Clinical Research Primer for Medical Students: Overview and Illustrative Experiences.

Background The ability to participate in clinical scholarship is a foundational component of modern evidence-based medical practice, empowering improvement across essentially every aspect of clinical care. In tandem, the need for comprehensive exposure to clinical research has been identified as a critical component of medical student training and preparation for residency that is underserved by traditional undergraduate medical education models. The goal of the current work was to provide guidelines and recommendations to assist novice medical students in taking ownership of their research education. Methods The Clinical Research Primer was composed from pooled research documents compiled by the study authors and our institutional neurosurgery student research group. The Primer was then structured as the natural evolution of a research project from its inception through the submission process. Results We divided the foundational components of the Clinical Research Primer into seven domains, each representing a landmark in the development of a peer-reviewed study, and a set of skills critical for junior scholars to develop. These vital components included the following: pitching and designing clinical studies, developing a research workflow, navigating the Institutional Review Board, data collection and analysis, manuscript writing and editing, submission mechanics, and tracking research projects for career development. Conclusion We anticipate that the tools included in the Clinical Research Primer will increase student research productivity and preparedness for residency. Although our recommendations are informed by our experiences within neurosurgery, they have been written in a manner that should generalize to almost any field of clinical study.

The current landscape of machine learning-based radiomics in arteriovenous malformations: a systematic review and radiomics quality score assessment.

Background: Arteriovenous malformations (AVMs) are rare vascular anomalies involving a disorganization of arteries and veins with no intervening capillaries. In the past 10 years, radiomics and machine learning (ML) models became increasingly popular for analyzing diagnostic medical images. The goal of this review was to provide a comprehensive summary of current radiomic models being employed for the diagnostic, therapeutic, prognostic, and predictive outcomes in AVM management. Methods: A systematic literature review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines, in which the PubMed and Embase databases were searched using the following terms: (cerebral OR brain OR intracranial OR central nervous system OR spine OR spinal) AND (AVM OR arteriovenous malformation OR arteriovenous malformations) AND (radiomics OR radiogenomics OR machine learning OR artificial intelligence OR deep learning OR computer-aided detection OR computer-aided prediction OR computer-aided treatment decision). A radiomics quality score (RQS) was calculated for all included studies. Results: Thirteen studies were included, which were all retrospective in nature. Three studies (23%) dealt with AVM diagnosis and grading, 1 study (8%) gauged treatment response, 8 (62%) predicted outcomes, and the last one (8%) addressed prognosis. No radiomics model had undergone external validation. The mean RQS was 15.92 (range: 10-18). Conclusion: We demonstrated that radiomics is currently being studied in different facets of AVM management. While not ready for clinical use, radiomics is a rapidly emerging field expected to play a significant future role in medical imaging. More prospective studies are warranted to determine the role of radiomics in the diagnosis, prediction of comorbidities, and treatment selection in AVM management.

Perioperative Assessment of the Hemodynamic Ventriculoarterial Junction of the Aortic Root by Three-Dimensional Echocardiography.

Improved strategies in aortic valve-preserving operations appreciate the dynamic, three-dimensional complexity of the aortic root and its valve. This depends not only on detailed four-dimensional imaging of the planar dimensions of the aortic root but also on quantitative assessment of the valvar leaflets and their competency. The zones of apposition and resulting hemodynamic ventriculoarterial junction formed in diastole determine valvar competency. Current understanding and assessment of this junction is limited, often relying on intraoperative direct surgical inspection. However, this direct inspection itself is limited by evaluation in a nonhemodynamic state with limited field of view. In this review, we discuss the anatomy of the aortic root, including its hemodynamic junction. We review current echocardiographic approaches toward interrogating the incompetent aortic valve for presurgical planning. Furthermore, we introduce and standardize a complementary approach to assessing this hemodynamic ventriculoarterial junction by three-dimensional echocardiography to further personalize presurgical planning for aortic valve surgery.

Ruptured vertebrobasilar junction aneurysm supplied by reversed flow from the anterior spinal artery: Illustrative case report.

BACKGROUND AND IMPORTANCE: In patients with vertebral artery (VA) occlusion, spontaneous flow reversal may occur in the anterior spinal artery (ASA) as a source of compensatory supply to the posterior circulation. Turbulent flow and increased flux through these small arteries may predispose to luminal damage and intracranial aneurysm formation. We report a novel case of a ruptured ASA-VA junction aneurysm in a patient with chronic bilateral VA occlusion, successfully treated with endovascular embolization. CLINICAL PRESENTATION: A 62-year-old female with uncontrolled hypertension presented with acute-onset headache, emesis, neck stiffness, and decreased level of consciousness. Head computed tomography demonstrated diffuse cisternal subarachnoid hemorrhage with intraventricular extension and ventriculomegaly. Computed tomography angiography showed left VA atresia and chronic right VA occlusion just distal to the posterior inferior cerebellar artery origin, as well as a complex, bilobed aneurysm at the ASA-VA junction. Angiography demonstrated flow reversal from the ASA into the distal stump of the occluded right VA, which in turn filled the aneurysm. Of note, the patient's posterior circulation was predominantly supplied by the dilated ASA, and associated collaterals from ASA and right VA stump. The aneurysm was accessed and embolized using superselective microcatheterization over a soft microguidewire through the right cervical VA perforators supplying retrograde flow into and through the ASA. CONCLUSION: ASA-VA aneurysms are exceedingly rare, and generally associated with atypical flow dynamics. Dynamic treatment strategies may be needed, especially in the setting of subarachnoid hemorrhage.

Impact of Obesity and Diabetes on Postoperative Outcomes Following Surgical Treatment of Nontraumatic Subarachnoid Hemorrhage: Analysis of the ACS-NSQIP Database.

BACKGROUND: Nontraumatic subarachnoid hemorrhage (SAH) refers to high pressure extravasation of blood into the subarachnoid space that typically occurs spontaneously from rupture of cerebral aneurysm. The purpose of this study was to identify postoperative complications requiring increased surveillance in obese, diabetic, and hypertensive patients. METHODS: Patients who underwent surgical treatment for nontraumatic SAH were queried in the American College of Surgeons National Surgical Quality Improvement Program database from the years 2012-2018. Cases were identified using International Classification of Diseases codes and then classified independently by 3 dichotomous diagnoses: obesity, diabetes, and hypertension. RESULTS: Among 1002 patients meeting inclusion criteria, 311 (31%) were obese (body mass index >30), 86 (9%) had diabetes treated with insulin or noninsulin agents, and 409 (41%) required medication for hypertension. There was a statistically significant association between diabetes and postoperative pneumonia (odds ratio [OR] = 1.694; 95% confidence interval [CI] = 0.995-2.883; P = 0.050), prolonged ventilator dependence (OR = 1.700; 95% CI = 1.087-2.661; P = 0.019), and death (OR = 1.846; 95% CI = 1.071-3.179; P = 0.025). Medication-dependent hypertension was statistically associated with incidence of stroke/cerebrovascular accident (OR = 1.763; 95% CI = 1.056-2.943; P = 0.023). Obesity was not associated with adverse outcomes in this population. CONCLUSIONS: In patients undergoing surgical management of SAH, hypertensive and diabetic patients had poorer outcomes, including prolonged ventilator dependence, pneumonia, stroke/cerebrovascular accident, and death. Surprisingly, preexisting obesity was not associated with poor outcomes. In fact, overweight body mass index, class I obesity, and class II obesity had decreased need for transfusion in the 30-day postoperative period.

Update on intrathecal management of cerebral vasospasm: a systematic review and meta-analysis.

OBJECTIVE: Aneurysmal subarachnoid hemorrhage (aSAH) accounts for a relatively small portion of strokes but has the potential to cause permanent neurological deficits. Vasospasm with delayed ischemic neurological deficit is thought to be responsible for much of the morbidity associated with aSAH. This has illuminated some treatment options that have the potential to target specific components of the vasospasm cascade. Intrathecal management via lumbar drain (LD) or external ventricular drain (EVD) offers unique advantages in this patient population. The aim of this review was to provide an update on intrathecal vasospasm treatments, emphasizing the need for larger-scale trials and updated protocols using data-driven evidence. METHODS: A search of PubMed, Ovid MEDLINE, and Cochrane databases included the search terms (subarachnoid hemorrhage) AND (vasospasm OR delayed cerebral ischemia) AND (intrathecal OR intraventricular OR lumbar drain OR lumbar catheter) for 2010 to the present. Next, a meta-analysis was performed of select therapeutic regimens. The primary endpoints of analysis were vasospasm, delayed cerebral ischemia (DCI), cerebral infarction, and functional outcome. RESULTS: Twenty-nine studies were included in the analysis. There were 10 studies in which CSF drainage was the primary experimental group. Calcium channel antagonists were the focus of 7 studies. Fibrinolytics and other vasodilators were each examined in 6 studies. The meta-analysis included studies examining CSF drainage via LD (n = 4), tissue plasminogen activator in addition to EVD (n = 3), intraventricular nimodipine (n = 2), and cisternal magnesium (n = 2). Results showed that intraventricular nimodipine decreased vasospasm (OR 0.59, 95% CI 0.37-0.94; p = 0.03). Therapies that significantly reduced DCI were CSF drainage via LD (OR 0.47, 95% CI 0.25-0.88; p = 0.02) and cisternal magnesium (OR 0.27, 95% CI 0.07-1.02; p = 0.05). CSF drainage via LD was also found to significantly reduce the incidence of cerebral infarction (OR 0.35, 95% 0.24-0.51; p < 0.001). Lastly, functional outcome was significantly better in patients who received CSF drainage via LD (OR 2.42, 95% CI 1.39-4.21; p = 0.002). CONCLUSIONS: The authors' results showed that intrathecal therapy is a safe and feasible option following aSAH. It has been shown to attenuate cerebral vasospasm, reduce the incidence of DCI, and improve clinical outcome. The authors support the use of intrathecal management in the prevention and rescue management of cerebral vasospasm. More randomized controlled trials are warranted to determine the best combination of pharmaceutical agents and administration route in order to formulate a standardized treatment approach.

Occipital condyle screw fixation after posterior decompression for Chiari malformation: Technical report and application.

BACKGROUND: Surgical techniques for stabilization of the occipital cervical junction have traditionally consisted of screw-based techniques applied in conjunction with occipital plating and rods connected to subaxial instrumentation in the form of pars, pedicle, or lateral mass screws. In patients with type 1 Chiari malformation (CM-1) and evidence of occipital cervical junction instability who have undergone posterior decompression, the occipital condyle (OC) represents a potential alternative cranial fixation point. To date, this technique has only been described in pediatric case reports and morphometric cadaver studies. METHODS: Patients underwent posterior fossa decompression for treatment of CM. Subsequently, patients received occipital cervical stabilization using OC screws. RESULTS: Patients were successfully treated with no post-operative morbidity. Patient 2 was found to have pseudoarthrosis and underwent revision. Both patients continue to do well at 1-year follow-up. CONCLUSION: Placement of the OC screw offers advantages over traditional plate-based occipital fixation in that bone removal for suboccipital decompression is not compromised by the need for hardware placement, screws are hidden underneath ample soft tissue in patients with thin skin which prevents erosion, and the OC consists of primarily cortical bone which provides for robust tricortical fixation. These cases demonstrate the novel application of the OC screw fixation technique to the treatment of occipital cervical junction instability in adult patients undergoing simultaneous posterior fossa decompression.

The Financial Impact of the COVID-19 Pandemic on Neurosurgery Practice in Spring 2020.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic has changed health care delivery across the United States. Few analyses have specifically looked at quantifying the financial impact of the pandemic on practicing neurosurgeons. A survey analysis was performed to address this need. METHODS: A 19-question survey was distributed to practicing neurosurgeons in the United States and its territories. The questions evaluated respondents' assessments of changes in patient and procedural volume, salary and benefits, practice expenses, staffing, applications for government assistance, and stroke management. Responses were stratified by geographic region. RESULTS: The response rate was 5.1% (267/5224). Most respondents from each region noted a >50% decrease in clinic volume. Respondents from the Northeast observed a 76% decrease in procedure volume, which was significantly greater than that of other regions (P = 0.003). Northeast respondents were also significantly more likely to have been reassigned to nonneurosurgical clinical duties during the pandemic (P < 0.001). Most respondents also noted decreased salary and benefits but experienced no changes in overall practice expenses. Most respondents did not experience significant reductions in nursing or midlevel staffing. These trends were not significantly different between regions. CONCLUSIONS: The COVID-19 pandemic has led to decreases in patient and procedural volume and physician compensation despite stable practice expenses. Significantly more respondents in the Northeast region noted decreases in procedural volume and reassignment to nonneurosurgical COVID-related medical duties. Future analysis is necessary as the pandemic evolves and the long-term clinical and economic implications become clear.

An Evaluation of Neurosurgical Practices During the Coronavirus Disease 2019 Pandemic.

OBJECTIVE: We sought to understand how the coronavirus disease 2019 pandemic has affected the neurosurgical workforce. METHODS: We created a survey consisting of 22 questions to assess the respondent's operative experience, location, type of practice, subspecialty, changes in clinic and operative volumes, changes to staff, and changes to income since the pandemic began. The survey was distributed electronically to neurosurgeons throughout the United States and Puerto Rico. RESULTS: Of the 724 who opened the survey link, 457 completed the survey. The respondents were from throughout the United States and Puerto Rico and represented all practices types and subspecialties. Nearly all respondents reported hospital restrictions on elective surgeries. Most reported a decline in clinic and operative volume. Nearly 70% of respondents saw a decrease in the work hours of their ancillary providers, and almost one half (49.1%) of the respondents had had to downsize their practice staff, office assistants, nurses, schedulers, and other personnel. Overall, 43.6% of survey respondents had experienced a decline in income, and 27.4% expected a decline in income in the upcoming billing cycle. More senior neurosurgeons and those with a private practice, whether solo or as part of a group, were more likely to experience a decline in income as a result of the pandemic compared with their colleagues. CONCLUSION: The coronavirus disease 2019 pandemic will likely have a lasting effect on the practice of medicine. Our survey results have described the early effects on the neurosurgical workforce. Nearly all neurosurgeons experienced a significant decline in clinical volume, which led to many downstream effects. Ultimately, analysis of the effects of such a pervasive pandemic will allow the neurosurgical workforce to be better prepared for similar events in the future.

An Evaluation of Neurosurgical Resident Education and Sentiment During the Coronavirus Disease 2019 Pandemic: A North American Survey.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic has had a tremendous impact on the healthcare system. Owing to restrictions in elective surgery and social distancing guidelines, the training curriculum for neurosurgical trainees has been rapidly evolving. This evolution could have significant long-term effects on the training of neurosurgery residents. The objective of the present study was to assess the effects of COVID-19 on neurosurgical training programs and residents. METHODS: A survey consisting of 31 questions assessing changes to resident clinical and educational workload and their sentiment regarding how these changes might affect their careers was distributed electronically to neurosurgery residents in the United States and Canada. RESULTS: The survey respondents were from 29 states and Canada and were relatively evenly spread across all levels of residency. Nearly 82% reported that the inpatient and outpatient volumes had been either greatly (44.0%) or moderately (37.8%) reduced. Greater than 91% reported that their work responsibilities or access to the hospital had been reduced, with a significant reduction in work hours and a significant increase in resident didactics (P < 0.001). Senior residents expressed concern about their educational experience and their future career prospects as a result of the pandemic. CONCLUSION: Universally, residents have experienced reduced work hours and a reduction in their operative case volumes. Programs have adapted by increasing didactic time and using electronic platforms. It is quite possible that this remarkable period will prompt a critical reappraisal of the pre-COVID-19 adequacy of educational content in our training programs and that the enhanced educational efforts driven by this pandemic could be lasting.

Initial Single-Center Technical Experience With the BrainPath System for Acute Intracerebral Hemorrhage Evacuation.

BACKGROUND: Surgical intervention has been proposed as a means of reducing the high morbidity and mortality associated with acute intracerebral hemorrhage (ICH), but many previously reported studies have failed to show a clinically significant benefit. Newer, minimally invasive approaches have shown some promise. OBJECTIVE: We report our early single-center technical experience with minimally invasive clot evacuation using the BrainPath system. METHODS: Prospective data were collected on patients who underwent ICH evacuation with BrainPath at the Cleveland Clinic from August 2013 to May 2015. RESULTS: Eighteen patients underwent BrainPath evacuation of ICH at our center. Mean ICH volume was 52.7 mL ± 22.9 mL, which decreased to 2.2 mL ± 3.6 mL postevacuation, resulting in a mean volume reduction of 95.7% ± 5.8% (range 0-14 mL, P < .001). In 65% of patients, a bleeding source was identified and treated. There were no hemorrhagic recurrences during the hospital stay. In this cohort, only 1 patient (5.6%) died in the first 30 days of follow-up. Median Glasgow Coma Score improved from 10 (interquartile range 5.75-12) preoperation to 14 (interquartile range 9-14.25) postoperation. Clinical follow-up in this cohort is ongoing. CONCLUSION: Evacuation of ICH using the BrainPath system is safe and technically effective. The volume of clot removed compares favorably with other published studies. Early improved clinical outcomes are suggested by improvement in Glasgow Coma Score and reduced 30-day mortality. Ongoing analysis is necessary to elucidate long-term clinical outcomes and the subsets of patients who are most likely to benefit from surgery.

Long-Term Effect of Flow Diversion on Large and Giant Aneurysms: MRI-DSA Clinical Correlation Study.

BACKGROUND: The long-term effect of flow diversion (FD) on aneurysms has not been well studied. OBJECTIVE: We aimed to assess the effect of the Pipeline embolization device (Covidien, Irvine, California, USA) on large and giant intracranial aneurysms with magnetic resonance imaging (MRI) and digital subtraction angiography (DSA) and then correlate with clinical follow-up. METHODS: We conducted a retrospective analysis of aneurysms treated solely with Pipeline without adjunctive therapy. The largest aneurysm diameters were compared with pretreatment and post treatment MRI and correlated with DSA and clinical symptoms. RESULTS: Twelve patients harboring large and giant saccular unruptured aneurysms, treated with Pipeline, were included. Mean follow-up times were as follows: MRI 22.8 months (range 1-57), DSA 18.2 months (range 1-33), and clinical 29 months (range 1-48). Ten (83%) of 12 treated aneurysms decreased in size on MRI, which was first seen at an average of 17 months (range 4-57). In 70% of patients the change was noted on MRI ≤1 year after treatment, at an average of 9.1 months (range 4-12). MRI reduction was more likely in angiographically occluded aneurysms. Five aneurysms with complete occlusion on early angiogram showed size reduction on MRI only at ≥12 months. Mean aneurysm size reduction was 57% (range 19.6-94.2), which correlated well with improvement of cranial neuropathies in 75% and headaches in 100% of patients. CONCLUSION: Most aneurysms treated with Pipeline decreased in size, correlating with clinical improvement. Some aneurysms remained unchanged on MRI until a later time point despite early DSA occlusion. It may be reasonable to eliminate early postprocedural imaging and start follow-up only as late as 1 year after FD treatment in clinically stable, asymptomatic patients.

Chronic Cerebral Ischemia: Where "Evidence-Based Medicine" Fails Patients.

BACKGROUND AND IMPORTANCE: The publication of the COSS (Carotid Occlusion Surgery Study) trial in 2011 concluded that the addition of external carotid to internal carotid (EC-IC) bypass to a medical regimen "did not reduce the risk of ipsilateral ischemic stroke at 2 years" for patients with symptomatic internal carotid artery occlusion. This has resulted in decreasing referrals for surgical management under the guise of "evidence-based" medicine. The conclusions drawn from a study can only be as good as the selected end points. COSS did not consider important end points such as the effects of long-term cerebral ischemia or recurrent debilitating transient ischemic attacks (TIAs). However, the study is often quoted as "proof" that EC-IC bypass has no role in the treatment of these patients. CLINICAL PRESENTATION: A middle-aged patient presented to a primary neurologist with left-sided weakness and 2 months of personality changes. Magnetic resonance imaging (MRI) showed small watershed infarcts in the right hemisphere. An angiogram showed right carotid occlusion. Perfusion scans confirmed hypoperfusion. The patient was managed medically. Without any further clinical stroke events, the patient progressed to complete hemispheric infarction on MRI over the next 5 months. CONCLUSION: The public perception of the results of large randomized clinical trials is significantly altered by their ubiquitous dissemination and broad generalization without adequate understanding of the details. Careful assessment of the methodology and end points of a trial are essential when applying the results for evidence-based medicine to individual patients. This patient would have been considered a medical "success" in COSS, but her outcome with surgical intervention will never be known.

Onyx resorbtion with AVM recanalization after complete AVM obliteration.

Brain arteriovenous malformations (BAVM) are some of the most complex lesions treated by clinical neuroscientists. The recent publication of the ARUBA trial, showing higher complication rates with treatment compared with the natural history over a short period of follow-up, puts even more pressure on the physician to achieve complete BAVM eradication without complication. These lesions are often treated by multimodality therapy with some combination of endovascular embolization, radiosurgery, and microsurgical resection; however, multimodality therapy involves the additive risk of procedural complication with each procedure. While surgical resection has long been accepted as monotherapy with good cure rates, staged pre-operative endovascular embolization has facilitated microsurgical resection with lower blood loss. Endovascular embolization is more often utilized in conjunction with surgical resection, and often the portions of the AVM and feeders that are completely embolized with Onyx or glue may not be surgically resected since they have been "internally obliterated." We present a case where the AVM was preoperatively embolized with Onyx and subsequently partially surgically resected. Post-operative angiography showed complete obliteration or "cure" of the AVM with no filling of the nidus or early venous drainage. The patient presented 12 months later with seizures and imaging showed volume loss in the residual Onyx cast and recanalization of the AVM nidus. The patient subsequently underwent repeat resection with complete removal of the residual AVM and Onyx cast. To our knowledge this is the first published report of volume loss within the Onyx cast leading to recanalization of the AVM nidus. This suggests that extreme care should be taken with partial resection of the AVM nidus or with embolization for cure, as late recanalization may occur.

Treatment of intracranial vasospasm following subarachnoid hemorrhage.

Vasospasm has been a long known source of delayed morbidity and mortality in aneurysmal subarachnoid hemorrhage patients. Delayed ischemic neurologic deficits associated with vasospasm may account for as high as 50% of the deaths in patients who survive the initial period after aneurysm rupture and its treatment. The diagnosis and treatment of vasospasm has still been met with some controversy. It is clear that subarachnoid hemorrhage is best cared for in tertiary care centers with modern resources and access to cerebral angiography. Ultimately, a high degree of suspicion for vasospasm must be kept during ICU care, and any signs or symptoms must be investigated and treated immediately to avoid permanent stroke and neurologic deficit. Treatment for vasospasm can occur through both ICU intervention and endovascular administration of intra-arterial vasodilators and balloon angioplasty. The best outcomes are often attained when these methods are used in conjunction. The following article reviews the literature on cerebral vasospasm and its treatment and provides the authors' approach to treatment of these patients.

Superselective Wada test for ruptured spontaneous fusiform middle cerebral artery aneurysm: a technical case report.

BACKGROUND: Spontaneous fusiform aneurysms of the middle cerebral artery (sfaMCA) are quite uncommon and tend to occur in young adults. The use of superselective angiography for ruptured and unruptured aneurysms can help delineate vital angioarchitecture and assist with perioperative planning and treatment modality. The use of superselective Wada testing (SWT) for treatment of a ruptured sfaMCA involving the dominant hemisphere, however, has never been described in the English literature. We report a case of a ruptured sfaMCA involving the dominant hemisphere where superselective angiography and SWT were utilized to predict the ability to occlude a major vessel without adverse neurological sequelae. CASE DESCRIPTION: A healthy young patient presented with subarachnoid hemorrhage. Initial CT-angiogram of the head identified a left-sided fusiform MCA aneurysm measuring 1.3 cm by 0.5 cm in maximum dimensions. Diagnostic angiography evaluation demonstrated an irregular, fusiform aneurysm involving the central (Rolandic) trunk of the left MCA. An SWT was then performed through an SL 10 microcatheter with injection of sodium amytal. Verbal, motor and cognitive testing were performed twice and revealed no neurological defects. The patient underwent subsequent coil embolization of the aneurysm. Formal post-procedure evaluation revealed no speech, language or cognitive deficits. She was eventually discharged home and remained without neurological deficits at her follow-up appointment 12 months after her initial presentation. CONCLUSION: Intraoperative SWT can be performed as part of the initial evaluation for patients with sfaMCA of the dominant cerebral hemisphere to help choose the appropriate treatment algorithm and predict post-treatment neurological deficits.

Level I to III craniofacial approaches based on Barrow classification for treatment of skull base meningiomas: surgical technique, microsurgical anatomy, and case illustrations.

OBJECT: Although craniofacial approaches to the midline skull base have been defined and surgical results have been published, clear descriptions of these complex approaches in a step-wise manner are lacking. The objective of this study is to demonstrate the surgical technique of craniofacial approaches based on Barrow classification (Levels I-III) and to study the microsurgical anatomy pertinent to these complex craniofacial approaches. METHODS: Ten adult cadaveric heads perfused with colored silicone and 24 dry human skulls were used to study the microsurgical anatomy and to demonstrate craniofacial approaches in a step-wise manner. In addition to cadaveric studies, case illustrations of anterior skull base meningiomas were presented to demonstrate the clinical application of the first 3 (Levels I-III) approaches. RESULTS: Cadaveric head dissection was performed in 10 heads using craniofacial approaches. Ethmoid and sphenoid sinuses, cribriform plate, orbit, planum sphenoidale, clivus, sellar, and parasellar regions were shown at Levels I, II, and III. In 24 human dry skulls (48 sides), a supraorbital notch (85.4%) was observed more frequently than the supraorbital foramen (14.6%). The mean distance between the supraorbital foramen notch to the midline was 21.9 mm on the right side and 21.8 mm on the left. By accepting the middle point of the nasofrontal suture as a landmark, the mean distances to the anterior ethmoidal foramen from the middle point of this suture were 32 mm on the right side and 34 mm on the left. The mean distance between the anterior and posterior ethmoidal foramina was 12.3 mm on both sides; the mean distance between the posterior ethmoidal foramen and distal opening of the optic canal was 7.1 mm on the right side and 7.3 mm on the left. CONCLUSIONS: Barrow classification is a simple and stepwise system to better understand the surgical anatomy and refine the techniques in performing these complex craniofacial approaches. On the other hand, thorough anatomical knowledge of the midline skull base and variations of the neurovascular structures is crucial to perform successful craniofacial approaches.

Microsurgical anatomy of the posterior spinal artery via a far-lateral transcondylar approach.

OBJECT: The posterior spinal artery (PSA) is a clinically significant vessel that may frequently be encountered during the far-lateral transcondylar approach. There have been a limited number of reports on the specific origin of the PSA in the literature. The aim of this study was to demonstrate the origin of the PSA. METHODS: Thirteen cadaveric heads (26 sides) were injected with colored silicon. A bilateral far-lateral transcondylar approach was performed on each side. In every specimen the site of the origin of the PSAs, as well as their course, branching pattern and anastomoses, external diameters, and neighboring vascular and nervous structures were recorded. Microanatomical dissections were performed using the surgical microscope. In addition, 8 surgical cases in which the far-lateral approach was used were collected prospectively to record the course and origin of the PSA. Altogether, a total of 34 sides were analyzed for their PSA origin and course. RESULTS: In the cadaveric specimens, the PSA was found to originate from the vertebral artery (VA) in 25 sides (96%). In 13 specimens (50%) the PSA originated from the V(4) segment of the VA intradurally. In 12 specimens (46%) the PSA originated from the V(3) segment of the VA extradurally. In 1 specimen (4%), in whom the posterior inferior cerebellar artery (PICA) had an early origin from the VA extradurally at the C-1 level, the PSA originated from the PICA. Of the 8 surgical cases, 2 patients had extradural origin of the PSA from the V(3) segment of the VA, whereas 6 patients had intradural origin of the PSA from the V(4) segment. CONCLUSIONS: Although the usual origin of the PSA is from the VA either intra- or extradurally, its origin is closely related to the origin of the PICA. The PSA originates from the PICA in cases in which the PICA originates extradurally from the VA. In the far-lateral transcondylar approach, the dura is opened in close proximity to the VA. Knowledge of the origin and course of the PSA is critically important when executing the far-lateral approach to avoid its injury.

Quantitative magnetic resonance angiography in the evaluation of the subclavian steal syndrome: report of 5 patients.

BACKGROUND AND PURPOSE: The indications for surgical or endovascular treatment of patients with subclavian stenosis (SS) or occlusion remain controversial. Multiple studies have shown that in most patients, SS results in steal that is evident radiographically, but requires no treatment. METHODS: This report describes 5 cases of SS, analyzed with phase contrast quantitative MRA (QMRA). QMRA provides quantitative blood flow data previously unavailable. A quantitative ischemic forearm challenge is also introduced using the QMRA technique. RESULTS: A basilar flow index, basilar artery (BA) flow as a percentage of total intracranial flow was defined. This varied from 12.6% to 20.4%. All patients in this report had VA flow reversal. None had BA flow reversal CONCLUSION: This report features novel methods using QMRA to identify ischemic patterns in the BA indicative of significant subclavian steal syndrome (SSS) in patients with SS.