Search PubMed⌕ Search

Biomedical subjects

P Bartenstein

Publications and source records attributed to P Bartenstein.

At least 55 records · Page 3Linked to original sources
PubMed2001

Dose-dependent regional cerebral blood flow changes during remifentanil infusion in humans: a positron emission tomography study.

BACKGROUND: The current study investigated dose-dependent effects of the mu-selective agonist remifentanil on regional cerebral blood flow (rCBF) in volunteers using positron emission tomography (PET). METHODS: Ten right-handed male volunteers were included in a 15O-water PET study. Seven underwent three conditions: control (saline), low remifentanil (0.05 microg x kg(-1) x min(-1)), and moderate remifentanil (0.15 microg x kg(-1) x min(-1)). The remaining three participated in the low and moderate conditions. A semirandomized study protocol was used with control and remifentanil conditions 3 or more months apart. The order of low and moderate conditions was randomized. Cardiovascular and respiratory parameters were monitored. Categoric comparisons between the control, low, and moderate conditions and a pixelwise correlation analysis across the three conditions were performed (P < 0.05, corrected for multiple comparisons) using statistical parametric mapping. RESULTS: Cardiorespiratory parameters were maintained constant over time. At the low remifentanil dose, significant increases in relative rCBF were noted in the lateral prefrontal cortices, inferior parietal cortices, and supplementary motor area. Relative rCBF decreases were observed in the basal mediofrontal cortex, cerebellum, superior temporal lobe, and midbrain gray matter. Moderate doses further increased rCBF in mediofrontal and anterior cingulate cortices, occipital lobe transition, and caudal periventricular grey. Significant decreases were detected in the inferior parietal lobes. These dose-dependent effects of remifentanil on rCBF were confirmed by a correlation analysis. CONCLUSION: Remifentanil induced dose-dependent changes in relative rCBF in areas involved in pain processing. At moderate doses, rCBF responses were additionally detected in structures known to participate in modulation of vigilance and alertness. Insight into the mechanisms of opioid analgesia within the pain-processing neural network may lead to a better understanding of antinociception and opioid treatment.

Analgesics, Opioid↗
PubMed2000

First experience with I-123-alpha-methyl-tyrosine spect in the 3-D radiation treatment planning of brain gliomas.

PURPOSE: This study compares the results of iodine-123-alpha-methyl-tyrosine single photon computed emission tomography (IMT-SPECT) with magnetic resonance imaging (MRI) in tumor volume definition of brain gliomas. Furthermore, it evaluates the influences of the information provided from IMT-SPECT for three-dimensional (3D) conformal treatment planning. METHODS AND MATERIALS: In 30 patients with nonresected, histologically proven brain gliomas (glioblastoma-13 patients, astrocytoma Grade III-12 patients, astrocytoma Grade II-3 patients, oligodendroglioma Grade III-1 patient, oligodendroglioma Grade II-1 patient), IMT-SPECT and MRI were performed pretherapeutically in the same week. A special software system allowed the coregistration of the IMT-SPECT and MRI data. The gross tumor volume (GTV) defined on the IMT-SPECT/T2-MRI fusion images (GTV-IMT/T2) was compared with the GTV-T2, defined on the T2-MRI alone. On the IMT-SPECT/T1Gd-MRI overlays, the volume of the IMT tumor uptake (GTV-IMT) was compared with the volume of the gadolinium (Gd) enhancement (GTV-T1Gd). The initial planning target volume (PTV) and the boost volume (BV) outlined on the IMT-SPECT/T2-MRI co-images were analyzed comparatively to the PTV and BV delineated using the T2-MRI alone. RESULTS: In all 30 patients a higher IMT uptake of tumor areas, compared to the normal brain tissue was observed. Mean GTV-IMT, mean GTV-T2, and mean GTV-T1Gd were 43, 82, and 16 cm(3), respectively. IMT tumor uptake outside the contrast enhancement regions was observed in all patients. Mean relative increase of tumor volume defined on the fusion images, GTV-IMT/T1Gd versus GTV-T1Gd alone was 78%. IMT tumor uptake areas outside the GTV-T2 were registered in 7 patients (23%). In these patients, the mean increase GTV-IMT/T2 was 33% higher than GTV-T2, defined according to the T2-MRI data alone. The additional information provided by IMT-SPECT modified minimally the initial PTV (mean relative increase PTV-IMT/T2 versus PTV-T2, 5%) but significantly the BV (mean relative increase BV-IMT/T2 versus BV-T2, 37%). CONCLUSION: In a significant number of patients, the IMT-SPECT investigation improves tumor detection and delineation in the planning process. This has important consequences in the 3D conformal treatment planning, especially in the delineation of BV and in dose escalation studies.

Adult↗
PubMed2000

Lasting cortical activation after repetitive TMS of the motor cortex: a glucose metabolic study.

OBJECTIVE: Cerebral [18F]fluorodeoxy-D-glucose PET ([18F]FDG-PET) was used to visualize the lasting neuronal activation after repetitive transcranial magnetic stimulation (rTMS) over the left hand area of the primary motor cortex (M1HAND). BACKGROUND: Applied over M1HAND, rTMS has been shown to produce a modulation of corticomotor excitability beyond the time of stimulation itself. METHODS: Eight right-handed subjects underwent nonquantitative [18F]FDG-PET measurements during two experimental conditions: at rest and after focal subthreshold 5-Hz rTMS over the left M1HAND. In the post-rTMS condition, [18F]FDG was injected immediately after the administration of 1,800 magnetic pulses over the left M1HAND. Relative differences in normalized regional cerebral metabolic rate of glucose (normalized rCMRglc) between conditions were determined using a voxel-by-voxel Student's t-test and volume-of-interest (VOI) analysis. Analysis was a priori restricted to the M1HAND, the supplementary motor area (SMA), and the primary auditory cortex of both hemispheres. RESULTS: A 5-Hz rTMS of the left M1HAND caused a lasting relative increase in normalized rCMRglc within the M1HAND bilaterally and the SMA. The magnitude and the topographic pattern of persisting relative rCMRglc increases within these motor cortical areas demonstrated considerable interindividual variations. CONCLUSIONS: Subthreshold 5-Hz repetitive transcranial magnetic stimulation (rTMS) over the hand area of the primary motor cortex is associated with a persisting neuronal activation in a distinct set of motor cortical areas beyond the time of stimulation. The current findings demonstrate that [18F]FDG-PET can localize and quantify regional net changes in synaptic cortical activity after rTMS and thus might elucidate the mechanisms underlying rTMS-associated therapeutic effects.

Adult↗
PubMed2000

Processing of histamine-induced itch in the human cerebral cortex: a correlation analysis with dermal reactions.

The subjective sensation of itch is a complex emotional experience depending on a variety of factors. In this study, the central nervous processing of pruritus was investigated in a human model. Activation of involved cerebral areas was correlated to scales of nociception and skin reactions. Six healthy male right-handed subjects participated in a standardized epidermal stimulus model with nine increasing doses of histamine dihydrochloride (0.03%-8%) on their right forearms. Controls consisted of three NaCl stimuli. Cerebral activation patterns were determined by H(2)(15)O positron emission tomography 120 s after stimulation. Dermal reactions to the stimulus (wheal, flare, temperature) were coregistered during the procedure. Itch sensation was determined by visual analog scale rating. Pain was not reported during the study; all volunteers had localized itch from 0.03% histamine on. Subtraction analysis versus control revealed significant activation of the left primary sensory cortex and motor-associated areas (mainly primary motor cortex, supplementary motor area, premotor cortex). Predominantly left-sided activations of frontal, orbitofrontal, and superior temporal cortex and anterior cingulate were also observed. Correlation analysis revealed coactivation of dermal reactions and cerebral response to itch in the following Brodmann areas with a Z score greater than 5: wheal, areas 5 (bilateral) and 19 (right); flare, areas 2-5 (left); temperature, area 10 (left) and left insula. Itch intensity ratings were mainly correlated with activation of the left sensory and motor areas. Functional covariates of the itch sensation in the central nervous system were identified. The intention to pruritofensive movements is probably mirrored by the activation of motor areas in the cortex. Other areas may be involved in emotional processing of sensations. Skin reactions wheal and flare also had significantly activated covariate areas in the central nervous system.J Invest Dermatol 115:1029-1033 2000

Adult↗
PubMed2000

Reduction of benzodiazepine receptor binding is related to the seizure onset zone in extratemporal focal cortical dysplasia.

PURPOSE: Comparison of regional reduction of GABA receptor binding and seizure onset zone in patients with extratemporal epilepsy due to focal cortical dysplasia. METHODS: Two patients with frontal lobe epilepsy who remained seizure free after partial frontal lobe resection were investigated with magnetic resonance imaging, positron emission tomography (PET) with 18F-fluoro-deoxy-glucose (FDG) and 11C-flumazenil, subdural EEG-video recordings, and postoperative benzodiazepine (BDZ)-receptor autoradiography. RESULTS: The area of reduced BDZ-receptor binding as documented by preoperative flumazenil-PET and postoperative BDZ-receptor autoradiography corresponded to the seizure onset zone and was smaller than the interictal hypometabolism documented by FDG-PET. CONCLUSION: Flumazenil-PET is a useful tool for localization of the epileptogenic zone in patients with extratemporal epilepsy caused by focal cortical dysplasia. Neuronal distribution of BDZ-receptor density confirms in vivo flumazenil-PET findings. The regional reduction of BDZ-receptor binding in focal cortical dysplasia seems to be confined to the seizure onset zone and not to the extent of dysplastic cortex.

Adolescent↗
PubMed2000

6-O-(2-[18F]fluoroethyl)-6-O-desmethyldiprenorphine ([18F]DPN): synthesis, biologic evaluation, and comparison with [11C]DPN in humans.

UNLABELLED: 6-O(2-[18F]fluoroethyl)-6- -desmethyldiprenorphine ([18F]DPN) was developed and biologically evaluated. Results of animal experiments, binding studies in vivo, and a human PET study are reported and compared with those of [11C]DPN. METHODS: [18F]DPN was obtained by 18F-fluoroethylation of 3-O-trityl-6-O-desmethyldiprenorphine and subsequent deprotection in good radiochemical yields (23% +/- 7%; 100 min; 37 TBq/mmol). Binding of [18F]DPN to mu, kappa, and delta opioid receptors was shown by autoradiography studies on rat brain slices. Quantification of cerebral opioid receptor binding in men was performed by spectral analysis of a dynamic PET scan (25 frames, 90 min) after intravenous application of 63 MBq [18F]DPN (36 GBq/micromol) and correction for metabolites. RESULTS: [18F]DPN shows high affinity to opioid receptors. Parametric images (impulse response function at 60 min) of this human study showed a binding pattern of [18F]DPN equal to that of a control group (n = 9 healthy volunteers) after administration of [11C]DPN. CONCLUSION: The advantage of the longer half-life of 18F will allow extended scanning periods, more flexible interventions (e.g., displacement studies), and DPN to be available to PET centers without an on-site cyclotron.

Adult↗
PubMed2000

Phantom limb pain in the human brain: unraveling neural circuitries of phantom limb sensations using positron emission tomography.

Pain and other phantom limb (PL) sensations have been proposed to be generated in the brain and to be reflected in activation of specific neural circuits. To test this hypothesis, hypnosis was used as a cognitive tool to alternate between the sensation of PL movement and pain in 8 amputees. Brain activity was measured using positron emission tomography. PL movement and pain were represented by a propagation of neuronal activity within the corresponding sensorimotor and pain-processing networks. The sensation of movement was significantly (corrected for multiple comparisons) related to activity in the supplementary motor area and the primary sensorimotor cortex. The sensation of a painful PL posture activated the same brain areas but was weaker and less extended in the supplementary motor area. In contrast to the sensation of movement, pain was significantly related to activity in the thalamus, anterior cingulate, and lateral prefrontal cortex. Subjectively rated PL pain sensation correlated positively to activations in the anterior and posterior cingulate. These findings provide evidence that PL sensations are produced by the same central nervous processes that underlie the experience of the body when it is intact and that the corporeal awareness of PL pain is encoded in a thalamocortical network.

Adult↗
PubMed2000

[Clinical applications of single photon emission tomography in neuromedicine. 1. Neuro-oncology, epilepsy, movement disorders, cerebrovascular disease].

Single photon emission tomography is, because of its availability and the relatively low costs, the functional imaging modality currently most widely used for clinical applications in the brain. Beside the application of radiopharmaceuticals for the assessment of regional cerebral blood flow there is an increasing clinical use of more selective SPECT-radiopharmaceuticals, like amino acid analogs or receptor ligands. This article gives in his first part a critical review of the clinical applications of SPECT in neuro-oncology, epilepsy, basal ganglia disorders and cerebrovascular disease.

Cerebrovascular Disorders↗
PubMed2000

[Clinical applications of single photon emission tomography in neurology. 2. Dementia, psychoses, inflammation, skull and brain injuries].

This article gives in his second part a critical review of the clinical applications of SPECT with perfusion markers and receptor ligands in dementing disorders and psychosis. In addition this review discusses clinical applications of SPECT investigations with perfusion markers in inflammatory diseases of the central nervous system and in brain trauma.

Brain↗
PubMed1999

Imaging functional activation of the auditory cortex during focal repetitive transcranial magnetic stimulation of the primary motor cortex in normal subjects.

Positron emission tomography (PET) during focal repetitive transcranial magnetic stimulation (rTMS) has emerged as a promising approach to study cortical connectivity in awake humans. However, the noise caused by the discharging magnetic coil might have confounding effects on the rTMS-related cortical activation pattern. In twelve healthy volunteers, 18-fluoro-2-deoxy-D-glucose (18FDG) PET was employed to visualize the functional activation of the primary auditory cortex (PAC) during 2 Hz rTMS of the left primary sensorimotor hand area. Magnetic stimuli (1800) were applied at an intensity of 140% of motor resting threshold during the uptake period of 18FDG. Though all subjects wore earplugs, rTMS-related noise induced a consistent bilateral increase of regional glucose utilization in the PAC (P < 0.05, corrected). Thus, rTMS-related acoustic input needs to be taken into account in combined rTMS/PET studies.

Adult↗
PubMed1999

Opioid receptors in the human cerebellum: evidence from [11C]diprenorphine PET, mRNA expression and autoradiography.

Little is known regarding opioid receptors in the human cerebellum. The present [11C]diprenorphine PET study investigated opioid receptor binding in the human cerebellum in vivo, and showed a differential binding level in cerebellar cortex, vermis and dentate nuclei. The additional study in vitro of opioid receptors in human cerebellar cortex and rat brain corroborated the presence of opioidergic mechanisms in the human cerebellum in contrast to the rat. A differential cellular distribution pattern was detected for the three major opioid receptors investigated. For the mu-receptor, and at a lower level for the kappa-receptor, mRNA expression was mainly observed over granule cells. Binding sites were most prominent in the molecular layer. For the delta-receptor no signal was detected. The consideration of cerebellar opioidergic mechanisms and the distribution patterns of the various opioid receptors may promote the understanding of cerebellar function and of opioidergic pharmacology in the human.

Adult↗
PubMed1999

A positron emission tomographic study of subthalamic nucleus stimulation in Parkinson disease: enhanced movement-related activity of motor-association cortex and decreased motor cortex resting activity.

BACKGROUND: Long-term high-frequency stimulation of the subthalamic nucleus (STN) improves akinesia in Parkinson disease. The neural correlates of STN stimulation are not well understood. Positron emission tomography can be applied to the in vivo study of the mechanisms of deep brain stimulation. OBJECTIVE: To study changes in regional cerebral blood flow as an index of synaptic activity in patients with Parkinson disease with effective STN stimulation on and off during rest and movement. METHODS: Eight patients with Parkinson disease who had electrodes implanted in the STN underwent 12 measurements of regional cerebral blood flow with water O 15 positron emission tomography at rest and during performance of paced freely selected joystick movements, both with and without STN stimulation (3 scans per experimental condition). Motor performance and reaction and movement times were monitored. Statistical parametric mapping was used to compare changes in regional cerebral blood flow between conditions and differences in activation. RESULTS: All patients showed improvement in reaction and movement times during scans with the stimulator on. As predicted, increases in activation of rostral supplementary motor area and premotor cortex ipsilateral to stimulation were observed when stimulation was on during contralateral movement (P<.001). Unpredicted observations included decreases in regional cerebral blood flow in primary motor cortex at rest induced by STN stimulation. CONCLUSION: Stimulation of the STN reduces the movement-related impairment of frontal motor association areas and the inappropriate motor cortex resting activity in Parkinson disease.

Adult↗
PubMed1999

MR measurement of regional relative cerebral blood volume in epilepsy.

The purpose of this study was to evaluate the utility of magnetic resonance (MR) relative cerebral blood volume (rCBV) maps for studying regional hemodynamic changes in interictal and ictal epilepsy patients. Ten epilepsy patients were examined on a 1.5 T MR system. Nine patients were investigated interictally and one patient ictally. In the nine interictal patients, the dynamic plane was defined coronally through the hippocampus symmetrically. For the ictal patient, an axial dynamic plane was defined and the patient was scanned during seizure. Positron emission tomography (PET) studies were performed in 8 of the 10 patients. Lower rCBV of the left hippocampus was predicted by rCBV maps in seven of the nine interictal patients. The mean ratios of rCBV were 1.96 for left hippocampus/white matter and 2.49 for right hippocampus/white matter. The difference between these two ratios is statistically significant (P = 0.01, t-test). In two of the nine interictal temporal lobe epilepsy patients, lower rCBV areas were observed in the right hippocampus. In the ictal patient, the regional rCBV map demonstrated increased blood volume in the lesions. In eight of eight patients who underwent PET studies, MR rCBV findings were consistent with PET findings. The results show that regional hemodynamic changes in epilepsy can be evaluated with dynamic contrast-enhanced MR imaging. MR rCBV maps are sensitive to characterize seizure foci both ictally and interictally.

Adult↗
PubMed1999

Region-specific encoding of sensory and affective components of pain in the human brain: a positron emission tomography correlation analysis.

Brain imaging with positron emission tomography has identified some of the principal cerebral structures of a central network activated by pain. To discover whether the different cortical and subcortical areas process different components of the multidimensional nature of pain, we performed a regression analysis between noxious heat-related regional blood flow increases and experimental pain parameters reflecting detection of pain, encoding of pain intensity, as well as pain unpleasantness. The results of our activation study indicate that different functions in pain processing can be attributed to different brain regions; ie, the gating function reflected by the pain threshold appeared to be related to anterior cingulate cortex, the frontal inferior cortex, and the thalamus, the coding of pain intensity to the periventricular gray as well as to the posterior cingulate cortex, and the encoding of pain unpleasantness to the posterior sector of the anterior cingulate cortex.

Adult↗
PubMed1999

[Noninvasive protocol for surgical treatment of focal epilepsies].

We present a non-invasive epilepsy surgery protocol, which includes EEG-video-monitoring, magnetic resonance imaging (MRI), interictal positron emission tomography (PET) and ictal single photon emission computerized tomography (SPECT). According to this non-invasive protocol 50 of 173 patients with medically intractable focal epilepsy underwent resective surgery. The localization of the epileptogenic zone was based on the congruence of the localizing results of EEG-video-monitoring, MRI, interictal PET and ictal SPECT. 46 (92%) of the patients had temporal and 4 (8%) had extratemporal epilepsies. 78% (n = 39) of all patients operated according to our non-invasive protocol were postoperatively completely or almost seizure free. Extramesiotemporal resections could be carried out without invasive EEG-recording if the epileptogenic zone was not adjacent to the eloquent cortex. We conclude from our results that in a considerable number of patients with medically intractable particularly temporal focal epilepsies, resective epilepsy surgery can be based on non-invasive EEG-evaluations and the risk of invasive recordings can be avoided.

Adolescent↗