Search

The Hopfield model is a paradigmatic model of neural networks that has been analyzed for many decades in the statistical physics, neuroscience, and machine learning communities. Inspired by the manifold hypothesis in machine learning, we propose and investigate a generalization of the standard setting that we name random-features Hopfield model. Here, P binary patterns of length N are generated by applying to Gaussian vectors sampled in a latent space of dimension D a random projection followed by a nonlinearity. Using the replica method from statistical physics, we derive the phase diagram of the model in the limit P,N,D→∞ with fixed ratios α=P/N and α_{D}=D/N. Besides the usual retrieval phase, where the patterns can be dynamically recovered from some initial corruption, we uncover a new phase where the features characterizing the projection can be recovered instead. We call this phenomena the learning phase transition, as the features are not explicitly given to the model but rather are inferred from the patterns in an unsupervised fashion.

Background: The management of ruptured posterior circulation perforator aneurysms (rPCPAs) remains unclear. We present our experience in treating rPCPAs with flow diverter stents (FDs) and evaluate their safety and efficacy at mid- to long-term follow-up. A diagnostic and therapeutic algorithm for rPCPAs is also proposed., Methods: We retrospectively analyzed data from all consecutive patients with rPCPAs treated with FDs at our institutions between January 2013 and July 2019. Clinical presentations, time of treatments, intra- and perioperative complications, and clinical and angiographic outcomes were recorded, with a mid- to long-term follow-up. A systematic review of the literature on rPCPAs treated with FDs was also performed., Results: Seven patients with seven rPCPAs were treated with FDs. All patients presented with an atypical subarachnoid hemorrhage distribution and a low to medium Hunt-Hess grade. In 29% of cases rPCPAs were identified on the initial angiogram. In 57% of cases, FDs were inserted within 2 days of the diagnosis. Immediate aneurysm occlusion was observed in 14% of the cases and in 71% at the first follow-up (mean 2.4 months). At mean follow-up of 33 months (range 3-72 months) one case of delayed ischemic complication occurred. Six patients had a modified Rankin Scale (mRS) score of 0 and one patient had an mRS score of 4 at the latest follow-up., Conclusions: The best management for rPCPAs remains unclear, but FDs seem to have lower complication rates than other treatment options. Further studies with larger series are needed to confirm the role of FDs in rPCPA., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2020. No commercial re-use. See rights and permissions. Published by BMJ.)

Background and Purpose: As numerous questions remain about the best anesthetic strategy during thrombectomy, we assessed functional and radiological outcomes in stroke patients treated with thrombectomy in presence of general anesthesia (GA) versus conscious sedation (CS) and local anesthesia (LA)., Methods: We conducted a cohort study on prospectively collected data from 4429 patients enrolled in the Italian Registry of Endovascular Treatment in Acute Stroke., Results: GA was used in 2013 patients, CS in 1285 patients, and LA in 1131 patients. The rates of 3-month modified Rankin Scale score of 0-1 were 32.7%, 33.7%, and 38.1% in the GA, CS, and LA groups: GA versus CS: odds ratios after adjustment for unbalanced variables (adjusted odds ratio [aOR]), 0.811 (95% CI, 0.602-1.091); and GA versus LA: aOR, 0.714 (95% CI, 0.515-0.990). The rates of modified Rankin Scale score of 0-2 were 42.5%, 46.6%, and 52.4% in the GA, CS, and LA groups: GA versus CS: aOR, 0.902 (95% CI, 0.689-1.180); and GA versus LA: aOR, 0.769 (95% CI, 0.566-0.998). The rates of 3-month death were 21.5%, 19.7%, and 14.8% in the GA, CS, and LA groups: GA versus CS: aOR, 0.872 (95% CI, 0.644-1.181); and GA versus LA: aOR, 1.235 (95% CI, 0.844-1.807). The rates of parenchymal hematoma were 9%, 12.6%, and 11.3% in the GA, CS, and LA groups: GA versus CS: aOR, 0.380 (95% CI, 0.262-0.551); and GA versus LA: aOR, 0.532 (95% CI, 0.337-0.838). After model of adjustment for predefined variables (age, sex, thrombolysis, National Institutes of Health Stroke Scale, onset-to-groin time, anterior large vessel occlusion, procedure time, prestroke modified Rankin Scale score of <1, antiplatelet, and anticoagulant), differences were found also between GA versus CS as regards modified Rankin Scale score of 0-2 (aOR, 0.659 [95% CI, 0.538-0.807]) and GA versus LA as regards death (aOR, 1.413 [95% CI, 1.095-1.823])., Conclusions: GA during thrombectomy was associated with worse 3-month functional outcomes, especially when compared with LA. The inclusion of an LA arm in future randomized clinical trials of anesthesia strategy is recommended.

Introduction: Flow-diverter stents are becoming a useful tool in treating patients with intracranial aneurysms with suitable anatomical feature. Purpose of this study was to evaluate effectiveness and safety of endovascular treatment with flow-diverting stents (FD) in unruptured intracranial aneurysms., Methods: From May 2009 and May 2014, we treated 49 patients with a total of 58 aneurysms, with FD technique. All patients were treated electively, under general anesthesia and were administered single antiplatelet drug 5 days before the procedure and double antiplatelet therapy for 3 months afterwards. Fifteen of the patients were asymptomatic, eight had headache, thirteen patients presented symptoms due to mass effect of the aneurysm on CNS structures, twelve were treated due to a post-surgical relapse and one patient presented relapsing TIAs due to distal embolization from the aneurysm dome. Choice of FD treatment was done according to aneurysm anatomy (fusiform over saccular, dome/neck ratio < 2) and whenever conventional treatment (coil embolization) appeared difficult (eg. Large aneurysm neck, fusiform aneurysms or difficult sac catheterization). We considered a dome/neck ratio > 2 as the only exclusion criteria., Results: Successful stent deployment was achieved in 50 procedures out of 52 (94.34%) while overall mortality was 2% (1/49). Forty-eight patients were evaluated at long-term follow-up for a total of 56 treated aneurysms. At 3 months, follow-up 75% (42/56) of the aneurysms were excluded from intracranial circulation, at 6 months 80.35% (45/56) and at 12 months 84% (47/56). Stent patency was observed in 100% of patients at short and long-term follow-up, with only two cases of intimal hyperplasia at 3 months, without any further complications., Conclusions: According to our study FD repair of unruptured intracranial aneurysms appeared to be a safe and effective technique, especially in selected patients with hostile anatomy for traditional embolization.

Objective: This study was designed to evaluate the effectiveness of endovascular treatment (EVAR) for ruptured abdominal aortic aneurysms (rAAAs)., Methods: Between September 2005 and December 2012, 44 patients with rAAA suitable for endovascular repair underwent emergency EVAR. We did not consider hemodynamic instability to be a contraindication for EVAR., Results: Successful stent-graft deployment was achieved in 42 patients, whereas 2 required open surgical conversion. The overall 30-day mortality was 10 of 44 patients (5/34 in stable patients, 5/10 in unstable patients). Postoperative complications were observed in 7 of 44 patients (16 %): 5 patients developed abdominal compartment syndrome requiring decompressive laparotomy; 1 patient developed bowel ischemia; 1 patient had limb ischemia, and 1 had hemodynamic shock. Mean length of intensive care unit stay was 2.9 (range 2–8) days, and mean length of hospital stay was 8.6 (range 0–18) days. At a mean follow-up of 22.2 (range 1–84) months, the overall incidence of endoleak was 23.5 %: 1 type I and 7 type II endoleaks., Conclusions: Our study demonstrates that EVAR of rAAA is associated with acceptable mortality and morbidity rates in dedicated centers.

Purpose: This study aimed to evaluate the effectiveness of transcatheter embolisation in the treatment of spontaneous extraperitoneal haemorrhage (SEH)., Materials and Methods: We retrospectively evaluated the technical and clinical success in terms of immediate and long-term mortality in a series of patients who underwent endovascular treatment of SEH from January 2005 to December 2010. A statistical comparison of pre- and postoperative transfusion requirements was performed by using the Student's t test, with statistical significance set at p < 0.005., Results: In the period considered, 30 patients (16 women and 14 men; mean age, 73.3 years ±15.6) with SEH underwent endovascular treatment. Technical success was obtained in all cases (100 %), and a statistically significant reduction in blood transfusion requirements was observed (mean preoperative requirement: 7.5 U/day ±3; mean postoperative requirement 2.8 U/day) (p < 0.005). We observed a postoperative mortality of 10 % (3/30 patients) and mortality at 6 and 12 months was 14.8 % (4/27 patients) and 26 % (6/23 patients), respectively., Conclusion: According to our experience and to the literature, transcatheter arterial embolisation represents the treatment of choice in patients with SEH, as it ensures complete therapeutic success.

Background: We sought to evaluate the best therapeutic management of postbiopsy arteriovenous fistulas (AVFs) in transplanted kidneys., Methods: Between January 2005 and December 2011, we observed 17 cases of postbiopsy AVF in transplanted kidneys (9 asymptomatic; 8 symptomatic). Asymptomatic cases were managed conservatively, while patients with symptomatic AVF underwent endovascular treatment. We used a technique that consisted in a superselective transcatheter embolization of the afferent branch. We evaluated the technical success (postoperative closure of AVF), the immediate clinical efficacy (cessation of symptoms), and clinical efficacy at follow-up (measurement of serum creatinine at 7 days and 6 and 12 months compared with preoperative levels using t-tests)., Results: Asymptomatic AVFs resolved spontaneously, while the endovascular treatment in symptomatic AVFs showed a complete technical and clinical success with prompt remission of the presented symptoms. We observed a statistically significant reduction in serum creatinine at 7 days and 6 and 12 months postoperatively (mean creatinine--preoperative: 3.23 ± 1.4 mg/dL; 7 days: 2.25 ± 0.8 mg/dL; 6 months: 1.65 ± 0.28 mg/dL; 12 months: 1.4 ± 0.26 mg/dL; in all cases P < 0.05)., Conclusions: In our experience, asymptomatic AVFs could be managed conservatively with close follow-up while the endovascular treatment for symptomatic AVFs is both safe and effective in the short- and long-term., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Purpose: This paper reports our preliminary experience with the endovascular treatment of intracranial aneurysms using flow-diverter stents (FDs) and compares it with the literature data., Materials and Methods: From May 2009 to April 2012, 28 patients (6 men and 22 women; mean age, 54 years) with a total of 35 aneurysms were treated with FDs. We evaluated postprocedural technical success and long-term efficacy, with follow-up examinations performed at 3-7 days [computed tomography (CT)/magnetic resonance (MR) angiography] and at 3, 6 and 12 months (digital subtraction angiography, DSA). A total of 43 FDs were placed, 36 Pipeline and 7 Silk., Results: A total of 30 procedures were performed (two patients were treated twice). Technical success was 96.6%, with one case of postprocedural death; the aneurysm exclusion rate at 3, 6 and 12 months was 60%, 73% and 89%, respectively. There was no case of acute stent thrombosis, and only two cases of nonsignificant stenosis. All covered side branches were patent, except one case of steno-occlusion of the ophthalmic artery., Conclusions: Our results are consistent with the literature and demonstrate the effectiveness and safety of FDs in selected cases of cerebral aneurysm (wide neck, fusiform, blister-like).

New Co(II) members of the family of multifunctional materials of general formula [DAMS](4)[M(2)Co(C(2)O(4))(6)]·2DAMBA·2H(2)O (M(III) = Rh, Fe, Cr; DAMBA = para-dimethylaminobenzaldehyde and [DAMS(+)] = trans-4-(4-dimethylaminostyryl)-1-methylpyridinium) have been isolated and characterized. Such new hybrid mixed metal oxalates are isostructural with the previously investigated containing Zn(II), Mn(II), and Ni(II). This allows to preserve the exceptional second harmonic generation (SHG) activity, due to both the large molecular quadratic hyperpolarizability of [DAMS(+)] and the efficiency of the crystalline network which organizes [DAMS(+)] into head-to-tail arranged J-type aggregates, and to further tune the magnetic properties. In particular, the magnetic data of the Rh(III) derivative demonstrate that high spin octacoordinated Co(II) centers behave very similarly to the hexacoordinated Co(II) ones, being dominated by a large orbital contribution. The Cr(III) derivative is characterized by ferromagnetic Cr(III)-Co(II) interactions. Most relevantly, the Fe(III) compound is characterized by a moderate antiferromagnetic interaction between Fe(III) and Co(II), resulting in a ferrimagnetic like structure. Its low temperature dynamic magnetic properties were found to follow a thermally activated behavior (τ(0) = 8.6 × 10(-11) s and ΔE = 21.4 K) and make this a candidate for the second oxalate-based single chain magnet (SCM) reported up to date, a property which in this case is coupled to the second order non linear optical (NLO) ones.