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Biomedical subjects

I Berry

Publications and source records attributed to I Berry.

At least 19 recordsLinked to original sources
PubMed2000

Cortical motor reorganization in akinetic patients with Parkinson's disease: a functional MRI study.

Using functional MRI (fMRI), we have studied the changes induced by the performance of a complex sequential motor task in the cortical areas of six akinetic patients with Parkinson's disease and six normal subjects. Compared with the normal subjects, the patients with Parkinson's disease exhibited a relatively decreased fMRI signal in the rostral part of the supplementary motor area (SMA) and in the right dorsolateral prefrontal cortex, as previously shown in PET studies. Concomitantly, the same patients exhibited a significant bilateral relative increase in fMRI signal in the primary sensorimotor cortex, lateral premotor cortex, inferior parietal cortex, caudal part of the SMA and anterior cingulate cortex. These fMRI data confirm that the frontal hypoactivation observed in patients with Parkinson's disease is restricted to the rostral part of the SMA and to the dorsolateral prefrontal cortex. These results also show that, apart from the lateral premotor and parietal cortices, increased fMRI signals can be found in other cortical motor areas of these patients, including the posterior SMA, the anterior cingulate cortex and the primary sensorimotor cortices, which are then likely to participate in the same putative attempt by the dopamine-denervated brain to recruit parallel motor circuits in order to overcome the functional deficit of the striatocortical motor loops.

Aged↗
PubMed1999

A multicenter measurement of magnetization transfer ratio in normal white matter.

To assess the importance of intercenter variations when measuring magnetization transfer ratio (MTR) in the brain, six European centers measured MTR in normal white matter. MTR ranged from 9 to 51 percent units (25 sequences). The effective flip angle of the saturating pulse divided by the pulse repetition time (ENRsat degrees/msec) was a good predictor of MTR (MTR = 3.25 ENRsat).

Brain↗
PubMed1999

Differential fMRI responses in the left posterior superior temporal gyrus and left supramarginal gyrus to habituation and change detection in syllables and tones.

Using a habituation-recovery paradigm adapted to functional magnetic resonance imaging, we investigated the brain responses to syllables and tones in six right-handed male subjects. We opposed a standard condition (STD) in which the subjects were listening to homogeneous sequences of four identical stimuli, to a deviant condition (DEV) in which the fourth stimulus of the sequence differed in pitch or spectral content for tones and in the initial stop consonant for syllables. The corresponding runs alternated four rest periods with two STD and two DEV conditions. In addition to a marked rightward asymmetry in the primary and secondary auditory cortex for tones and a right inferior frontal activation for the tone condition where the deviant had increased spectral content, the experiment revealed differential activations in the left posterior superior temporal gyrus and in the left supramarginal gyrus. Activations within the left posterior superior temporal gyrus were observed for the DEV condition with tones and for the STD and DEV conditions with syllables. Activation within the inferior part of the left supramarginal gyrus was only observed for the DEV condition with syllables. The analysis of the decreases and increases in the BOLD signal across the STD, DEV, and rest conditions suggests that the left posterior superior temporal gyrus is implicated in the preattentive change detection of acoustic changes in speech as well as nonspeech stimuli, whereas the left supramarginal gyrus is more specifically engaged in the detection of changes in phonological units.

Adult↗
PubMed1999

Usefulness of motor functional MRI correlated to cortical mapping in Rolandic low-grade astrocytomas.

The indications for surgery of slow growing tumours like low grade astrocytomas in eloquent areas are difficult. The timing and the benefit/risk ratio of the surgery must be evaluated, taking into account the potential post operative deficit. The purpose of this study was: a) to validate the data obtained with functional MRI (FMRI) by direct cortical stimulation in patients who are candidate for surgery; b) to demonstrate the usefulness of FMRI coupled with cortical brain mapping and 3D reconstructions of the surfaces of the brain in low grade astrocytoma. FMRI of the hand-motor cortex was performed in 8 patients with low grade astrocytomas. They subsequently underwent direct cortical mapping to correlate the results of FMRI and resective surgery sparing the functional area. In the 8 cases, the results of direct cortical mapping in the precentral region matched accurately those obtained from FMRI. When surgical resection of low grade astrocytoma in the motor areas is considered, FMRI used with intra-operative cortical mapping can help the surgeon to spare functional areas during tumour removal.

Adult↗
PubMed1999

Cortical intraoperative stimulation in brain tumors as a tool to evaluate spatial data from motor functional MRI.

RATIONALE AND OBJECTIVE: The purpose of this prospective, double-blind study was to correlate motor functional MRI (fMRI) with cortical brain mapping by intraoperative stimulation using 3D reconstructed images of the surface of the brain, and to validate the spatial data of fMRI in patients with brain tumors. METHODS: Fourteen patients with tumors of the rolandic region underwent functional MR mapping of the hand region and subsequently cortical mapping before tumor resection. Data obtained with fMRI and brain mapping were not known previously by the neurosurgeon and by the neuroradiologist, respectively (double-blind study). RESULTS: In each case, the results of direct cortical mapping matched those obtained with fMRI, both positively and negatively, although the extent of the functional activations was larger than the area required to elicit the corresponding movement during intraoperative brain mapping. CONCLUSION: fMRI can be used before surgery to assess motor functional area in patients with rolandic tumors. More studies are needed to validate during surgery the real extent of fMRI activations.

Adult↗
PubMed1999

Characterization of choline compounds with in vitro 1H magnetic resonance spectroscopy for the discrimination of primary brain tumors.

RATIONALE AND OBJECTIVES: The authors sought to compare 1H magnetic resonance spectroscopy (MRS) spectra from extracts of low-grade and high-grade gliomas, especially with respect to the signals of choline-containing compounds. METHODS: Perchloric acid extracts of six high-grade and six low-grade gliomas were analyzed by 1H MRS at 9.4 Tesla. RESULTS: The signals of glycerophosphocholine (GPC) at 3.23 ppm, phosphocholine (PC) at 3.22 ppm, and choline (Cho) at 3.21 ppm were identified in both types of tumors. The absolute concentrations of all Cho-containing compounds (GPC + PC + Cho) in high-grade and low-grade gliomas were significantly different. The relative contributions of each of the Cho-containing compounds to the total choline signal were also statistically different. For high-grade gliomas, the choline signal is composed of GPC, PC, and Cho in a well-balanced contribution, whereas in low-grade gliomas, the signal is largely due to GPC with a small involvement of PC and Cho. CONCLUSIONS: The differences in the concentration and the repartition of Cho-containing compounds seem to be a marker of high-grade gliomas. They could also help to discriminate between high- and low-grade gliomas in some difficult cases, especially if there is histologic uncertainty between anaplastic astrocytomas and low-grade oligodendrogliomas.

Adult↗
PubMed1999

Cerebral functional magnetic resonance imaging activation modulated by a single dose of the monoamine neurotransmission enhancers fluoxetine and fenozolone during hand sensorimotor tasks.

Fluoxetine inhibits the reuptake of serotonin, and dextroamphetamine enhances presynaptic release of monoamines. Although the excitatory effect of both noradrenaline and dopamine on motor behavior generally is accepted, the role of serotonin on motor output is under debate. In the current investigation, the authors evidenced a putative role of monoamines and, more specifically, of serotonin in the regulation of cerebral motor activity in healthy subjects. The effects on cerebral motor activity of a single dose of fluoxetine (20 mg), an inhibitor of serotonin reuptake, and fenozolone (20 mg/50 kg), an amphetamine-like drug, were assessed by functional magnetic resonance imaging. Subjects performed sensorimotor tasks with the right hand. Functional magnetic resonance imaging studies were performed in two sessions on two different days. The first session, with two scan experiments separated by 5 hours without any drug administration, served as time-effect control. A second, similar session but with drug administration after the first scan assessed drug effects. A large increase in evoked signal intensity occurred in the ipsilateral cerebellum, and a parallel, large reduction occurred in primary and secondary motor cortices (P < 10(-3)). These results are consistent with the known effects of habituation. Both drugs elicited comparable effects, that is, a more focused activation in the contralateral sensorimotor area, a greater involvement of posterior supplementary motor area, and a widespread decrease of bilateral cerebellar activation (P < 10(-3)). The authors demonstrated for the first time that cerebral motor activity can be modulated by a single dose of fluoxetine or fenozolone in healthy subjects. Drug effects demonstrated a direct or indirect involvement of monoamines and serotonin in the facilitation of cerebral motor activity.

Adult↗
PubMed1999

[Importance and limitations of the validation of functional MRI of motor function and language using preoperative cortical stimulation].

UNLABELLED: This chapter describes and discusses the value of the localization of functional areas obtained from functional MRI in brain tumor cases. Correlation method is cortical brain mapping by intraoperative stimulation. The experience reported here is focused on the study of motricity and language. METHODS: Twenty two patients with tumors of the rolandic region (n = 16) or in the temporal lobe (n = 6) underwent functional MR mapping and subsequently cortical mapping before tumor resection. The tasks chosen were a flexion and extension of the fingers or a naming task. We used 3D reconstructed images of the surface of the brain to assess intra and post operatively the functional MRI and stimulation data. RESULTS: For the motor correlation, in each case, the results of direct cortical mapping matched those obtained with functional MRI, both positively and negatively, although the extent of the functional activations was larger than the area required to elicit the corresponding movement during intraoperative brain mapping. For the language correlation and for the task chosen, only the results of the precentral areas matched those of functional MRI. CONCLUSIONS: Functional MRI can be used preoperatively to assess motor functional area in patients with rolandic tumors. More studies are needed to validate intraoperatively the language areas and the real extent of functional MRI activations. Finally, the observed discrepancy between functional MRI and cortical stimulation is likely due to the rather profound differences between both techniques, in terms of neurophysiology, practical applications and statistical analysis.

Adult↗
PubMed1998

Diffusion- and magnetisation transfer-weighted MRI in childhood moya-moya.

MRI in two children with moya-moya demonstrated low signal on T2-weighted images in the acute and subacute phases of ischaemia. Gradient-echo sequences, more sensitive to magnetic susceptibility, demonstrated these abnormalities better. Signal loss, due to temporary accumulation of iron, decreases progressively and disappears in the chronic stage of the disease. Diffusion-weighted MRI allows early detection of ischaemic lesions and can be used to monitor progressive spreading of the lesions. Magnetisation transfer maps provide sharp contrast, useful for demonstrating cortical atrophy.

Acute Disease↗
PubMed1998

Intracranial vascular involvement of brain pathologies and venous occlusions.

In this paper, the authors present the contribution of CT and MRI to the diagnosis of acute stroke caused by arterial or venous occlusion. The term "early" used in this context means within 6 h of the onset of symptoms. Signs of early ischemic edema are subtle and sometimes difficult to detect by CT or MRI. The purpose of this presentation is to familiarize the clinician and the radiologist with the subtle brain parenchymal changes seen within the first 6 h after onset of symptoms, in order to improve detection of early ischemic infarction and to improve patient care.

Acute Disease↗
PubMed1998

Magnetic resonance imaging in multiple sclerosis.

Conventional magnetic resonance imaging (MRI) techniques acquire signal mainly from differences in relaxation properties and density of free water protons. Thus, the sensitivity in depicting lesions is high but pathological specificity is poor. Efforts are being made to increase the diagnostic power of MRI; better correlation with the clinical presentation and the use of better MRI criteria have increased the specificity of the conventional T2 sequences. New sequences, such as fast spin echo, turbo spin echo (TSE) or those derived from inversion recovery (fluid attenuated inversion recovery), have improved the detection of lesions. Acute phase monitoring focuses on changes in disease activity (new, recurring, enlarging, gadolinium-enhancing lesions) and chronic phase monitoring allows appreciation of the burden of the disease. However, MRI is considered as a secondary outcome measure in phase III trials because of insufficient correlation with the clinical disability. There is a continuing search for techniques that correlate better with clinical measures of the disease, such as the quantification of 'black holes' on T1-weighted images or the cerebral and spinal atrophy. The basic aspects of the pathological lesions in multiple sclerosis such as oedema, membrane disruption, demyelination, gliosis, cellular infiltration and axonal loss, can be studied more precisely by the new magnetic resonance techniques, which should better describe the actual clinical impact of the destructive process. In the past year the importance of axonal loss has simultaneously been confirmed by magnetic resonance spectroscopy and pathological findings. However, magnetization transfer imaging, magnetic resonance diffusion imaging and functional MRI are under intensive investigation for a better analysis of these different factors that impact on the reversibility of the patients disability.

Diffusion↗
PubMed1998

Diffusion and perfusion MRI, measurements of acute stroke events and outcome: present practice and future hope.

The morphological, metabolic and functional changes of brain ischaemia can be studied using various MRI methods. These are readily available should the early visualisation of affected territories be needed. Morphological changes include the depiction of oedema on T1- and T2-weighted images, and metabolic changes are reflected on magnetic resonance spectroscopy. Functional changes reflect haemodynamic failure seen on diffusion- and perfusion-weighted imaging. Modelling of behaviour of T2 and diffusion changes could predict the histological outcome of affected tissue regarding cell recovery on necrosis. In addition, the combination of diffusion and perfusion MRI offers a potential prognostic value.

Acute Disease↗
PubMed1998

Functional magnetic resonance imaging in multiple sclerosis.

Functional magnetic resonance imaging (fMRI) is a method that combines high anatomical spatial resolution with the ability to localise function. Visual and motor systems are among those that have received most attention. Yet the clinical application is still limited. Recently, some investigators applied fMRI to study patients with multiple sclerosis. Patients with partial motor weakness disclosed a larger area of cortical activation bilaterally by contrast with healthy volunteers when using the affected arm, whereas patients with optical neuritis disclosed a smaller area of activation, when stimulating the affected eye. These results show that different systems might react heterogeneously.

Brain↗
PubMed1998

[Presurgical evaluation of cerebral tumors with functional MRI].

PURPOSE: To evaluate the capabilities and the limitations of motor functional magnetic resonance imaging (FMRI) in the presurgical planning of the cerebral tumors located in or near the motor homunculus and to correlate each type of activation with the histologic characteristics of each tumor. MATERIALS AND METHODS: FMRI was performed in 17 patients (14 adults and 3 children), without motor deficit, presenting with various intra cerebral tumors. Three FMRI activation paradigms were used, controlateral to the lesion: ballistic opposition of the fingers, flexion-extension of the foot and click of the tongue. Four patients, without motor deficit, with cerebral tumors far from the motor homunculus were used as control group to look for non specific activations. In all cases, the histopathology of the tumor was known accurately. RESULTS: In 11 patients with infiltrating tumors, the activated areas were clearly displaced. They were often intratumoral and scattered in correlation with the degree of infiltration. Two patients with non infiltrating tumors (meningioma) showed extratumoral shift of the activated areas. Four patients presenting cerebral tumors far from the homunculus motor did not show intratumoral activation. The supplementary motor area and the ipsilateral primary motor cortex were also sometimes activated during the motor tasks. The task of the tongue was often artifacted, probably because of the head motion. CONCLUSIONS: These preliminary results suggest that the histopathologic characteristics of a tumor and especially its microscopic structure plays a role, with others factors, on the motor functional area organization. In a small number of cases, the data obtained from the FMRI could be used intraoperatively, with a neuronavigation system.

Adolescent↗
PubMed1998

[MRI visualization of multiple sclerosis lesions].

Magnetic resonance imaging represents voxels (volume elements) of the body placed in a magnet, by their magnetization determined under various acquisition conditions weighting the contrast of the image by the density of free water protons and their relaxation times T1 and T2. Thus, the sensitivity in depicting lesions is high but pathological specificity is poor. Efforts are made to increase the diagnosis powerfulness of M.R.I. in multiple sclerosis: a careful correlation with the clinical presentation and the use of better M.R.I. criteria increase the specificity of the conventional T2 sequences. New sequences such as fast spin echo (F.S.E.), turbo spin echo (T.S.E.) or derived from inversion recovery (F.L.A.I.R.: fluid attenuated inversion recovery) improve the detection of lesions. Under specific conditions M.R.I. can be used to monitor the evolution of M.S. Acute phase monitoring focuses on changes in disease activity, new, recurring, enlarging, gadolinium (Gd) enhancing lesions, and chronic phase monitoring appreciate the burden of the disease. However M.R.I. is always considered as a secondary outcome in the phase III trials because insufficient correlations with the clinical disability. In the neurological daily practice conventional M.R.I. is of poor interest in the follow up of individual M.S. patients considering the weakness of prognosis value and the problems in the measurement of the lesions load which is emphasized in the methodology of the clinical trials. Nevertheless, there is a continuing search for techniques which correlate better with clinical measures of the disease such as the quantification of "black holes" on T1 w images or the cerebral and spinal atrophy. New techniques allow to weight the signal by the movement (diffusion imaging), by the complexity of the molecular architecture (magnetization transfer imaging), by the chemical shift (chemical shift imaging) or by the local status of oxygenation (functional M.R.I.). The basic aspects of the pathological lesions in M.S., edema, membrane disruption, demyelination, gliosis, cellular infiltration and axonal loss can be studied more precisely by these new M.R. techniques which should better describe the actual clinical impact of the destructive process. In the last year the importance of axonal loss has simultaneously been confirmed by M. R. spectroscopy and pathological findings. However, magnetization transfer imaging, M.R. diffusion imaging and functional M.R.I. are intensively under investigation for a better analysis of these different factors conditioning the reversibility of the patient disability.

Contrast Media↗
PubMed1997

Magnetization transfer with echo planar imaging.

The aim of magnetization transfer is to saturate the protons of the macromolecule pool with a radiofrequency (RF) pulse leading to differences in free water pool signal. Magnetization transfer (MT) contrast is difficult to achieve with the echo planar imaging (EPI) technique, although its short acquisition time would be most beneficial. Indeed, the RF saturation pulses can only be applied once before sampling the whole k-space in a single-short sequence. A possible solution to improve the sensitivity of EPI to magnetization transfer consists in applying a train of several saturation RF pulses before image acquisition. The different parameters of a RF pulse train and their influence on the MT rate have been tested to optimize an EPI clinical sequence. Our experimental procedure makes it possible to obtain a MT map in about 1 second. The technique is evaluated by multiple sclerosis lesion characterization.

Adult↗