Nonlinear diffusion and thermo-electric coupling in a two-variable model of cardiac action potential.

This work reports the results of the theoretical investigation of nonlinear dynamics and spiral wave breakup in a generalized two-variable model of cardiac action potential accounting for thermo-electric coupling and diffusion nonlinearities. As customary in excitable media, the common Q10 and Moore factors are used to describe thermo-electric feedback in a 10° range. Motivated by the porous nature of the cardiac tissue, in this study we also propose a nonlinear Fickian flux formulated by Taylor expanding the voltage dependent diffusion coefficient up to quadratic terms. A fine tuning of the diffusive parameters is performed a priori to match the conduction velocity of the equivalent cable model. The resulting combined effects are then studied by numerically simulating different stimulation protocols on a one-dimensional cable. Model features are compared in terms of action potential morphology, restitution curves, frequency spectra, and spatio-temporal phase differences. Two-dimensional long-run simulations are finally performed to characterize spiral breakup during sustained fibrillation at different thermal states. Temperature and nonlinear diffusion effects are found to impact the repolarization phase of the action potential wave with non-monotone patterns and to increase the propensity of arrhythmogenesis.

Genetic and cellular basis of cerebral cavernous malformations: implications for clinical management.

Cerebral cavernous malformations (CCMs) are a diffuse cerebrovascular disease affecting approximately 0.5% of the population. A CCM is characterized by abnormally enlarged and leaky capillaries arranged in mulberry-like structures with no clear flow pattern. The lesion might predispose to seizures, focal neurological deficits or fatal intracerebral hemorrhage. However, a CCM can also remain neurologically silent. It might either occur sporadically or as an inherited disorder with incomplete penetrance and variable expressivity. Due to advances in imaging techniques, the incidence of CCM diagnoses are increasing, and the patient must be managed on a multidisciplinary basis: genetic counselling, treatment if needed, and follow-up. Advances have been made using radiological and pathological correlates of CCM lesions adding to the accumulated knowledge of this disease, although management of these patients is very variable among centers. This review is aimed at providing an update in genetic and molecular insights of this condition. Included are implications for genetic counselling, and possible approaches to prevention and treatment that derive from the understanding of pathogenetic mechanisms.

Venous saving in olfactory meningioma's surgery.

Bifrontal craniotomy and interhemispherical approach, usually used to remove olfactory groove meningioma, does not allow a view of posterior pole, which is very important in the surgical management of this neoplasm, and, provides for an anatomical sacrifice of frontal bridging veins, not without complications as a result of venous infarction. From 1975 the pterional approach was performed on 20 patients with olfactory meningioma, with good results in 90% of cases. This approach presents several advantages over bifrontal craniotomy and, in order to minimise surgical damage, it avoids planned sacrifice of venous vessels.

Basal meningiomas. A retrospective study of 139 surgical cases.

BACKGROUND: Basal meningiomas represent a significant group of intracranial tumours. Their surgical treatment presents still today several difficulties since these tumours, as it is well known, may involve critical neurovascular structures. METHODS: This is a retrospective study of 139 consecutive cases of basal meningioma operated on in our institution during the last two decades. Meningiomas location: olfactory groove 20 cases; suprasellar region 22; anterior cranial fossa 6; sphenoid wing 37; cerebellopontine angle/clivus 21; tentorium 26. In most cases the meningioma was larger than 5 cm. The tumour was completely removed (grade I-II of Simpson classification) in 111 cases (79.9%). The authors dwell upon some clinical and surgical aspects of prevailing groups (olfactory, suprasellar, sphenoidal, petroclival and tentorial meningiomas); regarding to operative procedures, the authors in particular emphasise the usefulness of the pterional approach to remove olfactory groove meningiomas and of the combined supra- and infratentorial approach, with preservation of transverse and sigmoid sinuses, to remove petroclival meningiomas. RESULTS: The surgery was followed by excellent or good results in 115 cases (82.7%): patients having a normal life with a score 80-100 of Karnofsky scale; poor outcome occurred in 5.8% of cases, postoperatively died 16 patients (mortality rate 11.5%). Tumour recurrence occurred in 7 cases. CONCLUSIONS: Based on their experience and on analysis of the reviewed literature, the authors conclude that advances in microsurgical techniques and in neuroradiological imaging have radically improved the outcome so that today basal meningiomas can be successfully treated in most cases.

Is the size of an epidural haematoma related to outcome?

Recently we treated 54 patients with acute epidural haematoma, diagnosed by early CT scan and operated on quickly, within 6 hours after trauma. In 18 cases the volume of the haematoma, calculated by three different methods, was more than 150 cc, and GCS score was equal to or less than 8. In all 18 patients, as well as in another 36, we obtained good results: all patients survived and 17 fully recovered (only one was left with moderate neurological disability). Our experience leads us to the conclusion that even volumes of over 150 cc can be compatible not only with survival but also with very low morbidity, if rapid surgical treatment is performed.