The 1513 Monte Crenone rock avalanche: numerical model and geomorphological analysis

As a contribution to the knowledge of historical rockslides, this research focuses on the historical reconstruction, field mapping, and simulation of the expansion, through numerical modelling, of the 30 September 1513 Monte Crenone rock avalanche. Earth observation in 2-D and 3-D, as well as direct in situ field mapping, allowed the detachment zone and the perimeter and volume of the accumulation to be determined. Thanks to the reconstruction of the post-event digital elevation model based on historical topographic maps and the numerical modelling with the RAMMS::DEBRISFLOW software, the dynamics and runout of the rock avalanche were calibrated and reconstructed. The reconstruction of the runout model allowed confirmation of the historical data concerning this event, particularly the damming of the valley floor and the lake formation up to an elevation of 390 m a.s.l., which generated an enormous flood by dam breaching on 20 May 1515, known as the “Buzza di Biasca”.

Factors Related to the Delayed Cure of Hemifacial Spasm after Microvascular Decompression: An Analysis of 175 Consecutive Patients

Detailed studies assessing the factors related to delayed cure of hemifacial spasm (HFS) after microvascular decompression (MVD) are sparse. We aimed to evaluate the effect of 11 clinical factors on the time until the patient became spasm free after MVD. We enrolled 175 consecutive patients with HFS who underwent MVD between 2012 and 2018. The end point was defined as the time point at which the patient became spasm free based on the outpatient interview. Patients were divided into six groups depending on when they became spasm free after the operation, as follows: <7 days (n = 62), 7 days to 1 month (n = 28), 1 to 3 months (n = 38), 3 to 6 months (n = 25), 6 to 12 months (n = 17), and >12 months (n = 5). The median time to become spasm free after MVD was 30.0 days. Association of 11 factors (age, sex, laterality, number of offending arteries, vertebral artery compression, number of compression sites, compression at root detachment zone, preoperative Botox treatment, indentation of the brain stem on preoperative magnetic resonance image, transposition, and interposition) with spasm-free rate was assessed using the Cox's proportional hazards model. Spasm-free rate curve after MVD for the significant factor was obtained using the Kaplan–Meier method. In univariate and multivariate analyses, nontransposition was significantly related to delayed HFS cure after MVD (hazard ratio [HR], 0.60; 95% confidence interval [CI], 0.42, 0.87; p = 0.0068 and HR, 0.60; CI, 0.43, 0.85; p = 0.042, respectively). The spasm-free rate was higher in the transposition than in the nontransposition group (p = 0.0013). As shortening the time until spasm free after MVD improves patients' quality of life, transposition should be recommended. Prediction of spasm-free time could relieve the anxiety of postoperative patients.

Transvenous embolization of vein of galen aneurismal malformations using the “Chapot pressure cooker” technique

In some vein of galen aneurysmal malformation (VGAM) patients, transvenous embolization (TVE) is an attractive option, but its safety is unclear. Here we report the first two VGAM patients treated using the Chapot “pressure cooker” technique (ChPC). Methods Two patients, one 5-year-old and one 7-year-old, both presented with congestive heart failure in the newborn period and were subsequently treated in the newborn period with multiple, staged TAEs with n-BCA for choroidal VGAMs. Results We achieved progressive reduction in shunting and flow but were unable to accomplish complete closure of the malformation: in both patients, a small residual with numerous perforators persisted. The decision was made to perform TVE using the CHPC. In this technique, a guiding catheter is placed transjugular into the straight sinus (SS). One or two detachable tip microcatheters are advanced to the origin of the SS. Another microcatheter is advanced and the tip placed between the distal marker and the detachment zone of the former. Coils and n-BCA are used to prevent reflux of Onyx. Conclusions In this study, we recognized two important factors of traditional VGAM treatment that may cause interventionalists to consider the ChPC to treat VGAM: (1) without liquid embolic, deployed coils may not occlude the fistula entirely. (2) There is the concern of causing delayed bleeding should the arterial component of the fistula rupture. ChPC ameliorates these issues by offering complete closure of the fistula with liquid embolic material in TVE.

Electrothermal Coil Detachment Failure in Flow Diverter-Assisted Coiling of a Small Blister Aneurysm: Technical Considerations and Possible Solutions

Flow diversion stenting combined with coiling offers both immediate protection from rebleeding for ruptured aneurysms and long-term stability for wide-necked or blister aneurysms. It is particularly useful for tiny ruptured aneurysms, alleviating the concern that small coils may prolapse between the struts of conventional stents. We employed this technique in a very small, broad-based ruptured aneurysm of the internal carotid, jailing the coiling microcatheter with a Pipeline Embolization Device. However, coil detachment repeatedly failed, until we withdrew the detachment zone into the microcatheter. We suggest that if the tip of the coiling catheter is adjacent to the stent, contact between the junction zone of the coil and the high metal density of the flow diverter may prevent proper electrothermal coil detachment. Detachment can be undertaken successfully within the microcatheter, though care must be taken thereafter to fully push the detached coil tail into the aneurysm.

Development of an intra-carbonate detachment during thrusting: The variable influence of pressure solution on deformation style, Khao Khwang Fold and Thrust Belt, Thailand

Classic detachment zones in fold and thrust belts are generally defined by a weak lithology (typically salt or shale), often accompanied by high over-pressures. This study describes an atypical detachment that occurs entirely within a relatively strong Permian carbonate lithology, deformed during the Triassic Indosinian orogeny in Thailand under late diagenetic-anchimetamorphic conditions. The key differences between stratigraphic members that led to development of a detachment zone are bedding spacing and clay content. The lower, older, unit is the Khao Yai Member (KYM), which is a dark-gray to black, well-bedded, clay-rich limestone. The upper unit, the Na Phra Lan Member (NPM), comprises more massive, medium- to light-gray, commonly recrystallized limestones and marble. The KYM displays much tighter to even isoclinal, shorter-wavelength folds than the NPM. Pressure solution played a dominant role throughout the structural development—first forming early diagenetic bedding; later tectonic pressure solution preferentially followed this bedding instead of forming axial planar cleavage. The detachment zone between the two members is transitional over tens of meters. Moving up-section, tight to isoclinal folds with steeply inclined axial surfaces are replaced by folds with low-angle axial planes, thrusts, and thrust wedging, bed-parallel shearing, and by pressure solution along bedding-parallel seams (that reduce fold amplitude). In outcrops 100–300 m long, reduction of line-length shortening on folds from &gt;50% to &lt;10% shortening upwards indicates that deformation in the NPM is being accommodated differently from the KYM, probably predominantly by shortening on longer wavelength and/or spacing folds and thrusts, given the low amount of strain observed within the NPM, which excludes widespread layer-parallel thickening

Morphometric and topograpical analysis of retinal abnormalities in central serous chorioretinopathy

Objective: Quantitative morphometric and topographic analysis of specific changes of the retina in patients with the acute central serous chorioretinopathy (CSC) based on annotated tomograms.Methods: 39 patients with the acute CSC (44 eyes – 45 scans) were examined. A complex ophthalmological examination was carried out including 3D optical coherence tomography of maculae. The data was uploaded into CVAT. Three classes of pathological changes were differentiated: 1) retinal neuroepi‑ thelium detachment; 2) retinal pigment epithelium alteration; 3) percolation zones. The analysis of topographical localization of changes and their morphological relations were assessed with a programming language Python.Results: A moderate trend towards vertical asymmetry of the neuroepithelial detachment zone with an excess of cumulative distribution in the lower part of the macula was revealed. Retinal pigment epithelium alteration sites and percolation zones demonstrated a relative peak of representation in the upper nasal part of the macula. In 69.9% and 80% of cases, respectively, abnormalities of retinal pigment epithelium and percolation zones were localized within the limits of neuroepithelial detachment. Direct correlation between the area of neuroepithelial detachment and the area of percolation zones; the area of percolation zones and the area of retinal pigment epithelium alteration; the area of neuroepithelial detachment and the area of retinal pigment epithelium alteration.Conclusions: Percolation zones and abnormalities of retinal pigment epithelium demonstrate similar trends in topo‑ graphical localization and quantitative characteristics and are related to the area of neuroepithelial detachment in CSC. Thus, the number of retinal pigment epithelium abnormalities can serve as an indicator of disease severity.

Early Neoproterozoic Deformation Kinematics in the Chottanagpur Gneiss Complex (Eastern India): Evidence from the Curvilinear Hundru Falls Shear ZoneAnalysis

Curvilinear steep shear zones originate in different tectonic environments. In the Chottanagpur Gneiss Complex (CGC), the steeply dipping, left-lateral and transpressive Early Neoproterozoic Hundru Falls Shear Zone (HFSZ) with predominantly north-down kinematics comprises two domains, e.g., an arcuate NW-striking (in the west) to W-striking (in the east) domain with gently plunging stretching lineation that curves into a W-striking straight-walled domain with down-dip lineation. The basement-piercing HFSZ truncates a carapace of flat-lying amphibolite facies paraschist and granitoid mylonites, and recumbently folded anatectic gneisses. The carapace—inferred to be a midcrustal regional-scale low-angle detachment zone—structurally overlies an older basement of Early Mesoproterozoic anatectic gneisses intruded by Mid-Mesoproterozoic/Early Neoproterozoic granitoids unaffected by the Early Neoproterozoic extensional tectonics. The mean kinematic vorticity values in the steep HFSZ-hosted granitoids computed using the porphyroclast aspect ratio method are 0.74–0.83 and 0.51–0.65 in domains with shallow and steep lineations, respectively. The granitoid mylonites show a chessboard subgrain microstructure, but lack evidence for suprasolidus deformation. The timing relationship between the two domains is unclear. If the two HFSZ domains were contemporaneous, the domain of steep lineations with greater coaxial strain relative to the curvilinear domain formed due to strain partitioning induced by variations in mineralogy and/or temperature of the cooling granitoid plutons. Alternately, the domain of gently plunging lineations in the HFSZ was a distinct shear zone that curved into a subsequent straight-walled shear zone with steeply plunging lineation due to a northward shift in the convergence direction during deformation contemporaneous with the Early Neoproterozoic accretion of the CGC and the Singhbhum Craton.

Supplemental Material: Airblasts caused by large slope collapses

Figure S1. Sequence of satellite images showing the evolution of Yumthang rock avalanche; Figure S2. (A) View of the detachment zone of the Yumthang rock avalanche. Main discontinuities are indicated. (B) Hillshade with indication of the main sets of iscontinuities. The arrows indicate the downstream direction of the valleys. (C) Stereographic plots (Equal angle, lower hemisphere) with the kinematic analysis overlain. (D) General hillshade and satellite image showing the location of the detachment zone at the confluence of two valleys; Figure S3. Picture and schematic illustration of airblast interacting with the tree trunk on the distal part of the Yumthang airblast damage area; Table S1. Main discontinuities affecting the granite at the Yumthang headscarp.

Supplemental Material: Airblasts caused by large slope collapses

Figure S1. Sequence of satellite images showing the evolution of Yumthang rock avalanche; Figure S2. (A) View of the detachment zone of the Yumthang rock avalanche. Main discontinuities are indicated. (B) Hillshade with indication of the main sets of iscontinuities. The arrows indicate the downstream direction of the valleys. (C) Stereographic plots (Equal angle, lower hemisphere) with the kinematic analysis overlain. (D) General hillshade and satellite image showing the location of the detachment zone at the confluence of two valleys; Figure S3. Picture and schematic illustration of airblast interacting with the tree trunk on the distal part of the Yumthang airblast damage area; Table S1. Main discontinuities affecting the granite at the Yumthang headscarp.