A mean-field approach to the dynamics of networks of complex neurons, from nonlinear Integrate-and-Fire to Hodgkin-Huxley models.

We present a mean-field formalism able to predict the collective dynamics of large networks of conductance-based interacting spiking neurons. We apply this formalism to several neuronal models, from the simplest Adaptive Exponential Integrate-and-Fire model to the more complex Hodgkin-Huxley and Morris-Lecar models. We show that the resulting mean-field models are capable of predicting the correct spontaneous activity of both excitatory and inhibitory neurons in asynchronous irregular regimes, typical of cortical dynamics. Moreover, it is possible to quantitatively predict the population response to external stimuli in the form of external spike trains. This mean-field formalism therefore provides a paradigm to bridge the scale between population dynamics and the microscopic complexity of the individual cells physiology.NEW & NOTEWORTHY Population models are a powerful mathematical tool to study the dynamics of neuronal networks and to simulate the brain at macroscopic scales. We present a mean-field model capable of quantitatively predicting the temporal dynamics of a network of complex spiking neuronal models, from Integrate-and-Fire to Hodgkin-Huxley, thus linking population models to neurons electrophysiology. This opens a perspective on generating biologically realistic mean-field models from electrophysiological recordings.

Arteriovenous fistulas induced by femoral arterial catheterization: percutaneous treatment.

PURPOSE: To evaluate the use of stent-grafts for the percutaneous closure of arteriovenous fistulas that develop after cardiac catheterization. MATERIALS AND METHODS: From January 1994 to November 1997, 14 arteriovenous fistulas in 13 patients (eight men, five women; age range, 46-65 years; mean age, 53.5 years) were treated. Eleven fistulas were situated between the deep femoral artery and the common femoral vein, and three fistulas were between the superficial femoral artery and the common femoral vein. All fistulas were closed with stent-grafts positioned in the artery at the level of the fistula. RESULTS: The percutaneous treatment of arteriovenous fistulas was successful in all cases. The findings at angiography performed after the procedure demonstrated the closure of the fistulas and the correct positioning of the prostheses; veins were no longer visible. One complication occurred--a partial thrombosis of the common femoral vein at the puncture site after manual compression. CONCLUSION: On the basis of the preliminary data, the authors believe that the percutaneous closure of arteriovenous fistulas with stent-grafts is a safe and effective alternative to conventional surgery.

Percutaneous endoluminal bypass of iliac aneurysms with a covered stent.

To evaluate the feasibility of percutaneous treatment of iliac aneurysms, a covered stent was inserted in nine men suffering from common iliac artery aneurysms (six cases), external iliac aneurysms (one case), or pseudoaneurysms (two cases). Placement of the stent was successful in all patients. In one patient, an endoprosthesis thrombosed after 15 days, but was successfully treated by thrombolysis and additional stent placement. At the follow-up examinations (mean period 22 months) all stent-grafts had remained patent. No late leakage or stenosis was observed.

Feasibility of intraoperative balloon angioplasty and additional stent placement of isolated stenosis of the brachiocephalic trunk.

OBJECTIVE: We sought to evaluate the feasibility and results of intraoperative balloon angioplasty and additional stent placement of isolated stenosis of the brachiocephalic trunk. PATIENTS AND METHODS: Between May 1993 and October 1996, we treated eight patients with local stenosis of the innominate artery. Seven lesions were situated in the proximal and one in the middle third of the brachiocephalic trunk. Five patients were men and three were women, with ages ranging from 55 to 72 years (mean 59.5 years). All stenoses provoked severe blood flow reduction and caused clinical symptoms. Procedures were performed in an operating suite with fluoroscopic imaging capabilities. Through an anterolateral cervical approach the right common carotid artery was surgically exposed and then clamped to avoid atheroembolization during the subsequent procedure. Retrograde catheterization was performed to reach the stenosis of the brachiocephalic trunk. The lesion was dilated with a balloon catheter and successively stented. Follow-up examinations (color-coded duplex sonography, accompanied by clinical inspection and systolic blood pressure) were scheduled every 6 months. RESULTS: In all patients the dilation of the stenosis of the innominate artery and the stent placement were successful without any side effects. No embolic events or other complications occurred. The postintervention angiography showed successfully dilated stenoses and patent stents in all cases. The technical success rate was 100%. CONCLUSIONS: On the basis of our preliminary data, we believe that, in selected patients, intraoperative balloon angioplasty of stenosis of the innominate artery with stent placement from the right common carotid artery approach is a safe and effective alternative to conventional operations.

Exclusion of an internal carotid aneurysm by a covered stent.

The authors report a case of a patient with thromboembolic strokes caused by a high internal carotid artery aneurysm. Considering the position and the anatomic structure of this aneurysm the sac was excluded transluminally by placing an endovascular covered stent.

Combined surgical and endovascular treatment of a traumatic pseudo-aneurysm of the brachiocephalic trunk with anatomical anomaly.

The authors report a case of combined surgical and endovascular treatment of a traumatic pseudo-aneurysm of the innominate artery in which the left common carotid artery originated from the brachiocephalic trunk. After a conventional surgical intervention with the implantation of the left common artery on the left subclavian artery, to correct the anatomic anomaly, a safe and effective endovascular stent-graft placement excluded the aneurysm. This new technique proposes a good chance for polytraumatized patients to receive a better prognosis and a much faster rehabilitation.

Palmaz stent dislodgement into the left pulmonary artery complicating TIPS: percutaneous retrieval and extraction after venotomy.

A Palmaz stent had dislodged into the left pulmonary artery after TIPS. After transfemoral catheterization of the left pulmonary artery, the stent was retrieved into the right femoral vein employing an angioplastic balloon catheter and finally extracted after surgical venotomy.

[Percutaneous transjugular intrahepatic portosystemic shunt (TIPS). The preliminary experience and proposal of a new method]. / Derivazione portosistemica intraepatica per via percutanea trans-giugulare (TIPS). Esperienza preliminare e proposta di una nuova metodica.

A new interventional procedure employing metallic stents has been recently suggested to perform percutaneous portosystemic shunts in the treatment of variceal bleeding in portal hypertension; the technique is called TIPSS (transjugular intrahepatic portosystemic stent shunt). This percutaneous treatment presents several advantages over surgery: the shunt diameter can be calibrated according to the degree of portal hypertension; moreover, TIPSS can be performed in patients waiting for liver transplantation because it does not alter the vascular anatomy of liver. The original technique employed transhepatic portography. In this paper the authors report on their personal experience and present their series of 4 patients with portal hypertension and variceal bleeding, in whom TIPSS was performed utilizing noninvasive US guidance. Variceal bleeding was successfully treated in all patients and variceal distension was also obtained.

[An optoelectronic apparatus for the registration of stepping activity in small mammals]. / Su di un dispositivo optoelettronico per la registrazione dell'attivita' deambulatoria in mammiferi di piccola taglia.

In order to record the stepping activity in little size mammals, it was planned a set able to transform the stepping activity of the animals in electrical signals displayed on a polygraph. The set is formed by a complex transmitter-receiver, and transformer-recorder, that allow to record also high frequency stepping activity and its time variations.