Positron emission tomography imaging in gliomas: applications in clinical diagnosis, for assessment of prognosis and of treatment effects, and for detection of recurrences.

Neuroimaging plays a significant role in the diagnosis of intracranial tumours, especially brain gliomas, and must consist of an assessment of location and extent of the tumour and of its biological activity. Therefore, morphological imaging modalities and functional, metabolic or molecular imaging modalities should be combined for primary diagnosis and for following the course and evaluating therapeutic effects. Magnetic resonance imaging (MRI) is the gold standard for providing detailed morphological information and can supply some additional insights into metabolism (MR spectroscopy) and perfusion (perfusion-weighted imaging) but still has limitations in identifying tumour grade, invasive growth into neighbouring tissue and treatment-induced changes, as well as recurrences. These insights can be obtained by various positron emission tomography (PET) modalities, including imaging of glucose metabolism, amino acid uptake and nucleoside uptake. Diagnostic accuracy can benefit from coregistration of PET results and MRI, combining high-resolution morphological images with biological information. These procedures are optimized by the newly developed combination of PET and MRI modalities, permitting the simultaneous assessment of morphological, functional, metabolic and molecular information on the human brain.

Post-stroke cognitive decline: an update and perspectives for clinical research.

The close relationship between stroke and dementia is an important health issue. Ischaemic stroke can facilitate the onset of vascular dementia as well as aggravate pre-existing cognitive decline. The onset of cognitive decline may become manifest immediately following the onset of ischaemic stroke, but often there is a delay in the development of cognitive decline after a stroke. This delay can be seen as a therapeutic time window allowing interventions to be applied to preserve cognition following stroke. Both neurodegenerative and vascular mechanisms are activated and probably result in overlapping processes within the neurovascular unit. This review focuses on the incidence and prevalence of cognitive decline following stroke, predisposing stroke aetiologies, pre-stroke decline, imaging factors and biomarkers. Outcomes are discussed in relation to timing of assessment and neuropsychological tests used for evaluation of cognitive decline in ischaemic stroke patients. Including such tests in routine evaluations of stroke patients after some weeks or months is recommended. Finally, an outlook on ongoing and planned intervention trials is added and some recommendations for future research are proposed.

[PET in gliomas. Overview of current studies]. / PET bei Gliomen. Eine Übersicht der aktuellen Literatur.

Gliomas which represent 30% of intracranial tumours are morphologic lesions and therefore CT and MRI are the first line diagnostic procedures with MRI giving better soft tissue resolution and permitting additional functional information. These mainly morphologic imaging modalities yield only restricted information on grade of malignancy, on infiltration into and effects on surrounding brain tissue, on differentiation between necrotic and recurrent tumour, on prognosis and on efficacy of treatment. Information on these important issues for patient management can be obtained by PET-studies of glucose metabolism with FDG, of aminoacid-uptake and protein synthesis with 11C-methionin, 18F-fluorethyltyrosin and 18F-fluor-deoxyphenylalanin and of proliferation by 18F-deoxythymidin. With the increasing availability of 18F-tracers PET has obtained wider spread clinical application. In all these applications a coregistration with morphologic imaging should be obtained, and for that purpose hybrid installations (PET-MR) are already being used.

PET in coma and in vegetative state.

Advances in resuscitation and critical care management have resulted in the survival of many patients despite severe brain damage. These patients may remain in coma or in vegetative state. The probability of recovery of conscious function is dependent on the extent of structural brain damage, which is difficult to assess by clinical, laboratory or functional tests. Positron emission tomography (PET) of 18F-fluordeoxyglucose (FDG) can be used to investigate metabolic and functional impairment of the brain. In acute vegetative state (AVS, duration <1 month), overall glucose utilization was significantly reduced in comparison with age-matched controls. In a few cases with locked-in syndrome, cortical metabolism was in the normal range. 11C-Flumazenil (FMZ) measures the density of benzodiazepine receptors (BZRs) and thereby furnishes an estimate of neuronal integrity. PET with this tracer demonstrated a considerable reduction in BZRs in cortical areas, but indicated that the cerebellum was spared from neuronal loss. The comparison of FDG- and FMZ-PET findings in AVS demonstrates that alterations of cerebral glucose consumption do not represent mere functional inactivation, but also irreversible structural damage. In some cases with minimally conscious state, auditory stimuli with emotional valence induced more brain activation (investigated by H215O-PET) than meaningless noise; such studies can be used to detect residual cortical function. To improve prognostication of chances for recovery, a combination of functional activation studies and assessment of the extent of neuronal damage might be the optimal procedure and should be tested in larger cohorts of patients with comatose states of different severity.

Neurotransmitter changes in dementia with Lewy bodies and Parkinson disease dementia in vivo.

OBJECTIVE: Although Parkinson disease with dementia (PDD) and dementia with Lewy bodies (DLB) show a wide clinical and neuropathologic overlap, they are differentiated according to the order and latency of cognitive and motor symptom appearance. Whether both are distinct disease entities is an ongoing controversy. Therefore, we directly compared patients with DLB and PDD with multitracer PET. METHODS: PET with (18)fluorodopa (FDOPA), N-(11)C-methyl-4-piperidyl acetate (MP4A), and (18)fluorodeoxyglucose (FDG) was performed in 8 patients with PDD, 6 patients with DLB, and 9 patients with PD without dementia vs age-matched controls. Data were analyzed with voxel-based statistical parametric mapping and region of interest-based statistics. RESULTS: We found a reduced FDOPA uptake in the striatum and in limbic and associative prefrontal areas in all patient groups. Patients with PDD and patients with DLB showed a severe MP4A and FDG binding reduction in the neocortex with increasing signal diminution from frontal to occipital regions. Significant differences between PDD and DLB were not found in any of the radioligands used. Patients with PD without dementia had a mild cholinergic deficit and no FDG reductions vs controls. CONCLUSIONS: Patients with dementia with Lewy bodies and Parkinson disease dementia share the same dopaminergic and cholinergic deficit profile in the brain and seem to represent 2 sides of the same coin in a continuum of Lewy body diseases. Cholinergic deficits seem to be crucial for the development of dementia in addition to motor symptoms. The spatial congruence of cholinergic deficits and energy hypometabolism argues for cortical deafferentation due to the degeneration of projection fibers from the basal forebrain.

A double-blind, placebo-controlled, randomized trial to evaluate the safety and efficacy of Cerebrolysin in patients with acute ischaemic stroke in Asia--CASTA.

Cerebrolysin has exhibited neuroprotective as well as neurotrophic properties in various animal models of cerebral ischaemia and has shown clinical efficacy and good safety in several small controlled clinical studies in ischaemic stroke. Therefore, a large double-blind placebo-controlled randomized clinical trial was launched in Asia to prove the validity of this treatment strategy. In the more than 50 participating centres patients with acute ischemic hemispheric stroke are randomized within 12 hours of symptoms onset to treatment (30 ml Cerebrolysin diluted in physiologic saline) or placebo (saline) given as intravenous infusion once daily added to standard care for 10 days. The patients are followed with regular visits for 90 days. Efficacy is evaluated on day 90 by three outcome scales - modified Rankin Scale, Barthel Index and NIH Stroke Scale - combined to single global directional test. Additionally, adverse events are documented to prove safety. In this study a total of 1060 patients will be included and analysis of data will be completed in 2010. If positive, this trial will add an effective strategy to the treatment of acute ischaemic stroke.

Performance of FDG PET for detection of Alzheimer's disease in two independent multicentre samples (NEST-DD and ADNI).

AIM: We investigated the performance of FDG PET using an automated procedure for discrimination between Alzheimer's disease (AD) and controls, and studied the influence of demographic and technical factors. METHODS: FDG PET data were obtained from the Alzheimer's Disease Neuroimaging Initiative (ADNI) [102 controls (76.0 +/- 4.9 years) and 89 AD patients (75.7 +/- 7.6 years, MMSE 23.5 +/- 2.1) and the Network for Standardisation of Dementia Diagnosis (NEST-DD) [36 controls (62.2 +/- 5.0 years) and 237 AD patients (70.8 +/- 8.3 years, MMSE 20.9 +/- 4.4). The procedure created t-maps of abnormal voxels. The sum of t-values in predefined areas that are typically affected by AD (AD t-sum) provided a measure of scan abnormality associated with a preset threshold for discrimination between patients and controls. RESULTS: AD patients had much higher AD t-sum scores compared to controls (p < 0.01), which were significantly related to dementia severity (ADNI: r = -0.62, p < 0.01; NEST-DD: r = -0.59, p < 0.01). Early-onset AD patients had significantly higher AD t-sum scores than late-onset AD patients (p < 0.01). Differences between databases were mainly due to different age distributions. The predefined AD t-sum threshold yielded a sensitivity and specificity of 83 and 78% in ADNI and 78 and 94% in NEST-DD, respectively. CONCLUSION: The automated FDG PET analysis procedure provided good discrimination power, and was most accurate for early-onset AD.

Frontal FDG-PET activity correlates with cognitive outcome after STN-DBS in Parkinson disease.

BACKGROUND: Inconsistent changes of cognitive functioning have been reported in patients with Parkinson disease (PD) with deep brain stimulation (DBS) of the subthalamic nucleus (STN). To investigate the underlying pathomechanisms, we correlated alterations of cognitive test performance and changes of neuronal energy metabolism in frontal basal ganglia projection areas under bilateral STN stimulation. METHODS: We conducted verbal fluency, learning, and memory tests and 18-fluorodeoxyglucose (FDG) PET in nine patients with PD with STN-DBS before and 6 months after surgery. Using coregistered MRI, postoperative changes of the normalized cerebral metabolic rates of glucose (nCMRGlc) in the dorsolateral prefrontal cortex (DLPFC), lateral orbitofrontal cortex (LOFC), ventral and dorsal cingulum (v/dACC), and in Broca area were determined and correlated with alterations of neuropsychological test results. RESULTS: After surgery, highly variable changes of both cognitive test performance and frontal nCMRGlc values were found with significant correlations between verbal fluency and FDG uptake in the left DLPFC (Brodmann area [BA] 9, 46), left Broca area (BA 44/45), and the right dACC (BA 32). A decrease of nCMRGlc in the left OFC (BA 11/47) and dACC (BA 32) correlated with a decline of verbal learning. All patients showed reduced metabolic activity in the right anterior cingulate cortex after DBS. Baseline cognitive abilities did not predict verbal learning or fluency changes after surgery. CONCLUSIONS: These data show a significant linear relationship between changes in frontal 18-fluorodeoxyglucose PET activity and changes in cognitive outcome after deep brain stimulation of the subthalamic nucleus (STN) in advanced Parkinson disease. The best correlations were found in the left frontal lobe (dorsolateral prefrontal cortex and Broca area). Baseline performance on cognitive tests did not predict cognitive or metabolic changes after STN electrode implantation.

High resolution positron emission tomography demonstrates basal ganglia dysfunction in early Parkinson's disease.

High resolution positron emission tomography (PET) with the newly developed HRRT scanner (Siemens/CTI) permits the reliable quantification of 18-Fluorodeoxyglucose (FDG) uptake as a marker of neuronal activity in small subcortical nuclei which are involved in the pathophysiology of Parkinson's disease (PD). We investigated the normalized cerebral metabolic rates of glucose (nCMRGlc) with HRRT PET in basal ganglia (BG) nuclei of 10 early-stage PD patients and in 9 healthy volunteers. PET data were co-registered to magnetic resonance images and analyzed in a three-dimensional volume-of-interest (VOI) approach. After normalization for global brain activity, PD patients showed a significantly higher nCMRGlc than controls bilaterally in the BG output nuclei (pallidum, substantia nigra) and unilateral in the caudate and putamen. The metabolic activity of the nucleus accumbens, the subthalamic nucleus, the corpus amygdaloideum and the red nucleus was normal. These first HRRT PET data in living parkinsonian humans extend previous brain imaging findings of abnormal network activity in the BG and confirm output nuclei and striatal overactivation also in early stage PD patients.

Comparison of PET and DW/PW-MRI in acute ischemic stroke.

The penumbra--tissue perfused below the flow threshold for functional disturbance but above that for maintenance of morphological integrity--is the target for therapy in acute ischemic stroke. Irreversible tissue damage and penumbra can be reliably identified by multitracer positron emission tomography (PET) which has severe limitations due to complexity, invasiveness and radiation exposure. Therefore other modalities served as surrogate markers, with diffusion/perfusion-weighted magnetic resonance imaging (DW/PW-MRI) and perfusion computed tomography (PCT) being applied widely in clinical routine. In order to evaluate the limitations of DW/PW-MRI a comparative study was performed in acute stroke patients in whom cerebral perfusion was assessed by perfusion-weighted magnetic resonance imaging (PW-MRI) and H2(15)O-PET, tissue damage was estimated by diffusion-weighted magnetic resonance imaging (DW-MRI) and 11C-flumazenil (FMZ) PET and DW/PW-MRI mismatch was related to the tissue with increased oxygen extraction fraction (OEF) as an indicator of penumbra. The lesions in DW-MRI and in FMZ-PET were reliable predictors of final infarct on late MRI, but DW-MRI showed a high false positive rate. PW-MRI was limited in estimating flow and yielded values comparable to H2(15)O-PET only in the range between 20 and 30 ml/100 g/min. The DW/PW-MRI mismatch overestimated the penumbra as determined by increased OEF. These limitations of DW/PW-MRI have to be considered if used for selection of patients for treatment and might have an impact on the outcome of clinical trials based on this surrogate marker.

CSF total and phosphorylated tau protein, regional glucose metabolism and dementia severity in Alzheimer's disease.

BACKGROUND AND PURPOSE: We investigated associations between severity of cognitive impairment, cerebrospinal fluid (CSF) concentrations of total-tau (t-tau) protein and tau phosphorylated at threonin 181 (p-tau(181)) and regional glucose metabolism measured with 18F-fluorodeoxyglucose-positron emission tomography (18F-FDG-PET) in patients with probable Alzheimer's disease (AD). METHODS: In 38 patients (mean age 66.5 +/- 8.0 years) with AD, Mini-Mental State Examination (MMSE) scores were evaluated and CSF levels of t-tau and p-tau(181) measured. All patients underwent an 18F-FDG-PET scan. Image analysis including correlation analysis and principal component analysis (PCA) were performed using SPM5 and VINCI. RESULTS: Dementia severity (MMSE 21.2 +/- 4.9) correlated well with metabolic impairment especially in left hemisphere association areas that are typically affected in patients with AD (e.g. inferior parietal lobule, r = 0.512; medial temporal gyrus, r = 0.478; inferior temporal gyrus, r = 0.488; precuneus, r = 0.468; PCA: r = 0.639, F = 7.751; all P < 0.001). There were no associations between t-tau and p-tau(181) with dementia severity and only weak correlations between t-tau and cerebral glucose metabolism (superior parietal gyrus, r = -0.325, P < 0.05; precentral gyrus r = -0.418, P < 0.01; amygdala r = -0.362, P < 0.05). No correlations were found between p-tau(181) and regional hypometabolism in FDG-PET. CONCLUSION: MMSE and CSF t-tau represent different aspects of disease severity. Whilst MMSE is closely related to impaired cerebral glucose metabolism, CSF t-tau is less closely related and appears to be less well suited for assessment of disease progression.

STN-DBS activates the target area in Parkinson disease: an FDG-PET study.

OBJECTIVE: The immediate effects of deep brain stimulation (DBS) on subcortical neurons of its target region are controversial. METHODS: We measured the regional normalized resting cerebral metabolic rate of glucose (nCMRGlc) with 18-fluorodeoxyglucose (FDG) and PET in 12 patients with Parkinson disease (PD) and bilateral DBS of the subthalamic nucleus (STN) compared to 10 age-matched controls. PET was performed before surgery and 6 months after electrode implantation in DBS off- and on-conditions. Stereotactic coordinates of active STN electrode poles were determined with intraoperative skull x-ray and transferred to preoperative MR images. Subsequently, volumes of interest (VOIs) were placed around active electrode contacts, in the STN and in the globus pallidus. DBS induced changes of nCMRGlc values were determined in each VOI after PET and MRI coregistration. RESULTS: Electrode placement without stimulation led to significant FDG uptake reduction in the electrode region and in the STN (microlesional effect). Under active DBS, the local nCMRGlc significantly increased in all VOIs under investigation. CONCLUSIONS: The data demonstrate that deep brain stimulation (DBS) induced metabolic activation of the subthalamic region and the directly connected globus pallidus which is in line with local and remote excitation of neurons by high frequency stimulation. These PET findings most likely reflect tonic driving of the DBS target area and its projection sites via ortho- and antidromic fiber conduction. We conclude that subthalamic nucleus DBS has predominant excitatory properties and does, therefore, fundamentally differ from lesional neurosurgery.

In vivo evaluation of the uptake of [(123)I]FIAU, [(123)I]IVFRU and [(123)I]IVFAU by normal mouse brain: potential for noninvasive assessment of HSV-1 thymidine kinase gene expression in gliomas.

Radioiodinated 5-iodo-1-(2-fluoro-2-deoxy-beta-D-arabinofuranosyl)uracil (F *IAU) is most commonly used for noninvasive assessment of herpes simplex virus type 1 thymidine kinase (HSV-1-tk) gene expression. However, it does not permeate the intact blood-brain barrier (BBB) because of its moderate lipophilicity. In this work, three iodo-nucleosides, FIAU, IVFRU, and IVFAU, were radiolabeled with iodine-123 and tested for permeation of the BBB in mice and for potential measurement of HSV-1-tk gene expression in gliomas. The results demonstrate that brain uptake and retention of these nucleosides is not directly related to their lipophilicity. The low brain uptake of IVFAU, in conjunction with its higher and constant brain/blood ratio, may reflect greater stability against hydrolysis of the N-glycosidic bond. In vivo PET evaluations of [(124)I]IVFRU and [(124)I]IVFAU in tumor-bearing mice are warranted.

Imaging of acetylcholine esterase activity in brainstem nuclei involved in regulation of sleep and wakefulness.

Positron emission tomography with 11C-N-methyl-4-piperidyl-acetate (MP4A) was applied in eight healthy volunteers and two patients with mild Alzheimer's disease (AD) to assess acetylcholine esterase (AChE) activity in magnetic resonance imaging-identified brainstem nuclei. Uptake ratios in lateral dorsal tegmental and pedunculopontine nuclei relative to cerebellum yielded reproducible values for the AChE activity in controls and reduced values in AD, more marked in a patient with complaints of disturbed sleep. Cortical AChE activity was related to the extent of cognitive impairment which was more severe in the AD patient without sleep disturbance. This preliminary observational study demonstrates the feasibility to image and assess AChE activity in small nuclei of the brain stem. This approach may be helpful to investigate the interaction of various nuclei in the complex network regulating sleep and wakefulness in representative patient groups with documented sleep disturbance.

Role of in vivo imaging of the central nervous system for developing novel drugs.

Over the past decade imaging technologies employed in clinical neurosciences have significantly advanced. Imaging is not only used for the diagnostic work-up of neurological disorders but also crucial to follow up on therapeutic efforts. Using disease-specific imaging parameters, as read-outs for the efficiency of individual therapies, has facilitated the development of various novel treatments for neurological disease. Here, we review various imaging technologies, such as cranial computed tomography (CT), magnetic resonance imaging (MRI) and spectroscopy (MRS), positron emission tomography (PET) and single-photon emission computed tomography (SPECT), with respect to their current applications in non-invasive disease phenotyping and the measurement of therapeutic outcomes in neurology. In particular, applications in neuro-oncology, Parkinson's disease, Alzheimer's disease, and cerebral ischemia are discussed. Non-invasive imaging provides further insights into the molecular pathophysiology of human diseases and facilitates the design and implementation of improved therapies.

Primary stroke unit treatment followed by very early carotid endarterectomy for carotid artery stenosis after acute stroke.

BACKGROUND: Although it is recognized that carotid endarterectomy (CEA) is the treatment of choice in symptomatic internal carotid artery (ICA) stenosis, in the past, very early CEA has been shown to carry substantial risks. We assessed an interdisciplinary concept of very early CEA in patients with high-grade (>70%) symptomatic ICA stenosis at a single center. PATIENTS AND METHODS: The course of treatment and outcomes of patients who underwent CEA as early as possible after being referred to the stroke unit for symptoms of transient ischemic attack and stroke were prospectively evaluated, including the following parameters: age, severity of ischemia-related symptoms according to the modified Rankin scale, duration of symptoms until admission, multimodal imaging findings (color-coded duplex, cranial computed tomography, magnetic resonance imaging, positron emission tomography), duration until CEA, perioperative course and complications, as well as duration of in-hospital care. RESULTS: Fifty consecutive patients (median age 68 years, range 44-90) with clinical and imaging signs of transient ischemic attack (n = 19) or stroke (n = 31) were included from January 2000 until December 2004. All except 1 patient showed a preoperative Rankin < 4. There was a median time period of 6 h between the onset of symptoms and admission (range 1 h to 15 days) and a median duration of 4 days after admission until operation (range 1-21 days). Seven patients underwent CEA of the contralateral, severely stenosed ICA after symptomatic ipsilateral ICA occlusion. Four out of 5 patients who primarily underwent systemic thrombolysis recovered almost completely. Three patients (6%) experienced a clinical deterioration before surgery. In the majority of patients (43/50), CEA was performed under local anesthesia with selective shunt use which became necessary in 26%. Three patients (6%) had postoperative worsening due to new infarcts. In 2 cases, an intracerebral hemorrhage occurred, of which 1 remained asymptomatic. In 1 case, surgical revision was necessary because of an ICA thrombosis without permanent neurological decline. Patients were discharged after a median time of 14.5 days (range 4-44). CONCLUSIONS: After careful selection and preparation in a stroke unit, patients with acute stroke due to carotid stenosis can undergo very early CEA under local anesthesia with a perioperative risk comparable with the risk of later endarterectomy, therefore preventing very early stroke recurrences.

A proposed regional hierarchy in recovery of post-stroke aphasia.

Activation studies in patients with aphasia due to stroke or tumours in the dominant hemisphere have revealed effects of disinhibition in ipsilateral perilesional and in contralateral homotopic cortical regions, referred to as collateral and transcallosal disinhibition. These findings were supported by studies with selective disturbance of cortical areas by repetitive transcranial magnetic stimulation (rTMS) in healthy volunteers and in patients with focal brain lesions. Both, collateral as well as transcallosal disinhibition might be relevant for the compensation of lesions within a functional network. From these data a hierarchical organization of recovery of aphasia after stroke and of compensation of language defects due to brain tumours can be deduced, by which the reactivation of undamaged network areas of the ipsilateral hemisphere usually lead to better outcome than the involvement of homotopic contra-lateral regions. rTMS can be used to identify areas relevant for speech production and might play a role in treatment strategies targeted at modulating the activity of contralateral homotopic areas of the functional network which might interfere with language recovery.

[Fatal familial insomnia: case presentation and discussion of typical clinical and imaging findings]. / Fatale familiäre Insomnie: Kasuistik zur Darstellung der klinischen und bildgebenden Befunde.

Fatal familial insomnia (FFI) is a hereditary prion disease caused by a mutation in codon 178 of the prion protein gene PRNP on chromosome 20. It is characterized by disturbed night sleep, resulting in daily vigilance perturbations and a variety of other neurological symptoms. We present the case of a 46-year-old woman deteriorating despite immunosuppressive treatment which was initiated suspecting cerebral vasculitis as the cause of her progressive neurological symptoms. The correct diagnosis was established only post mortem. Based on the case presented here, we discuss typical clinical symptoms and imaging findings. In particular, we outline how modern diagnostic methods such as positron emission tomography with [(15)O]H(2)O and [(18)F]FDG and single photon emission computed tomography can add valuable information to results from conventionally performed imaging techniques and genetic testing.

No effect of intravenous immunoglobulins on cytokine-producing lymphocytes in secondary progressive multiple sclerosis.

Intravenous immunoglobulins (IVIG) have been effective in reducing multiple sclerosis (MS) disease activity and improving disability scores. However, the mechanism by which this beneficial effect is achieved remains unclear. An effect of IVIG on pro- and anti-inflammatory cytokines which are thought to play a role in the disease process - has been postulated in a number of animal and ex vivo studies. Hence, we performed a study on 34 patients with secondary progressive (SP) MS being treated with monthly IVIG or placebo for two years according to the protocol of the ESIMS study. Clinical outcome measures and cytokine production (interferon gamma, tumour necrosis factor alpha, interleukin-4 and -10) were recorded in all patients and compared with respect to the treatment group. Against our expectations, IVIG did not reduce the relapse rate or the progression of disability or cytokine production. Our data argue against an enduring immunomodulating effect of IVIG, at least in SPMS.