Magnetic resonance imaging analysis of human skull diploic venous anatomy.

BACKGROUND: The skull diploic venous space (DVS) represents a potential route for cerebrospinal fluid (CSF) diversion and absorption in the treatment of hydrocephalus. The goal of this study was to carry out a detailed characterization of the drainage pattern of the DVS of the skull using high-resolution MRI, especially the diploic veins draining to the lacunae laterales (LLs) since the LLs constitute an important channel for the CSF to access the superior sagittal sinus and subsequently the systemic circulation. The objective was to identify those skull regions optimally suited for an intraosseous CSF diversion system. METHODS: High-resolution, T1-weighted MRI scans from 20 adult and 16 pediatric subjects were selected for analysis. Skulls were divided into four regions, that is, frontal, parietal, temporal, and occipital. On each scan, a trained observer counted all diploic veins in every skull region. Each diploic vein was also followed to determine its final drainage pathway (i.e., dural venous sinus, dural vein, LL, or indeterminate). RESULTS: In the adult age group, the frontal and occipital skull regions showed the highest number of diploic veins. However, the highest number of draining diploic veins connecting to the lacunae lateralis was found in the frontal and parietal skull region, just anterior and just posterior to the coronal suture. In the pediatric age group, the parietal skull region, just posterior to the coronal suture, showed the highest overall number of diploic veins and also the highest number of draining diploic veins connecting to the LL. CONCLUSION: This study suggested that diploic venous density across the skull varies with age, with more parietal diploic veins in the pediatric age range, and more occipital and frontal diploic veins in adults. If the DVS is ultimately used for CSF diversion, our anatomical data point to optimal sites for the insertion of specially designed intraosseous infusion devices for the treatment of hydrocephalus. Likely the optimal sites for CSF diversion would be the parietal region just posterior to the coronal suture in children, and in adults, frontal and/or parietal just anterior or just posterior to the coronal suture.

Imaging of vascular complications and their consequences following transplantation in the abdomen.

Transplantation is the surgical treatment of choice for end-stage organ failure. Transplantation procedures performed in the abdomen include liver, renal, pancreas, islet, intestinal, and multivisceral transplantations. Imaging plays a pivotal role in the posttransplantation setting for monitoring the transplant allograft and screening for complications. Knowledge of the surgical techniques employed in abdominal transplantation is essential because it facilitates radiologic understanding and interpretation of the posttransplantation anatomy. This article includes a basic description of the standard surgical techniques performed in the abdomen, with emphasis on the relevant vascular anastomotic reconstructions used. Posttransplantation complications can be broadly classified as vascular or nonvascular in origin. Many of these complications can be accurately depicted and characterized at imaging and dealt with definitively by using interventional radiology techniques, which can be graft- and life-saving and can obviate further complex surgical intervention. The article discusses imaging appearances of vascular complications and their consequences after transplantation in the abdomen. These vascular complications include arterial thrombosis, arterial stenosis, venous thrombosis and stenosis, arteriovenous fistula formation, and pseudoaneurysm formation. The relevant predisposing factors, clinical features, imaging appearances, and potential treatment options for vascular complications of various types of transplantation are presented in a logical and integrated fashion. Knowledge and imaging recognition of the posttransplantation vascular complications discussed in this article will aid radiologists in accurate imaging characterization and thereby facilitate appropriate clinical management and therapy.

Airway sonography in live models and cadavers.

Sonography using cadavers is beneficial in teaching and learning sonoanatomy, which is particularly important because imaging of the airway can be challenging due to the cartilaginous landmarks and air artifacts. In this exploratory study, we have attempted to compare the airway sonoanatomy of cadavers and live models. Our observations support the use of cadavers as teaching tools for learning airway sonoanatomy and practicing procedures involving airway structures, such as superior laryngeal nerve blocks, transtracheal injections, and needle cricothyroidotomy, before performance on patients in clinical situations. We believe this process will improve patient safety and enhance the competency of trainees and practitioners in rare procedures such as needle cricothyroidotomy.

Diploic venous anatomy studied in-vivo by MRI.

Calvarial diploic venous anatomy has been studied post-mortem, but few studies have addressed these venous structures in-vivo. Previous work in our laboratory has shown that intraosseous infusion through the skull diploic space near the diploic veins in animals and humans does access the superior sagittal sinus and the systemic venous system. We developed a volumetric method of imaging the diploic veins in-vivo using MRI, intravenous gadolinium, and digital subtraction to provide for three-dimensional depiction and exact localization of these veins. We hypothesized that this technique would allow for an assessment of the probability of existence, distribution, and concentration of diploic veins in the skull. We scanned 31 neurosurgical patients, and were able to create 3D diploic venous maps in 74% of them. These maps were processed using Adobe Photoshop CS2. Mathworks MatLab 6.5, once customized, counted the number of pixels occupied by the diploic veins in the processed image. The probability of veins was highest in the occipital regions (100%). The inferior occipital (4.1%) and posterior parietal (4.1%) regions had the highest concentrations of diploic veins. Digital subtraction venography using a volumetric MRI sequence can demonstrate the diploic veins in-vivo. The inferior occipital region may be the best area for an intraosseous infusion device because it has the greatest likelihood of containing a vein and also has the highest concentration of veins.

Ultrasound imaging in cadavers: training in imaging for regional blockade at the trunk.

PURPOSE: The unique strategy of using cadaveric models for teaching ultrasound-guided blocks has been described for blocks of the upper and lower extremities. This report considers the parallels between cadaveric and live imaging relevant to scanning of the trunk. The inter-individual variation between subjects (particularly for epidural blocks) is also considered, for practicing ultrasound-guided or supported trunk and central neuraxial techniques. TECHNICAL FEATURES: Ultrasound images using a portable machine C60 5-2 MHz curved array probe or HFL38 13-6 MHz linear array probe were obtained from scanning the trunk of a male adult cadaver, and were compared with ultrasound and magnetic resonance images from an adult male volunteer. OBSERVATIONS: Ultrasound imaging at the midline of the spine in the transverse/coronal plane provided an overview of the vertebral column, while scanning in a medial-to-lateral direction using longitudinal/sagittal plane sequentially localized the spinous, articular and transverse process. At the thoracic spine, further lateral longitudinal scanning will identify costal structures with the rib necks alternating with the hyperechoic ligamentous tissue of the costovertebral joints. Ultrasound imaging in the live subject in the paramedian longitudinal plane could be used at the thoracic and lumber spinal levels to capture the optimal ultrasound window of the epidural space. Imaging in the cadaver, especially when viewing the epidural space, is primarily limited by the tissue rigidity and lack of spine flexibility. CONCLUSION: Cadavers may provide viable training options for practicing ultrasound imaging and real-time ultrasound needle guidance for nerve blocks at the trunk and epidural space. The training can be performed in a stress-free pre-clinical environment without time constraints and the potential for patient discomfort.

Access to cerebrospinal fluid absorption sites by infusion into vascular channels of the skull diplö.

OBJECT: The purpose of this human cadaver study was to determine whether or not an intraosseous skull infusion would access the superior sagittal sinus (SSS) via intradural venous channels. The diploic space of the skull bone contains a sinusoidal vascular network that communicates with the underlying dura mater. Diploic veins in the parasagittal area connect with endothelium-lined intradural channels in the subjacent dura and ultimately with the dural venous sinuses. A significant proportion of cerebrospinal fluid (CSF) absorption is thought to occur via arachnoid granulations in the region of the SSS and especially along the parasagittal dura where arachnoid granulations are surrounded by intradural venous channels (lateral lacunae). The CSF is likely to be conducted from the subarachnoid space into the venous system via the fine intradural channels making up the lateral lacunae. METHODS: Infusion of vinyl acetate casting material into the diploic space of the human cadaveric skull resulted in complete filling of the lateral lacunae and SSS. Corrosion casting techniques and examination under magnification were used to characterize the anatomical connections between diploic spaces and dural venous sinuses. RESULTS: Corrosion casting, performed on five formalin-fixed cadavers, clearly showed the anatomical connections between the diploic infusion site and the venous sinuses in the underlying parasagittal dura where some of the CSF is thought to be absorbed. CONCLUSIONS: The diploic vascular channels of the human skull may represent an indirect pathway into the dural venous sinuses. Intraosseous skull infusion may represent another possible strategy for diversion of CSF into the vascular system in the treatment of hydrocephalus.