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Michelle J. Clarke and Fredric B. Meyer

✓The mathematical modeling of hydrocephalus is a relatively young field. The discipline evolved from Hakim's initial description of the brain as a water-filled sponge. Nagashima and colleagues subsequently translated this description into a computer-driven model by defining five important system rules. A number of researchers have since criticized and refined the method, providing additional system constraints or alternative approaches. Such efforts have led to an increased understanding of ventricular shape change and the development of periventricular lucency on imaging studies. However, severe limitations exist, precluding the use of the mathematical model to influence the operative decisions of practicing surgeons. In this paper, the authors explore the history, limitations, and future of the mathematical model of hydrocephalus.

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Michelle J. Clarke and Katrin Frimannsdottir

OBJECTIVE

Structured performance evaluations are important for the professional development and personal growth of resident learners. This process is formalized by the Accreditation Council for Graduate Medical Education milestones assessment system. The primary aim of this study was to understand the current feedback delivery mechanism by exploring the culture of feedback, the mechanics of delivery, and the evaluation of the feedback itself.

METHODS

Face-to-face interviews were conducted with 10 neurosurgery residents exploring their perceptions of summative feedback. Coded data were analyzed qualitatively for overriding themes using the matrix framework method. A priori themes of definition of feedback, feedback delivery, and impact of feedback were combined with de novo themes discovered during analysis.

RESULTS

Trainees prioritized formative over summative feedback. Summative and milestone feedback were criticized as being vague, misaligned with practice, and often perceived as erroneous. Barriers to implementation of summative feedback included perceived veracity of feedback, high interrater variability, and the inconstant adoption of a developmental progression model. Gender bias was noted in degree of feedback provided and language used.

CONCLUSIONS

Trainee perception of feedback provided multiple areas of improvement. This paper can serve as a baseline to study improvements in the milestone feedback process and optimize learning.

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Ross C. Puffer, Ryan Planchard, Grant W. Mallory, and Michelle J. Clarke

OBJECT

Health care-related costs after lumbar spine surgery vary depending on procedure type and patient characteristics. Age, body mass index (BMI), number of spinal levels, and presence of comorbidities probably have significant effects on overall costs. The present study assessed the impact of patient characteristics on hospital costs in patients undergoing elective lumbar decompressive spine surgery.

METHODS

This study was a retrospective review of elective lumbar decompression surgeries, with a focus on specific patient characteristics to determine which factors drive postoperative, hospital-related costs. Records between January 2010 and July 2012 were searched retrospectively. Only elective lumbar decompressions including discectomy or laminectomy were included. Cost data were obtained using a database that allows standardization of a list of hospital costs to the fiscal year 2013–2014. The relationship between cost and patient factors including age, BMI, and American Society of Anesthesiologists (ASA) Physical Status Classification System grade were analyzed using Student t-tests, ANOVA, and multivariate regression analyses.

RESULTS

There were 1201 patients included in the analysis, with a mean age of 61.6 years. Sixty percent of patients in the study were male. Laminectomies were performed in 557 patients (46%) and discectomies in 644 (54%). Laminectomies led to an increased hospital stay of 1.4 days (p < 0.001) and increased hospital costs by $1523 (p < 0.001) when compared with discectomies. For laminectomies, age, BMI, ASA grade, number of levels, and durotomy all led to significantly increased hospital costs and length of stay on univariate analysis, but ASA grade and presence of a durotomy did not maintain significance on multivariate analysis for hospital costs. For a laminectomy, patient age ≥ 65 years was associated with a 0.6-day increased length of stay and a $945 increase in hospital costs when compared with patient age < 65 years (p < 0.001). A durotomy during a laminectomy increased length of stay by 1.0 day and increased hospital costs by $1382 (p < 0.03). For discectomies, age, ASA grade, and durotomy were significantly associated with increased hospital costs on univariate analysis, but BMI was not. Only age and presence of a durotomy maintained significance on multivariate analysis. There was a significant increase in hospital length of stay in patients undergoing discectomy with increasing age, BMI, ASA grade, and presence of a durotomy on univariate analysis. However, only age and presence of a durotomy maintained significance on multivariate analysis. For discectomies, age ≥ 65 years was associated with a 0.7-day increased length of stay (p < 0.001) and an increase of $931 in postoperative hospital costs (p < 0.01) when compared with age < 65 years.

CONCLUSIONS

Patient factors such as age, BMI, and comorbidities have significant and measurable effects on the postoperative hospital costs of elective lumbar decompression spinal surgeries. Knowledge of how these factors affect costs will become important as reimbursement models change.

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Michelle J. Clarke, Andrew B. Foy, Nicholas Wetjen, and Corey Raffel

Object

Subependymal giant cell astrocytomas (SEGAs) are a common manifestation of tuberous sclerosis (TS). These evolving tumors have a propensity to cause obstructive hydrocephalus, usually due to obstruction at the level of the foramen of Monro. Differentiating SEGAs from subependymal nodules (SENs) before obstruction occurs may improve the morbidity associated with these tumors. In this study the authors' aim was to determine imaging characteristics of proven tumors in a single-center pediatric population.

Methods

The authors retrospectively reviewed all records and images obtained in patients with TS in whom results of biopsy sampling had proven that their tumors were SEGAs. Time to presentation, signs and symptoms at presentation, and imaging characteristics of the evolving tumors were noted. Twelve patients with 14 SEGAs proven by the results of biopsy sampling were reviewed. Resection was recommended for symptomatic and neuroimaging evidence of hydrocephalus (41%), tumor growth without evidence of hydrocephalus (33%), and for poorly controlled seizures (25%). The mean diameter of the tumors at the time of resection was 1.9 cm (range 0.3–4 cm), and no tumor recurred. Because of the pathological and radiographic continuum of SENs and SEGAs, it remains difficult to predict whether and when a given lesion will progress. Tumor growth and contrast enhancement are the most common signs of progression on neuroimages, and may be seen prior to the development of obstructive hydrocephalus.

Conclusions

Patients with SENs and SEGAs should undergo follow-up neuroimaging at yearly intervals, and if lesions show signs of progression (contrast enhancement or growth), these intervals should be shortened and consideration given to early resection.

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Ross C. Puffer, William E. Clifton, Grant W. Mallory, and Michelle J. Clarke

OBJECT

Delayed cervical palsy (DCP) is a known complication following cervical spine surgery. While most DCPs eventually improve, they can result in significant temporary disability. Postoperative complications affect hospital length of stay (LOS) as well as overall hospital cost. The authors sought to determine the hospital cost of DCP after cervical spine fusion operations.

METHODS

A retrospective review of patients undergoing cervical fusion for degenerative disease at the Mayo Clinic from 2008 to 2012 was performed. Patients who developed DCPs not attributable to intraoperative trauma were included. All nonoperative-related costs were compared with similar costs in a control group matched according to age, sex, and surgical approach. All costs and services were reflective of the standard costs for the current year. Raw cost data were presented using ratios due to institutional policy against publishing cost data.

RESULTS

There were 27 patients (18 men, 9 women) who underwent fusion and developed a DCP over the study period. These patients were compared with 24 controls (15 men, 9 women) undergoing fusion in the same time period. There was no difference between patients and controls in mean age (62.4 ± 3.1 years vs 63.8 ± 2.5 years, respectively; p = 0.74), LOS (4.2 ± 3.3 days vs 3.8 ± 4.5 days, respectively; p = 0.43), or operating room–related costs (1.08 ± 0.09 vs 1.0 ± 0.07, respectively; p = 0.58). There was a significant difference in nonoperative hospital-related costs between patients and controls (1.67 ± 0.15 vs 1.0 ± 0.09, respectively; p = 0.04). There was a significantly higher utilization of postoperative imaging (CT or MRI) in the DCP group (14/27, 52%) when compared with the matched cohort (4/24, 17%; p = 0.018), and a significantly higher utilization of physiatry services (24/27 [89%] vs 15/24 [63%], respectively; p = 0.046).

CONCLUSIONS

While DCPs did not significantly prolong the length of hospitalization, they did increase hospital-related costs. This method could be further extrapolated to model costs of other complications as well.

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Deena M. Nasr, Waleed Brinjikji, Michelle J. Clarke, and Giuseppe Lanzino

OBJECTIVE

Spinal epidural arteriovenous fistulas (SEDAVFs) constitute a rare but treatable cause of vascular myelopathy and are a different subtype from the more common Type I spinal dural AVFs. The purpose of this study was to review a consecutive series of SEDAVFs from a single institution and report on the clinical presentations, functional status, and treatment outcomes.

METHODS

The authors identified all SEDAVFs treated at their institution from 2005 to 2015. SEDAVFs were defined as spinal AVFs in which the fistulous connection occurred in the epidural venous plexus. The clinical presentation, functional status, immediate treatment outcomes, and long-term neurological outcomes were analyzed.

RESULTS

Twenty-four patients with SEDAVFs were included in this study. The patients' mean age at presentation was 66.9 years. The most common presenting symptoms were pain and numbness (22 patients, 91.7%), followed by lower-extremity weakness (21 patients, 87.5%). The mean duration of symptoms prior to diagnosis was 11.8 months. Eighteen patients (75.0%) were treated with endovascular therapy alone, 4 (16.7) with surgery, and 2 (8.3%) with a combination of techniques. There was 1 major treatment-related complication (4.2%). Fifteen patients (62.5%) had improvement in disability, and 12 patients (54.5%) had improvement in sensory symptoms.

CONCLUSIONS

SEDAVFs often present with lower-extremity motor dysfunction and sensory symptoms. With the availability of newer liquid embolic agents, these lesions can be effectively treated with endovascular techniques. Surgery is also effective at treating these lesions, especially in situations where endovascular embolization fails or is not safe and in patients presenting with mass effect from compressive varices.

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Very low pressure hydrocephalus

Report of two cases

Michelle J. Clarke, Cormac O. Maher, Georgia Nothdurft, and Fredric Meyer

✓ Low-pressure hydrocephalus is an extremely rare condition. Authors of the few previous reports on this subject have suggested that symptoms are gradual in onset and successfully treated. In this report the authors presented two unique cases of very low pressure hydrocephalus in which the patients experienced rapid deterioration requiring negative-pressure cerebrospinal fluid drainage to achieve the best possible neurological function; outcomes in both patients ultimately were poor. The constellation of findings suggests that this may be a distinct clinical entity.

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Megan M. J. Bauman, Kimberly Wang, Archis R. Bhandarkar, Kristen M. Scheitler, and Michelle J. Clarke

OBJECTIVE

At present, females constitute less than 10% of neurosurgeons in the US, despite representing approximately half of all medical students. Multiple barriers have been described for females entering the neurosurgical field, particularly academic neurosurgery. Understanding the environment that female neurosurgeons face and any potential barriers preventing career advancement is needed to recruit, promote, and retain females in neurosurgery.

METHODS

The gender composition of editorial boards for 5 high-impact neurosurgery journals was analyzed from 2000 to 2020. The names of editorial board members were obtained directly from the journal administration, physical copies of the published journal, or publicly available data through each journal’s website. The gender, degrees, academic titles, H-index, and country were determined for each individual and statistical tests were performed to identify significant differences.

RESULTS

Of the 466 identified individuals that served on at least one editorial board between 2000 and 2020, there were 36 females (7.7%) and 430 males (92.3%). There were no significant differences between males and females serving on multiple editorial boards. Most females possessed an additional graduate degree (58.3%), while only one-third of males (33.5%) obtained such a degree (p = 0.002). In addition, males had significantly higher average H-indices than females (p = 0.002). These trends were also observed when analyzing only US-based editorial board members. Although females were more likely overall to be identified as associate professors, males were more likely to be appointed as full professors (p = 0.001); this trend did not remain true in the US-based cohort. When analyzing the editorial boards for individual journals, all 5 journals experienced an increase of female representation since 2000 or since their inception after 2000. The highest proportion of females for a single journal was 27.3% in 2020. All other journals ranged from 11.0% to 13.5% in 2020.

CONCLUSIONS

When entering the field of neurosurgery, females continue to face significant social and academic barriers. While the proportion of females on editorial boards for neurosurgery journals in 2020 is consistent with the proportion of practicing female neurosurgeons, there is a statistically significantly higher likelihood that females possess additional graduate degrees and lower H-indices compared to their male counterparts. The authors encourage neurosurgical journals to continue expanding female representation on editorial boards.

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Michelle J. Clarke, James Guzzo, Jean-Paul Wolinsky, Ziya Gokaslan, and James H. Black III

Iatrogenic aortic injuries are a potentially devastating complication of spine surgery. In instrumented cases, injuries may occur in the perioperative period due to iatrogenic vessel injury, or they may occur years later as prominent implants erode or penetrate major vessels. The authors present a case of a 71-year-old man in whom a thoracic pedicle screw was found perforating the thoracic aorta during routine follow-up 6 months after surgery. Due to the risk of future complications, the screw was removed while simultaneously delivering an endovascular aortic stent to gain vascular control. Surgical considerations and potential technical limitations are discussed.