Atti SUN -Laparoscopic management of sacral neurinoma causing hydronephrosis

We report the case of a sacral neurinoma, which presented with mild hydronephrosis, due to compression of the right ureter, in a 71-yr old woman admitted to our hospital with recurrent urinary tract infections. CT and MRI detected a 4 x 4 cm mass pressing on the right ureter at the sacral level, in continuity with the second sacral foramen. Given this finding, the mass was thought to be of presumable neurogenic origin. In order to both reach a conclusive diagnosis and relieve the compression of the ureter, a laparoscopic resection of the mass was performed. Surgery was successful and the pathologic examination revealed a sacral Antoni A neurinoma. Neurinomas, also called Schwannomas, are uncommon benign nerve sheath tumors arising from Schwann cells. Their diagnosis can be extremely difficult due to their aspecific symptoms and the lack of pathognomonic characteristics on imaging exams. Therefore, histopathologic evaluation is essential in establishing the diagnosis. Surgical resection seems to be the best approach, both for diagnostic and therapeutic purposes.     

The Rayleigh-Taylor condition for the evolution of irrotational fluid interfaces

For the free boundary dynamics of the two-phase Hele-Shaw and Muskat problems, and also for the irrotational incompressible Euler equation, we prove existence locally in time when the Rayleigh–Taylor condition is initially satisfied for a 2D interface. The result for water waves was first obtained by Wu in a slightly different scenario (vanishing at infinity), but our approach is different because it emphasizes the active scalar character of the system and does not require the presence of gravity.     

Sublinear summation of afferent inputs to the nucleus accumbens in the awake rat

The mechanisms by which the nucleus accumbens integrates afferent input from limbic and cortical structures have been influential in the development of models of psychiatric disorders such as schizophrenia. Previous studies of the response of nucleus accumbens (Nacb) cells to the stimulation of afferent inputs from hippocampus (HC) and prefrontal cortex (PFC) have demonstrated that PFC throughput can be modulated by preceding HC input. Examination of the post-synaptic potential size has suggested, however, that summation of these inputs is sublinear. All studies to date examining Nacb integration of inputs via stimulation of afferents have been performed in the anaesthetized rat. The present experiments compare the response of Nacb cells to different combinations of PFC and HC stimulation in awake and isoflurane-anaesthetized rats that were chronically implanted with both stimulating and recording electrodes. The results of these experiments suggest that summation of afferent input in the Nacb of the awake rat is predominantly sublinear, with only a minority of neurons demonstrating modulation of PFC inputs by the HC in the awake or the anaesthetized animal. The response profile of many cells changed during anaesthesia when compared to the awake condition, and on average showed suppression to PFC input 50 and 150 ms following HC stimulation while under deep isoflurane anaesthesia. These results suggest that sublinear integration of afferent input from the PFC and HC is the dominant mode of integration of Nacb cells in the awake animal, which has implications for corticostriatal models of psychiatric dysfunction.