Considerations for the use of porcine organ donation models in preclinical organ donor intervention research.

Use of animal models in preclinical transplant research is essential to the optimization of human allografts for clinical transplantation. Animal models of organ donation and preservation help to advance and improve technical elements of solid organ recovery and facilitate research of ischemia-reperfusion injury, organ preservation strategies, and future donor-based interventions. Important considerations include cost, public opinion regarding the conduct of animal research, translational value, and relevance of the animal model for clinical practice. We present an overview of two porcine models of organ donation: donation following brain death (DBD) and donation following circulatory death (DCD). The cardiovascular anatomy and physiology of pigs closely resembles those of humans, making this species the most appropriate for pre-clinical research. Pigs are also considered a potential source of organs for human heart and kidney xenotransplantation. It is imperative to minimize animal loss during procedures that are surgically complex. We present our experience with these models and describe in detail the use cases, procedural approach, challenges, alternatives, and limitations of each model.

The complete anterior petrosectomy: an expanded extended-middle fossa approach with removal of the infratrigeminal petrous apex and drilling of the lateral clivus.

Intradural exposure in the extended middle fossa anterior transpetrosal approach is traditionally limited to the inferior petrosal sinus inferomedially. Expanding bone removal of the petrous apex around the petrous internal carotid artery (ICA), underneath the trigeminal ganglion/mandibular nerve, and into the lateral component of the clivus can significantly expand the limits of this approach beyond the inferior petrosal sinus and allows for exposure of the midline structures, aspects of the contralateral inferior clival region, and, when high riding, the vertebrobasilar junction. To date, no descriptive techniques for drilling into the lateral clivus in this approach have been published. The authors provide a detailed stepwise description of their complete anterior petrosectomy, in use at their institution, that involves skeletonization of the posteromedial petrous ICA, gentle elevation of the trigeminal ganglion/mandibular nerve, removal of the infratrigeminal petrous apex, and two techniques for drilling into the lateral clivus along the petroclival fissure. These techniques provide a direct and unobstructed corridor to the midpetroclival region and ventral brainstem with greater maneuverability and enhanced control of the midline structures, which is especially useful for resection of petroclival meningiomas, chondrosarcomas, and giant vascular lesions of the mid- and upper basilar artery and its proximal branches.

Correlation Between Neurosurgical Residency Written Board Scores and Case Logs.

OBJECTIVE: There are few objective measures for evaluating individual performance throughout surgical residency. Two commonly used objective measures are the case log numbers and written board examination scores. The objective of this study was to investigate possible correlations between these measures. METHODS: We conducted a retrospective review of the American Board of Neurological Surgery (ABNS) written board scores and the Accreditation Council for Graduate Medical Education case logs of 27 recent alumni from neurologic surgery residency training programs at The Ohio State Wexner Medical Center and the University of Nebraska Medical Center. RESULTS: The number of spine cases logged was significantly correlated with the ABNS written examination performance in univariate linear regression (r2 = 0.182, P = 0.0265). However, case numbers from all other neurosurgical subspecialties did not significantly correlate with ABNS written board performance (P > 0.1). CONCLUSIONS: Identifying which objective measures correlate most closely with resident education could help optimize the structure of residency training programs. We believe that early exposure to focused aspects of neurosurgery helps the young resident learn quickly and efficiently and ultimately score highly on standardized examinations. Therefore program directors may want to ensure focused exposure during the early years of residency, with particular attention to worthwhile rotations in spine neurosurgery.

Association of Preoperative Patient Frailty and Operative Stress With Postoperative Mortality.

Importance: Patients with frailty have higher risk for postoperative mortality and complications; however, most research has focused on small groups of high-risk procedures. The associations among frailty, operative stress, and mortality are poorly understood. Objective: To assess the association between frailty and mortality at varying levels of operative stress as measured by the Operative Stress Score, a novel measure created for this study. Design, Setting, and Participants: This retrospective cohort study included veterans in the Veterans Administration Surgical Quality Improvement Program from April 1, 2010, through March 31, 2014, who underwent a noncardiac surgical procedure at Veterans Health Administration Hospitals and had information available on vital status (whether the patient was alive or deceased) at 1 year postoperatively. A Delphi consensus method was used to stratify surgical procedures into 5 categories of physiologic stress. Exposures: Frailty as measured by the Risk Analysis Index and operative stress as measured by the Operative Stress Score. Main Outcomes and Measures: Postoperative mortality at 30, 90, and 180 days. Results: Of 432 828 unique patients (401 453 males [92.8%]; mean (SD) age, 61.0 [12.9] years), 36 579 (8.5%) were frail and 9113 (2.1%) were very frail. The 30-day mortality rate among patients who were frail and underwent the lowest-stress surgical procedures (eg, cystoscopy) was 1.55% (95% CI, 1.20%-1.97%) and among patients with frailty who underwent the moderate-stress surgical procedures (eg, laparoscopic cholecystectomy) was 5.13% (95% CI, 4.79%-5.48%); these rates exceeded the 1% mortality rate often used to define high-risk surgery. Among patients who were very frail, 30-day mortality rates were higher after the lowest-stress surgical procedures (10.34%; 95% CI, 7.73%-13.48%) and after the moderate-stress surgical procedures (18.74%; 95% CI, 17.72%-19.80%). For patients who were frail and very frail, mortality continued to increase at 90 and 180 days, reaching 43.00% (95% CI, 41.69%-44.32%) for very frail patients at 180 days after moderate-stress surgical procedures. Conclusions and Relevance: We developed a novel operative stress score to quantify physiologic stress for surgical procedures. Patients who were frail and very frail had high rates of postoperative mortality across all levels of the Operative Stress Score. These findings suggest that frailty screening should be applied universally because low- and moderate-stress procedures may be high risk among patients who are frail.

Pilot project to assess and improve neurosurgery resident and staff perception of feedback to residents for self-improvement goal formation.

OBJECTIVE: The Accreditation Council for Graduate Medical Education (ACGME) has pushed for more frequent and comprehensive feedback for residents during their training, but there is scant evidence for how neurosurgery residents view the current feedback system as it applies to providing information for self-improvement and goal formation. The authors sought to assess neurosurgery resident and staff perceptions of the current resident feedback system in providing specific, meaningful, achievable, realistic, and timely (SMART) goals. The authors then created a pilot project to improve the most unfavorably viewed aspect of the feedback system. METHODS: The authors conducted an anonymous survey of neurosurgery residents and staff at an academic medical institution to assess SMART goals for resident feedback and used the results to create a pilot intervention to address the most unfavorably viewed aspect of the feedback system. The authors then conducted a postintervention survey to see if perceptions had improved for the target of the intervention. RESULTS: Neurosurgery residents and staff completed an anonymous online survey, for which the results indicated that resident feedback was not occurring in a timely manner. The authors created a simple anonymous feedback form. The form was distributed monthly to neurosurgery residents, neurosurgical staff, and nurses, and the results were reported monthly to each resident for 6 months. A postintervention survey was then administered, and the results indicated that the opinions of the neurosurgery residents and staff on the timeliness of resident feedback had changed from a negative to a nonnegative opinion (p = 0.01). CONCLUSIONS: The required ACGME feedback methods may not be providing adequate feedback for goal formation for self-improvement for neurosurgery residents. Simple interventions, such as anonymous feedback questionnaires, can improve neurosurgery resident and staff perception of feedback to residents for self-improvement and goal formation.

Suction forces generated by passive bile bag drainage on a model of post-subdural hematoma evacuation.

BACKGROUND: Passive drainage systems are commonly used after subdural hematoma evacuation but there is a dearth of published data regarding the suction forces created. We set out to quantify the suction forces generated by a passive drainage system. METHOD: We created a model of passive drainage after subdural hematoma evacuation. We measured the maximum suction force generated with a bile bag drain for both empty drain tubing and fluid-filled drain tube causing a siphoning effect. We took measurements at varying heights of the bile bag to analyze if bile bag height changed suction forces generated. RESULTS: An empty bile bag with no fluid in the drainage tube connected to a rigid, fluid-filled model creates minimal suction force of 0.9 mmHg (95% CI 0.64-1.16 mmHg). When fluid fills the drain tubing, a siphoning effect is created and can generate suction forces ranging from 18.7 to 30.6 mmHg depending on the relative position of the bile bag and filled amount of the bile bag. The suction forces generated are statistically different if the bile bag is 50 cm below, level with or 50 cm above the experimental model. CONCLUSION: Passive bile bag drainage does not generate significant suction on a fluid-filled rigid model if the drain tubing is empty. If fluid fills the drain tubing then siphoning occurs and can increase the suction force of a passive bile bag drainage system to levels comparable to partially filled Jackson-Pratt bulb drainage.

Hemorrhage Rate After External Ventricular Drain Placement in Subarachnoid Hemorrhage: Time to Heparin Administration.

OBJECTIVE: The use of antiplatelet or anticoagulants has previously been shown to increase hemorrhagic complications of ventricular catheterization. Although heparin use 24 h after ventriculostomy appears safe, the safety of heparin immediately (within 4 h) after ventriculostomy is unknown. The objective of this study was to assess the safety of heparin immediately (within 4 h) after ventriculostomy in subarachnoid hemorrhage (SAH) patients undergoing endovascular treatment. PATIENTS AND METHODS: This is a retrospective cohort study of 46 patients with aneurysmal SAH secondary to aneurysm rupture who required ventriculostomy. Post-ventriculostomy imaging was carefully reviewed for tract hemorrhaging. Timing of heparinization was noted. Early heparinization was within 4 h after ventriculostomy, and intermediate heparinization was between 4 and 24 h after ventriculostomy. RESULTS: Overall, the tract hemorrhage rate was 26.1% for the study cohort-mostly grade I tract hemorrhages-consistent with the existing literature. The tract hemorrhage rate in the early (<4 h) heparin group was a remarkable 58.8%. The hemorrhages were also notably larger in the early (<4 h) heparin group. CONCLUSION: Although heparin appears to be safe after 4 h, immediate heparinization (within 4 h) after ventriculostomy significantly increases the odds of tract hemorrhage. Additional time should be afforded between ventriculostomy and heparinization to avoid potentially devastating external ventricular drain tract hemorrhage. It is advisable to wait a sufficient time (at least 4 h) after ventriculostomy before embarking on endovascular treatment of ruptured aneurysms.

Occipital Bony Abnormality and Multiple Strokes in a Pediatric Patient: Case Report and Review of the Current Literature.

This study presents a case of a 15-year-old boy who had a right vertebral artery dissection with distal embolization from repeated trauma from an occipital bony spicule. The authors hypothesize that this bony spicule was contacting the left vertebral artery during head rotation, resulting in trauma to the vessel and formation of emboli which then showered distally, causing strokes in the posterior circulation of the brain. This specific phenomenon has previously been reported three times, only one of which was in pediatric literature. It is important for individuals to be aware of this rare anatomic cause of vertebral artery dissection in patients presenting with an odd constellation of symptoms related to strokes from vertebro-basilar system. Treatment options including early intervention with intravascular coil embolization are also discussed.

Implications of carotid sinus hypersensitivity following preoperative embolization of a carotid body tumor. An indication for prophylactic intraoperative cardiac pacing.

IMPORTANCE Carotid body tumors are rare neoplasms of neural crest origin that are both highly vascularized and locally invasive. Treatment options for these tumors often include surgery with preoperative embolization, which can pose major cardiovascular risk to patients. As demonstrated by this case report, hemodynamic instability following preoperative embolization of a carotid body tumor may indicate severe carotid sinus hypersensitivity and the need for temporary cardiac pacing. OBSERVATIONS This case report describes a man in his early 30s who presented for staged surgical resection of bilateral carotid body tumors with preoperative embolization. After embolization of the second tumor, the patient displayed transient episodes of bradycardia and hypotension, which resolved with medical management. Surgery commenced, and with minimal manipulation intraoperatively, the patient became asystolic and required resuscitation. Following a negative cardiac workup, a temporary pacemaker was implanted, and surgical resection of the tumor was successfully completed. CONCLUSIONS AND RELEVANCE Carotid sinus hypersensitivity is a rare but serious risk of preoperative embolization of carotid body tumors. Postembolization bradycardia or hypotension should be assessed as potential harbingers of carotid sinus hypersensitivity, and the need for temporary intraoperative cardiac pacing should be strongly considered.

Diffuse anaplastic leptomeningeal oligodendrogliomatosis mimicking neurosarcoidosis.

Diffuse leptomeningeal oligodendrogliomatosis is a rare, frequently fatal CNS malignancy that most often affects children.1 Although potentially treatable with chemotherapy and radiation, the radiologic findings are nonspecific and pathologic confirmation of the diagnosis is difficult. We describe an adult patient whose initial presentation mimicked neurosarcoidosis. Despite extensive imaging abnormalities, 3 biopsies were required before the diagnosis of diffuse leptomeningeal oligodendrogliomatosis was confirmed.

Compartmentalization of immune responses during Staphylococcus aureus cranial bone flap infection.

Decompressive craniectomy is often required after head trauma, stroke, or cranial bleeding to control subsequent brain swelling and prevent death. The infection rate after cranial bone flap replacement ranges from 0.8% to 15%, with an alarming frequency caused by methicillin-resistant Staphylococcus aureus, which is problematic because of recalcitrance to antibiotic therapy. Herein we report the establishment of a novel mouse model of S. aureus cranial bone flap infection that mimics several aspects of human disease. Bacteria colonized bone flaps for up to 4 months after infection, as revealed by scanning electron microscopy and quantitative culture, demonstrating the chronicity of the model. Analysis of a human cranial bone flap with confirmed S. aureus infection by scanning electron microscopy revealed similar structural attributes as the mouse model, demonstrating that it closely parallels structural facets of human disease. Inflammatory indices were most pronounced within the subcutaneous galeal compartment compared with the underlying brain parenchyma. Specifically, neutrophil influx and chemokine expression (CXCL2 and CCL5) were markedly elevated in the galea, which demonstrated substantial edema on magnetic resonance images, whereas the underlying brain parenchyma exhibited minimal involvement. Evaluation of immune mechanisms required for bacterial containment and inflammation revealed critical roles for MyD88-dependent signaling and neutrophils. This novel mouse model of cranial bone flap infection can be used to identify key immunologic and therapeutic mechanisms relevant to persistent bone flap infection in humans.

Headaches secondary to intraventricular silicone oil successfully managed with ventriculoperitoneal shunt.

PURPOSE: To describe a case of intravitreal silicone oil (SO) migration into the cerebral ventricles with secondary chronic headaches. METHODS: Retrospective case report. Chart review. Single patient. RESULTS: A 51-year-old man with a history of proliferative diabetic retinopathy underwent surgery for traction retinal detachment using SO. Postoperatively, he developed elevated intraocular pressure, headaches, and a blind painful eye, which was enucleated. Neuroimaging revealed SO within the cerebral ventricles. Five years after the initial retinal detachment surgery, the patient developed chronic headaches. Lumbar puncture revealed an elevated opening pressure. The headaches were initially managed medically. A ventriculoperitoneal shunt was placed after the headaches persisted, which resulted in their complete resolution at 6 weeks after shunt placement. CONCLUSION: Ocular hypertension after intravitreal SO placement may play a role in SO intracranial migration. In the case presented, intraventricular SO was the apparent cause of elevated intracranial pressure and headaches. As all published cases of intraventricular SO migration reporting intraocular pressure to this point have described ocular hypertension, careful monitoring of intraocular pressure and aggressive control of ocular hypertension in the presence of intravitreal SO is recommended.

Hybrid peratrial double device closure of a patent foramen ovale and sinus venosus defect in an infant with vein of Galen malformation.

Vein of Galen aneurysmal malformation is the most common cerebral arteriovenous malformation in children. Neurointerventional embolization has improved outcomes with this lesion. An association with cardiac defects has been recognized and can increase the risk of systemic embolic events during treatment. Cardiopulmonary bypass (CPB) to correct the cardiac defect before repair of the malformation may be associated with compromised cerebral perfusion and possible neurologic injury. We describe a successful hybrid peratrial closure of two intracardiac shunts (a patent foramen ovale and a sinus venosus ASD) before neurointervention, avoiding CPB, and eliminating the intracardiac embolic risk during treatment of the vein of Galen malformation.

Type I spinal dural arteriovenous fistulas: historical review and illustrative case.

Type I spinal dural arteriovenous fistulas are the most common vascular malformation of the spinal cord, and an important cause of reversible progressive myelopathy. This lesion remains underdiagnosed, with most patients presenting late in the course of the disease. In this article the authors provide a review of the literature with particular attention to historical aspects related to the pathophysiology, diagnosis, classification, clinical findings, natural history, and treatment of this lesion. An illustrative case is also provided.

Single-dose vs multiple-dose antibiotic prophylaxis in instrumented lumbar fusion--a prospective study.

BACKGROUND: This prospective investigation was designed to determine if the postoperative infection rate in instrumented lumbar spinal fusion is affected by postoperative antibiotic use. METHODS: Two hundred sixty-nine patients were randomized into either a preoperative only protocol or preoperative with an extended postoperative antibiotic protocol. The preoperative only protocol received a single dose of cefazolin IV. The extended postoperative antibiotic protocol received the same preoperative dose plus postoperative cefazolin IV every 8 hours for 3 days followed by oral cephalexin every 6 hours for 7 days. Because of untoward drug reaction or deviation from the antibiotic protocol, 36 of the 269 patients were eliminated from the study. Therefore, 233 patients completed the entire study. RESULTS: There was no significant difference in infection rates between the 2 antibiotic protocols. The postoperative infection rates were 4.3% for the preoperative only protocol and 1.7% for the preoperative with extended antibiotic protocol. The overall postoperative infection rate was 3%. However, 5 variables of blood transfusion, electrophysiologic monitoring, increased height, increased weight, and increased body mass index appeared to demonstrate a trend toward increase in infection rate. Increased tobacco use trended toward a lower infection rate. CONCLUSION: Statistical significance was not proven in this prospective study comparing single-dose preoperative antibiotic protocol vs preoperative with an extended postoperative antibiotic protocol. A larger study of 1400 patients would possibly provide more statistically significant information.

Aneurysm regression after coil embolization of a concurrent aneurysm.

A 43-year-old woman with two incidental paraclinoid internal carotid artery aneurysms underwent coil embolization of the larger superior hypophyseal aneurysm and 10 weeks later underwent follow-up angiography that showed regression of the smaller, more distal paraclinoid aneurysm. We demonstrate that, although it is a rare occurrence, aneurysms can involute. We discuss potential mechanisms of this phenomenon and review the literature on aneurysm regression.

Y-configured dual intracranial stent-assisted coil embolization for the treatment of wide-necked basilar tip aneurysms.

OBJECTIVE: Despite advances in both the surgical and endovascular treatment of intracranial aneurysms, wide-necked basilar tip aneurysms (i.e., basilar tip aneurysms in which both posterior cerebral arteries emanate from the base of a wide-necked aneurysm) represent a subset of aneurysms that continues to pose technical challenges in treatment. We sought to demonstrate the safety and short-term durability of a novel dual stent-assisted coil embolization technique. METHODS: Two Neuroform stents (Boston Scientific/Target, Fremont, CA) were deployed in the posterior cerebral arteries and the basilar artery, one passing through the interstices of the other in a Y-configuration, thereby recreating an aneurysm neck and enabling safe coil delivery while preserving the parent vessels. RESULTS: Seven patients with unruptured, asymptomatic, wide-necked basilar tip aneurysms involving both posterior cerebral arteries and ranging in size from 7 to 20 mm underwent treatment with this stent-assisted coiling technique. Two stents were successfully deployed in six of the patients and one stent was successfully deployed in the seventh. One patient developed a transient internuclear ophthalmoplegia, and another experienced transient partial right oculomotor nerve palsy. All aneurysms had complete or near-complete embolization with the initial procedure. Follow-up angiography performed 6 months (six patients) and 1 year (one patient) after treatment demonstrated coil compaction and slight recanalization in one patient and recanalization requiring retreatment in another. All patients were neurologically intact at least 6 months after the initial procedure, as well as subsequent procedures, without clinical signs of subarachnoid hemorrhage. CONCLUSION: These initial technical and clinical results are highly encouraging, and this technique may significantly improve the endovascular treatment of intracranial aneurysms.

Optical coherence tomography: a new method to assess aneurysm healing.

OBJECT: Aneurysmal subarachnoid hemorrhage affects approximately 10/100,000 people per year. Endovascular coil embolization is used increasingly to treat cerebral aneurysms and its safety and durability is rapidly developing. The long-term durability of coil embolization of cerebral aneurysms remains in question; patients treated using this modality require multiple follow-up angiography studies and occasional repeated treatments. METHODS: Optical coherence tomography (OCT) is an emerging imaging modality that uses backscattered light to produce high-resolution tomography of optically accessible biological tissues such as the eye, luminal surface of blood vessels, and gastrointestinal tract. Vascular OCT probes in the form of imaging microwires are presently available--although not Food and Drug Administration-approved--and may be adapted for use in the cerebral circulation. In this study the authors describe the initial use of OCT to make visible the neck of aneurysms created in a canine model and treated with coil embolization. Optical coherence tomography images demonstrate changes that correlate with the histological findings of healing at the aneurysm neck and thus may be capable of demonstrating human cerebral aneurysm healing. CONCLUSIONS: Optical coherence tomography may obviate the need for subsequent follow-up angiography studies as well as aid in the understanding of endovascular tissue healing. Data in this study demonstrate that further investigation of in vivo imaging with such probes is warranted.