Step Ladder Expansive Cranioplasty: A Novel Perspective in Cranial Volume Augmentation Surgery.

Background In face of a refractory raised intracranial pressure (ICP), surgeons most commonly resort to decompressive craniectomy (DC). Procedure leaves an unprotected brain underlying the craniectomy defect and Monro-Kellie doctrine: disrupted. Different variants of hinge craniotomies (HC) have been used with clinical outcomes comparable to DC as single stage alternatives. However, both DC and every variant of HC have a limit to the achievable volume augmentation and all invariably cause a compression of the cerebral cortex and its vasculature at the craniotomy site. We believe both these limitations adversely affect the outcome. Methods A team of neuroscientists in Indian Armed Forces Medical Services has been working for the last 9 years toward developing a novel surgical technique that can mitigate both these drawbacks. Desired procedure should take the centripetal pressure exerted by the combination of the tensile strength of the scalp (with or, without an underlying bone flap) and atmospheric pressure off the brain surface while achieving an assured augmentation of intracranial volume that can be optimized on a case-to-case basis. We call it a "step ladder expansive cranioplasty." Results The distance of the parietal eminence was found to have increased by 10.2 mm on the operated side after expansive cranioplasty. Conclusion From drawing board to bedside, we have made some progress toward our goal, but it is still far away from completion. More studies are required to fill in the gaps in our knowledge necessary to optimize the various parameters of the surgery. Procedure has promise to be of special role in in war and disaster scenarios.

Large Scale Mapping of Fractures and Groundwater Pathways in Crystalline Hardrock By AEM.

In hardrocks that cover about 20% of the Earth's surface, it is difficult to locate steady sources for groundwater due to inadequate understanding of the fracture networks. A comprehensive knowledge of fracture distribution at the regional scale is necessary to delineate sustainable aquifers and manage them efficiently. The resistivity maps derived from the airborne electromagnetic (AEM) survey over the Ankasandra watershed in Karnataka, India, reveal sharp and deep zones of low formation resistivity, which indicate groundwater-bearing zones. It is found that some of these zones are hydrogeologically connected through fracture networks resulting in augmented yield. AEM results in combination with an in-depth understanding of the geological structures successfully map these groundwater-saturated fracture networks (or hydrogeological lineaments) that we term as 'Hydrolins'. As groundwater occurrence is generally associated with lineaments, we analyzed the drilling and geophysical logs from 21 wells within a 380 sq.km area to study the relationships of various lineaments with 'Hydrolins', particularly in respect of their groundwater potential. AEM results, though calibrated and correlated with a limited number of well data, revealed a threshold groundwater horizon (TGWH), found to be at 80 m depth for Ankasandra watershed, beyond which a strong correlation exists between the depth of a well and its yield. While the TGWH may differ for different watersheds, the approach presented here can be readily adopted to map sustainable groundwater sources in hardrocks worldwide.