Faculty Bibliography

OBJECTIVE The precise threshold differentiating normal and elevated intracranial pressure (ICP) is variable among individuals. In the context of several pathophysiological conditions, elevated ICP leads to abnormalities in global cerebral functioning and impacts the function of cranial nerves (CNs), either or both of which may contribute to ocular dysmotility. The purpose of this study was to assess the impact of elevated ICP on eye-tracking performed while patients were watching a short film clip. METHODS Awake patients requiring placement of an ICP monitor for clinical purposes underwent eye tracking while watching a 220-second continuously playing video moving around the perimeter of a viewing monitor. Pupil position was recorded at 500 Hz and metrics associated with each eye individually and both eyes together were calculated. Linear regression with generalized estimating equations was performed to test the association of eye-tracking metrics with changes in ICP. RESULTS Eye tracking was performed at ICP levels ranging from -3 to 30 mm Hg in 23 patients (12 women, 11 men, mean age 46.8 years) on 55 separate occasions. Eye-tracking measures correlating with CN function linearly decreased with increasing ICP (p < 0.001). Measures for CN VI were most prominently affected. The area under the curve (AUC) for eye-tracking metrics to discriminate between ICP < 12 and >/= 12 mm Hg was 0.798. To discriminate an ICP < 15 from >/= 15 mm Hg the AUC was 0.833, and to discriminate ICP < 20 from >/= 20 mm Hg the AUC was 0.889. CONCLUSIONS Increasingly elevated ICP was associated with increasingly abnormal eye tracking detected while patients were watching a short film clip. These results suggest that eye tracking may be used as a noninvasive, automatable means to quantitate the physiological impact of elevated ICP, which has clinical application for assessment of shunt malfunction, pseudotumor cerebri, concussion, and prevention of second-impact syndrome.

There has been no major advancement in a quarter of a century for the treatment of acute severe traumatic brain injury (TBI). This review summarizes 40 years of clinical and pre-clinical research on the treatment of acute TBI with hyperbaric oxygen therapy (HBO₂) in the context of an impending National Institute of Neurologic Disorders and Stroke-funded, multi-center, randomized, adaptive Phase II clinical trial -the Hyperbaric Oxygen Brain Injury Treatment (HOBIT) trial. Thirty studies (eight clinical and 22 pre-clinical) that administered HBO₂within 30 days of a TBI were identified from PubMed searches. The pre-clinical studies consistently reported positive treatment effects across a variety of outcome measures with almost no safety concerns, thus providing strong proof-of-concept evidence for treating severe TBI in the acute setting. Of the eight clinical studies reviewed, four were based on the senior author's (GR) investigation of HBO₂as a treatment for acute severe TBI. These studies provided evidence that HBO₂significantly improves physiologic measures without causing cerebral or pulmonary toxicity and can potentially improve clinical outcome. These results were consistent across the other four reviewed clinical studies, thus providing preliminary clinical data supporting the HOBIT trial. This comprehensive review demonstrates that HBO₂has the potential to be the first significant treatment in the acute phase of severe TBI.

Helmets are one of the earliest and most enduring methods of personal protection in human civilization. Although primarily developed for combat purposes in ancient times, modern helmets have become highly diversified to sports, recreation, and transportation. History and the scientific literature exhibit that helmets continue to be the primary and most effective prevention method against traumatic brain injury (TBI), which presents high mortality and morbidity rates in the US. The neurosurgical and neurotrauma literature on helmets and TBI indicate that helmets provide effectual protection against moderate to severe head trauma resulting in severe disability or death. However, there is a dearth of scientific data on helmet efficacy against concussion in both civilian and military aspects. The objective of this literature review was to explore the historical evolution of helmets, consider the effectiveness of helmets in protecting against severe intracranial injuries, and examine recent evidence on helmet efficacy against concussion. It was also the goal of this report to emphasize the need for more research on helmet efficacy with improved experimental design and quantitative standardization of assessments for concussion and TBI, and to promote expanded involvement of neurosurgery in studying the quantitative diagnostics of concussion and TBI. Recent evidence summarized by this literature review suggests that helmeted patients do not have better relative clinical outcome and protection against concussion than unhelmeted patients.

OBJECTIVE: The aim of this study was to validate computed tomography (CT)-based longitudinal markers of the progression of Alzheimer disease (AD). MATERIALS AND METHODS: We retrospectively studied 33 AD patients and 39 nondemented patients with other neurological illnesses (non-AD) having 4 to 12 CT examinations of the head, with over a mean (SD) of 3.9 (1.7) years. At each time point, we applied an automatic software to measure whole brain, cerebrospinal fluid, and intracranial space volumes. Longitudinal measures were then related to disease status and time since the first scan using hierarchical models. RESULTS: Absolute brain volume loss accelerated for non-AD patients by 0.86 mL/y (95% confidence interval [CI], 0.64-1.08 mL/y) and 1.5x faster, that is, 1.32 mL/y (95% CI, 1.09-1.56 mL/y) for AD patients (P = 0.006). In terms of brain volume normalized to intracranial space, the acceleration in atrophy rate for non-AD patients was 0.0578%/y (95% CI, 0.0389%/y to 0.0767%/y), again 1.5x faster, that is, 0.0919%/y (95% CI, 0.0716%/y to 0.1122%/y) for AD patients (P = 0.017). This translates to an increase in atrophy rate from 0.5% to 1.4% in AD versus to 1.1% in non-AD group after 10 years. CONCLUSIONS: Brain volumetry on CT reliably detected accelerated volume loss in AD and significantly lower acceleration factor in age-matched non-AD patients, leading to the possibility of its use to monitor the progression of cognitive decline and dementia.

OBJECT Women compose a minority of neurosurgery residents, averaging just over 10% of matched applicants per year during this decade. A recent review by Lynch et al. raises the concern that women may be at a higher risk than men for attrition, based on analysis of a cohort matched between 1990 and 1999. This manuscript aims to characterize the trends in enrollment, attrition, and postattrition careers for women who matched in neurosurgery between 2000 and 2009. METHODS Databases from the American Association of Neurological Surgeons (AANS) and the American Board of Neurological Surgery (ABNS) were analyzed for all residents who matched into neurosurgery during the years 2000-2009. Residents were sorted by female gender, matched against graduation records, and if graduation was not reported from neurosurgery residency programs, an Internet search was used to determine the residents' alternative path. The primary outcome was to determine the number of women residents who did not complete neurosurgery training programs during 2000-2009. Secondary outcomes included the total number of women who matched into neurosurgery per year, year in training in which attrition occurred, and alternative career paths that these women chose to pursue. RESULTS Women comprised 240 of 1992 (12%) matched neurosurgery residents during 2000-2009. Among female residents there was a 17% attrition rate, compared with a 5.3% male attrition rate, with an overall attrition rate of 6.7%. The majority who left the field did so within the first 3 years of neurosurgical training and stayed in medicine-pursuing anesthesia, neurology, and radiology. CONCLUSIONS Although the percentage of women entering neurosurgical residency has continued to increase, this number is still disproportionate to the overall number of women in medicine. The female attrition rate in neurosurgery in the 2000-2009 cohort is comparable to that of the other surgical specialties, but for neurosurgery, there is disparity between the male and female attrition rates. Women who left the field tended to stay within medicine and usually pursued a neuroscience-related career. Given the need for talented women to pursue neurosurgery and the increasing numbers of women matching annually, the recruitment and retention of women in neurosurgery should be benchmarked and assessed.

Object/UNASSIGNED:The purpose of the current study is to determine the sensitivity and specificity of an eye tracking method as a classifier for identifying concussion. Methods/UNASSIGNED:Brain injured and control subjects prospectively underwent both eye tracking and Sport Concussion Assessment Tool 3. The results of eye tracking biomarker based classifier models were then validated against a dataset of individuals not used in building a model. The area under the curve (AUC) of receiver operating characteristics was examined. Results/UNASSIGNED:An optimal classifier based on best subset had an AUC of 0.878, and a cross-validated AUC of 0.852 in CT- subjects and an AUC of 0.831 in a validation dataset. The optimal misclassification rate in an external dataset (n = 254) was 13%. Conclusion/UNASSIGNED:If one defines concussion based on history, examination, radiographic and Sport Concussion Assessment Tool 3 criteria, it is possible to generate an eye tracking based biomarker that enables detection of concussion with reasonably high sensitivity and specificity.