Microsurgical Manipulations Research Articles

A novel low-cost device for tool targeting training and microsurgical hand tremor assessment.

The spatial accuracy of microsurgical manipulations is one of the critical factors in successful surgical interventions. The purpose of this study was to create a low-cost, high-fidelity, and easy-to-use simulator for microsurgical skills training, which can be made by residents themselves at home. In response to the COVID-19 pandemic, we created a device for spatial accuracy microsurgical skills training and implemented it in our resident's training program. We propose a design for basic and advanced models. The simulator consisted of commonly available products. A low-cost, durable, and high-fidelity basic model has been developed at a total cost of <10 dollars per unit. The model allows trainees to practice the critical microsurgical skills of tool targeting in a home-based setting. The developed device can be assembled at an affordable price using commercially available materials. Such simulation models can provide valuable training opportunities for microsurgery residents.

Microsurgical dissection methods for embryonic cloning of monozygotic twins

To date, biotechnological methods for producing double grains play an important role in increasing the production of milk and meat. At the same time, monozygotic twins are of particular interest for assessing the heritability of quantitative traits, breeding value when studying the influence of the maternal effect on offspring and creating reserve genes with known properties. However, in cattle, the frequency of birth of twins is only 0.025%, and the appearance of identical twins is only 0.01%. The reasons for the separation of embryos in the process of ontogenesis are unknown, but their production became possible with the development of genetic engineering methods, which include embryonic cloning by microsurgery of early embryos (dissection). The results of research in this area are mostly not applied, which is due to the high cost of micromanipulation equipment and the complexity of the procedure due to the large number of micro-tools. Today, the development of simplified methods of microsurgical manipulations on embryos remains an urgent task. In this regard, the aim of the research was to study the possibility of simplifying the existing technology of microsurgical dissection of preimplantation embryos by developing appropriate tools. In connection with this goal, the tasks of developing a device for simplifying the dissection procedure and determining its effectiveness in comparison with the use of a micromanipulator with one tool were determined. The development of the device and its practical application were carried out in 2021-2023 at the Regional Research and Production Center for the Reproduction of Farm Animals of the Kalmyk State University named after B.B. Gorodovikov. The conducted studies showed the following results: the efficiency of using a micromanipulator with one microscalpel was 86.1%: as a result of dissection of 61 embryos, 105 full-fledged demiembryons out of 122 possible ones were obtained. The efficiency of the developed device was 10.2% higher – after separation, 27 embryos received 52 compacted demiembryons out of 54 possible (96.3%).

Microsurgical Manipulations to Isolate Collectively Migrating Mesendoderm.

Mesendoderm mantle closure completes the gastrulation movements of the <i>Xenopus laevis</i> embryo and provides an unparalleled opportunity to study collective cell behaviors within a mesenchymal tissue. Free-edge sheet-like collective movements of these tissues contrast with movements of epithelial tissues in that mesendodermal cells are not constrained by tight junctions or adherens junctions, yet migrate in a coherent and persistent mode over several hours. Mesendoderm cells are the largest motile cells in the <i>Xenopus</i> embryo and complete a 500-µm migratory path. When mesendoderm is cultured on rigid glass substrates, these cells can exceed 100 µm in length and show a highly persistent leading lamellipodia that can exceed 20 µm from tip to base. These large collectively migrating cells provide a unique imaging opportunity to visualize polarized adhesive and cytoskeletal structures with high-numerical-aperture objectives. Mesendodermal cells in the early embryo originate from around the entirety of the marginal zone and may also be distinguished by their source along the animal-vegetal axis. Here we use the term mesendoderm but note alternative terms for these cells can include head mesoderm, endomesoderm, and prechordal mesoderm. This protocol summarizes microsurgical preparation of mesendoderm tissue explants and "windowed" embryos. Skills needed to dissect fragments of the mesendoderm mantle are marginally greater than those needed to isolate animal cap ectoderm and can be mastered within 2 weeks; skills needed to isolate the mesendoderm "donut" or "ring" or to prepare windowed embryos are significantly greater and may require several additional weeks of training.

Real-time 3D optoacoustic tracking of cell-sized magnetic microrobots circulating in the mouse brain vasculature.

Mobile microrobots hold remarkable potential to revolutionize health care by enabling unprecedented active medical interventions and theranostics, such as active cargo delivery and microsurgical manipulations in hard-to-reach body sites. High-resolution imaging and control of cell-sized microrobots in the in vivo vascular system remains an unsolved challenge toward their clinical use. To overcome this limitation, we propose noninvasive real-time detection and tracking of circulating microrobots using optoacoustic imaging. We devised cell-sized nickel-based spherical Janus magnetic microrobots whose near-infrared optoacoustic signature is enhanced via gold conjugation. The 5-, 10-, and 20-μm-diameter microrobots are detected volumetrically both in bloodless ex vivo tissues and under real-life conditions with a strongly light-absorbing blood background. We further demonstrate real-time three-dimensional tracking and magnetic manipulation of the microrobots circulating in murine cerebral vasculature, thus paving the way toward effective and safe operation of cell-sized microrobots in challenging and clinically relevant intravascular environments.

A Novel Standardized Peripheral Nerve Transection Method and a Novel Digital Pressure Sensor Device Construction for Peripheral Nerve Crush Injury.

Peripheral nerve injury (PNI) is common in all walks of life, and the most common PNIs are nerve crush and nerve transection. While optimal functional recovery after crush injury occurs over weeks, functional recovery after nerve transection with microsurgical repair and grafting is poor, and associated with permanent disability. The gold-standard treatment for nerve transection injury is microsurgical tensionless end-to-end suture repair. Since it is unethical to do experimental PNI studies in humans, it is therefore indispensable to have a simple, reliable, and reproducible pre-clinical animal model for successful evaluation of the efficacy of a novel treatment strategy. The objective of this article is two-fold: (A) To present a novel standardized peripheral nerve transection method in mice, using fibrin glue for modeling peripheral nerve transection injury, with reproducible gap distance between the severed nerve ends, and (B) to document the step-wise description of constructing a pressure sensor device for crush injury pressure measurements. We have successfully established a novel nerve transection model in mice using fibrin glue, and demonstrated that this transection method decreases surgical difficulties and variability by avoiding microsurgical manipulations on the nerve, ensuring the reproducibility and reliability of this animal model. Although it is quite impossible to exactly mimic the pathophysiological changes seen in nerve transection with sutures, we hope that the close resemblance of our novel pre-clinical model with gold-standard suturing can be easily reproduced by any lab, and that the data generated by this method significantly contributes to better understanding of nerve pathophysiology, molecular mechanisms of nerve regeneration, and the development of novel strategies for optimal functional recovery. In case of peripheral nerve crush injury, current methods rely on inter-device and operator precision to limit the variation with applied pressure. While the inability to accurately quantify the crush pressure may result in reduced reproducibility between animals and studies, there is no documentation of a pressure monitoring device that can be readily used for real-time pressure measurements. To address this deficit, we constructed a novel portable device comprised of an Arduino UNO microcontroller board and force sensitive resistor (FSR) capable of reporting the real-time pressure applied to a nerve. This novel digital pressure sensor device is cheap, easy to construct and assemble, and we believe that this device will be useful for any lab performing nerve crush injury in rodents.

How to Organize Affordable Microsurgical Training Laboratory: Optimal Price-quality Solution.

Summary:Today, microsurgery is an integral part of plastic surgery, maxillofacial surgery, hand surgery, and neurosurgery. More and more surgical procedures are accompanied by microsurgical intervention. Long training is required to develop the necessary skills for fine work with microsurgical instruments and delicate tissues under magnification. We suggest a methodology as to how to organize an inexpensive microsurgical training laboratory with minimal investment. Suggested guidelines provide information about cost-effective ways of arranging a comfortable training environment. An adapted stereoscopic microscope allows working with a wide range of magnification and focus distance. An ergonomic working position is set up by adjustable handmade table and chair. For performing basic microsurgical manipulations, a set of four instruments and inexpensive suture materials are used. A total amount of 323.5 USD was spent to purchase all of the necessary components for the microsurgical laboratory. The described components are available worldwide regardless of manufacturers. We suggest an inexpensive way to arrange a microsurgical laboratory. This approach is especially beneficial for students and residents from low-income countries.

Effects of exogenous factors on spatial accuracy in neurosurgery

The study aimed to assess the effect of exogenous factors such as surgeon posture, surgical instrument length, fatigue after a night shift, exercise and caffeine consumption on the spatial accuracy of neurosurgical manipulations. For the evaluation and simulation of neurosurgical manipulations, a testing device developed by the authors was used. The experimental results were compared using nonparametric analysis (Wilcoxon test) and multivariate analysis, which was performed using mixed models. The results were considered statistically significant at p < 0.05. The study included 11 first-year neurosurgery residents who met the inclusion criteria. Hand support in the sitting position (Wilcoxon test p value = 0.0033), caffeine consumption (p = 0.0058) and the length of the microsurgical instrument (p = 0.0032) had statistically significant influences on the spatial accuracy of surgical manipulations (univariate analysis). The spatial accuracy did not significantly depend on the type of standing position (Wilcoxon test p value = 0.2860), whether the surgeon was standing/sitting (p = 0.1029), fatigue following a night shift (p = 0.3281), or physical exertion prior to surgery (p = 0.2845).When conducting the multivariate analysis, the spatial accuracy significantly depended on the test subject (p < 0.0001), the use of support during the test (p = 0.0001), and the length of the microsurgical instrument (p = 0.0397). To increase the spatial accuracy of microsurgical manipulations, hand support and shorter tools should be used. Caffeine consumption in high doses should also be avoided prior to surgery.

Ependymomas of Filum Terminale: Clinical Characteristics and Surgical Management of 5 Patients

To retrospective review a series of patients with ependymomas of filum terminale (FTEs) who underwent microsurgical resection and had long-term follow-up. Five adults with FTEs were surgically treated and enrolled in the study. Clinical manifestations, imaging data, intraoperative findings, and postoperative outcome were recorded. Six FTEs were discovered on preoperative lumbar magnetic resonance imaging, with 1 rare case of a single FTE accompanied by a neurofibroma. Gross total resection was achieved in all patients; en bloc excision was carried out in 2 patients for 2 FTEs and 1 neurofibroma, while piecemeal resection was done in 3 patients for 4 FTEs. Most preoperative symptoms were relieved soon after surgery; 1 patient with urination difficulty achieved complete recovery 1 year postoperatively. Tumor recurrence was found in 1 patient 54 months after her first surgery. FTEs are rare subdural extramedullary tumors. Patients usually present initially with back and leg pain. Elaborate microsurgical manipulations and intraoperative electrophysiologic monitoring are helpful in ensuring satisfactory excision and neurological prognosis. Regular long-term follow-up is recommended for all postoperative patients.

In ovo technique for cell injection in the CPM followed by bead implantation in the BA2 of chicken embryos

The major advantage of chicken embryos model is their accessibility for microsurgical manipulations and the dissection of tissues for ex vivo explant culture. Branchial arches are embryonic structure located next to the top of developing heart. Each arch is made of surface ectoderm, endoderm, myogenic mesoderm cells and cranial neural crest cells. The myogenic mesoderm originates from cranial paraxial mesoderm (CPM), which is transiently migrated to branchial arches (BAs). The first branchial arch (BA1) mesoderm contributes to formation of mastication muscles. The second branchial arch (BA2) mesoderm gives rise to facial expression muscles. This article focuses on cell injection in the CPM and bead implantation (gain of function approaches) in the BA2. In order to follow the migration of mesoderm progenitor cells from CPM to BA2, we injected quail cells in the CPM of stage HH10-11 embryos, followed by implantation of SDF-1 bead at stage HH15-16. Later the attraction of quail cells (CXCR4+) towards the SDF-1 source has been observed, using whole-mount immunostaining of a specific quail antibody (QCPN) at stage HH19-22.•Our method, which involves bead implantation followed by quail cell injection, provides useful tools for tracing migratory mesodermal cells in vivo.•The proposed method does not require any commercial kits and can be used for various developmental process.•It does not employ any complicated methods such as genetically engineered permanent cell labeling, multiplicity of fluorescent markers or clonal analysis.

Finger and thumb replantation: From biomechanics to practical surgical applications

Finger and thumb amputations, which are always dramatic injuries with major functional and psychological repercussions, remain a surgical challenge. This review on digit replantation develops the underlying biomechanical and surgical aspects as well as practical indications. The different stages from trauma to postoperative monitoring are described. We describe the steps to follow from theory to practice in order to optimize the surgical acts that must as effective possible in terms of management and decision-making efficiency. Indications recognized as standards such as thumb amputation, multi-digit amputations and distal amputations are detailed, as well as the more controversial ring finger replantations. The challenge of successful finger and thumb replantation lies in searching for the best functional and cosmetic outcome and not performing irrelevant microsurgical manipulations.

High-Tech Diagnostic Methods and Enteroscopic Treatment of Children with Peutz-Jeghers Syndrome.

Peutz-Jeghers syndrome (PJS) is an autosomal dominant hereditary hamartomatous polyposis with predominant localization in the jejunum and ileum and high risk of bowel perforation after traditional polypectomy. The modern enteroscopy is the only possible technique for visualizing and performing intraluminal endoscopic microsurgical manipulations in the deep sections of the small intestine. The study aims to develop an optimal method for the diagnosis and treatment of polyps in children with PJS. During 2015 to 2018 we conducted 30 comprehensive examinations of children with PJS in The Department of Endoscopic Research of the National Medical Research Center for Children's Health. We performed esophagogastroduodenoscopy and colonoscopy with removal of polyps more than 7 mm, then video capsule endoscopy and, guided by this, therapeutic single-balloon enteroscopy. Our technique for removal of polyps is general in all parts: (1) creating a "resistant pillow"; (2) electroexcision of polyp; (3) clipping the removal site. Successfully performed electroexcision of polyps, which were located in the deep parts of the small intestine at a distance of 30 segments (one segment is 10 cm), reached a diameter of 2.5 cm, had a long pedicle. The postoperative period was uneventful. We have developed an optimal method of diagnostic and therapeutic measures, the observance of which allows us to avoid delayed perforations of the small intestine in the area of polypectomy in the postoperative period in children with PJS. Thanks to this technique, modern enteroscopy is becoming the only possible alternative to bowel resection in children with PJS.

Application of Fluorescein Fluorescence in Vascular Neurosurgery.

Background: Fluorescein sodium (FNa) is a fluorescent drug with a long history of use for assessing retinal blood flow in ophthalmology; however, its application in vascular neurosurgery is only now gaining popularity. This review summarizes the current knowledge about using FNa videoangiography in vascular neurosurgery.Methods: We performed a literature review on the usage of FNa for fluorescent videoangiography procedures in neurosurgery. We analyzed methods of injection, dosages of FNa, visualizing platforms, and interpretation of FNa videoangiography. We also reviewed practical applications of FNa videoangiography during various vascular neurosurgeries.Results: FNa videoangiography can be performed with intraarterial (intracarotid) or intravenous dye injections. Both methods provide excellent resolution with enhanced fluorescence that shows intravascular blood flow on top of visible surrounding anatomy, and both allow simultaneous purposeful microsurgical manipulations. Although it is invasive, an intracarotid FNa injection results in faster contrast appearance and higher-intensity fluorescence and requires a lower dose per injection (reported range, 1–50 mg) compared with peripheral intravenous FNa injection (reported range, 75–2,000 mg or 1–1.5 mg/kg body weight). Four optical excitation/detection tools for FNa videoangiography have been successfully used: conventional xenon-light operating microscope with a special filter set, pencil-type light-emitting diode probe with a filter set, laser-illumination operating microscope, and an endoscope with a filter set. FNa videoangiography was reported to be feasible and useful in various clinical scenarios, such as examining the feeders and drainers in arteriovenous malformation surgery, checking the patency of a microvascular anastomosis, and assessing blood flow during aneurysm clipping. FNa videoangiography can be repeated during the same procedure and used along with indocyanine green (ICG) videoangiography.Conclusions: Compared with ICG videoangiography, FNa videoangiography has the advantages of enabling real-time inspection and better visualization at deep locations; however, thick vessel walls limit visualization of FNa in larger vessels. FNa videoangiography is a useful tool in multiple neurovascular scenarios and merits further studies to establish its clinical value.

Surgical strategies of intramedullary medullocervical ependymomas: a report of 120 cases

Objective To explore the clinical characteristics and microsurgical skills of intramedullary medullocervical ependymomas for increasing the rate of gross total resection (GTR) and decreasing the disabling rate. Methods A total of 120 patients with medullocervical ependymomas were admitted to Department of Neurosurgery, Changzheng Hospital, the Second Military Medical University of PLA, from January 2001 to November 2016. A retrospective analysis was conducted regarding their clinical manifestations, imaging characteristics, microsurgical manipulations, extent of resection and postoperative follow-up data. In all cases, the tumor resection was performed using posterior suboccipital midline approach. Results Among the 120 patients, GTR was achieved in 111 (92.5%) cases and subtotal resection was performed in 9 (7.5%) cases. The maximal tumor size was 25.0×2.0×2.0 cm and affected all cervical levels, and the minimal size of the tumor was 1.0×1.0×0.6 cm. Follow-up was successfully conducted in 106 (95.5%) patients and for 3 to 108 months with an average of (23.0±18.5) months. The patient's sensory and motor functions were relieved or remained unchanged post surgery in 83 (78.3%) cases and aggravated in 22 (20.8%) cases. One (0.9%) death occurred. Four patients (3.8%) were reoperated on due to tumor recurrence. The neurological function was graded based on the McCormick system as 60 (56.6%) cases in grade I, 28 (26.4%) cases in grade II, 16 cases (15.1%) in grade III and 1(0.9%) case in grade IV. Conclusion For most intramedullary medullocervical ependymomas, proper surgical strategies and qualified operational skills, combined with imaging and neuroelectrophysiological technologies could be applied to realize the GTR of tumors and preservation of neurological functions. Key words: Medulla oblongata; Spinal cord; Ependymoma; Microsurgery; Prognosis

High-frequency jet ventilation for endolaryngotracheal surgery--chart review and procedure analysis from the surgeon's and the anaesthesiologist's point of view.

High-frequency jet ventilation (HFJV) arose as a ventilation alternative in laryngotracheal surgery as it offers the surgeon a better overview and more space for microsurgical manipulations. On the contrary, anaesthesiologic monitoring is limited and (relative) contraindications exist. The aim of this study was to evaluate the procedure. Contraindications and limitations are discussed from the surgeon's and the anaesthesiologist's point of view, and relevant aspects of oncologic surgery are identified. Retrospective chart review and analysis of clinical experiences. University Teaching hospital. Eighty adult patients (97 cases) treated at our institution between June 2012 and September 2013 were included. HFJV was performed using thin, subglottically placed catheters. The analysis focuses on complications and practical steps. Indications were benign (63%) and malignant pathologies (37%). The CO2 laser was used in 34 cases (35%). The mean operating time averaged 53 min (3-404 min) and the mean duration of anaesthesia was 81 min (16-438 min). Two thirds of the operated patients had a body mass index higher than 25 kg/m(2) . Eighty-four per cent were classified as ASA I and II according to the American Society of Anesthesiologists. All pathologies could well be exposed by the surgeon. Two reversible desaturations to 70% were documented. In another case, emergency re-intubation was necessary as the saturation dropped below 50%. In 8 (8%) cases, elective re-intubation to conventional tubes was performed during the course of the operation as HFJV did not establish optimal oxygenation conditions. No severe intra-operative bleeding was observed. High-frequency jet ventilation represents a safe ventilation approach for laryngotracheal surgery in experienced hands. Due to the better overview, it offers a better orientation on anatomical structures and on the pathology. Special attention has to be laid on obesity, reflux and cardiopulmonary diseases. However, individual decisions can be made under consideration of all co-morbidities. A close pre- and intra-operative interdisciplinary work up is required.

Axolotls with an under- or oversupply of neural crest can regulate the sizes of their dorsal root ganglia to normal levels

How animals adjust the size of their organs is a fundamental, enduring question in biology. Here we manipulate the amount of neural crest (NC) precursors for the dorsal root ganglia (DRG) in axolotl. We produce embryos with an under- or over-supply of pre-migratory NC in order to find out if DRG can regulate their sizes during development. Axolotl embryos are perfectly suitable for this research. Firstly, they are optimal for microsurgical manipulations and tissue repair. Secondly, they possess, unlike most other vertebrates, only one neural crest string located on top of the neural tube. This condition and position enables NC cells to migrate to either side of the embryo and participate in the regulation of NC cell distribution. We show that size compensation of DRG in axolotl occurs in 2cm juveniles after undersupply of NC (up-regulation) and in 5cm juveniles after oversupply of NC (down-regulation). The size of DRG is likely to be regulated locally within the DRG and not via adaptations of the pre-migratory NC or during NC cell migration. Ipsi- and contralateral NC cell migration occurs both in embryos with one and two neural folds, and contralateral migration of NC is the only source for contralateral DRG formation in embryos with only one neural fold. Compensatory size increase is accompanied by an increase in cell division of a DRG precursor pool (PCNA+/SOX2−), rather than by DRG neurons or glial cells. During compensatory size decrease, increased apoptosis and reduced proliferation of DRG cells are observed.

A new bayonet spring microsurgical instrument handle with a bar for microneurosurgery

Background:The bayonet-shaped spring surgical instrument is essential and perhaps the most important tool in microneurosurgery. It is needed to be handled gently, and so stable handling to the spring tension of the long instrument handle is necessary for fine action in narrow and deep operative fields under an operating microscope.Methods:A bayonet spring microsurgical instrument handle with a bar as a stabilizer is presented for facilitating delicate microsurgical manipulations stably in microneurosurgery. The bar with the handle is a metric projection. The grip of this instrument is a modified writing grasp, which is composed of writing grasp and sandwiching a lateral-projected bar with handle between the medial side of the index finger and the lateral side of the middle finger. Then, this bar as a stabilizer of the instrument is suitable to fix it.Results:Microneurosurgical operations using this instrument system were performed. This was advantageous to stabilize the instrument in deep and narrow operative fields, to be sensitive to move its functional tips by fingertips, and to reduce unwanted movements under an operating microscope. This was disadvantageous to limit the rotational movement within fingers. There were no complications.Conclusion:This handle would provide a steady and balanced grip to ensure precise manipulation of the functional tips of the bayonet instrument for microneurosurgery. It may be useful particularly for the beginners or for the non-dominant hand of microsurgeons.

La « double horloge » ou comment apprendre la microchirurgie sans animal

Animal experimentation is the most common way to learn microsurgery. However, this practice should be performed according to ethical rules and financial cost. This study has a triple aim: improving students' skills in microsurgery, respecting ethics and reducing costs by using fewer animals. We propose an ethical, practical and inexpensive training method that uses sewing needles. This training consists in microsurgery wire's passages in the eye of sewing needles arranged into circle. Specifically, 24 needles were arranged into two circles on a polystyrene block representing a "double clock". A specific scorecard for this exercise was made to evaluate the students. In total, between November 2010 and June 2011, fifteen residents followed the university degree in microsurgery provided by the faculty of medicine Henri Warembourg (Lille, France). The "double clock" was added to the eight already existing microsurgical manipulations. All of the participants were tested and this exercise was found to be effective as a teaching procedure. Also, each student used an average of 20 rats per year. This year we have reduced our animal control by 10% or about 30 rats. Our goals were achieved as we have improved student's microsurgical skills and also limiting cost by using fewer animals.

Coronary Artery Ligation and Intramyocardial Injection in a Murine Model of Infarction

Mouse models are a valuable tool for studying acute injury and chronic remodeling of the myocardium in vivo. With the advent of genetic modifications to the whole organism or the myocardium and an array of biological and/or synthetic materials, there is great potential for any combination of these to assuage the extent of acute ischemic injury and impede the onset of heart failure pursuant to myocardial remodeling. Here we present the methods and materials used to reliably perform this microsurgery and the modifications involved for temporary (with reperfusion) or permanent coronary artery occlusion studies as well as intramyocardial injections. The effects on the heart that can be seen during the procedure and at the termination of the experiment in addition to histological evaluation will verify efficacy. Briefly, surgical preparation involves anesthetizing the mice, removing the fur on the chest, and then disinfecting the surgical area. Intratracheal intubation is achieved by transesophageal illumination using a fiber optic light. The tubing is then connected to a ventilator. An incision made on the chest exposes the pectoral muscles which will be cut to view the ribs. For ischemia/reperfusion studies, a 1 cm piece of PE tubing placed over the heart is used to tie the ligature to so that occlusion/reperfusion can be customized. For intramyocardial injections, a Hamilton syringe with sterile 30gauge beveled needle is used. When the myocardial manipulations are complete, the rib cage, the pectoral muscles, and the skin are closed sequentially. Line block analgesia is effected by 0.25% marcaine in sterile saline which is applied to muscle layer prior to closure of the skin. The mice are given a subcutaneous injection of saline and placed in a warming chamber until they are sternally recumbent. They are then returned to the vivarium and housed under standard conditions until the time of tissue collection. At the time of sacrifice, the mice are anesthetized, the heart is arrested in diastole with KCl or BDM, rinsed with saline, and immersed in fixative. Subsequently, routine procedures for processing, embedding, sectioning, and histological staining are performed. Nonsurgical intubation of a mouse and the microsurgical manipulations described make this a technically challenging model to learn and achieve reproducibility. These procedures, combined with the difficulty in performing consistent manipulations of the ligature for timed occlusion(s) and reperfusion or intramyocardial injections, can also affect the survival rate so optimization and consistency are critical.

Coronary Artery Ligation and Intramyocardial Injection in a Murine Model of Infarction

Mouse models are a valuable tool for studying acute injury and chronic remodeling of the myocardium in vivo. With the advent of genetic modifications to the whole organism or the myocardium and an array of biological and/or synthetic materials, there is great potential for any combination of these to assuage the extent of acute ischemic injury and impede the onset of heart failure pursuant to myocardial remodeling. Here we present the methods and materials used to reliably perform this microsurgery and the modifications involved for temporary (with reperfusion) or permanent coronary artery occlusion studies as well as intramyocardial injections. The effects on the heart that can be seen during the procedure and at the termination of the experiment in addition to histological evaluation will verify efficacy. Briefly, surgical preparation involves anesthetizing the mice, removing the fur on the chest, and then disinfecting the surgical area. Intratracheal intubation is achieved by transesophageal illumination using a fiber optic light. The tubing is then connected to a ventilator. An incision made on the chest exposes the pectoral muscles which will be cut to view the ribs. For ischemia/reperfusion studies, a 1 cm piece of PE tubing placed over the heart is used to tie the ligature to so that occlusion/reperfusion can be customized. For intramyocardial injections, a Hamilton syringe with sterile 30gauge beveled needle is used. When the myocardial manipulations are complete, the rib cage, the pectoral muscles, and the skin are closed sequentially. Line block analgesia is effected by 0.25% marcaine in sterile saline which is applied to muscle layer prior to closure of the skin. The mice are given a subcutaneous injection of saline and placed in a warming chamber until they are sternally recumbent. They are then returned to the vivarium and housed under standard conditions until the time of tissue collection. At the time of sacrifice, the mice are anesthetized, the heart is arrested in diastole with KCl or BDM, rinsed with saline, and immersed in fixative. Subsequently, routine procedures for processing, embedding, sectioning, and histological staining are performed. Nonsurgical intubation of a mouse and the microsurgical manipulations described make this a technically challenging model to learn and achieve reproducibility. These procedures, combined with the difficulty in performing consistent manipulations of the ligature for timed occlusion(s) and reperfusion or intramyocardial injections, can also affect the survival rate so optimization and consistency are critical.

Intraoperative monitoring of cortically recorded visual response for posterior visual pathway

Intraoperative monitoring of visual evoked potentials (VEPs) has been regarded as having limited significance for the preservation of visual function during neurosurgical procedures, mainly due to its poor spatial resolution and signal-to-noise ratio. The authors evaluated the usefulness of cortically recorded VEPs, instead of the usual scalp VEPs, as intraoperative monitoring focusing on the posterior visual pathway. In 17 consecutive patients who underwent microsurgical procedures for lesions near the posterior visual pathway, cortical responses were recorded using 1-Hz flashing light-emitting diodes and subdural strip electrodes after induction of general anesthesia with sevoflurane or propofol. The detectability and waveform of the initial response, stability, and changes during microsurgical manipulations were analyzed in association with the position of electrodes and postoperative changes in visual function. Initial VEPs were detected in 82% of all patients. The VEPs were detected in 94% of patients without total hemianopia in whom electrodes were placed sufficiently near the occipital pole; in these cases the recordings were not significantly affected by anesthesia. The detectability rates of the negative peak before 100 msec (N1), positive peak approximately 100 msec (P100), and negative peak after 100 msec (N2) were 36, 50, and 100%, respectively. The mean latencies and amplitudes of N1, P100, and N2 were 90.0 +/- 15.9 msec and 61.0 +/- 64.0 microV, 103.9 +/- 13.5 msec and 34.3 +/- 38.6 microV, and 125.7 +/- 12.2 msec and 44.9 +/- 48.9 microV, respectively, showing great variability. In 11 patients, the initial waveforms of VEP remained stable during microsurgical procedures, and the visual status did not change postoperatively, while it disappeared in 2 patients who presented with postoperative hemianopia. Direct recording from the visual cortices under general anesthesia achieved satisfactory detectability of the visual response to a light-emitting diode flashing light. Although the initial waveforms varied greatly among patients, they were stable during microsurgical procedures, and the changes were consistent with postoperative visual function. Intraoperative cortical VEP monitoring is a potentially useful procedure to monitor the functional integrity of the posterior visual pathway.