Biomedical subjects

R H Lazeron

Publications and source records attributed to R H Lazeron.

12 recordsLinked to original sources

PubMed2001

Magnetization transfer histogram parameters reflect all dimensions of MS pathology, including atrophy.

INTRODUCTION: Magnetization transfer ratio (MTR) histogram analysis can be used as a method for quantifying overall disease burden in MS. We studied correlations between MTR histogram and clinical parameters in MS subgroups. Contrary to earlier studies we placed special emphasis on the lower MTR range, to explore the effect of partial volume averaging effects with CSF. METHODS: Seventy-nine patients with MS [26 primary progressive (PP), and 53 'relapse-onset', including 26 secondary progressive (SP)], and 23 healthy individuals were studied. MR imaging included 3 mm 2D gradient-echo images with and without an off-resonance MT pulse. According to the visually determined cut-off, histogram parameters were classified as parenchymal or CSF-related variables. Clinical measurements included the Expanded Disability Status Scale (EDSS) as a measure of global impairment/disability and the Paced Auditory Serial Addition Test (PASAT) as a measure of cognition. RESULTS: SP MS patients differed from the other subgroups on many MTR variables, originating from both the lower and the higher MTR range. CSF-related low MTRs were clearly over-represented in SP patients, and showed a significant distinction between the SP and PP MS group. In the total group, as well as in the relapse-onset patients, significant correlations were found between MTR parameters and clinical parameters. No associations were found in the PP group. CONCLUSION: This explorative study suggests that MTR histogram analysis can distinguish between MS patients and controls, and best identifies the SP phenotype, partly as a result of increased CSF volume (atrophy). In addition, we show that MTR histogram analysis gives information about the level of impairment and disability in patients with a 'relapse-onset' course of MS, and therefore provides a useful tool to monitor the evolution of the disease in these patients.

Adult↗

PubMed2001

Concurrent validity of the MS Functional Composite using MRI as a biological disease marker.

INTRODUCTION: The MS Functional Composite (MSFC), a recently developed outcome measure for MS clinical trials measuring three dimensions (ambulation/leg function, arm/hand function, and cognition), was applied to 134 patients with MS to study the concurrent validity, using MRI measurements as a biological disease marker. The results were compared to correlations between the traditionally applied Expanded Disability Status Scale (EDSS) and MRI measurements in the same patients. METHODS: The assessments of MSFC and EDSS were performed in combination with brain MRI. MRI consisted of T1- and T2-weighted images, from which the hypointense and hyperintense lesion loads were quantified. RESULTS: The MSFC score ranged from -2.54 to 0.99. The median EDSS was 3.0 (interquartile range [IQR] 1.5 to 6.0). The median T2-weighted lesion load was 8.4 cm(3) (IQR 3.4 to 19.8) and the median T1-weighted lesion load was 1.1 cm(3) (IQR 0.3 to 3.2). Correlations between the MSFC and both T1 (-0.24) and T2 (-0.25) lesion loads were demonstrated, but not between the EDSS and both MRI parameters. Significant correlations between MSFC components and T1 and T2 lesion loads existed for cognitive function and arm/hand function, but not for ambulation. If relapse-onset patients (relapsing-remitting and secondary progressive) were combined, the correlation between MSFC and MRI parameters became stronger for both T1 (-0.37) and T2 lesion loads (-0.35). CONCLUSIONS: The authors present the concurrent validity of the MSFC with a biological disease marker by showing correlations with MRI. Specifically, they demonstrate significant correlations with cognition and arm/hand function assessments, domains that are not well represented in the EDSS.

Adolescent↗

PubMed2001

Parahippocampal activation during successful recognition of words: a self-paced event-related fMRI study.

In this study, we investigated retrieval from verbal episodic memory using a self-paced event-related fMRI paradigm, similar to the designs typically used in behavioral studies of memory function. We tested the hypothesis that the medial temporal lobe (MTL) is involved in the actual recovery of verbal information (retrieval success) rather than in the attempt to retrieve information (retrieval attempt). To this end, we used a verbal recognition task, distinguishing correctly recognized words, correctly rejected words, and a low-level baseline condition. Directly contrasting correct recognition with correct rejection of words, we found activation in the left fusiform/parahippocampal gyrus, indicating that this region has a distinct role in the successful retrieval of verbal information. Furthermore, our results were in agreement with those of previous imaging studies that compared a fixed-paced verbal recognition task to a baseline condition, showing activation in bilateral inferior frontal cortex, left dorsolateral prefrontal cortex, left anterior insular cortex, and anterior cingulate. This demonstrates the applicability of a self-paced event-related design within imaging studies of memory function.

Adult↗

PubMed2001

The brief repeatable battery of neuropsychological tests: normative values allow application in multiple sclerosis clinical practice.

The Brief Repeatable Battery of Neuropsychological Tests (BRB-N) is a sensitive measure of cognitive impairment in multiple sclerosis (MS) patients. It consists of the Selective Reminding Test, the 10/36 Spatial Recall Test, the Symbol Digit Modalities Test, the Paced Auditory Serial Addition Test and the Word List Generation Test. We administered one of two parallel versions of the test battery to 140 healthy subjects to produce normative values for both versions. As expected, test scores were influenced by certain variables like age, gender and education. Although constructed as two equivalent versions, for some tests the two versions showed significant differences in test scores, which could not be explained by differences in these variables.

Attention↗

PubMed2000

MS functional composite: relation to disease phenotype and disability strata.

OBJECTIVE: The MS Functional Composite (MSFC), a recently developed outcome measure for clinical trials, was applied to 240 patients with MS to explore its utility in different subgroups of MS and for comparison with the Expanded Disability Status Scale (EDSS). METHOD: Three clinical dimensions were examined: arm/hand function, leg function/ambulation, and cognition. Predictions of relative scores on the MSFC and its components in three major MS phenotypes (relapsing-remitting, primary progressive, and secondary progressive) and three strata of disability were developed and tested. Also, correlations with EDSS were calculated and the effect of an external reference population was assessed. RESULTS: Mean MSFC score was positive in the relapsing-remitting (0.4) and mildly disabled (0.4) groups and negative in the secondary progressive (-0.3), primary progressive (-0.4), and moderately (-0.07) and severely disabled (-1.0) groups. The correlation between EDSS and MSFC was strong (-0.68). EDSS correlated strongly with ambulation in secondary and primary progressive patients and severely disabled patients, moderately with arm/hand function for all analyzed groups, and not at all with cognition. Comparison with an external reference population showed changes in MSFC- and Z-scores, but did not result in altered differences between the subgroups. CONCLUSION: Our prospective study in subgroups of MS confirmed and extended the construct validity of the MSFC. The MSFC also showed good concurrent validity with the EDSS, and includes information about cognition.

Adolescent↗

PubMed2000

Magnetization transfer ratio of the spinal cord in multiple sclerosis: relationship to atrophy and neurologic disability.

The authors compare the spinal cord magnetization transfer ratio (MTR) of multiple sclerosis (MS) patients to healthy volunteers, relate MTR to spinal cord atrophy, and relate these and other magnetic resonance (MR) imaging parameters to disability. Sixty-five patients with MS (14 relapsing remitting [RR], 34 secondary progressive [SP], and 17 primary progressive [PP] MS), and 9 healthy volunteers were studied using MR at 1.0 T. Disability of the patients was assessed using the expanded disability status scale (EDSS). Magnetic resonance parameters were upper spinal cord MTR, number of focal spinal lesions, presence of diffuse abnormalities, and spinal cord cross-sectional area (CSA). Correlations were assessed using Spearman's rank correlation coefficient (r). Magnetization transfer ratio was higher in the controls (median, 33%; range, 30%-38%) than in patients with MS (median, 30%; range, 16-36; p < 0.05). In patients with MS EDSS correlated with spinal cord MTR, albeit weakly (r = -0.25, p < 0.05). Correlation between EDSS and spinal cord CSA was better (SRCC = -0.40, p < 0.01). No correlation was found between MTR and CSA (r = 0.1, p = 0.4). Combining MTR with spinal cord CSA improved correlation with EDSS (r = -0.46, p < 0.001), suggesting an independent correlation between disability and these 2 MR parameters. Expanded disability status scale scores were higher in patients who had diffuse spinal cord abnormality regardless of focal lesions (median, 6; range, 1.5-7.5) than in patients without diffuse abnormalities (median, 3.5; range, 0-8; p < 0.01). CSA was lower in patients with diffuse spinal cord abnormality (median, 62; range, 46-89 mm2) than in patients without diffuse abnormalities (median, 73; range, 47-89 mm2; p < 0.01). MTR was slightly lower in patients with diffuse spinal cord abnormalities (median, 29; range, 21%-33%) than in patients without diffuse abnormalities (median, 31; range, 16-36; t-test, p < 0.05).

Adult↗

PubMed2000

Neuropsychological impairment in multiple sclerosis patients: the role of (juxta)cortical lesion on FLAIR.

In this study we evaluated the correlation between neuropsychological impairment (measured with the Brief Repeatable Battery Neuropsychological Tests) and (juxta)cortical lesions detected with FLAIR and the relative sensitivity of the FLAIR sequence compared to spin-echo MRI sequences in detecting (juxta)cortical MS lesions. A total of 39 patients with definite MS were evaluated by MRI with a conventional and fast spin echo sequence and fast FLAIR sequence, and neuropsychological tests of the Brief Repeatable Battery Neuropsychological tests were performed. The Z-score of all subtests were used to calculate a Cognitive Impairment Index. The results show that a high number of (juxta)cortical lesions is detected with thin slice FLAIR (30% of all lesions seen). This percentage was not superior to spin-echo, reflecting the thin slice thickness (3 mm) we used. The lesions detected with FLAIR were to a certain degree different ones than the lesions detected with the other techniques. While the number of non-cortical lesions correlated with the expanded disability status scale (r=0.32, P=0.045), the number of (juxta)cortical lesions detected with the FLAIR showed a correlation (r=0.34, P=0.035) with the Cognitive Impairment Index. Our study underlines the high number of (juxta)cortical lesions in MS and the value of thin slice FLAIR sequence to detect such lesions with MRI. It also stresses the importance of (juxta)cortical lesions on determining neuropsychological impairment. Multiple Sclerosis (2000) 6 280 - 285

Adult↗

PubMed2000

Visualizing brain activation during planning: the tower of London test adapted for functional MR imaging.

BACKGROUND AND PURPOSE: Recent positron emission tomography and single-photon emission CT studies using the Tower of London test have shown that brain activation during planning activities primarily resides in the prefrontal cortex. In this study, we adapted the Tower of London test for functional MR imaging. METHODS: For use with functional MR imaging, a block design of the test was created, in which planning stages were contrasted with counting of colored balls. For nine healthy participants, multisection echo-planar functional MR imaging was performed to assess brain activation based on changes in blood oxygen level. Activation maps for individual participants and a group average map were created. RESULTS: In the group average map, activation in the dorsolateral prefrontal cortex, the anterior part of the cingulate cortex, the cuneus and precuneus, the supramarginal and angular gyrus in the parietal lobe, and the frontal opercular area of the insula was seen. These findings are in agreement with grouped data of previous positron emission tomography results. Functional MR imaging enabled us to investigate brain activation during planning activities with high spatial (and temporal) resolution in individual patients, showing that the dorsolateral prefrontal cortex was activated in all participants studied. CONCLUSION: Presented is a working functional MR imaging version of the planning task. The high sensitivity of functional MR imaging may allow the use of this test for patients with possible (pre)frontal disorders.

Adult↗

PubMed1998

Magnetization transfer contrast (MTC) and long repetition time spin-echo MR imaging in multiple sclerosis.

PURPOSE: To study whether application of magnetization transfer contrast (MTC) improves visibility and detection of multiple sclerosis (MS) lesions on long repetition time (TR) conventional spin-echo (CSE) or fast spin-echo (FSE) magnetic resonance (MR) imaging. MATERIAL AND METHODS: In 20 patients and 5 controls, MR images were obtained using long repetition time CSE and FSE sequences with and without MTC. Signal-to-noise ratios of normal appearing white matter (NAWM) and selected lesions, and contrast-to-noise ratios between lesions and NAWM, were calculated. Lesions were counted and total lesion volume was measured in a blinded fashion for each sequence. RESULTS: In controls, MT effect in white matter (16.3% vs. 12.2%) was higher for CSE than for FSE (p < 0.01). Application of MTC to either CSE or FSE resulted in a significantly lower decrease in signal intensity of NAWM in patients compared to white matter in controls (p < 0.01). Furthermore, in patients signal intensity of lesions was less decreased than signal intensity of NAWM (p < 0.01). Compared to sequences without MTC, contrast-to-noise ratios were significantly higher on both CSE (10.9%) and FSE (6.3%) when MTC was applied (p < 0.01). Despite better visibility, the number of lesions detected on either sequences did not increase when MTC was applied. For CSE with MTC, we found an almost equal number of lesions and for FSE with MTC, we found even less lesions (p < 0.01). Total lesion volume did not change significantly when MTC was applied. CONCLUSION: Although contrast between lesions and NAWM improved when magnetization transfer contrast was applied, this did not increase detection of MS lesions on either CSE or FSE MR imaging.

Adult↗

PubMed1998

Visual activation patterns in patients with optic neuritis: an fMRI pilot study.

We studied the use of functional MRI (fMRI) with visual stimulation in nine patients with unilateral optic neuritis. Eight healthy subjects served as controls. Patients showed reduced activation upon stimulation of the affected eye, on average 33% (range 0 to 156%) of the average monocular activation in the control group. Decreased activation was also seen for the unaffected eye (61% of control values, range 3 to 133%). We conclude that fMRI with visual stimulation is feasible in patients with optic neuritis and deserves future study.

Adult↗

PubMed1996

Gravitational artefact in frequency spectra of movement acceleration: implications for actigraphy in young and elderly subjects.

Actigraphy, the long-term assessment of wrist movements by means of a small solid-state recorder, is widely used in a variety of human research fields, among which sheep, circadian rhythms and aging. Actigraphs assess movement with the use of accelerometers, which sense accelerations resulting from muscle force as well as accelerations due to changes in the position of the sensor in the gravitational field. In the present paper a method is described to minimise gravitational artefact in movement assessment by calculating the instantaneous acceleration vector from 3 perpendicular acceleration signals. It is shown that the power spectra of single axis acceleration signals are dominated by low-frequency components (+/- 0.25 Hz) due to gravitational artefact. Spectra of the instantaneous acceleration vector indicate that 'true' movement accelerations resulting from muscle force are present in a much wider range: from 0.25 to 11 Hz. Wrist accelerations in elderly subjects were found to be of lower amplitude and frequency as compared to young subjects. It is furthermore shown that a bandpass filter of 0.25 to 2 or 3 Hz, as has been used in commercially available actigraphs, is far from optional, and may even result in a positive bias for movement detection in the elderly. This bias may underly contradictory findings in actigraphic studies on human aging. When a bandpass filter of 0.5-11 Hz is applied to a single-axis acceleration signal, the influence of gravitational artefact and bias are minimized, and the age-related decline in activity is properly detected.

Acceleration↗

PubMedDate not supplied

Functional MR imaging in Alzheimer's disease during memory encoding.

BACKGROUND AND PURPOSE: We applied functional MR imaging with a learning task in healthy elderly volunteers and in patients with Alzheimer's disease to study brain activation during memory performance. The purpose was to determine the feasibility of functional MR imaging during a learning task in healthy elderly volunteers and in patients with Alzheimer's disease and to test our hypothesis that brain activation is decreased in the medial temporal lobe (MTL) memory system in patients with Alzheimer's disease compared with control volunteers. METHODS: In 12 patients with mild to moderate forms of Alzheimer's disease and 10 elderly control volunteers, activation of the MTL memory system was studied. We used two learning tasks that required the encoding of new information into memory. After the functional MR imaging experiment, participants were tested for recognition of the encoded objects. RESULTS: In the elderly control volunteers, activation during memory encoding was observed in medial and lateral temporal lobe structures (fusiform, parietal and occipital parts, and hippocampal formation) and in the frontal cortex, as reported previously in studies of young control volunteers. Focusing on the MTL, we observed that activation was significantly decreased in patients with Alzheimer's disease compared with control volunteers in the left hippocampus and parahippocampal gyrus bilaterally during the first encoding task but not during the second (P < .05, uncorrected). CONCLUSION: Functional MR imaging with a learning task seems feasible in elderly volunteers and in patients with Alzheimer's disease. The measured functional signal decrease in MTL areas warrants further exploration of the (early) diagnostic usefulness of functional MR imaging in cases of Alzheimer's disease and other dementias.

Aged↗