial base. The mean age of patients was 37 years, the male/female ratio 1:1.1. The most frequent complaints were diplopia with oculomotor disorders (51%), headache (31%), and decreased hearing, dizziness, and tinnitus with statoacusticus dysfunction (21%). The mean duration of symptoms before diagnosis was 27 months. The chondrosarcomas were located in the petrosal bone in 37% (47 cases), in the occipital bone and clivus in 23% (30 cases), in the sphenoid bone in 20% (25 cases) and to a lesser extent in frontal, ethmoidal, and parietal bones (14%). In 6% (eight cases) the primary location was in dural tissue. Radiological examinations showed bone destruction and variable calcification (CT), involvement of neuronal and vascular structures (MRI), and mostly hypovascularity on angiography. On histological examination 51% of tumours were classified as grade I, 11% grade II, 30% mesenchymal, and 8% myxoid. The mesenchymal type was the most malignant as illustrated by a strong tendency to intradural and cerebral growth and possibly occurrence in younger age groups. The treatment of choice until recently was surgery because of the critical location and local aggressive nature. Regrowth of tumour after surgery occurred in 53% of the patients (average after 32 months). Charged particle irradiation gave a five year survival of 83-94% and a local control rate of 78%-91%. Both in surgery and radiotherapy there is treatment related morbidity and mortality that should be considered when offering these therapies. Recent promising results imply that charged particle radiotherapy, in combination with surgery, may be the therapeutical choice of the future.

Adolescent↗
PubMed1989

Very-low-birth-weight, preterm infants with or without intracranial hemorrhage. Neurologic, cognitive and cranial MRI correlations at 4-8-year follow-up.

Fourteen very-low-birth-weight (VLBW) preterm infants with and without intracranial hemorrhage (ICH) were prospectively followed from birth to 4 to 8 years for the purpose of determining neurologic and cognitive sequelae associated with ICH severity and to correlate outcomes with brain morphology as determined by Magnetic Resonance Imaging (MRI). Intracranial hemorrhage was documented by cranial ultrasonography performed in early life. Follow-up assessments included neurologic and psychometric examinations and cranial MRI scans. Of six children with no ICH, five had normal results on all three follow-up measures. Three children with Grade I-II ICH had mild to moderate neurologic and cognitive sequelae with focal white matter MRI abnormalities. Five children with Grade III-IV ICH had severe neurologic, cognitive, and MRI deficits, including MRI regional and diffuse white matter abnormalities and/or cortical atrophy. Focal and diffuse neurologic deficits correlated with the extent of MRI morphologic abnormalities. Results of this study indicate that ICH severity correlated with outcomes in children at follow-up; the more severe the ICH, the more adverse the neurologic, cognitive, and MRI results. MRI white matter abnormalities were present in all children with any degree ICH, while ventriculomegaly was seen only in severe ICH (Grade III-IV ICH). Neurologic deficits correlated with MRI structural abnormalities.

Brain↗
PubMed1996

A positron emission tomography study of primary orthostatic tremor.

Primary orthostatic tremor (OT), a clinical syndrome in which a rapid (14 to 16 Hz), regular lower limb tremor causes unsteadiness on standing, may be associated with a postural upper limb tremor of similar frequency. We used H2 15O PET to analyze the abnormal pattern of cerebral activation associated with the postural upper limb tremor in four patients with primary OT. Patients had regional cerebral bloodflow (rCBF) measured during involuntary tremor while maintaining a posture with their outstretched right upper limb and again at rest. Tremor was associated with abnormal bilateral cerebellar and contralateral lentiform and thalamic activation. These findings were evident on group analysis of pooled PET data after transformation into standard stereotactic space and in single subjects when PET images were coregistered with structural MRI of the brain. At rest, cerebellar blood flow was significantly increased bilaterally in OT when compared with age- and sex-matched controls. We have previously demonstrated similar abnormal bilateral cerebellar activation in essential and writing tremors and conclude that abnormal bilateral overactivity of cerebellar connections is a common feature of tremulous disorders.

Aged↗
PubMed1997

Autosomal dominant progressive syndrome of motor-speech loss without dementia.

This patient report describes a 68-year-old man with progressive dissolution in motor-speech without concomitant language or cognitive decline, with presumed autosomal dominant inheritance. Motor-speech impairments included marked difficulty in articulating words and in coordinating articulation, phonation, and respiration. Brain imaging results revealed severe focal atrophy of the posterior frontal region extending to the anterior parietal and superior temporal regions bilaterally on structural (MRI) and functional (single photon emission computed tomography) brain imaging studies. The involved neural substrate represented the primary motor cortex, premotor cortex (supplementary motor area), and the postcentral gyrus. Familial history included similar difficulties in his mother, her sister, and his own sister. The isolated involvement of the motor-speech processes alone indicated that this syndrome was distinguishable from progressive aphasia associated with prominent loss of language and from Alzheimer's disease.

Aged↗
PubMed2001

Frontotemporal dementia (Pick's disease): clinical features and assessment.

The clinical presentation in frontotemporal dementia (FTD) reflects the distribution of the pathologic changes rather than the exact histologic subtype of the disease. Three major clinical syndromes can be identified: 1) frontal variant FTD (dementia of frontal type) in which changes in social behavior and personality predominate, reflecting the orbitobasal frontal lobe focus of the pathology. Traditional cognitive tests are insensitive, but more specific measures are under development; 2) semantic dementia (progressive fluent aphasia) in which there is a breakdown in the conceptual database which underlies language production and comprehension, although deficits in nonverbal semantic knowledge can also be shown on neuropsychologic testing. Patients with semantic dementia have asymmetric anterolateral temporal atrophy with relative sparing of the hippocampal formation, which is typically worse on the left side. A variant of this syndrome affecting the right temporal lobe presents with progressive prosopagnosia; 3) progressive nonfluent aphasia in which the phonologic and syntactic components of language are affected in association with left peri-Sylvian atrophy. The assessment of patients with potential FTD involves a multidisciplinary approach. The development of comprehensive caregiver-based neuropsychiatric instruments, neuropsychologic tasks sensitive to semantic memory and other key cognitive impairments, and functional (hexamethyly-propyleneamine-SPECT) and structural (MRI) brain imaging represent significant advances in the field.

Aphasia, Primary Progressive↗
PubMed2000

Cortical areas differentially involved in multiplication and subtraction: a functional magnetic resonance imaging study and correlation with a case of selective acalculia.

A patient with an intracranial hemorrhage showed differential impairment among arithmetic types (impaired in multiplication but not in subtraction). A functional magnetic resonance imaging (fMRI) experiment using normal volunteers also revealed a differential activation between the two arithmetic types. The fMRI result could account for the selective acalculia of the patient in that the lesion shown by structural MRI included the region with multiplication-higher activation and spared subtraction-higher regions. These findings suggest that the cognitive mechanism and neural substrates differ among the simple arithmetic operations.

Adult↗
PubMed1988

Neck pain.

Six conditions cause most of the neck pain complaints seen by primary care physicians: cervical muscle strain or sprain, torticollis, acceleration injury, myofascial pain dysfunction syndrome, and cervical osteoarthritis or rheumatoid arthritis. Most of them can be diagnosed and treated by the primary care physician. Of the more unusual causes, one should not miss a clinical fracture; a herniated cervical disc, spinal cord compression from a disc, or epidural tumor; infection of the disc or the vertebral body; subluxation of the vertebral bodies; or pain referred from the chest or mediastinal structures. MRI offers new opportunity for early diagnosis of myelopathy owing to OA or RA, vertebral osteomyelitis, and metastatic involvement of cervical vertebrae.

Humans↗
PubMedDate not supplied

[Neuropsychological consequences of perinatal asphyxia].

Perinatal asphyxia has been classically related to important neurological diseases such as cerebral palsy, but it it also stated that a high percentage of child with a good outcome did not show any sequelae. We reviewed cerebral lesions demonstrated by post-mortem analysis and the structural MRI contributions to the anatomo-functional correlates. The most frequent neuropsychological disturbances showed by these patients in the general intelligence, perceptive functions, memory and emotional and social behavior were also summarized.

Asphyxia Neonatorum↗
PubMed1998

[Progressive aphasia without dementia].

INTRODUCTION: Slowly progressive aphasia without generalized dementia is considered as a degenerative disorder that can be differentiated of others well-known neurodegenerative disorders. CLINICAL CASE: We present a case report of a patient with slowly progressive aphasia, characterized by a progressive anomia and without generalized dementia. The patient was evaluated in the last four years: a neuropsychological assessment, a neurological exploration and structural (MRI) and functional (SPECT) neuroimaging were performed. CONCLUSION: This case is interesting on account of a selective implication of the left temporal hemisphere is showed in the pathogenesis of this disorder.

Anomia↗
PubMed1995

Use of MRI for measuring structures in frozen postmortem brain.

A method was developed for magnetic resonance imaging (MRI) of human autopsy brains stored long-term at -70 degrees C. Scanning brains at temperatures between -70 and -8 degrees C gave minimal MRI signals consistent with protons having limited freedom of movement at low temperature. Raising brain temperature improved the signal such that scanning at -1 degree C generated images with good in-plane resolution, grey/white matter contrast, and fine detail of cortical sulcal/gyral patterns. To validate the method, volume and area measurements were made using computerized image analysis on stored digital images of 14 brains from adult subjects of both genders and various ages. The data confirmed that brain volume was inversely correlated with age, and female subjects had smaller brains. This is a valuable new method for acquiring morphometric data from previously unscanned pathologic brains that are to be used for neurochemical and molecular investigations.

Analysis of Variance↗