Biomedical subjects

Norbert Schuff

Publications and source records attributed to Norbert Schuff.

31 records · Page 2Linked to original sources

PubMed2004

Right and left medial orbitofrontal volumes show an opposite relationship to agreeableness in FTD.

Recent investigations of the neuroanatomy of complex social behaviors suggest that the underlying brain circuits involve multiple cortical and subcortical structures. The neuroanatomic origins of agreeableness have not yet been clearly elucidated. However, frontotemporal dementia (FTD) patients can evidence dramatic alterations in agreeableness arising from frontal and temporal lobe damage. Based on previous research, we hypothesized that agreeableness would be negatively correlated with left medial orbitofrontal cortex size and positively correlated with right amygdala volume. First-degree relatives of 27 FTD patients (diagnosed according to the Lund-Manchester criteria) were asked to fill out the NEO-Five Factor Inventory to assess the patients' current level of agreeableness, a construct comprised of the facets trust, straightforwardness, altruism, compliance, modesty, and tender-mindedness. These patients underwent T(1)-weighted MRI imaging, and gray matter volumes for right and left orbitofrontal lobes and amygdalas were derived via segmentation and region of interest tracing, normalizing for total intracranial volume. Regression analysis revealed that 38% of the variance in the NEO agreeableness score was predicted by a model in which right orbitofrontal volume (beta = 0.731) was positively correlated with agreeableness, and left orbitofrontal lobe volume (beta = -0.638) was negatively correlated with agreeableness (p < 0.01). Contrary to our hypothesis, amygdala volume did not significantly predict agreeableness. This finding partly replicates a previous study that used a different measure of social functioning, the Interpersonal Adjective Scale, to delineate a left frontal-right amygdala circuit for agreeableness. These data support the hypothesis that regulation of agreeableness arises from a balanced, mutually inhibitory circuit involving both hemispheres.

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PubMed2003

Cortisol levels are positively correlated with hippocampal N-acetylaspartate.

BACKGROUND: This study examined the relationship of hypothalamic-pituitary-adrenal measures and hippocampal N-acetylaspartate (NAA) in posttraumatic stress disorder (PTSD) patients and control subjects. METHODS: Eleven patients with combat-related PTSD and 11 control subjects were evaluated with magnetic resonance spectroscopy as well as by morning salivary cortisol samples before and after administration of low-dose dexamethasone (.5 mg). RESULTS: Left hippocampal NAA was strongly associated with both pre-dexamethasone cortisol levels (n = 22, r =.53, p =.013) and post-dexamethasone cortisol levels (n = 22, r =.63, p =.002). After accounting for clinical symptom severity and hippocampal volume, cortisol levels accounted for 21.9% of the variance (F = 5.6, p =.004) in left hippocampal NAA and 12.6% of the variance (F = 3.2, p =.035) in right hippocampal NAA. CONCLUSIONS: This study shows a positive relationship between cortisol levels and hippocampal NAA in subjects without hypercortisolemia. Within the range of values seen in our subjects, cortisol may have a trophic effect on the hippocampus.

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PubMed2003

Cinguloparietal atrophy distinguishes Alzheimer disease from semantic dementia.

BACKGROUND: Progressive brain atrophy is associated with Alzheimer disease (AD) and other dementias. Regional differences in brain atrophy may reflect clinical features of disease. OBJECTIVE: To identify regions of cerebral atrophy that are associated with AD vs other dementias. SETTING: University hospital dementia clinic. PARTICIPANTS: Eleven patients with AD and 11 with semantic dementia (SD), matched for age, sex, education, and degree of overall cognitive impairment and 15 normal controls. METHODS: Voxel-based morphometry was used to compare patterns of gray matter loss, measured on T1-weighted magnetic resonance images, between patients with AD or SD, a subtype of frontotemporal lobar degeneration, and controls. Statistically significant differences in regional gray matter concentration, after multiple-comparisons correction, between groups of subjects were identified. RESULTS: Patients with AD were more impaired than those with SD on tests of visuospatial function and on simple calculations. Consistent with these neuropsychological deficits, the most significant area of atrophy in the AD group was the left parietal cortex vs controls (z = 5.0; P =.04). Compared with SD, AD was associated with more atrophy in the left parietal lobe (z = 5.6; P =.04) and bilaterally in the posterior cingulate/precuneus (z = 5.1; P =.04). A discriminant function analysis demonstrated that the degree of atrophy of right posterior cingulate, left parietal lobe, right amygdala, and right anterior temporal lobe structures correctly classified 96% of the patients. CONCLUSION: Alzheimer disease is associated with a specific pattern of cortical atrophy compared with SD.

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PubMed2003

Improved perfusion-weighted MRI by a novel double inversion with proximal labeling of both tagged and control acquisitions.

A novel pulsed arterial spin labeling (PASL) technique for multislice perfusion-weighted imaging is proposed that compensates for magnetization transfer (MT) effects without sacrificing tag efficiency, and balances transient magnetic field effects (eddy currents) induced by pulsed field gradients. Improved compensation for MT is demonstrated using a phantom. Improvement in perfusion measurement was compared to other PASL techniques by acquiring perfusion images from 13 healthy volunteers (nine women and four men; age range 29-64 years; mean age 45 +/- 14 years) and second-order image texture analysis. The main improvements with the new method were significantly higher image contrast, higher mean signal intensity, and better signal uniformity across slices. In conclusion, this new PASL method should provide improved accuracy in measuring brain perfusion.

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PubMed2003

Magnetic resonance spectroscopic imaging reconstruction with deformable shape-intensity models.

A new method, based on a deformable shape-intensity model (DSM), was developed to improve the signal-to-noise ratio (SNR) of multidimensional magnetic resonance spectroscopic imaging (MRSI) data sets without affecting spectral lineshapes and linewidths. Improvements with DSM, compared to digital filters using conventional signal apodization, were demonstrated on both simulated and experimental in vivo (1)H MRS images from 22 cognitively normal (CN) elderly subjects and 25 patients with Alzheimer's disease (AD). Simulated MRSI data showed that DSM achieved superior noise suppression compared to a matched apodization filter. Experimental MRSI data showed that SNR could be increased 2.1-fold with DSM without distorting spectral resolution, thus maintaining all spectral features of the raw, unfiltered data. In conclusion, DSM should be used to achieve high SNR in reconstructing MRSI data.

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PubMed2003

Evidence of neuronal injury outside the medial temporal lobe in temporal lobe epilepsy: N-acetylaspartate concentration reductions detected with multisection proton MR spectroscopic imaging--initial experience.

PURPOSE: To determine whether magnetic resonance (MR) spectroscopic imaging reveals metabolic changes, especially decreased N-acetylaspartate (NAA) concentrations outside the medial temporal lobe in patients with mesial temporal lobe epilepsy (TLE), consistent with neuropathologic findings of extratemporal neuronal impairment. MATERIALS AND METHODS: Eleven patients with mesial TLE and 13 control subjects were examined with multisection MR spectroscopic imaging. Three MR spectroscopic imaging sections were acquired. Thirteen brain regions in each hemisphere and the midbrain were analyzed in each patient, and the NAA to creatine-phosphocreatine (Cr) plus choline-containing compounds (Ch) (NAA/[Cr + Ch]) ratios were determined. In addition, hemispheric and whole-brain values were calculated and statistically analyzed. RESULTS: The NAA/(Cr + Ch) ratio in the ipsilateral hippocampus was significantly reduced, compared with that in the contralateral hippocampus (P <.002) and compared with that in control subjects (P <.03), confirming findings in previous studies. In patients, whole-brain NAA/(Cr + Ch) ratio outside the hippocampus was significantly lower than that in control subjects (P <.002). For the ipsilateral hemisphere in patients, NAA/(Cr + Ch) ratio was significantly lower than that in control subjects (P <.0002). Comparisons between individual brain regions revealed trends toward lower NAA/(Cr + Ch) ratios in many areas of the ipsilateral and, to a lesser extent, the contralateral hemisphere outside the hippocampus and temporal lobe, suggesting diffuse impairment. CONCLUSION: Results suggest that repeated seizure activity damages neurons outside of the seizure focus.

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PubMed2002

Comparison of automated and manual MRI volumetry of hippocampus in normal aging and dementia.

PURPOSE: To determine whether automatic and manual measurements of hippocampal volume differences on MRI between normal aging, cognitive impairment (CI), and Alzheimer's disease (AD) yield similar results. MATERIALS AND METHODS: Reliability was determined for an automatic and a manual method on nine volunteers (22-83 years old) who underwent MRI twice in 1 day. Hippocampal volumes of 20 cognitively normal subjects (mean age 74.0 +/- 6.2 years) and age-matched patients (20 CI and 20 AD) were compared. RESULTS: The intraclass correlation for automatic calculations of hippocampal volume was 0.94; for manual tracing it was 0.99. Volume differences between cognitively normal, CI, and AD subjects from the automatic and manual methods were similar. CONCLUSION: Because the automatic calculations were faster and less susceptible to rater bias than manual tracing, this automated method is expected to be very useful for analyzing hippocampal changes in studies of aging and dementia.

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PubMed2002

Quantitative 1H magnetic resonance spectroscopy and MRI of Parkinson's disease.

Magnetic resonance imaging (MRI) and (1)H magnetic resonance spectroscopy (MRS) of the substantia nigra, basal ganglia, and cerebral cortex were performed on 10 patients with Parkinson's disease (PD) and 13 age-matched, healthy control subjects. Compared to controls, PD patients had approximately 24% lower creatine in the region of the substantia nigra and smaller volumes of the putamen (11%), globus pallidus (16%), and prefrontal cortex (6%; all P < 0.05). No other significant between-group differences were found in nine regions examined. Thus, quantitative MRI may show regional neurodegenerative changes outside the substantia nigra in PD but PD-linked extranigral metabolic abnormalities, if they exist, may be difficult to detect with current (1)H MRS methods. In additional, exploratory tests, volumes of the caudate (r = -0.56), putamen (r = -0.66), and globus pallidus (r = -0.60; all P < 0.05) were negatively correlated with the volume of the substantia nigra pars compacta in controls. In PD these correlations did not hold. Instead, pallidal volume in PD was positively correlated with compacta volume (r = 0.64; P < 0.05). This relationship suggests that basal ganglia volumes may be influenced by dopaminergic innervation from the substantia nigra in normal and PD subjects.

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PubMed2002

Emotion comprehension in the temporal variant of frontotemporal dementia.

Frontotemporal dementia (FTD) is a neurodegenerative disease characterized by behavioural disorders that suggest abnormalities of emotional processing. Patients with the temporal variant of FTD (tvFTD) are particularly at risk for developing deficits in emotional processing secondary to atrophy in the amygdala, anterior temporal cortex (ATC) and orbital frontal cortex (OFC), structures that are components of the brain's emotional processing systems. In addition, previous studies have suggested that predominantly right, as opposed to left temporal atrophy is more likely to be associated with behavioural and emotional impairments in tvFTD. However, emotional processing has never been assessed directly in this group. We examined one aspect of emotional processing, namely the comprehension of facial expressions of emotion (emotional comprehension) in nine individuals with tvFTD, and correlated performance on this measure with atrophy (as measured from T(1)-weighted MRI scans by region of interest analysis) in the amygdala, ATC and OFC. Compared with age-matched controls, the tvFTD group was impaired in emotional comprehension, with more severe impairment for emotions with negative valence, including sadness, anger and fear, than for happiness. Emotional comprehension was correlated with atrophy in the right amygdala and the right OFC, and not with atrophy in other structures. When individual profiles of amygdala atrophy were examined across patients and compared with control values, right amygdala atrophy was always accompanied by left amygdala atrophy, whereas patients with volume loss in the left amygdala could have normal or decreased right amygdala volumes. Thus, emotional comprehension appeared to be most impaired when bilateral amygdala atrophy was present, and was not associated with the degree of left amygdala atrophy. Our data indicate that tvFTD is associated with impairments in emotional processing that may underlie some behavioural problems in this disorder, and that the emergence of such deficits depends on the specific pattern of anatomical injury. These results have implications both for the clinical presentation in tvFTD patients and for the study of the neuroanatomical basis of emotion.

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PubMedDate not supplied

Effects of Alzheimer disease on fronto-parietal brain N-acetyl aspartate and myo-inositol using magnetic resonance spectroscopic imaging.

Previous magnetic resonance (MR) spectroscopy studies of Alzheimer disease (AD) reporting reduced N-acetyl aspartate (NAA) and increased myo-Inositol (mI) used single voxel techniques, which have limited ability to assess the regional distribution of the metabolite abnormalities. The objective of this study was to determine the regional distribution of NAA and mI alterations in AD by using MR spectroscopic imaging. Fourteen patients with AD and 22 cognitively normal elderly were studied using structural MR imaging and MR spectroscopic imaging. Changes of NAA, mI, and various metabolite ratios were measured in frontal and parietal lobe gray matter (GM) and white matter. This study found: (1) when compared with cognitively normal subjects, AD patients had increased mI and mI/creatine (Cr) ratios primarily in parietal lobe GM, whereas frontal lobe GM and white matter were spared; (2) in the same region where mI was increased, AD patients had also decreased NAA and NAA/Cr ratios, replicating previous findings; (3) however, increased mI or mI/Cr ratios did not correlate with decreased NAA or NAA/Cr ratios; and (4) using mI/Cr and NAA/Cr together improved sensitivity and specificity to AD from control as compared with NAA/Cr alone. In conclusion, decreased NAA and increased mI in AD are primarily localized in parietal lobe GM regions. However, the NAA and mI changes are not correlated with each other, suggesting that they represent different processes that might help staging of AD.

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PubMedDate not supplied

Patterns of cerebral atrophy in primary progressive aphasia.

The authors illustrate the spectrum of clinical and imaging patterns in primary progressive aphasia (PPA), a syndrome of slowly progressive speech and language impairment occurring with neurodegenerative disease. Although PPA presents with relatively isolated impairment in language, many patients progress to global cognitive or behavioral dysfunction. The syndrome may be associated with frontotemporal dementia (FTD)- or Alzheimer disease (AD)-type changes. Authors describe the clinical presentation in three cases of PPA and analyze the pattern of cerebral atrophy in each case with voxel-based morphometry. Two patients presented with nonfluent progressive aphasia. Subtle differences in the clinical features were suggestive of FTD in one case and AD in the other. Neuroimaging revealed a predominance of frontal atrophy in the first case and temporo-parietal atrophy in the second. The third case presented with the syndrome of semantic dementia and showed the typical behavioral problems associated with FTD and a pattern of left-greater-than-right temporal atrophy. Different clinical syndromes in PPA are associated with different patterns of atrophy. In the future, combined analysis of imaging and clinical characteristics may allow more accurate etiologic diagnosis.

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PubMedDate not supplied

Quantitative magnetic resonance imaging differences between Alzheimer disease with and without subcortical lacunes.

Previous reports showed that patients with Alzheimer disease (AD) frequently have coexisting vascular-related pathologies, such as cerebral infarcts and white matter lesions. The aim of this study was to determine the effects of subcortical lacunar infarcts on brain structure in patients with AD. Semi-automated tissue segmentation and volumetry of magnetic resonance imaging data were performed in 38 AD patients without lacunes (AD-L), 24 AD patients with subcortical lacunes (AD+L), and 40 age-matched cognitively healthy subjects without lacunes. The following tissue volumes were quantified, expressed as percentage of total intracranial volume: ventricular cerebrospinal fluid (CSF), sulcal CSF, cortical gray matter (GM), subcortical GM, white matter (WM), white matter signal hyperintensities (WMSH), lacunes, and hippocampus. There was no difference in the Mini-Mental State Examination between the two AD groups. AD+L patients compared with AD-L subjects had significantly greater volumes of WMSH and ventricular CSF spaces (as expected) but smaller sulcal CSF spaces and no significant increase in cortical GM atrophy (both unexpected). In the AD groups, ventricular CSF correlated inversely with cortical GM but not with WM; sulcal CSF correlated inversely with cortical GM and WM. Cognitive impairment was associated with sulcal CSF volume but not with volumes of WMSH or lacunes. In conclusion, the presence of subcortical lacunes in those with AD is associated with more WM lesions and ventriculomegaly but not with cortical atrophy.

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PubMedDate not supplied

Comparisons between global and focal brain atrophy rates in normal aging and Alzheimer disease: Boundary Shift Integral versus tracing of the entorhinal cortex and hippocampus.

The objectives of this study were to (1) compare atrophy rates associated with normal aging and Alzheimer disease (AD) using the semi-automated Boundary Shift Integral (BSI) method and manual tracing of the entorhinal cortex (ERC) and hippocampus and (2) calculate power of BSI vs. ERC and hippocampal volume changes for clinical trials in AD. We quantified whole brain and ventricular BSI atrophy rates and ERC and hippocampal atrophy rates from longitudinal MRI data in 20 AD patients and 22 age-matched healthy controls. All methods revealed significant brain atrophy in controls and AD patients. AD patients had approximately 2.5 times greater whole brain BSI atrophy rates and more than 5 times greater ERC and hippocampal atrophy rates than controls. ERC and hippocampal atrophy rates were higher in both groups than whole brain BSI atrophy rates, but lower than ventricular BSI atrophy rates. Effect size and power calculations suggest that ERC and hippocampal measurements may be more sensitive than ventricular or whole brain BSI for detecting AD progression and the potential effects of disease modifying agents. Logistic regression analysis revealed that combined rates of ERC and ventricular BSI were the best explanatory variables for classifying AD from controls.

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