Decompressive craniectomy is reclaiming a role in neurocritical care. The altered pathophysiology found in a cranium converted from a 'closed' box to an 'open' box' carries benefits and risks. In some craniectomy patients, the forces of atmospheric pressure and gravity overwhelm intracranial pressures, and the brain appears sunken. This can lead to paradoxical herniation and the sinking skin flap syndrome, also called the syndrome of the trephined. At the other polar extreme, external brain tamponade occurs when subgaleal fluid accumulates under pressure and 'pushes' on the brain across the craniectomy defect. The neuro-intensive care team should be prepared to diagnose and treat a spectrum of decompressive craniectomy complications including: cerebral contusions, infections, seizures, intra- and extra-axial hemorrhages and fluid collections, sinking skin flap syndrome or syndrome of the trephined, paradoxical herniation, and external brain tamponade. The treating physicians must set aside the Monro-Kellie doctrine and recognize the new pathophysiologic state of these 'open box' patients.
Several methods have been proposed in the literature for analyzing drawdown data for the determination of fracture conductivity of vertically fractured wells. These techniques have paved accurate, but in some cases the fracture conductivity calculated is much smaller than anticipated. This study shows that producing fractured wells at high flow rates will cause nondarcy effects in the fracture, resulting in a pessimistic fracture conductivity.Numerical and semianalytical models were developed to analyze the unsteady flow behavior of finite conductivity fractures producing at high flow rates. Two methods are presented for determining the true fracture conductivity when drawdown data are available at two different flow rates. The amount of turbulent effects also is quantified by the techniques. Examples are presented to illustrate the solution methods.
The increasing use of hydraulic fracturing as a means of improving the productivity of oil and gas wells in low-permeability formations has resulted in many research efforts aimed at increasing fracturing capabilities as well as evaluating the characteristics of the fracture in the postfracturing period. With the advent of the massive postfracturing period. With the advent of the massive hydraulic fracturing (MHF) treatment in recent years, the need for new solutions for evaluating these systems has increased. The problem with the older solutions was the need for many assumptions to arrive at a simple solution. One of the more common assumptions made in these systems was the use of linear flow to describe the flow within the fracture. In gas wells with finite-conductivity fractures producing at high flow rates, the non-Darcy effect is created within the fracture. Hence, new solutions must be developed for these systems. The objective of this paper is to present a new semianalytical solution to this problem that can be applied both to the linear and to the nondarcy flow regimes within the fracture.Over the years. several methods have been developed to analyze postfracture data. Gringarien et al. first solved the fracture system analytically for three special cases: infinite-conductivity vertical fracture, uniform flux vertical fracture, and horizontal fracture. At that time, its application became quite useful. But since not all systems behaved in this manner, the need for further solutions was warranted. Cinco-L. et al. investigated the general case of finite-conductivity vertical fractures, which included the above solution. as well as fracture conductivities as low as 0.1. This research also led to the need to analyze short-time data to obtain unique solutions. Similar results were obtained by Agarwat et al., who presented a finite-difference solution to this problem, considering both the constant rate as well as the problem, considering both the constant rate as well as the constant pressure cases.One of the first papers written on the effects of non-Darcy flow in fractured systems was by Wattenbarger and Ramey. They investigated the effects of non-Darcy flow in the formation and concluded that these effects cannot be felt if the fracture is long or intermediate in size. They further concluded that the effects of turbulent flow within the fracture were more significant.Holditch and Morse investigated the effect of turbulent flow in a fracture and analyzed the transient behavior of specific conductivities (low, medium, and high), giving a qualitative approach to the solution. They stressed the need for greater detail on these solutions and showed that there was indeed a large reduction in the fracture conductivity when non-Darcy flow was included. Although Holditch and Morse gave a detailed descriptive insight into the flow regime problem, they did not develop any general methods for determining the actual conductivity of the fracture.
En bloc resection of cervical chordomas has led to longer survival rates but has resulted in significant morbidities from the procedure, especially when the tumor is multilevel and located in the high-cervical (C1–3) region. To date, there have been only 5 reported cases of multilevel en bloc resection of chordomas in the high-cervical spine. In this technical report the authors describe a sixth case. A complete spondylectomy was performed at C-2 and C-3 with spinal reconstruction and stabilization, using several new modalities that were not used in the previous cases. The use of 1) preoperative endovascular sacrificing of the vertebral artery, 2) CT image-guidance, 3) an ultrasonic aspirator for skeletonizing the vertebral artery, and 4) the custom design of an anterior cage all contributed to absence of intraoperative or long-term (20 months) hardware failure and pseudarthrosis.
Cerebral abscesses in the immunocompromised patient may no longer be assumed to be caused solely by Aspergillus species. The literature reveals several rare cases of uncommon fungi found in these abscesses. Only four cases of cerebral infections caused by the genus Chaetomium have been reported. The case presented represents the first time a patient who had undergone a bone marrow transplant with a cerebral abscess was found to be caused by the pathogen C. atrobrunneum.
Low pressure hydrocephalus is a challenging diagnosis. The genesis of LPH was associated with a drop in EVD output, symptomatic ventriculomegaly, and a remarkable absence of intracranial hypertension. When LPH was treated with the sub-zero method, a 'diuresis' of CSF ensued. These observations support a Darcy's flux of brain interstitial fluid due to altered brain poroelastance; in simpler terms, a boggy brain state.
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