Sub-telo-velo-tonsillar approach to resect dorsal pons cavernoma through fourth ventricular floor opening: how I do it.

BACKGROUND: Dorsal pons cavernoma can be approached through telo-velar approach instead of transvermian approach, with lower risk of neurological deficits since it uses natural clefts to reach the floor of the fourth ventricle. MATERIALS AND METHODS: We present our surgical technique for telo-velar approach to address pathologies of the dorsal pons, assisted by neuronavigation and neuromonitoring. This surgical technique is illustrated by a surgical video of a dorsal pons cavernoma. CONCLUSION: Dorsal pons cavernomas can be reached through telo-velar approach after suboccipital midline craniotomy. The accurate patient positioning, cisternal dissection, and neuromonitoring use are mandatory to avoid neural injuries and identify the safe entry points into the brainstem.

Geographical distance and physical barriers shape the genetic structure of Eurasian red squirrels (Sciurus vulgaris) in the Italian Alps.

Red squirrels (Sciurus vulgaris) are widely distributed throughout Eurasia, occurring in many types of coniferous and mixed-deciduous forests. In fragmented landscapes, small and partly isolated populations with low immigration rates show reduced genetic diversity, but reforestation can increase gene flow and restore levels of genetic variation in a few decades. No studies have so far investigated the genetic structure of red squirrel in large, continuous forests. The Italian Alps are presently characterized by almost continuous, recently reconnected forest habitats, that were affected by deep landscape changes during last glaciations but remained mostly unchanged between 10 000 and 200 years bp, when forest cover was heavily reduced. In this study we analyse patterns of genetic variability of red squirrels in and between seven sites distributed over 250 km of Alpine habitat, using mitochondrial DNA (mtDNA) and microsatellites. We use isolation-by-distance (IBD) models to investigate the relative importance that past (Pleistocene glaciations) and recent (fragmentation, bottlenecks) events had on the present genetic situation. Both nuclear and mtDNA data indicate a significant differentiation among study sites and a significant correlation between genetic and geographical distance only over a large scale. No recent bottlenecks are recorded through microsatellites and demographic models strongly support equilibrium between gene flow and drift; however, mtDNA suggests that there may have been local demographic crashes, probably in correspondence with the 19th-century forest fragmentation. These findings indicate that local landscape factors other than geographical distance per se, such as barriers of unsuitable habitat, affect gene flow and determine differentiation.