PubMed Health⌕ Search

Biomedical subjects

G Ende

Publications and source records attributed to G Ende.

At least 19 recordsLinked to original sources
PubMed2005

[One decade of functional imaging in schizophrenia research. From visualisation of basic information processing steps to molecular-genetic oriented imaging].

Modern neuroimaging techniques such as magnetic resonance imaging (MRI) and positron emission tomography (PET) have contributed tremendously to our current understanding of psychiatric disorders in the context of functional, biochemical and microstructural alterations of the brain. Since the mid-nineties, functional MRI has provided major insights into the neurobiological correlates of signs and symptoms in schizophrenia. The current paper reviews important fMRI studies of the past decade in the domains of motor, visual, auditory, attentional and working memory function. Special emphasis is given to new methodological approaches, such as the visualisation of medication effects and the functional characterisation of risk genes.

Biomarkers↗
PubMed2005

[Functional imaging of neurocognitive dysfunction in attention deficit hyperactivity disorder].

Attention Deficit Hyperactivity Disorder (ADHD) is a neurobiological disorder of early childhood onset. Defining symptoms are chronic impairments of attention, impulse control and motor hyperactivity that frequently persist until adulthood. Miscellaneous causes of the disorder have been discussed. Accumulating evidence from imaging- and molecular genetic studies strengthened the theory of ADHS being a predominantly inherited disorder of neurobiological origin. In the last 15 years, non-invasive brain imaging methods were successfully implemented in pediatric research. Functional magnetic resonance imaging studies gave major insight into the neurobiological correlates of executive malfunction, inhibitory deficits and psychomotoric soft signs. These findings are in good accordance with brain morphometric data indicating a significant volumetric decrease of major components of striato-thalamo-cortical feedback loops, primarily influencing prefrontal executive functioning (e.g. basal ganglia). Empirical evidence points to a broad array of associated behavioral disturbances like deficient visuomotor abilities and oculomotor dysfunctions. This paper reviews the current empirical evidence derived from prior imaging studies. Special emphasis is given to the relevance of oculomotor dysfunctions in clinical and research settings, as well as their assessment in the MR environment.

Attention Deficit and Disruptive Behavior Disorder↗
PubMed2003

Signal enhancement through heteronuclear polarisation transfer in in-vivo 31P MR spectroscopy of the human brain.

Significant (31)P NMR signal enhancement through heteronuclear polarisation transfer was obtained in model solutions and in vivo on a 1.5-T whole-body MR scanner equipped with two RF channels. The much higher population differences involved in proton Zeeman energy levels can be transferred to the (31)P levels with the refocused INEPT (insensitive nucleus enhancement by polarisation transfer) double-resonance experiment by means of a series of simultaneously applied broadband RF pulses. INEPT achieves a polarisation transfer from (1)H to (31)P spin states by directly reordering the populations in spin systems with heteronuclear scalar coupling. Thus, only the (31)P NMR signal of metabolites with scalar (1)H-(31)P coupling is amplified, while the other metabolite signals in the spectra are suppressed. Compared to Ernst-angle excitation, a repetition-time-dependent signal enhancement of eta=(29+/-3)% for methylene diphosphonic acid (MDPA) and eta=(56+/-1)% for phosphorylethanolamine (PE) was obtained on model solutions through optimisation of the temporal parameters of the pulse experiment. The results are in good agreement with numerical calculations of the theoretical model for the studied spin systems. With optimised echo times, in-vivo (31)P signal enhancement of the same order was obtained in studies of the human brain.

Brain↗
PubMed2002

Temporal lobectomy for epilepsy: recovery of the contralateral hippocampus measured by (1)H MRS.

(1)H MRS imaging was obtained from 10 patients with mesial temporal lobe epilepsy before and after surgery. After surgery, metabolic recovery in the contralateral hippocampus was detected. Preoperatively, reduced N-acetylaspartate (p < 0.04) increased after surgery nonsignificantly to equal control values. Cholines increased after surgery (p < 0.02) and creatine-phosphocreatine showed a trend to higher values. The results suggest that the contralateral hippocampus is affected by repeated seizure activity in the ipsilateral hippocampus, rather than presence of bilateral mesial temporal sclerosis.

Adult↗
PubMed2002

A fully automated method for tissue segmentation and CSF-correction of proton MRSI metabolites corroborates abnormal hippocampal NAA in schizophrenia.

In this report, we describe the implementation and application of a fully automated segmentation routine using SPM99 algorithms and MATLAB for clinical Magnetic Resonance Spectroscopic Imaging (MRSI) studies. By segmenting high-resolution 3-D image data and coregistering the results to the spatial localizer slices of a spectroscopy examination, the program offers the possibility to easily calculate segmentation maps for a large variety of MRSI experiments. The segmented data are corrected for the individual point-spread function, slice and VOI profiles for measurement sequences with selective pulses as well as for the chemical shifts of different metabolites. The new method was applied to investigate discrete hippocampal metabolite abnormalities in a small sample of schizophrenic patients in comparison to healthy controls (15 patients, 15 controls). Only after correction was the N-acetyl-aspartate (NAA) signal significantly lower in patients compared to controls. No differences were found for the corrected signals from the creatine/phosphocreatine (Cr) or choline-containing compounds (Ch). These results are in good agreement with neuropathological and previous MR spectroscopy studies of the hippocampus in schizophrenic patients.

Adult↗
PubMed2001

In vivo hippocampal glucose metabolism in mesial temporal lobe epilepsy.

BACKGROUND: The appearance of decreased 2-[(18)F]fluoro-2-deoxy-D-glucose (FDG) uptake in the mesial temporal region in temporal lobe epilepsy may simply reflect loss of gray matter due to hippocampal atrophy. Increased partial volume effects due to atrophic hippocampi may further increase appearance of hypometabolism. METHODS: The authors used a combination of MRI-PET coregistration, with MRI-based gray matter segmentation, and partial volume correction to improve the examination of hippocampal specific glucose uptake in FDG PET. The goal was to determine 1) if relative mesial temporal hypometabolism is an artifact of gray matter (hippocampal) atrophy, 2) whether hippocampal metabolism correlates with atrophy evaluated on MRI, and 3) if MRI-based partial volume correction influences measurement of hippocampal metabolic-volume relationships, including epilepsy lateralization. RESULTS: Findings showed that ipsilateral hippocampi of mesial temporal lobe epilepsy (MTLE) are relatively hypometabolic per unit of gray matter volume, and that hippocampal metabolism directly correlates with hippocampal volume. Specifically, partial volume corrected hippocampal metabolism correlated strongly (r = 0.613, p < 0.001) with hippocampal volume. Without partial volume correction, a weaker, but still significant, correlation was present (r = 0.482, p < 0.001). Degree of asymmetry was consistently greater and provided higher sensitivity of lateralization with partial volume vs non-partial volume corrected metabolic measurements. CONCLUSIONS: Although, decreased metabolism may occur in the absence of neuronal cell loss, hippocampal atrophy and presumed degree of neuronal cell loss appears to be a primary factor involved in the cause of decreased metabolism in epileptogenic hippocampi. Partial volume correction is recommended for optimal interpretation of hippocampal structure and function relationships.

Adolescent↗
PubMed2001

Hippocampal 1H-MRSI in ecstasy users.

In recent years the illicit drug ecstasy (MDMA, 3,4-methylenedioxymethamphetamine) has come into widespread use among young people. Despite clear evidence for the neurotoxic potential of MDMA in animals, corresponding evidence in humans is limited to indirect findings. In an exploratory study we compared the hippocampal 1H-MRSI (magnetic resonance spectroscopic imaging) spectra of five MDMA users with those of controls with no history of substance abuse. Although 1H

Adult↗
PubMed2001

Favorable effect on neuronal viability in the anterior cingulate gyrus due to long-term treatment with atypical antipsychotics: an MRSI study.

In the present study, we evaluated 23 chronic schizophrenic patients under stable clinical conditions to determine the association between neuronal viability, as measured by in vivo(1)H magnetic resonance spectroscopic imaging (MRSI), and antipsychotic drug effects in the anterior cingulate cortex. Careful screening of the medication history showed that 11 of these patients had been treated with traditional neuroleptics only, while the others had switched to atypical antipsychotics due to non-response to traditional drugs. The group of patients receiving typical neuroleptic medication showed a mean NAA that was lower than in the group of patients receiving atypical antipsychotic drugs. Removing the duration of illness effect indicated a significant correlation between the NAA signal in the anterior cingulate gyrus and time on atypical drugs in patients under long-term atypical antipsychotic treatment. In contrast, patients with traditional medication revealed progressive decrease in the NAA level. These results suggest a favorable effect on neuronal viability in the anterior cingulate gyrus due to long-term treatment with atypical antipsychotics.

Adult↗
PubMed2001

Lower concentration of thalamic n-acetylaspartate in patients with schizophrenia: a replication study.

OBJECTIVE: Using proton magnetic resonance spectroscopic imaging, the authors measured thalamic N-acetylaspartate (NAA) concentrations in patients with schizophrenia. METHOD: The study included 15 schizophrenic patients on a stable medication regimen and 15 age-matched healthy comparison subjects. Concentrations of NAA, creatine plus phosphocreatine, and choline-containing compounds in bilateral thalamic regions were determined. RESULTS: Previous findings of lower NAA concentration in the left and right mediodorsal region of the thalamus and significant correlations between left and right thalamic NAA measures in patients with schizophrenia were corroborated. Furthermore, the concentrations of choline-containing compounds were significantly lower in the schizophrenic patients. No group differences in creatine plus phosphocreatine were found. CONCLUSIONS: There is strong evidence for neuronal dysfunction or loss in the mediodorsal region of the thalamus in patients with schizophrenia.

Adult↗
PubMed2000

Cortical response to motor stimulation in neuroleptic-naive first episode schizophrenics.

The purpose of the present study was to evaluate the cortical response to motor stimulation in neuroleptic-naive first episode schizophrenics in comparison to matched controls using a high speed functional magnetic resonance imaging technique (fMRI). Twelve patients satisfying ICD 10 criteria (F20.0) for schizophrenia (paranoid subtype) as well as sex- and age-matched healthy volunteers participated in this study. All subjects underwent fMRI examination on a conventional 1.5 T MR unit equipped with an echo-planar imaging booster. The blood oxygen level dependent (BOLD) response of the sensorimotor cortex and the higher order SMA region was evaluated during performance of a left hand sequential finger opposition task. Special care was taken to minimize performance and motion artifacts. Patients and controls showed no notable difference with respect to laterality, changes of signal intensity or spatial extent of activation within the primary and higher order motor regions. Using high speed fMRI no fundamental motor cortical dysfunction was evident in a group of paranoid neuroleptic-naive first episode schizophrenic patients. In contrast to data previously reported for chronic disorganized medicated patients, these results suggest that motor dysfunction is not part of the phenomenology of acute paranoid first episode patients.

Acute Disease↗
PubMed2000

Effects of age, medication, and illness duration on the N-acetyl aspartate signal of the anterior cingulate region in schizophrenia.

The authors performed a MRSI study of the anterior cingulate gyrus in 19 schizophrenic patients under stable medication and 16 controls in order to corroborate previous findings of reduced NAA in the anterior cingulate region in schizophrenia. Furthermore, correlations between NAA in the anterior cingulate gyrus and age or illness duration have been determined. A decreased NAA signal was found in the anterior cingulate gyrus of patients compared to controls. Subdividing the patient group into two groups depending on medication revealed that the group of patients receiving a typical neuroleptic medication showed a lower mean NAA in comparison to the group of patients receiving atypical antipsychotic drugs. No significant group differences in the creatine and phosphocreatine signal or the signal from choline-containing compounds were found. The NAA signal significantly correlated with age, and therefore, individual NAA values were corrected for the age effect found in the control group. The age-corrected NAA signal in schizophrenia correlated significantly with the duration of illness. The detected correlations of NAA decrease with age and illness duration are consistent with recent imaging studies where progressing cortical atrophy in schizophrenia was found. Further studies will be needed to corroborate a possible favorable effect of atypical antipsychotics on the NAA signal.

Adult↗
PubMed2000

The hippocampus in patients treated with electroconvulsive therapy: a proton magnetic resonance spectroscopic imaging study.

BACKGROUND: We monitored the effect of electroconvulsive therapy (ECT) on the nuclear magnetic resonance-detectable metabolites N-acetylaspartate, creatine and phosphocreatine, and choline-containing compounds in the hippocampus by means of hydrogen 1 magnetic resonance spectroscopic imaging. We hypothesized that if ECT-induced memory deterioration was associated with neuronal loss in the hippocampus, the N-acetylaspartate signal would decrease after ECT and any increased membrane turnover would result in an increase in the signal from choline-containing compounds. METHODS: Seventeen patients received complete courses of ECT, during which repeated proton magnetic resonance spectroscopic imaging studies of the hippocampal region were performed. Individual changes during the course of ECT were compared with values obtained in 24 healthy control subjects and 6 patients remitted from major depression without ECT. RESULTS: No changes in the hippocampal N-acetylaspartate signals were detected after ECT. A significant mean increase of 16% of the signal from choline-containing compounds after 5 or more ECT treatments was observed. Despite the mostly unilateral ECT application (14 of 17 patients), the increase in the choline-containing compound signal was observed bilaterally. Lactate or elevated lipid signals were not detected. All patients showed clinical amelioration of depression after ECT. CONCLUSIONS: Electroconvulsive therapy is not likely to induce hippocampal atrophy or cell death, which would be reflected by a decrease in the N-acetylaspartate signal. Compared with an age-matched control group, the choline-containing compounds signal in patients with a major depressive episode was significantly lower than normal, before ECT and normalized during ECT.

Adult↗
PubMed1999

Antipsychotic drug effects on motor activation measured by functional magnetic resonance imaging in schizophrenic patients.

Brain function and laterality in schizophrenia were investigated by means of a simple motor task with a self-generated left-hand sequential finger opposition (SFO) using a whole-brain high-speed (100 ms per slice) functional imaging technique. Neuroleptic-naïve, acutely ill schizophrenic patients were compared to schizophrenic patients under stable neuroleptic medication and matched controls. The goal was to evaluate both the motor function in first-episode patients and possible effects of different neuroleptic treatments on functional MRI results. Forty patients satisfying ICD 10 criteria (F20.x) for schizophrenia and sex- and age-matched healthy volunteers participated in this study. All subjects underwent fMRI examinations on a conventional 1.5 T MR unit. The primary sensorimotor cortex and the high-order supplementary motor area (SMA) were evaluated. There was a close similarity in the activation of the primary and high-order (SMA) sensorimotor areas between first-episode schizophrenic patients and controls. In contrast, a significant reduction in the overall blood oxygen level dependent (BOLD) response was seen in sensorimotor cortices (contra- and ipsilateral) in schizophrenic patients under stable medication with typical neuroleptics. This effect was not present in patients treated with atypical antipsychotics. Both antipsychotic treatments, however, led to a significant reduction in activation of the SMA region compared to controls and neuroleptic-naïve subjects. Thus, the present study provides no evidence for the localized involvement of the primary motor cortex or the SMA as a relatively stable vulnerability marker in schizophrenia. There is, however, strong evidence that neuroleptics themselves influence fMRI activation patterns and that there are major differences between typical neuroleptics and atypical antipsychotics.

Adult↗
PubMed1999

[Phosphorus-31-MR spectroscopy imaging in preoperative embolization treatment of meningioma].

PURPOSE: 31P MR spectroscopic imaging (31P SI) was evaluated in a clinical study as a method for monitoring presurgical devascularization of meningiomas. The aim was to assess noninvasively metabolic alterations in tumor and in healthy brain tissue before and after embolization. METHODS: Localized 31P MR spectra of the brain were obtained by means of 2D-SI (voxel size: 36 cm3) using a 1,5-T whole-body MR tomograph. RESULTS: Eleven of 19 patients with intracranial meningiomas examined in this study underwent preoperative embolization therapy; eight patients were examined before and after treatment. After embolization, alterations of pH and of the concentrations of high-energy phosphates (nucleoside-5' triphosphate = NTP, phosphocreatine = PCr), inorganic phosphate (Pi), and membrane constituents were observed in the tumors. A tendency of [Pi] increase and decrease of [NTP], [PCr], and pH predominated, which is explained by ischemic processes after tumor devascularization. CONCLUSION: 31P SI is applicable in clinical studies and detects alterations of phosphate metabolism in a meningioma after embolization.

Adult↗
PubMed1997

Hippocampal N-acetylaspartate in neocortical epilepsy and mesial temporal lobe epilepsy.

Previous magnetic resonance spectroscopy (MRS) studies have shown that N-acetylaspartate (NAA) is reduced not only in the ipsilateral but also in the contralateral hippocampus of many patients with mesial temporal lobe epilepsy (mTLE). The reason for the contralateral damage is not clear. To test whether the hippocampus is also damaged if the focus is outside the hippocampus, we have measured patients with neocortical epilepsy (NE). Therefore, the goals of this study were to determine if hippocampal NAA is reduced in NE and if hippocampal NAA discriminates NE from mTLE. MRS imaging (MRSI) studies were performed on 10 NE patients and compared with MRSI results in 23 unilateral mTLE patients and 16 controls. The results show that, in contrast to mTLE, NAA was not reduced in the hippocampus of NE patients, neither ipsilateral nor contralateral to the seizure focus. These results suggest that repeated seizures do not cause secondary damage to the hippocampus. The absence of spectroscopic differences in NE may help to distinguish NE from mTLE.

Adult↗
PubMed1997

Presurgical multimodality neuroimaging in electroencephalographic lateralized temporal lobe epilepsy.

The purpose of this study was to compare 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET), hippocampal volumetry (HV), T2 relaxometry, and proton magnetic resonance spectroscopic imaging (1H-MRSI) in the presurgical neuroimaging lateralization of patients with nonlesional, electroencephalogram (EEG)-defined unilateral temporal lobe epilepsy (TLE). Twenty-five patients were prospectively studied, along with age-matched controls. T2 relaxometry examinations were performed in 13 patients. Comparison of FDG-PET, HV, and 1H-MRSI was possible in 23 patients. FDG-PET lateralized 87% of patients, HV 65%, N-acetyl aspartate (NAA)/(choline [Cho] + creatine [Cr]) 61%, and [NAA] 57%. Combined HV and NAA/(Cho + Cr) results lateralized 83% of the patients, a value similar to PET. Of 10 patients with normal magnetic resonance imaging (MRI) scans, 2 were lateralized with HV, 6 with FDG-PET, 4 with NAA/(Cho + Cr), and 3 with [NAA]. T2 relaxometry lateralized no patients without hippocampal atrophy. Bilateral abnormality was present in 29 to 33% of patients with 1H-MRSI measures and 17% with HV. Only hippocampal atrophy correlated with postoperative seizure-free outcome. FDG-PET remains the most sensitive imaging method to correlate with EEG-lateralized TLE. Both FDG-PET and 1H-MRSI can lateralize patients with normal MRI, but only the presence of relative unilateral hippocampal atrophy is predictive of seizure-free outcome. Bilaterally abnormal MRI and 1H-MRSI measures do not preclude good surgical outcome.

Adult↗
PubMed1997

Real-time direct volume rendering in functional magnetic resonance imaging.

Direct volume rendering is a visualization method that allows display of all information hidden in three-dimensional data sets of, for example, computed tomography or magnetic resonance imaging (MRI). In contrast to commonly used surface rendering methods, these algorithms need no preprocessing but suffer from a high computational complexity. A real-time rendering system, VIRIM (Vitec: Visualization Technology GmbH, Mannheim, Germany), cuts down rendering times of minutes on normal workstations to an interactive rate of 1 second or less. The immediate visual feedback allows interactive steering of the visualization process to achieve insight into the internal three-dimensional structure of objects. Additional information is obtained by using an interactive gray-value segmentation tool that both allows segmentation of the data set according to bone, tissue, and liquor and display of multifunctional data sets (e.g., functional MRI [fMRI] data sets). Thus, real-time direct volume rendering allows segmentation and volume data processing of functional and anatomical MR data sets simultaneously. As this method can be integrated in the clinical routine, it is of great importance for real-time motion artifact detection and the interpretation of fMRI data acquired during cognitive experiments with normal subjects and psychiatric patients. Because of the free programmability of VIRIM, more complex matching procedures are currently being investigated for future implementation.

Brain↗