Hyperbolic graph embedding of MEG brain networks to study brain alterations in individuals with subjective cognitive decline

An expansive area of research focuses on discerning patterns of alterations in functional brain networks from the early stages of Alzheimer's disease, even at the subjective cognitive decline (SCD) stage. Here, we developed a novel hyperbolic MEG brain network embedding framework for transforming high-dimensional complex MEG brain networks into lower-dimensional hyperbolic representations. Using this model, we computed hyperbolic embeddings of the MEG brain networks of two distinct participant groups: individuals with SCD and healthy controls. We demonstrated that these embeddings preserve both local and global geometric information, presenting reduced distortion compared to rival models, even when brain networks are mapped into low-dimensional spaces. In addition, our findings showed that the hyperbolic embeddings encompass unique SCD-related information that improves the discriminatory power above and beyond that of connectivity features alone. Notably, we introduced a unique metric-the radius of the node embeddings-which effectively proxies the hierarchical organization of the brain. Using this metric, we identified subtle hierarchy organizational differences between the two participant groups, suggesting increased hierarchy in the dorsal attention, frontoparietal, and ventral attention subnetworks among the SCD group. Last, we assessed the correlation between these hierarchical variations and cognitive assessment scores, revealing associations with diminished performance across multiple cognitive evaluations in the SCD group. Overall, this study presents the first evaluation of hyperbolic embeddings of MEG brain networks, offering novel insights into brain organization, cognitive decline, and potential diagnostic avenues of Alzheimer's disease.

Effects of spaceflight on the EEG alpha power and functional connectivity

Electroencephalography (EEG) can detect changes in cerebral activity during spaceflight. This study evaluates the effect of spaceflight on brain networks through analysis of the Default Mode Network (DMN)'s alpha frequency band power and functional connectivity (FC), and the persistence of these changes. Five astronauts' resting state EEGs under three conditions were analyzed (pre-flight, in-flight, and post-flight). DMN's alpha band power and FC were computed using eLORETA and phase-locking value. Eyes-opened (EO) and eyes-closed (EC) conditions were differentiated. We found a DMN alpha band power reduction during in-flight (EC: p < 0.001; EO: p < 0.05) and post-flight (EC: p < 0.001; EO: p < 0.01) when compared to pre-flight condition. FC strength decreased during in-flight (EC: p < 0.01; EO: p < 0.01) and post-flight (EC: ns; EO: p < 0.01) compared to pre-flight condition. The DMN alpha band power and FC strength reduction persisted until 20 days after landing. Spaceflight caused electrocerebral alterations that persisted after return to earth. Periodic assessment by EEG-derived DMN analysis has the potential to become a neurophysiologic marker of cerebral functional integrity during exploration missions to space.

An individual data-driven virtual resection model based on epileptic network dynamics in children with intractable epilepsy: a magnetoencephalography interictal activity application

Epilepsy surgery continues to be a recommended treatment for intractable (medication-resistant) epilepsy; however, 30-70% of epilepsy surgery patients can continue to have seizures. Surgical failures are often associated with incomplete resection or inaccurate localization of the epileptogenic zone. This retrospective study aims to improve surgical outcome through in silico testing of surgical hypotheses through a personalized computational neurosurgery model created from individualized patient's magnetoencephalography recording and MRI. The framework assesses the extent of the epileptic network and evaluates underlying spike dynamics, resulting in identification of one single brain volume as a candidate for resection. Dynamic-locked networks were utilized for virtual cortical resection. This in silico protocol was tested in a cohort of 24 paediatric patients with focal drug-resistant epilepsy who underwent epilepsy surgery. Of 24 patients who were included in the analysis, 79% (19 of 24) of the models agreed with the patient's clinical surgery outcome and 21% (5 of 24) were considered as model failures (accuracy 0.79, sensitivity 0.77, specificity 0.82). Patients with unsuccessful surgery outcome typically showed a model cluster outside of the resected cavity, while those with successful surgery showed the cluster model within the cavity. Two of the model failures showed the cluster in the vicinity of the resected tissue and either a functional disconnection or lack of precision of the magnetoencephalography-MRI overlapping could explain the results. Two other cases were seizure free for 1 year but developed late recurrence. This is the first study that provides in silico personalized protocol for epilepsy surgery planning using magnetoencephalography spike network analysis. This model could provide complementary information to the traditional pre-surgical assessment methods and increase the proportion of patients achieving seizure-free outcome from surgery.

Noise characteristics in spaceflight multichannel EEG

The cognitive performance of the crew has a major impact on mission safety and success in space flight. Monitoring of cognitive performance during long-duration space flight therefore is of paramount importance and can be performed using compact state-of-the-art mobile EEG. However, signal quality of EEG may be compromised due to the vicinity to various electronic devices and constant movements. We compare noise characteristics between in-flight extraterrestrial microgravity and ground-level terrestrial electroencephalography (EEG) recordings. EEG data recordings from either aboard International Space Station (ISS) or on earth's surface, utilizing three EEG amplifiers and two electrode types, were compared. In-flight recordings showed noise level of an order of magnitude lower when compared to pre- and post-flight ground-level recordings with the same EEG system. Noise levels between ground-level recordings with actively shielded cables, and in-flight recordings without shielded cables, were similar. Furthermore, noise level characteristics of shielded ground-level EEG recordings, using wet and dry electrodes, and in-flight EEG recordings were similar. Actively shielded mobile dry EEG systems will support neuroscientific research and neurocognitive monitoring during spaceflight, especially during long-duration space missions.

Containment measures during the COVID pandemic: The role of non-pharmaceutical health policies

Many countries have imposed a set of non-pharmaceutical health policy interventions in an effort to slow the spread of the COVID-19 pandemic. The objective of this paper is to examine the effects of the interventions, drawing on evidence from the OECD countries. A special feature here is the mechanism that underlies the impact of the containment policies. To this end, a causal mediation analysis decomposing the total effect into a direct and an indirect effect is conducted. The key finding is a dual cause-effect channel. On the one hand, there is a direct effect of the non-pharmaceutical interventions on the various health variables. Beyond this, a quantitatively dominant indirect impact of non-pharmaceutical interventions operating via voluntary changes in social distancing is shown.

Complete corpus callosotomy using a frameless navigation probe through a minicraniotomy in children with medically refractory epilepsy: A case series and technical note

Background

Medically refractory epilepsy constitutes up to one-third of the epilepsy pediatric patients. Corpus callosotomy (CC) has been used for the treatment of medically refractory epilepsy in children with atonic seizures and generalized tonic-clonic (GTC) seizures. In this case series study, we are describing a novel technique for CC using the frameless navigation probe through a minicraniotomy.

Methods

Thirteen pediatric patients with the diagnosis of medically refractory epilepsy predominantly GTC with drop attack who underwent extensive Phase I. An L-shape was done, then through a 4 × 3 cm craniotomy, we were able to open the interhemispheric fissure until the corpus callosum is visualized. The Stealth probe is then used to go down to the midline raphe which is followed anteriorly then traced posteriorly to the anterior border of the vein of Galen. Finally, the Stealth probe is used to confirm the completeness of the callosotomy.

Results

The procedure was accomplished successfully with no intraoperative complications; mean surgical time is 3 h:07 m. The mean follow-up was 31.5 months. All patients achieved significant seizure control. No patients experienced worsening of their atonic seizures after surgery compared with their preoperative state; however, six patients achieved Engel Class I, four patients achieved Engel Class II, and three patients achieved Engel Class III.

Conclusion

Complete CC using a frameless navigation probe is a novel and effective technique for the treatment of medically refractory epilepsy with a very good surgical and seizure outcomes, minimal neurological morbidity, minimal blood loss, and short OR time.

Has Germany's temporary VAT rates cut as part of the COVID-19 fiscal stimulus boosted growth?

On 3 June 2020, the German government announced a EUR 130 billion fiscal stimulus package to stimulate market demand and jumpstart the economy in the wake of the COVID-19 pandemic lockdown in the spring of 2020. The most prominent measure of this package is an unconventional fiscal policy in the form of a temporary VAT rates cut for six months, from 1 July to 31 December 2020. Employing a dynamic stochastic general equilibrium (DSGE) framework, we study the efficiency of the VAT tax rates cut for ameliorating the consequences of the pandemic recession. The simulation of the calibrated DSGE model yields a tax policy-induced real GDP increase of about 0.3% points for 2020.

The People's bank of China's response to the coronavirus pandemic: A quantitative assessment

The People's Bank of China (PBoC) has implemented numerous measures to cushion the impacts of the COVID-19 health crisis on the Chinese economy. Since the current monetary policy framework features a multi-instrument mix of liquidity tools and pricing signals, we employ a dynamic-factor modelling approach to derive a composite indicator of China's monetary policy stance. Our quantitative assessment shows that the PBoC's policy response to the outbreak of the COVID-19 pandemic has been swift and decisive. Specifically, our estimates reveal that the PBoC has implemented novel policy measures to ensure that commercial banks maintain liquidity access and credit provision during the COVID-19 crisis.

Towards Best Practices in Clinical Magnetoencephalography: Patient Preparation and Data Acquisition

A magnetoencephalography (MEG) recording for clinical purposes requires a different level of attention and detail than that for research. As contrasted with a research subject, the MEG technologist must work with a patient who may not fully cooperate with instructions. The patient is on a clinical schedule, with generally no opportunity to return due to an erroneous or poor acquisition. The data will generally be processed by separate MEG analysts, who require a consistent and high-quality recording to complete their analysis and clinical report. To assure a quality recording, (1) MEG technologists must immediately recheck their scalp measurement data during the patient preparation, to catch disturbances and ensure registration accuracy of the patient fiducials, electrodes, and head position indicator coils. During the recording, (2) the technologist must ensure that the patient remains quiet and as far as possible into the helmet. After the recording, (3) the technologist must consistently prepare the data for subsequent clinical analysis. This article aims to comprehensively address these matters for practitioners of clinical MEG in a helpful and practical way. Based on the authors' experiences in recording over three thousand patients between them, presented here are a collection of techniques for implementation into daily routines that ensure good operation and high data quality. The techniques address a gap in the clinical literature addressing the multitude of potential sources of error during patient preparation and data acquisition, and how to prevent, recognize, or correct those.

Publisher Correction: Dimensionally and environmentally ultra-stable polymer composites reinforced with carbon fibres

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Publisher Correction: Dimensionally and environmentally ultra-stable polymer composites reinforced with carbon fibres

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Real-Time Warning Signs of Emerging and Collapsing Chinese House Price Bubbles

The recent increase in Chinese house prices has led to concerns that China is vulnerable to asset price shocks. In this paper, we apply recently developed recursive unit root tests to spot the beginning and the end of potential speculative bubbles in Chinese house price cycles. Overall, we find that except for 2009–10 actual house prices are not significantly disconnected from fundamentals. Thus, the evidence for speculative house price bubbles in China is in general weak.

Dimensionally and environmentally ultra-stable polymer composites reinforced with carbon fibres

The quest to develop materials that enable the manufacture of dimensionally ultra-stable structures for critical-dimension components in spacecraft has led to much research over many decades and the evolution of carbon fibre reinforced polymer materials. This has resulted in structural designs that feature a near-zero coefficient of thermal expansion. However, the dimensional instabilities that result from moisture ingression and release remain the fundamental vulnerability of the matrix, which restricts many applications. Here, we address this challenge by developing a space-qualifiable physical surface barrier that blends within the mechanical properties of the composite, thus becoming part of the composite itself. The resulting enhanced composite features mechanical integrity and a strength that is superior to the underlying composite, while remaining impervious to moisture and outgassing. We demonstrate production capability for a model-sized component for the Sentinel-5 mission and demonstrate such capability for future European Space Agency (ESA) and National Aeronautics and Space Administration (NASA) programmes such as Copernicus Extension, Earth Explorer and Science Cosmic Visions.

Corrigendum: The Importance of the Validation of M/EEG With Current Biomarkers in Alzheimer's Disease

[This corrects the article DOI: 10.3389/fnhum.2019.00017.].

The Importance of the Validation of M/EEG With Current Biomarkers in Alzheimer's Disease

Current biomarkers used in research and in clinical practice in Alzheimer's Disease (AD) are the analysis of cerebral spinal fluid (CSF) to detect levels of Aβ42 and phosphorylated-tau, amyloid and FDG-PET, and MRI volumetry. Some of these procedures are still invasive for patients or expensive. Electroencephalography (EEG) and Magnetoencephalography (MEG) are two non-invasive techniques able to detect the early synaptic dysfunction and track the course of the disease. However, in spite of its added value they are not part of the standard of care in clinical practice in dementia. In this paper we review what these neurophysiological techniques can add to the early diagnosis of AD, whether results in both modalities are related to each other or not, as well as the need of its validation against current biomarkers. We discuss their potential implications for the better understanding of the pathophysiological mechanisms of the disease as well as the need of performing simultaneous M/EEG recordings to better understand discrepancies between these two techniques. Finally, more studies are needed studying M/EEG with amyloid and Tau biomarkers.

[Diagnostic imaging of breast cancer : An update]

Advances in imaging of the female breast have substantially influenced the diagnosis and probably also the therapy and prognosis of breast cancer in the past few years. This article gives an overview of the most important imaging modalities in the diagnosis of breast cancer. Digital mammography is considered to be the gold standard for the early detection of breast cancer. Digital breast tomosynthesis can increase the diagnostic accuracy of mammography and is used for the assessment of equivocal or suspicious mammography findings. Other modalities, such as ultrasound and contrast-enhanced magnetic resonance imaging (MRI) play an important role in the diagnostics, staging and follow-up of breast cancer. Percutaneous needle biopsy is a rapid and minimally invasive method for the histological verification of breast cancer. New breast imaging modalities, such as contrast-enhanced spectral mammography, diffusion-weighted MRI and MR spectroscopy can possibly further improve breast cancer diagnostics; however, further studies are necessary to prove the advantages of these methods so that they cannot yet be recommended for routine clinical use.

A multicenter study of the early detection of synaptic dysfunction in Mild Cognitive Impairment using Magnetoencephalography-derived functional connectivity

Synaptic disruption is an early pathological sign of the neurodegeneration of Dementia of the Alzheimer's type (DAT). The changes in network synchronization are evident in patients with Mild Cognitive Impairment (MCI) at the group level, but there are very few Magnetoencephalography (MEG) studies regarding discrimination at the individual level. In an international multicenter study, we used MEG and functional connectivity metrics to discriminate MCI from normal aging at the individual person level. A labeled sample of features (links) that distinguished MCI patients from controls in a training dataset was used to classify MCI subjects in two testing datasets from four other MEG centers. We identified a pattern of neuronal hypersynchronization in MCI, in which the features that best discriminated MCI were fronto-parietal and interhemispheric links. The hypersynchronization pattern found in the MCI patients was stable across the five different centers, and may be considered an early sign of synaptic disruption and a possible preclinical biomarker for MCI/DAT.

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Across centers reliable abnormalities in the neuronal network organization of MCI patients

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These findings are consistent with the view that AD may, in its earliest stages, represent a disconnection syndrome.

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A high rate of classification accuracy in a blind study, especially for individuals who were cognitively normal

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All these suggest that MEG may be a useful marker of preclinical synaptic disruption.

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The hypersynchronization found in MCI patients may represent a compensatory response.

Buried under gypsum powder – A rare respiratory complication

Gypsum is a mineral dust consisting of calcium sulfate and is commonly used in building construction. We here report the first case of an acute calcium sulfate aspiration.

An accidental avalanche of fine gypsum powder covered entirely a silo worker. He aspirated a large amount of gypsum powder without loosing consciousness. At admission to the emergency department the patient was breathing spontaneously and directly underwent emergency bronchoscopy. Acute tracheobronchitis was diagnosed. Remaining calcium sulfate was removed by aspiration without rinsing with additional water in order to avoid further exothermic damage to the bronchial mucosa from chemical reactions. He received steroid treatment and antibiotics, as well as bronchodilatative therapy in an attempt to increase mucociliary clearance. Within a month the patient was symptomfree without any residual radiological or functional impairment.

This unusual aspiration accident is to our knowledge the first case report of an accidental calcium sulfate aspiration. Our treatment choice left the patient without residual pulmonary impairment.

[Visualisation of bioabsorbable suture anchors with digital projection radiography and magnetic resonance imaging]

BACKGROUND

During the last few years bioabsorbable suture anchors have become widely established along side metallic suture anchors in orthopaedic surgery. However, there are still some difficulties in evaluating the postoperative situation after implanting bioabsorbable suture anchors. The aim of this study was to examine the visualisation of bioabsorbable suture anchors with digital projection radiography and magnetic resonance imaging.

MATERIALS AND METHODS

Ten Mitek-Anchor-Panalok® suture anchors made of polylactic acid were implanted in an ex-vivo animal study design. After implantation the specimens were examined with digital projection radiography and MRI. The analysis was performed with regard to the bony defects and the anchor material itself.

RESULTS

With digital projection radiography and MRI, it was possible to detect the bony defects after implantation of the anchors. The anchor material could not be visualised.

CONCLUSION

The results of this study demonstrate that neither digital projection radiography nor MRI is well suited for the detection of the bioabsorbable suture anchors in the postoperative situation. Whereas the bony defects can be well described, the anchors cannot be directly visualised. The visualisation of bioabsorbable anchors remains a clinical problem in orthopaedic surgery.

Neurophysiological investigation of idiopathic acquired auditory-visual synesthesia

We present a case of acquired auditory-visual synesthesia and its neurophysiological investigation in a healthy 42-year-old woman. She started experiencing persistent positive and intermittent negative visual phenomena at age 37 followed by auditory-visual synesthesia. Her neurophysiological investigation included video-EEG, fMRI, and MEG. Auditory stimuli (700 Hz, 50 ms duration, 0.5 s ISI) were presented binaurally at 60 db above the hearing threshold in a dark room. The patient had bilateral symmetrical auditory-evoked neuromagnetic responses followed by an occipital-evoked field 16.3 ms later. The activation of occipital cortex following auditory stimuli may represent recruitment of existing cross-modal sensory pathways.

Magnetoencephalography as a putative biomarker for Alzheimer's disease

Alzheimer's Disease (AD) is the most common dementia in the elderly and is estimated to affect tens of millions of people worldwide. AD is believed to have a prodromal stage lasting ten or more years. While amyloid deposits, tau filaments, and loss of brain cells are characteristics of the disease, the loss of dendritic spines and of synapses predate such changes. Popular preclinical detection strategies mainly involve cerebrospinal fluid biomarkers, magnetic resonance imaging, metabolic PET scans, and amyloid imaging. One strategy missing from this list involves neurophysiological measures, which might be more sensitive to detect alterations in brain function. The Magnetoencephalography International Consortium of Alzheimer's Disease arose out of the need to advance the use of Magnetoencephalography (MEG), as a tool in AD and pre-AD research. This paper presents a framework for using MEG in dementia research, and for short-term research priorities.

Magnetoencephalography and magnetic source imaging in epilepsy

Magnetoencephalograpy (MEG) and Electroencephalography (EEG) provide physicians with complementary data and should not be regarded as mutually exclusive evaluative methods of cerebral activity. Relevant to this edition, MEG applications related to the surgical treatment of epilepsy will be discussed exclusively. Combined MEG/EEG data collection and analysis should be a routine diagnostic practice for patients who are still suffering seizures due to the failure of drug therapy. Clinicians in the field of epilepsy agree that a greater number of patients would benefit from surgery than are currently referred for pre-surgical evaluation. Regardless of age or presumed epilepsy syndrome, all patients deserve the possibility of living seizure-free through surgery. Technological advances in superconducting elements as well as the digital revolution were necessary for the development of MEG into a clinically valuable diagnostic tool. Compared to the examination of electrical activity of the brain, investigation into its magnetic concomitant is a more recent development. In MEG, cerebral magnetic activity is recorded using magnetometer or gradiometer whole-head systems. MEG spikes usually have a shorter duration and a steeper ascending slope than EEG spikes, and variable phase relationships to EEG. When co-registered spikes are compared, it is apparent that EEG and MEG spikes differ. There is agreement among investigators that more interictal epileptiform spikes are seen in MEG than EEG. When MEG is co-registered with invasive intracranial EEG data, the detection rate of interictal epileptiform discharges depends on the number of electrocorticographic channels that record a spike. When patients have a non-localizing video-EEG recording, MEG pinpoints the resected area in 58-72% of the cases.

Acquired auditory-visual synesthesia: A window to early cross-modal sensory interactions

Synesthesia is experienced when sensory stimulation of one sensory modality elicits an involuntary sensation in another sensory modality. Auditory-visual synesthesia occurs when auditory stimuli elicit visual sensations. It has developmental, induced and acquired varieties. The acquired variety has been reported in association with deafferentation of the visual system as well as temporal lobe pathology with intact visual pathways. The induced variety has been reported in experimental and post-surgical blindfolding, as well as intake of hallucinogenic or psychedelics. Although in humans there is no known anatomical pathway connecting auditory areas to primary and/or early visual association areas, there is imaging and neurophysiologic evidence to the presence of early cross modal interactions between the auditory and visual sensory pathways. Synesthesia may be a window of opportunity to study these cross modal interactions. Here we review the existing literature in the acquired and induced auditory-visual synesthesias and discuss the possible neural mechanisms.

Hypersensitivity pneumonitis secondary to lovebirds: a new cause of bird fancier's disease

Hypersensitivity pneumonitis (HP) is an immunologically mediated lung disease due to the repetitive inhalation of antigens. Most new cases arise from residential exposures, notably to birds, and are thus more difficult to recognise. The present authors report a 59-yr-old male who complained of dyspnoea and cough while being treated with amiodarone. Pulmonary function tests revealed restriction and obstruction with low diffusing lung capacity for carbon monoxide and partial pressure of oxygen. A high-resolution computed tomography chest scan and bronchoalveolar lavage showed diffuse bilateral ground-glass attenuation and lymphocytic alveolitis, respectively. Initial diagnosis was amiodarone pulmonary toxicity, but because of a rapidly favourable evolution, this diagnosis was questioned. A careful environmental history revealed a close contact with lovebirds shortly before the onset of symptoms. Precipitins were strongly positive against lovebird droppings, but were negative against other avian antigens. The patient was diagnosed with hypersensitivity pneumonitis to lovebirds. Avoidance of lovebirds and steroid treatment led to rapid improvement. The present observation identifies a new causative agent for hypersensitivity pneumonitis and highlights the importance of a thorough environmental history and of searching for precipitins against antigens directly extracted from the patient's environment. These two procedures should allow a more precise classification of some cases of pneumonitis, and thus might avoid progression of active undiagnosed hypersensitivity pneumonitis to irreversible fibrosis or emphysema.

Objective documentation of traumatic brain injury subsequent to mild head trauma: multimodal brain imaging with MEG, SPECT, and MRI

OBJECTIVE

To determine to what extent magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT), and magnetoencephalography (MEG) can provide objective evidence of brain injury in adult patients with persistent (>1 year) postconcussive symptoms following mild blunt head trauma.

DESIGN

A retrospective and blind review of imaging data with respect to the presence of specific somatic, psychiatric, and cognitive complaints.

SETTING/PARTICIPANTS

Thirty complete data sets (with MRI, SPECT, MEG, and neuropsychological testing results) were collected between 1994 and 2000 from the MEG programs at the Albuquerque VAMC and the University of Utah.

MAIN OUTCOME MEASURES

MRI data were evaluated for focal and diffuse structural abnormalities, SPECT data for regions of hypoperfusion, and resting MEG data for abnormal dipolar slow wave activity (DSWA) and epileptiform transients.

RESULTS

Structural MRI was abnormal for 4 patients. SPECT showed regions of hypoperfusion in 12 patients, while MEG showed abnormal activity in 19 patients. None of the imaging methods produced findings statistically associated with postconcussive psychiatric symptoms. A significant association was found between basal ganglia hypoperfusion and postconcussive headaches. For patients with cognitive complaints, abnormalities were more likely to be detected by MEG (86%) than either SPECT (40%) or MRI (18%) (P<.01). MEG also revealed significant (P<.01) associations between temporal lobe DSWA and memory problems, parietal DSWA and attention problems, and frontal DSWA and problems in executive function.

CONCLUSIONS

Functional brain imaging data collected in a resting state can provide objective evidence of brain injury in mild blunt head trauma patients with persistent postconcussive somatic and/or cognitive symptoms. MEG proved to be particularly informative for patients with cognitive symptoms.

[Rapidly progressing cyst of the pancreas as a manifestation of an undifferentiated pancreatic carcinoma with osteoclastic giant cells]

HISTORY AND FINDINGS ON ADMISSION

A 62-year-old woman presented with acute abdominal pain.

INVESTIGATIONS AND DIAGNOSIS

Examination revealed a 3 cm large cyst of the pancreatic head accompanied by an acute pancreatitis.

TREATMENT AND COURSE

The cystic mass showed rapid increase. After explorative laparatomy a pancreaticoduodenectomy was performed. Pathologic examination revealed an undifferentiated carcinoma with osteoclast-like giant cells. The tumor grew rapidly and the patient died 10 weeks after admission.

CONCLUSIONS

An undifferentiated carcinoma with osteoclast-like giant-cells is a very rare cystic tumor of the pancreas. An accurate preoperative diagnosis of cystic tumors is only achieved in about 30 percent. Therefore, surgical exploration should be considered for all cystic neoplasms and cystic tumors that are not clearly defined.

Erste Erfahrungen mit einem Flächendetektor-Volumen-CT (fpVCT) in der experimentellen Osteoporosediagnostik am Kleintiermodell

BACKGROUND

Flat-panel volumetric computed tomography (fpVCT) is a new, noninvasive CT imaging modality with increased isotropic resolution. Technical details, potential applications, and our initial experience with a fpVCT prototype scanner in the imaging of osteoporosis in a rat model are presented.

METHODS

To date, 21 rats have been investigated in vivo with fpVCT. Pharmacologic effects on bone mineral density (BMD) and structure were of special interest. Image evaluation focussed on the second lumbar vertebra and the left femoral bone. To validate measurement results, BMD values calculated with fpVCT were correlated with results of BMD measurements from ashing of the second lumbar vertebra and femoral bones.

RESULTS

Our initial results show that fpVCT is capable of detecting differences in BMD between ovariectomized rats treated with estradiol and a control group with high statistical significance (p<0.05), corresponding to ashing as the gold standard.

CONCLUSIONS

In a rat model, fpVCT imaging is especially useful in longitudinal in vivo investigations of BMD measures. Spatial resolution of up to 150 microm allows imaging of the trabecular structure only in human cadaveric bones.

Optimal evaluation of digital electroencephalograms

Currently available digital EEG equipment provides considerably greater opportunities for clinical data analysis than is generally appreciated especially when appropriate software is used. Data from 7 different laboratories that had been obtained for routine diagnostic evaluations on 7 different EEG instruments and stored on compact disks were investigated. Since the instruments do not filter the data at input, ultra slow activity down to 0.01 Hz is currently being recorded but the attenuation factor is instrument dependent. Nevertheless, relevant clinical information is potentially available in these data and needs to be explored. Several examples in regard to epilepsy are presented. Determination of seizure onset may depend on the frequencies that are examined. The use of appropriate filter settings and viewing windows for the clinical question to be answered is stressed. Differentiation between simple and complex spike wave discharges, as well as spread of spikes, can readily be achieved by expanding the time base to 1 or 2 seconds and placing a cursor on the peak of the negative spike. Latencies in the millisecond range can then become apparent. EEGs co-registered with MEG should be evaluated with the same software in order to allow an adequate assessment of the similarities and differences between electrical and magnetic activity. An example of a comparison of EEG, planar gradiometers and magnetometers for an averaged spike is shown.

Cerebral Electromagnetic Activity in the Subdelta Range

The frequency range between 0.1 and 0.9 Hz was investigated with magnetoelectroencephalography-EEG coregistration in 10 adult patients with epilepsy and five children with other neurologic conditions. In all instances, a dominant rhythm between 0.2 and 0.4 Hz could be observed in the waking and sleeping states. It showed a waxing and waning quality and was unrelated to eye opening or closing but increased in amplitude during sleep. The maximum was usually in the occipital areas but occasionally in the frontal regions. The rhythm was more persistent and better seen in the magnetoelectroencephalogram, but subdelta activity was also discernible in the EEG. The magnetoelectroencephalographic rhythmicity and frequency suggested possible respiration artifact. Two normal control subjects were therefore investigated by electroencephalography while respirations were monitored. A clear relation to respiration was established. It persisted during breath-holding, albeit at lower amplitude. Larger amplitude transients occurred before and at the cessation of breath-holding as well as hyperventilation. An observed frequency increase before voluntary hyperventilation suggests a relation to the readiness potential and event-related desynchronization as well as synchronization. Subdelta frequencies, which can be readily recorded without special DC amplifiers, provide additional information for clinical as well as research data. They may also be an interface between autonomic and voluntary functions, especially in regard to respiration.

Cardio-respiratory contributions to the magnetoencephalogram

Modern MEG technology provides whole head helmet systems which extend posterior to the base of the skull. While this provides better visualization of low temporal structures it also allows the intrusion of activity that is of cardiac origin. This consists not only of the QRS complex of the MCG but a late component (LC) during the SP interval. This tends to consist of a series of waves and has a different topographic distribution from the magnetic QRS complex. The LC is usually most prominent in the low occipital and sub-occipital sensors but can occur also in other areas. When the high pass filter is set to 0.1 Hz it can be seen that the LC rides on a slow wave of about 0.3 Hz, which is linked to respiration. Principal component analysis of cardiac cycles averaged from the ECG separates the MCG from the LC. The physiology of the LC is unknown at this time but it may be related to the ballistocardiogram. Algorhythms designed to remove the cardiac contributions to the MEG will have to take the LC and its marked variability into account.