Detection of Tectonic and Crustal Deformation using GNSS Data Processing: The Case of PPGnet

Aitolo-Akarnania prefecture, western Greece, is an area with strong earthquakes and large active fault systems. The most prominent are the Katouna sinistral strike slip fault and the Trichonis Lake normal fault system. Their proximity to large cities, and the lack of detailed information on their seismogenic potential, calls for multiparametric research. Since 2013, the area’s crustal deformation has been monitored by a dense GNSS Network (PPGNet), consisting of five stations, equipped with Leica and Septentrio receivers. The objective of this network is to define the rate of deformation across these two main fault systems. Data is recorded using two sampling frequencies, 1 Hz and 10Hz, producing hourly and daily files. Daily data is processed using Bernese GNSS Processing Software using final orbits of International GNSS Service. Double-difference solution is computed using phase measurements from the PPGNet network complemented by four stations from Athens’ National Observatory GNSS network and six stations from METRICA network. First results show a NNE movement at PVOG station of 12 mm/y and a similar movement at RETS station of about 9 mm/y. This means that the Trichonis Lake normal fault system, located between these two stations, depicts a slip rate of 3 mm/y. KTCH and RGNI stations move eastwards at a velocity of about 5 mm/y due to the Katouna-Stamna fault system. Data from PPGNet has provided important results on crustal deformation in the area, i.e. slip rates have been attributed to specific fault systems. The comparison and links of these data with broader geodynamic models is now possible and we expect, in a later phase that will provide a more detailed image of the associated seismic hazard for Aitolo-Akarnania. Doi: 10.28991/cej-2021-03091633 Full Text: PD

FDG-PET underscores the key role of the thalamus in frontotemporal lobar degeneration caused by C9ORF72 mutations

C9ORF72 mutations are the most common cause of familial frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS). MRI studies have investigated structural changes in C9ORF72-associated FTLD (C9FTLD) and provided first insights about a prominent involvement of the thalamus and the cerebellum. Our multicenter, F-18-fluorodeoxyglucose positron-emission tomography study of 22 mutation carriers with FTLD, 22 matched non-carriers with FTLD, and 23 cognitively healthy controls provided valuable insights into functional changes in C9FTLD: compared to non-carriers, mutation carriers showed a significant reduction of glucose metabolism in both thalami, underscoring the key role of the thalamus in C9FTLD. Thalamic metabolism did not correlate with disease severity, duration of disease, or the presence of psychotic symptoms. Against our expectations we could not demonstrate a cerebellar hypometabolism in carriers or non-carriers. Future imaging and neuropathological studies in large patient cohorts are required to further elucidate the central role of the thalamus in C9FTLD

Crustal deformation in Aitolo-Akarnania prefecture using permanent GNSS stations

The present PhD thesis examines the tectonic deformation in the area of Aitoloakarnania prefecture, Western Greece, using GNSS data, as well as the study of the seismic hazard of the above area. Although the rough characteristics and the main tectonic elements in the area have been recognized, there is a lack of continuous and dense monitoring of the crustal deformation in the area.Since 2013 crustal deformation in the area, is monitored by a network of five GNSS stations, complementary to permanent seismic network. The GNSS Network PPGNet consists of five stations in Aitolo-Akarnania, i.e. Katochi, (KTCH), Lepenou (LEPE), Paravola (PVOG), Rigani (RGNI) and Kato Retsina (RETS). Seismic hazard assessment attracts the interest of the scientific community especially in earthquake pone areas where there are complex fault systems. The traditional seismic hazard assessment methods suffer from large uncertainty and incompleteness problems. This dissertation summarizes the preexisting literature and the main deformation models that have been proposed so far, but also the seismic hazard assessment methodology follow fault specific approaches where seismic sources are geologically constrained active faults. The main goal of the present PhD thesis is the extraction of reliable results and to obtain a higher spatial resolution of hazard assessment in the examined area of Aitolo-Αkarnania. It is believed that data from PPGNet will provide valuable information on the Aitolo-Akarnania area internal deformation and eventually will help us understand how this deformation is linked to the major active structures in the broader area.Η παρούσα διδακτορική διατριβή εξετάζει την τεκτονική παραμόρφωση στην περιοχή του νομού Αιτωλοακαρνανίας, στη Δυτική Ελλάδα, χρησιμοποιώντας δεδομένα GNSS, καθώς και τη σεισμική επικινδυνότητα της παραπάνω περιοχής. Αν και τα γενικά τεκτονικά χαρακτηριστικά της περιοχής είναι γνωστά, εντούτοις υπάρχει ανάγκη για συνεχή και λεπτομερή παρακολούθησή της. Από το 2013 η παραμόρφωση του φλοιού στην περιοχή παρακολουθείται από ένα δίκτυο GNSS, συμπληρωματικά προς το μόνιμο σεισμικό δίκτυο. Το δίκτυο GNSS PPGNet αποτελείται από πέντε σταθμούς στην Αιτωλοκαρνανία, και συγκεκριμένα στις περιοχές Κατοχή, (KTCH), Λεπενού (ΛΕΠΕ), Παραβόλα (PVOG), Ρίγανη (RGNI) και Κάτω Ρετσίνα (RETS). H εκτίμηση της σεισμικής επικινδυνότητας προσελκύει το ενδιαφέρον της επιστημονικής κοινότητας, ειδικά σε έντονα σεισμογενείς περιοχές όπου υπάρχουν σύνθετα συστήματα ρηγμάτων. Οι παραδοσιακές μέθοδοι εκτίμησης του σεισμικού κινδύνου εμφανίζουν μεγάλα προβλήματα αβεβαιότητας. Η παρούσα διδακτορική διατριβή συνοψίζει την προϋπάρχουσα βιβλιογραφία και τα κύρια μοντέλα παραμόρφωσης που έχουν προταθεί μέχρι τώρα, η κύρια μεθοδολογία της όμως για την εκτίμηση της σεισμικής επικινδυνότητας βασίζεται στην ανάλυση των κύριων ρηγμάτων. Κύριος στόχος της παρούσας διδακτορικής διατριβής είναι η εξαγωγή αξιόπιστων αποτελεσμάτων και η επίτευξη υψηλότερης χωρικής ανάλυσης εκτίμησης επικινδυνότητας στην εξεταζόμενη περιοχή της Αιτωλοακαρνανίας. Η συμπερίληψη των δεδομένων από το PPGNet παρέχει πολύτιμες πληροφορίες για την παραμόρφωση της περιοχής της Αιτωλοακαρνανίας και πώς αυτή η παραμόρφωση συνδέεται με τις κύριες ενεργές δομές στην ευρύτερη περιοχή

Parkinson's disease and cognitive dysfunction: association with motor phenotype and the neuronal nicotinic acetylcholine receptor alpha4 subunit gene

Study A. Aim: To investigate whether there is an association of the postural instability and gait difficulty (PIGD) motor subtype with cognitive dysfunction in non-demented Parkinson’s disease (PD) patients. Methods: We administered a battery of selected neuropsychological tests to assess attention, psychomotor speed, executive functions (set shifting ability and inhibitory control), visuospatial perception and visual constructive ability to two groups of non-demented patients with mild to moderate disease classified either as PIGD or as non-PIGD subtype and to a group of healthy controls. Groups were matched on potential confounders of neuropsychological performance. Results: No significant differences were revealed between the two groups of patients in the performance of any of the administered neuropsychological tests. However, relative to controls there was a tendency towards a differential pattern of cognitive dysfunction. The PIGD group had slower performance in a test of psychomotor speed and cognitive flexibility, whilst the non-PIGD group performed worse in measures of verbal learning and visuo-spatial perception. Conclusions: The PIGD subtype was not associated with more severe cognitive deficits and may to a certain extent share common mechanisms of cognitive dysfunction with non-PIGD subtypes. Study B. Aim: to investigate whether there is an association between PD and a variation in the CHRNA4 gene coding for the α4 subunit, the primary subunit of the α4β2 brain nicotinic acetylcholine receptors. Methods: Patients (N=100) and controls (N=105), matched on the basis of sex, age and ethnicity, were genotyped for a single nucleotide polymorphism at cDNA position 1860 lying within the 5th exon of the CHRNA4 gene. DNA was extracted from peripheral blood samples and genotyping was done by PCR-based restriction fragment length polymorphism analysis. A subset of 42 patients also received detailed clinical and cognitive assessments. Comparisons of allele and genotype frequencies between groups were performed using the χ² test, and the Fisher exact test if one cell had n 50 ετών) σε σχέση με αυτούς που εμφάνισαν πρώιμης έναρξης νόσο (< 50 ετών). Οι ασθενείς με ΝP που ανιχνεύθηκαν να φέρουν το γονότυπο CC και υποβλήθηκαν σε νευροψυχολογική αξιολόγηση έτειναν να έχουν καλύτερα διατηρημένες τις γνωστικές λειτουργίες που σχετίζονται με την προσοχή και την ταχύτητα επεξεργασίας των πληροφοριών. Συμπεράσματα: Η παρουσία του αλληλομόρφου C (dbSNP rs1044396) του γονιδίου CHRNA4 συνδέεται με μειωμένο κίνδυνο ΝΡ κατά 35%. Επίσης, τα άτομα με το γονότυπο CC εμφανίζουν σχεδόν τρισήμισυ (3,5) φορές χαμηλότερο κίνδυνο νόσου του Parkinson. Η ποικιλομορφία του γονιδίου CHRNA4 φαίνεται ότι σχετίζεται ιδιαίτερα με την επιρρέπεια εκδήλωσης της ΝΡ με ηλικιακά όψιμη έναρξη της νόσου, και επίσης με τις γνωστικές λειτουργίες των ασθενών χωρίς άνοια, ειδικά αυτές που εξαρτώνται από την προσοχή και την οπτικοκινητική αντίληψη

Optic nerve sheath diameter: present and future perspectives for neurologists and critical care physicians

Estimation of intracranial pressure (ICP) may be helpful in the management of neurological critically ill patients. It has been shown that ultrasonography of the optic nerve sheath diameter (ONSD) is a reliable tool for non-invasive estimation of increased intracranial pressure (ICP) at hospital admission or in intensive care. Less is known about the estimation of increased ICP and usefulness of ONSD in the prehospital setting. The aim of this review was to elucidate both prevailing and novel applications of ONSD for neurologists and critical care physicians

FDG-PET underscores the key role of the thalamus in frontotemporal lobar degeneration caused by C9ORF72 mutations

C9ORF72 mutations are the most common cause of familial frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS). MRI studies have investigated structural changes in C9ORF72-associated FTLD (C9FTLD) and provided first insights about a prominent involvement of the thalamus and the cerebellum. Our multicenter, 18F-fluorodeoxyglucose positron-emission tomography study of 22 mutation carriers with FTLD, 22 matched non-carriers with FTLD, and 23 cognitively healthy controls provided valuable insights into functional changes in C9FTLD: compared to non-carriers, mutation carriers showed a significant reduction of glucose metabolism in both thalami, underscoring the key role of the thalamus in C9FTLD. Thalamic metabolism did not correlate with disease severity, duration of disease, or the presence of psychotic symptoms. Against our expectations we could not demonstrate a cerebellar hypometabolism in carriers or non-carriers. Future imaging and neuropathological studies in large patient cohorts are required to further elucidate the central role of the thalamus in C9FTLD

FDG-PET underscores the key role of the thalamus in frontotemporal lobar degeneration caused by C9ORF72 mutations

C9ORF72 mutations are the most common cause of familial frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS). MRI studies have investigated structural changes in C9ORF72-associated FTLD (C9FTLD) and provided first insights about a prominent involvement of the thalamus and the cerebellum. Our multicenter, F-18-fluorodeoxyglucose positron-emission tomography study of 22 mutation carriers with FTLD, 22 matched non-carriers with FTLD, and 23 cognitively healthy controls provided valuable insights into functional changes in C9FTLD: compared to non-carriers, mutation carriers showed a significant reduction of glucose metabolism in both thalami, underscoring the key role of the thalamus in C9FTLD. Thalamic metabolism did not correlate with disease severity, duration of disease, or the presence of psychotic symptoms. Against our expectations we could not demonstrate a cerebellar hypometabolism in carriers or non-carriers. Future imaging and neuropathological studies in large patient cohorts are required to further elucidate the central role of the thalamus in C9FTLD