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Human modification of landscapes includes extensive addition of linear features, such as roads and transmission lines. These can alter animal movement and space use and affect the intensity of interactions among species, including predation and competition. Effects of linear features on animal movement have seen relatively little research in avian systems, despite ample evidence of their effects in mammalian systems and that some types of linear features, including both roads and transmission lines, are substantial sources of mortality. Here, we used satellite telemetry combined with step-selection functions designed to explicitly incorporate the energy landscape (el-SSFs) to investigate the effects of linear features and habitat on movements and space use of a large soaring bird, the golden eagleAquila chrysaetos, during migration. Our sample consisted of 32 adult eagles tracked for 45 spring and 39 fall migrations from 2014-2017. Fitted el-SSFs indicated eagles had a strong general preference for south-facing slopes, where thermal uplift develops predictably, and that these areas are likely important aspects of migratory pathways. el-SSFs also revealed that roads and railroads affected movement during both spring and fall migrations, but eagles selected areas near roads to a greater degree in spring compared to fall and at higher latitudes compared to lower latitudes. During spring, time spent near linear features often occurred during slower-paced or stopover movements, perhaps in part to access carrion produced by vehicle collisions. Regardless of the behavioral mechanism of selection, use of these features could expose eagles and other soaring species to elevated risk via collision with vehicles and/or transmission lines. Linear features have been previously documented to affect the ecology of terrestrial species (e.g., large mammals) by modifying individuals’ movement patterns; our work shows these effects on movement extend to avian taxa.

In populations across many taxa, a large fraction of sexually mature individuals do not breed but are attempting to enter the breeding population. Such individuals, often referred to as "floaters," can play critical roles in the dynamics and stability of these populations and buffer them through periods of high adult mortality. Floaters are difficult to study, however, so we lack data needed to understand their roles in the population ecology and conservation status of many species. Here, we analyzed satellite telemetry data with a newly developed mechanistic space use model based on an Ornstein-Uhlenbeck process to help overcome the paucity of data in studying the differential habitat selection and space use of floater and territorial golden eagles Aquila chrysaetos. Our sample consisted of 49 individuals tracked over complete breeding seasons across 4 years, totaling 104 eagle breeding seasons. Modeling these data mechanistically was required to disentangle key differences in movement and particularly to separate aspects of movement driven by resource selection from those driven by use of a central place. We found that floaters generally had more expansive space use patterns and larger home ranges, as well as evidence that they partition space with territorial individuals seemingly on fine scales through differential habitat and resource selection. Floater and territorial eagle home ranges overlapped markedly, suggesting that floaters use the interstices between territories. Furthermore, floater and territorial eagles differed in how they selected for uplift variables, key components of soaring birds' energy landscape, with territorial eagles apparently better able to find and use thermal uplift. We also found relatively low individual heterogeneity in resource selection, especially among territorial individuals, suggesting a narrow realized niche for breeding individuals, which varied from the level of among-individual variation present during migration. This work furthers our understanding of floaters' potential roles in the population ecology of territorial species and suggests that conserving landscapes occupied by territorial eagles also protects floaters.

In populations of many taxa, a large fraction of sexually mature individuals do not breed but are attempting to enter the breeding population. Such individuals, often referred to as “floaters” play critical roles in determining dynamics and stability of these populations. Floaters are difficult to study, however, so we lack data on the roles they play in population ecology and conservation status of many species. Here, we paired satellite telemetry and a new mechanistic space use model based on an Ornstein-Uhlenbeck process to study the differential habitat selection and space use of floater and territorial golden eaglesAquila chrysaetos. Our sample consisted of 49 individuals tracked over complete breeding seasons across four years, totalling 104 eagle breeding seasons. Modeling these data with the new mechanistic approach was required to parse key differences in movement and separate aspects of resource selection from central place behavior. We found that floaters generally had more expansive space use patterns and larger home ranges, partitioning space with territorial individuals seemingly on fine scales through differential habitat and resource selection. Floater and territorial eagle home ranges overlapped markedly, suggesting floaters use the interstices between territories. Further, floater and territorial eagles differed in how they selected for uplift variables, key components of soaring birds’ energy landscape, with territorial eagles apparently better able to find and use thermal uplift. We also found relatively low individual heterogeneity in resource selection, especially among territorial individuals, suggesting a narrow realized niche for breeding individuals. This work furthers our understanding of floaters’ potential roles in population ecology of territorial species, as well as suggests that conserving landscapes occupied by territorial eagles also protects floaters.

Ecological “big data” Human activities are rapidly altering the natural world. Nowhere is this more evident, perhaps, than in the Arctic, yet this region remains one of the most remote and difficult to study. Researchers have increasingly relied on animal tracking data in these regions to understand individual species' responses, but if we want to understand larger-scale change, we need to integrate our understanding across species. Davidson et al. introduce an open-source data archive that currently hosts more than 15 million location data points across 96 species and use it to show distinct climate change responses across species. Such ecological “big data” can lead to a wider understanding of change. Science , this issue p. 712

Migratory species display a range of migration patterns between irruptive (facultative) to regular (obligate), as a response to different predictability of resources. In the Arctic, snow directly influences resource availability. The causes and consequences of different migration patterns of migratory species as a response to the snow conditions remains however unexplored. Birds migrating to the Arctic are expected to follow the spring snowmelt to optimise their arrival time and select for snow-free areas to maximise prey encounter en-route. Based on large-scale movement data, we compared the migration patterns of three top predator species of the tundra in relation to the spatio-temporal dynamics of snow cover. The snowy owl, an irruptive migrant, the rough-legged buzzard, with an intermediary migration pattern, and the peregrine falcon as a regular migrant, all followed, as expected, the spring snowmelt during their migrations. However, the owl stayed ahead, the buzzard stayed on, and the falcon stayed behind the spatio-temporal peak in snowmelt. Although none of the species avoided snow-covered areas, they presumably used snow presence as a cue to time their arrival at their breeding grounds. We show the importance of environmental cues for species with different migration patterns.

This study assessed whether cytoskeletal protein alpha-II spectrin breakdown products (SBDP150, SBDP145, and SBDP120) would identify the presence of aSAH and be associated with severity (GCS score, WFNS grade and survival to hospital discharge). This prospective case-control study, conducted at a tertiary care Level I trauma center, enrolled adult patients with angiography confirmed aSAH who underwent ventriculostomy placement for cerebrospinal fluid (CSF) drainage. There were 40 patients enrolled in the study, 20 with aSAH and 20 control subjects. Patients with aSAH were a mean age of 54 (SD15) and 75% were female. There were significant differences in SBDP150, SBDP145, and SBDP120 CSF levels between patients with and without aSAH (p

Migratory species display a range of migration patterns between irruptive (facultative) to regular (obligate), as a response to different predictability of resources. In the Arctic, snow directly influences resource availability. The causes and consequences of different migration patterns of migratory species as a response to the snow conditions remains however unexplored. Birds migrating to the Arctic are expected to follow the spring snowmelt to optimise their arrival time and select for snow-free areas to maximise prey encounter en-route. Based on large-scale movement data, we compared the migration patterns of three top predator species of the tundra in relation to the spatio-temporal dynamics of snow cover. The snowy owl, an irruptive migrant, the rough-legged buzzard, with an intermediary migration pattern, and the peregrine falcon as a regular migrant, all followed, as expected, the spring snowmelt during their migrations. However, the owl stayed ahead, the buzzard stayed on, and the falcon stayed behind the spatio-temporal peak in snowmelt. Although none of the species avoided snow-covered areas, they presumably used snow presence as a cue to time their arrival at their breeding grounds. We show the importance of environmental cues for species with different migration patterns.

Background Transsphenoidal surgical approaches involve dissection of the posterior wall of the sphenoid sinus in close proximity to the internal carotid arteries. To reduce the risk of vascular injury, a detailed study of embalmed cadavers' sellae was conducted and found the internal carotid artery approached within 4 mm of the midline in 10% of cases, and the closest intercarotid distance (ICD) occurred in the cavernous sinus, sphenoid sinus, and supraclinoid segments in 82%, 14%, and 4% of cases, respectively. These measurements have not previously been compared with living patients with modern imaging techniques. Methods This study measured the closest ICD of 233 coronal magnetic resonance imaging head scans from 183 patients (male = 88, female = 95) at the cavernous sinus, sphenoid sinus, or supraclinoid segments of the internal carotid artery. ICD at the sphenoid sinus was taken for all scans. RESULTS The internal carotid approached within 4 mm of the midline in 1.3% of cases. The closest ICD occurred in the cavernous sinus, sphenoid sinus, and supraclinoid segments in 24.5%, 35.8%, and 39.7%, respectively. Both results were significantly different from previous cadaveric studies (chi-squared tests, P = 1.4 × 10−4 and P = 6.1 × 10−8, respectively). Conclusions Surgically relevant measurements of the carotid arteries in the sellar are different in cadavers and living subjects. This is likely due to postmortem changes of surrounding structures. This study suggests clinically relevant anatomic studies using measurements taken from cadaveric specimens be updated with modern imaging techniques taken from living patients.

AstractLong distance migration can increase lifetime fitness, but can be costly, incurring increased energetic expenses and higher mortality risks. Stopover and other en route behaviors allow animals to rest and replenish energy stores and avoid or mitigate other hazards during migration. Some animals, such as soaring birds, can subsidize the energetic costs of migration by extracting energy from flowing air. However, it is unclear how these energy sources affect or interact with behavioral processes and stopover in long-distance soaring migrants. To understand these behaviors and the effects of processes that might enhance use of flight subsidies, we developed a flexible mechanistic model to predict how flight subsidies drive migrant behavior and movement processes. The novel modelling framework incorporated time-varying parameters informed by environmental covariates to characterize a continuous range of behaviors during migration. This model framework was fit to GPS satellite telemetry data collected from a large soaring and opportunist foraging bird, the golden eagle (Aquila chrysaetos), during migration in western North America. Fitted dynamic model parameters revealed a clear circadian rhythm in eagle movement and behavior, which was directly related to thermal uplift. Behavioral budgets were complex, however, with evidence for a joint migrating/foraging behavior, resembling a slower paced fly-and-forage migration, which could facilitate efficient refueling while still ensuring migration progress. In previous work, ecological and foraging conditions are normally considered to be the key aspects of stopover location quality, but taxa that can tap energy sources from moving fluids to drive migratory locomotion, such as the golden eagle, may pace migration based on both foraging opportunities and available flight subsidies.

For migrating animals, realized migration routes and timing emerge from hundreds or thousands of movement decisions made along migration routes. Local weather conditions along migration routes continually influence these decisions, and even relatively small changes in en route weather may cumulatively result in major shifts in migration patterns. Here, we analysed satellite tracking data to score a discrete navigation decision by a large migratory bird as it navigated a high-latitude, 5000 m elevation mountain range to understand how those navigational decisions changed under different weather conditions. We showed that wind conditions in particular areas along the migration pathway drove a navigational decision to reroute a migration; conditions encountered predictably resulted in migrants routing either north or south of the mountain range. With abiotic conditions continuing to change globally, simple decisions, such as the one described here, might additively emerge into new, very different migration routes.

Migratory Golden Eagles (Aquila chrysaetos) from Alaska winter across a vast region of western North America, much of which is undergoing rapid change from a diversity of indirect and direct human activities. To address recent conservation concerns, we are studying the year-round movements of migratory Golden Eagles from interior and northern Alaska to identify and evaluate potential risks to their survival. We are also developing new survey techniques to estimate population size and trends. As part of our ongoing studies, we observed migrating Golden Eagles in spring and autumn 2014 during field investigations to locate Golden Eagle capture sites in eastern interior Alaska, and in spring 2015 during capture activities. We observed large numbers of Golden Eagles in both spring and autumn, suggesting that the Mentasta Mountains are an important migration corridor for this species. Further, our observations, including 1364 migrating Golden Eagles in October 2014, suggested that the Alaska Golden Ea...

Areas de Campeo y Movimientos de Falco rusticolus en el Delta de Yukon-Kuskokwim, Alaska Los individuos adultos de Falco rusticolus no han sido seguidos con telemetria satelital en America del Norte continental, dejando un vacio substancial en nuestro conocimiento de la biologia de esta especie. Marcamos dos adultos y dos volantones hembra de F. rusticolus con transmisores satelitales en sus sitios de nidificacion en el Delta de Yukon-Kuskokwim, Alaska, entre 2004 y 2006. Generamos estimados de areas de campeo de kernel fijo de 95% y 50% para las epocas reproductivas y no reproductivas de los adultos y describimos los movimientos de los volantones al dejar el nido utilizando Sistemas de Informacion Geografica. Los estimados promedios de las areas de campeo de kernel fijo de 95% para individuos adultos en la epoca reproductiva y no reproductiva fueron de 521 km2 y 330 km2, respectivamente, aunque hubo una variacion substancial y superposicion entre individuos. Nuestros estimados del tamano del area de camp...

The concept of subspecies is an important tool to help categorize and conserve biodiversity; thus, delineating the range of subspecies can have important management and conservation implications. The Peregrine Falcon (Falco peregrinus) is a widespread species that occurs throughout North America, where three subspecies are recognized: F. p. anatum, F. p. pealei, and F. p. tundrius. In Alaska, all three subspecies breed and their general distributions during the breeding season are well documented. However, the limits of their distributions were unclear or unconfirmed, especially those of F. p. anatum and F. p. pealei along the Lost Coast in the northeastern Gulf of Alaska. We describe plumage, morphology, and/or movements of Peregrine Falcons known to have nested (n = 6) or hatched (n = 3) within the Lost Coast and used this information to determine their subspecific group. For all nine birds, we found these characteristics to be consistent with F. p. anatum. Our results underscore the import...

Background Desmoplastic neurotropic melanoma (DNM) is a rare, highly malignant, and locally invasive form of cutaneous melanoma with a tendency for perineural invasion (PNI). Methods We report a case of a 61-year-old man presenting with right-sided trigeminal neuralgia and progressive facial paresis due to the PNI of the intracranial trigeminal nerve and the intraparotid facial nerve from DNM. We also present a review of the literature with six cases of DNM with PNI of the intracranial trigeminal nerve identified. Results The combined transtemporal-infratemporal fossa approach was performed to achieve total en bloc resection of the tumor mass followed by postoperative radiotherapy (PORT). After 24 months of follow-up, the patient remains disease free with no signs of recurrence on magnetic resonance imaging. Conclusion We recommend the en bloc resection of the tumor mass followed by PORT for the management of DNM with PNI. A high index of suspicion for PNI as a cause of cranial neuropathies is essential for the early detection and treatment of patients with known melanoma.

Subspecies relationships within the peregrine falcon (Falco peregrinus) have been long debated because of the polytypic nature of melanin-based plumage characteristics used in subspecies designations and potential differentiation of local subpopulations due to philopatry. In North America, understanding the evolutionary relationships among subspecies may have been further complicated by the introduction of captive bred peregrines originating from non-native stock, as part of recovery efforts associated with mid 20th century population declines resulting from organochloride pollution. Alaska hosts all three nominal subspecies of North American peregrine falcons-F. p. tundrius, anatum, and pealei-for which distributions in Alaska are broadly associated with nesting locales within Arctic, boreal, and south coastal maritime habitats, respectively. Unlike elsewhere, populations of peregrine falcon in Alaska were not augmented by captive-bred birds during the late 20th century recovery efforts. Population genetic differentiation analyses of peregrine populations in Alaska, based on sequence data from the mitochondrial DNA control region and fragment data from microsatellite loci, failed to uncover genetic distinction between populations of peregrines occupying Arctic and boreal Alaskan locales. However, the maritime subspecies, pealei, was genetically differentiated from Arctic and boreal populations, and substructured into eastern and western populations. Levels of interpopulational gene flow between anatum and tundrius were generally higher than between pealei and either anatum or tundrius. Estimates based on both marker types revealed gene flow between augmented Canadian populations and unaugmented Alaskan populations. While we make no attempt at formal taxonomic revision, our data suggest that peregrine falcons occupying habitats in Alaska and the North Pacific coast of North America belong to two distinct regional groupings-a coastal grouping (pealei) and a boreal/Arctic grouping (currently anatum and tundrius)-each comprised of discrete populations that are variously intra-regionally connected.

Kittlitz's Murrelet (Brachyramphus brevirostris) is a dispersed-nesting seabird endemic to Alaska and eastern Russia that may have experienced considerable population declines in some parts of its range in the past few decades. Poor reproduction has been suggested as the demographic bottleneck, yet there are no direct estimates of reproduction in a glaciated area where this species reaches its highest densities at sea during the breeding season. The lack of demographic information in glacial habitats has limited our ability to interpret population trends and to clarify whether the presence of glaciers affects reproductive performance. Between 2007 and 2012, we radio-tagged Kittlitz's Murrelets to measure breeding propensity, nesting success, and fecundity in the heavily glaciated landscape of Icy Bay, Alaska, USA. Of 156 radio-tagged birds, 20% were breeders, 68% were potential breeders, and 12% were nonbreeders. Radio-tagged males (29%) were more likely to be breeders compared to females (11%). ...

The Kittlitz's murrelet (Brachyramphus brevirostris) is a small, dispersed-nesting seabird that often occurs in glacially influenced marine waters of Alaska and eastern Russia during the breeding season. Owing to its association with glacial habitats and apparent population declines in some parts of its range, the Kittlitz's murrelet has been the subject of considerable conservation concern in recent years. We present the first-ever estimates of breeding season and annual survival of the Kittlitz's murrelet. We estimated survival by capturing 914 murrelets and radiotagging 191 of them in Icy Bay, Alaska, 2007–2012. We used a multi-state mark–recapture framework to estimate breeding season survival. Daily survival probabilities were similar in the 3 spatial states (Icy Bay, Gulf of Alaska, nest; range = 0.996–0.999), resulting in an overall 60-day breeding season survival probability of 0.89 (SE = 0.04). The only apparent source of fatality of Kittlitz's murrelets during the breeding season was avian predators, specifically bald eagle (Haliaeetus leucocephalus) and peregrine falcon (Falco peregrinus). We estimated mean apparent annual survival across all years as 0.80 (SE = 0.33) with a recapture probability of 0.079 (SE = 0.032), resulting in a 305-day non-breeding season survival probability of 0.90 (SE = 0.37). We found that survival was lower than expected based on life-history theory and allometry, and that fatality risk was greater in the breeding season compared to other parts of the year. Our results indicating low survival rates of Kittlitz's murrelets are consistent with the observed decline of 10% per annum in the local population of this species in Icy Bay. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Background Quantifying individual variability in movement behavior is critical to understanding population-level patterns in animals. Here, we explore intraspecific variation in movement strategies of bald eagles (Haliaeetus leucocephalus) in the north Pacific, where there is high spatiotemporal resource variability. We tracked 28 bald eagles (five immature, 23 adult) using GPS transmitters between May 2010 and January 2016. Results We found evidence of four movement strategies among bald eagles in southeastern Alaska and western Canada: breeding individuals that were largely sedentary and remained near nest sites year-round, non-breeding migratory individuals that made regular seasonal travel between northern summer and southern winter ranges, non-breeding localized individuals that displayed fidelity to foraging sites, and non-breeding nomadic individuals with irregular movement. On average, males traveled farther per day than females. Most nomadic individuals were immature, and all residential individuals (i.e. breeders and localized birds) were adults. Conclusions Alternative movement strategies among north Pacific eagles are likely associated with the age and sex class, as well as breeding status, of an individual. Intraspecific variation in movement strategies within the population results in different space use patterns among contingents, which has important implications for conservation and management.

The North American Breeding Bird Survey, Christmas Bird Count, and regional and national conservation assessments provide convincing evidence that the short-eared owl (Asio flammeus) is experiencing a range-wide, long-term decline in abundance in North America. However, the species has received little conservation or research attention. The short-eared owl is vulnerable to decline because it relies heavily on large, intact grasslands and a specialized diet of unpredictable small mammal prey. The species' nomadic movements compound these vulnerabilities by making a decline difficult to detect with current monitoring programs while obfuscating stewardship responsibilities for managers. The primary threat to the species is loss, fragmentation, and degradation of large tracts of native grasslands and wetlands. We propose the following conservation priorities to better understand and begin addressing the short-eared owl's decline: 1) better define and protect important habitats; 2) improve population monitoring; 3) determine seasonal and annual movements; 4) re-evaluate NatureServe's short-eared owl national conservation classifications; 5) develop management plans and tools; and 6) classify raptors, including short-eared owls, as migratory birds in Canada. We contend that the short-eared owl's need for habitat conservation at large spatial scales, status as a predator, and high reproductive potential that affords the species capacity to recover, make it an effective and useful candidate as an umbrella species for grassland conservation. © 2014 The Wildlife Society.

Background Quantifying individual variability in movement behavior is critical to understanding population-level patterns in animals. Here, we explore intraspecific variation in movement strategies of bald eagles (Haliaeetus leucocephalus) in the north Pacific, where there is high spatiotemporal resource variability. We tracked 28 bald eagles (five immature, 23 adult) using GPS transmitters between May 2010 and January 2016. Results We found evidence of four movement strategies among bald eagles in southeastern Alaska and western Canada: breeding individuals that were largely sedentary and remained near nest sites year-round, non-breeding migratory individuals that made regular seasonal travel between northern summer and southern winter ranges, non-breeding localized individuals that displayed fidelity to foraging sites, and non-breeding nomadic individuals with irregular movement. On average, males traveled farther per day than females. Most nomadic individuals were immature, and all residential individuals (i.e. breeders and localized birds) were adults. Conclusions Alternative movement strategies among north Pacific eagles are likely associated with the age and sex class, as well as breeding status, of an individual. Intraspecific variation in movement strategies within the population results in different space use patterns among contingents, which has important implications for conservation and management. Electronic supplementary material The online version of this article (doi:10.1186/s40462-017-0102-4) contains supplementary material, which is available to authorized users.

Background External ventricular drainage (EVD) catheters provide reliable and accurate means of monitoring intracranial pressure and alleviating elevated pressures via drainage of cerebrospinal fluid (CSF). CSF infections occur in approximately 9% of patients. Antibiotic-impregnated (AI) EVD catheters were developed with the goal of reducing the occurrence of EVD catheter-related CSF infections and their associated complications. Objective To present an international, prospective, randomized, open-label trial to evaluate infection incidence of AI vs standard EVD catheters. Methods Infection was defined as (1) proven infection, positive CSF culture and positive Gram stain or (2) suspected infection: (A) positive CSF culture with no organisms identified on initial Gram stain; (B) negative CSF culture with a gram-positive or -negative stain; (C) CSF leukocytosis with a white blood cell/red blood cell count >0.02. Results Four hundred thirty-four patients underwent implantation of an EVD catheter. One hundred seventy-six patients in the AI-EVD cohort and 181 in the standard EVD catheter cohort were eligible for evaluation of infection. The 2 groups were similar in all clinical characteristics. Proven infection was documented in 9 (2.5%) patients (AI: 4 [2.3%] vs standard: 5 [2.8%], P = 1.0). Suspected infection was documented in 31 (17.6%) patients receiving AI and 37 (20.4%) patients receiving standard EVD catheters, P = .504. Duration of time to suspected infection was prolonged in the AI cohort (8.8 ± 6.1 days) compared with the standard EVD cohort (4.6 ± 4.2 days), P = .002. Conclusion AI-EVD catheters were associated with an extremely low rate of catheter-related infections. AI catheters were not associated with risk reduction in EVD infection compared to standard catheters. Use of AI-EVD catheters is a safe option for a wide variety of patients requiring CSF drainage and monitoring, but the efficacy of AI-EVD catheters was not supported in this trial.

Background After intradural cranial surgery, a dural substitute is often required for dural closure. Although preferred, limitations of autograft include local availability and additional surgical site morbidity. Thus, allografts, xenografts, and synthetics are frequently used. Objective To report 6-month results of a randomized, controlled trial of a biosynthesized cellulose (BSC) composed duraplasty device compared with commercially available dural replacements. Methods A total of 99 patients (62 BSC; 37 control) were treated on protocol, using a 2:1 (BSC:control) blocked randomization schedule. Physical examinations were performed pre- and postoperatively within 10 days and at 1, 3, and 6 months. Magnetic resonance imaging was performed preoperatively and at 6 months. The primary study endpoint was the absence of pseudomeningocele and extracerebral fluid collection confirmed radiographically and the absence of cerebrospinal fluid fistula at 6 months. Results At 6 months, the primary hypothesis, noninferiority of the BSC implant compared with the control group, was confirmed (P = .0206). Overall success was achieved by 96.6% of BSC and 97.1% of control patients. No significant difference was revealed between treatment groups for surgical site infection (P = 1.0000) or wound healing assessment (P ≥ .3685) outcomes, or radiologic endpoints (P ≥ .4061). Device strength and seal quality favored BSC. Conclusion This randomized, controlled trial establishes BSC as noninferior to commercially available dural replacement devices. BSC offers a hypothetical advantage concerning prion and other infectious agent exposure; superior handling qualities are evident. Longer term data are necessary to identify limitations of BSC and its potential equivalence to the gold standard of pericranium.

Papaverine has been associated with transient cranial nerve dysfunction after topical application during craniotomy. The authors report similar dysfunction after the use of papaverine affected brainstem structures. Two patients undergoing craniotomy for clipping of an aneurysm experienced bilateral depression of cortical somatosensory evoked potentials to both median and tibial nerve stimulation after administration of papaverine. Arterial blood gas analysis, hemodynamic parameters, and anesthetic levels remained constant throughout these somatosensory evoked potential changes. In addition, intraoperative angiography and immediate postoperative CT imaging showed intact blood flow with complete exclusion of the aneurysm. Both patients recovered within 1–2 hours and had normal neurological examination findings after extubation. Topical papaverine use may be associated with direct effects on brainstem structures. The transient nature of those changes suggests that aggressive intervention may not be needed. Maneuvers to limit the spread of papaverine to basal cisterns should be considered.

Patch-occupancy models offer a realistic approach to monitoring populations of nocturnal owls. However, because most owls are relatively rare, increasing the probability of detecting an owl at an occupied site will make estimates of occupancy more precise. We investigated the influence of temporal, biological, and environmental factors on rates of detection of forest owls in southeastern Alaska, 2005–2006. Following MacKenzie et al. (2006), we modeled probabilities of detection of the Northern Saw-whet Owl (Aegolius acadicus), Western Screech-Owl (Megascops kennicottii), and Barred Owl (Strix varia). We conducted 479 point counts over 100 days and detected owls 147 times. Sound broadcast increased detections 21–86% over silent surveys. During peak detection (9 April–8 May), probabilities (SE) of detection were 0.39 (0.13) for the Western Screech, 0.44 (0.16) for the Saw-whet, and 0.54 (0.25) for the Barred. For the Barred and Saw-whet, estimated occupancy probabilities (ψ) were constant (i.e., d...

Distance sampling along a line transect is used commonly for monitoring changes of birds' abundance at sea. A critical yet rarely tested assumption of line-transect-sampling theory is that all birds along the transect line (i.e., directly in front of the boat) are detected or that probability of detecting a bird on the line can be estimated. As part of a long-term research and monitoring program for the Kittlitz's Murrelet (Brachyramphus brevirostris), we tested the assumption of complete detection of murrelets on the water along a transect line directly in front of a moving boat. Following standard survey procedures, we approached groups of murrelets (n = 57) at sea and recorded their distance, response (diving or flying), and duration of response. Flying murrelets (n = 27) were easily detected, but diving birds (n = 30) were more difficult to detect because of the duration of their dive. The probability that a bird dove and remained underwater long enough to avoid detection was low because bir...

There are few studies comparing the economic costs and reimbursements for aneurysm clipping versus coiling, and none are from the United States. Our hypothesis predicted that coiling would result in shorter lengths of hospitalization than clipping in patients with unruptured aneurysms and would therefore result in lower hospital charges. However, because of the severity of subarachnoid hemorrhage, there would be no difference in length of hospitalization or hospital charges in patients with ruptured aneurysms.We compared aneurysm coiling with aneurysm clipping in patients with unruptured and ruptured aneurysms treated at the University of Florida from January 2005 to June 2007 for differences in length of hospitalization, hospital costs, hospital collections, and surgeon collections. Patient demographic and aneurysm characteristic data were obtained from a clinical database. Length of hospitalization, cost, billing, and collection data were obtained from the hospital cost accounting database. Multivariate statistical analyses of length of hospitalization, hospital costs, hospital collections, and surgeon collections were performed using factors including patient age, sex, aneurysm size, aneurysm location, aneurysm treatment, presence of subarachnoid hemorrhage, clinical grade, payor, hospital billing, and surgeon billing.There were 565 patients with cerebral aneurysms treated either surgically (306 patients, 54%) or endovascularly (259 patients, 46%). In patients without subarachnoid hemorrhage (unruptured aneurysms) (n = 367), surgery, compared with endovascular treatment, was associated with longer hospitalization (P0.001), but lower hospital costs (P0.001), higher surgeon collections (P = 0.003), and similar hospital collections. In patients with subarachnoid hemorrhage (ruptured aneurysms) (n = 198), surgery was associated with lower hospital costs (P = 0.011), but similar length of stay, surgeon collections, and hospital collections. Larger aneurysm size was significantly associated with longer hospitalization in the patients with unruptured aneurysms (P0.001) and higher hospital costs for both patients with unruptured (P0.001) and ruptured (P = 0.015) aneurysms. The payor was significantly associated with hospital costs in patients with ruptured aneurysms (P = 0.034) and length of stay (unruptured aneurysms, P0.001; ruptured aneurysms, P0.001), hospital collections (unruptured aneurysms, P0.001; ruptured aneurysms, P0.001), and surgeon collections (unruptured aneurysms, P0.001; ruptured aneurysms, P0.001) in both patients with unruptured and ruptured aneurysms. A worse clinical grade was significantly associated with higher hospital costs (P0.001).Despite a shorter length of hospitalization in patients with unruptured aneurysms, coiling was associated with higher hospital costs in both patients with unruptured and ruptured aneurysms. This is likely attributable to the higher device cost of coils than clips. The advantages of coiling over clipping would be better realized if the cost of coils could be comparably reduced to that of clips.

Multiple reports document that a foreign-body giant cell reaction forms around Proplast-Teflon temporomandibular joint (TMJ) implants. This results in destruction of surrounding bone and instability of the implants. This case presents a patient whose Proplast-Teflon TMJ implants became displaced into her middle cranial fossa. The staged reconstruction of this patient is described, including removal of the TMJ implants, reconstruction of the defect, concomitant orthodontic treatment and final reconstruction with TMJ Concepts. This process involved a multidisciplinary approach between several medical and dental specialties. At her 3-year follow up, the patient had a stable postoperative result.

OBJECTIVE Intracranial arteriovenous malformations (AVM) may be managed through staged preoperative embolization and resection. Two commonly used liquid embolics are N-butyl cyanoacrylate (nBCA; Cordis Microvascular, Inc., New Brunswick, NJ) and Onyx (ev3, Inc., Irvine, CA). We sought to compare the utility of these agents in terms of fluoroscopy and procedure times. METHODS All intracranial AVMs embolized from 2002 to 2006 at the University of Florida were included in this study. Patients were stratified into three treatment groups: nBCA, Onyx, and patients who received both nBCA and Onyx during separate embolizations. Cohorts were compared by sex, age, Spetzler-Martin grade, AVM volume, fluoroscopy time, procedure time, surgical blood loss, and complications. RESULTS A total of 182 embolizations were performed on 88 patients (nBCA, 60 patients and 106 procedures; Onyx, 20 patients and 43 procedures; and nBCA/Onyx, eight patients and 16 nBCA and 17 Onyx procedures). There were no significant differences in patient demographics, AVM volumes, and Spetzler-Martin grades. Mean fluoroscopy and procedure times were increased for Onyx (57 min; 2.6 h) compared with nBCA (37 min; 2.1 h) embolizations (P < 0.0001 and P = 0.001, respectively). Cumulative mean fluoroscopy time was increased for Onyx (135 min) and nBCA/Onyx (180 min) cohorts relative to nBCA (64 min; P < 0.0001). Cumulative mean procedure time was increased in the nBCA/Onyx group (10.4 h) compared with nBCA (3.7 h) and Onyx (5.4 h; P < 0.0001). Seventy patients (80%) underwent AVM resection. No significant differences in surgical blood loss or complication rates were observed among the cohorts. CONCLUSION Onyx AVM embolization requires increased fluoroscopy and procedure times compared with nBCA. Further investigation is necessary to justify increased radiation exposure and procedure time associated with Onyx.

OBJECTIVE The incidence of reoperation for ventriculoperitoneal shunts (VPS) in adults, although lower than in pediatric patients, is not insignificant. We hypothesize that adult VPS placed for hemorrhage-related hydrocephalus have a lower incidence of reoperation than those placed for other types of hydrocephalus. METHODS We retrospectively reviewed all adult (≥ 20 yr) VPS initially placed from February 2001 to August 2006 at the University of Florida. We determined the incidence and time interval to reoperation. Follow-up was conducted by telephone interview and review of medical records. RESULTS A total of 286 adult VPS were initially placed: 96 (34%) hemorrhage and 190 (66%) nonhemorrhage. A total of 15 (16%) hemorrhage patients underwent 22 shunt reoperations, compared with 50 (27%) nonhemorrhage patients who underwent 82 shunt reoperations (P = 0.0316). A Poisson regression analysis of the number of reoperations, factoring hemorrhage, age, and sex, demonstrated a significantly lower incidence of reoperation in hemorrhage patients (P = 0.0900). A Cox proportional hazards model analysis of time to first reoperation, factoring hemorrhage, age, and sex, demonstrated a significantly longer shunt survival in hemorrhage patients (P = 0.0404). CONCLUSION Adult VPS placed for hemorrhage-related hydrocephalus have a significantly lower incidence of reoperation and significantly longer shunt survival. This result may be related to an incidence of transient shunt dependency in patients with hemorrhage-related hydrocephalus. However, the precise mechanism remains unclear.

The Kittlitz's Murrelet (Brachyramphus brevirostris) is a rare, non-colonial seabird often associated with tidewater glaciers and a recent candidate for listing under the Endangered Species Act. We estimated abundance of Kittlitz's Murrelets across space and time from at-sea surveys along the coast of Alaska (USA) and then used these data to develop spatial models to describe abundance patterns and identify environmental factors affecting abundance. Over a five-week period in the summer of 2005, we recorded 794 Kittlitz's Murrelets, 16 Marbled Murrelets (B. marmoratus), and 70 unidentified murrelets. The overall population estimate (N, mean +/- SE) during the peak period (3-9 July) was 1317 +/- 294 birds, decreasing to 68 +/- 37 by the last survey period (31 July-6 August). Density of Kittlitz's Murrelets was highest in pelagic waters of Taan Fjord (18.6 +/- 7.8 birds/km2, mean +/- SE) during 10-16 July. Spatial models identified consistent "hotspots" of Kittlitz's Murrelets, including several small areas where high densities of murrelets were found throughout the survey period. Of the explanatory variables that we evaluated, tidal current strength influenced murrelet abundance most consistently, with higher abundance associated with strong tidal currents. Simulations based on the empirically derived estimates of variation demonstrated that spatial variation strongly influenced power to detect trend, although power changed little across the threefold difference in the coefficient of variation on detection probability. We include recommendations for monitoring Kittlitz's Murrelets (or other marine species) when there is a high degree of uncertainty about factors affecting abundance, especially spatial variability.

Genetic risk factors for intracranial aneurysm (IA) are not yet fully understood. Genomewide association studies have been successful at identifying common variants; however, the role of rare variation in IA susceptibility has not been fully explored. In this study, we report the use of whole exome sequencing (WES) in seven densely-affected families (45 individuals) recruited as part of the Familial Intracranial Aneurysm study. WES variants were prioritized by functional prediction, frequency, predicted pathogenicity, and segregation within families. Using these criteria, 68 variants in 68 genes were prioritized across the seven families. Of the genes that were expressed in IA tissue, one gene (TMEM132B) was differentially expressed in aneurysmal samples (n=44) as compared to control samples (n=16) (false discovery rate adjusted p-value=0.023). We demonstrate that sequencing of densely affected families permits exploration of the role of rare variants in a relatively common disease such as IA, although there are important study design considerations for applying sequencing to complex disorders. In this study, we explore methods of WES variant prioritization, including the incorporation of unaffected individuals, multipoint linkage analysis, biological pathway information, and transcriptome profiling. Further studies are needed to validate and characterize the set of variants and genes identified in this study.

Northern goshawks (Accipiter gentilis; hereafter, goshawks) occur throughout forests of North America and have received much attention as a target species for management (Reynolds et al. 1992, Iverson et al. 1996, Andersen et al. 2003). Goshawks nest in forest stands with high timber volumes and dense overstory canopies above relatively open understories (Reynolds et al. 1982, Squires and Reynolds 1997, Daw and DeStefano 2001), and goshawk foraging is often associated with similar high-volume forest stands (Widen 1989, Beier and Drennan 1997). This association with high-volume forests has caused concern about the effects of forest management on goshawk populations (Crocker-Bedford 1990, Kennedy 1997, Andersen et al. 2003). Initially, management for goshawks concentrated on nesting habitat (Reynolds et al. 1982, Reynolds 1983), but recently the focus has been on managing for abundant and available prey populations (Reynolds et al. 1992, Graham et al. 1999). Thus, understanding the goshawks’ diet is a practical step in any attempt to manage this species. Across their range, goshawks consume a wide variety of smallto medium-sized birds and mammals associated with forested habitats, including grouse, tree squirrels, corvids, large passerines, woodpeckers, and hares (Cramp and Simmons 1980, Squires and Reynolds 1997). However, goshawks can also be local specialists, so diet patterns might be different across geographic scales. In 1991, the Alaska Department of Fish and Game (ADFG50 years (Iverson et al. 1996, USFS 1997). Concern for the effects of this logging led to the filing of a petition to list the goshawk as endangered in this region (Federal Register 1995); this petition continued to be litigated in federal court through 2004 (P. Schempf, U.S. Fish and Wildlife Service, personal communication). The most contentious issues for the Tongass relate to management of mediumto highvolume forests, which are critical to wildlife and valuable to the timber industry (Schoen et al. 1988). A better understanding of goshawk diet during the nesting season in southeast Alaska can provide insight into the importance of different habitats for nesting goshawks. The USFS recognizes that the link among goshawk prey species, prey habitats, and habitat management practices are key elements for conservation of the goshawk and the biotic communities in which it occurs (Reynolds et al. 1992, Iverson et al. 1996). Our objectives were to describe and quantify the nesting season diet of northern goshawks in southeast Alaska, USA, and to examine spatial and temporal variability in goshawk diet within this region.

Traumatic brain injury (TBI) is a major national health problem without a US Food and Drug Administration-approved therapy. This review summarizes the importance of discovering relevant TBI protein biomarkers and presents logical rationale that neuroproteomic technologies are uniquely suited for the discovery of otherwise unnoticed TBI biomarkers. It highlights that one must make careful decisions when choosing which paradigm (human vs. animal models) and which biologic samples to use for such proteomic studies. It further outlines some of the desirable attributes of an ideal TBI biomarker and discusses how biomarkers discovered proteomically are complementary to those identified by traditional approaches. Lastly, the most important sequela of any proteomically identified TBI biomarker is validation in preclinical or clinical samples.

Use of genetic marks to identify individuals and generate population estimates using mark–recapture methodologies has become increasingly common. Recently, brown bear (Ursus arctos) population estimates have been made using DNA isolated from hair follicles as the mark, obtaining hair with a barbed-wire enclosure around a scent lure. While this method has been successfully used in low-density populations, it would be difficult to use in areas with dense concentrations of bears because of the high probability of collecting hair from multiple bears at a single site during a single trap session. We designed and evaluated a single-catch snare to collect bear hair in a dense brown bear population during late summer. We hung snares, modeled after a wolf (Canis lupus) neck snare, on bear trails along streams where bears congregated to feed on spawning salmon (Oncorhynchus spp.). During 2 years 1,000 snares were tripped and 455 contained bear hair. We determined genotypes from 309 hair samples collected. ...

Purpose. Our purpose was to discuss the optimal treatment and outcomes for patients with skull base chordomas. Methods. We reviewed the pertinent literature for this study. Results. Skull base chordomas usually arise in the clivus and are rarely completely resectable. Therefore, most are treated with radiotherapy (RT). Because of the risk of severe late com- plications, the dose is often limited with conventional photon RT, and the probability of cure is low. Proton RT alone or combined with photon RT (proton/photon RT) offers the advantage of improved dose distribution and the ability to treat the tumor to a higher dose without exceeding normal tissue tolerance. The 10-year local control rate after proton/photon RT is approx- imately 40% to 50%. The probability of local control is related to minimum tumor dose and dose inhomogeneity. Conclusions. Skull base chordoma is a rare neoplasm that is rarely cured after surgery alone or combined with conventional RT. Proton/photon RT offers the advantage of increasing the tumor dose while minimizing the dose to normal tissues, thus reducing the risk of late complications. The optimal treatment may be photon/proton RT alone or combined with a gross total resection, when feasible. A 2005 Wiley Periodicals, Inc. Head Neck 27: 159-165, 2005

Video recording of prey deliveries to nests is a new technique for collecting data on raptor diet, but no thorough comparison of results from traditional methods based on collections of prey remains and pellets has been undertaken. We compared data from these 3 methods to determine relative merits of different methods for assessing raptor diet as part of a study of the breeding-season diet of northern goshawks (Accipiter gentilis) in Southeast Alaska. We applied these methods to 5 nests during each of the northern goshawk breeding seasons of 1998 and 1999 and identified 1,540 prey from deliveries, 209 prey from remains, and 209 prey from pellets. The proportions of birds and mammals varied among techniques, as did relative proportions of prey groups and age groups. Prey remains and pellets gave the least-similar diet descriptions. Over 2-day intervals during which data were collected using all 3 methods, prey-delivery data gave more individual prey and prey categories than the 2 other sources of information. We found that prey were not directly tracked in either prey remains or pellets compared with prey delivery videography. Analysis of prey-delivery videography provided the most complete description of diet, and we recommend that studies attempting to describe diet use this technique, at least as part of their methodology.

Object. Aneurysms located on the distal portion of the posterior inferior cerebellar artery (PICA) are uncommon, and their underlying pathology, natural history, and clinical management are poorly understood. To clarify these lesions more fully, the authors undertook a retrospective analysis of the clinical features and management results of 22 distal PICA aneurysms in 20 consecutive patients treated at one institution by the same surgeon during the past decade. Methods. The series included 10 men and 10 women (mean age at presentation 51 years). Nine patients presented with only subarachnoid and/or intraventricular hemorrhage (median Hunt and Hess Grade II). In seven patients intracerebellar hemorrhage was also found; two patients presented with pressure effects and two hemorrhages were incidentally discovered. Prominent comorbidities included cigarette smoking (50%) and hypertension (50%). The 13 saccular and nine fusiform distal PICA aneurysms were distributed on the following segments of the PICA: lateral medullary (seven lesions), tonsillomedullary (five lesions), telovelotonsillar (five lesions), and cortical (five lesions). Six cases were associated with cerebellar arteriovenous malformations. Skull-base and far-lateral transcondylar surgical approaches were used to secure the aneurysms in 86% of cases, either by direct clipping (13 lesions), vessel sacrifice (four lesions), or vessel sacrifice plus bypass (two lesions). Two aneurysms were treated using endovascular PICA ablation. Overall outcome at hospital discharge was excellent or good in 70% of cases. At long-term follow up (100% of patients, mean 123 days), an excellent or good outcome had been achieved in 85% of cases. Conclusions. Depending on the PICA segment that was affected, variations in clipping strategies and surgical exposures aimed at the PICA branch and main trunk preservation were major contributors to good long-term results.

Objective Transcranial Doppler (TCD) flow velocity (FV) assessment may provide a useful index of autoregulatory impairment after severe head injury. It may define a therapeutic end point against which cerebral perfusion pressure (CPP) can be titrated. This study examines the relationship between cerebral blood flow (CBF) and TCD FV indices in a laboratory model before and after autoregulatory impairment. Methods CPP, CBF, and middle cerebral artery TCD FV were measured continuously in nine anesthetized and ventilated sheep. CPP was decreased by hemorrhagic hypotension. The process was repeated after impairment of autoregulation by cisternal infusion, which maintained CPP at 0 mm Hg for 15 minutes. Points of significant change (i.e., breakpoints) from baseline values for each of the measured flow parameters were identified by using a ratio of variance technique. Results Before any significant change in CBF or systolic TCD, diastolic TCD FV decreased (mean breakpoint, 69 mm Hg; range, 56-78 mm Hg) as CPP was reduced. This divergence of diastolic and systolic TCD FV, which occurred before autoregulatory failure, was associated with an increasing TCD pulsatility index (mean breakpoint, 63 mm Hg; range, 53-70 mm Hg). At diastolic TCD FV congruent with 10 cm/s, systolic TCD FV (mean breakpoint, 48 mm Hg; range, 46-53 mm Hg) and CBF (mean breakpoint, 49 mm Hg; range, 47-51 mm Hg) decreased rapidly, indicating autoregulatory failure. After autoregulatory impairment, the breakpoints for all four indices shifted to higher CPP values (mean, 16 mm Hg). Conclusion TCD FV assessment identified two CPP thresholds of autoregulatory loss. Before autoregulatory failure, an earlier phase of autoregulatory disturbance may be detected by divergent systolic and diastolic TCD FVs. It is important to note that this phase may be detected before CBF decreases. These TCD FV breakpoints depend on the state of autoregulatory impairment and may provide potential targets for CPP-directed therapy.

Preventable secondary injury remains disturbingly common and can only be reduced by highly organized and integrated services, and careful and continuous monitoring. Continuous non- or relatively non-invasive bedside monitoring of factors closely related to brain metabolism and function is becoming a practical reality. To the extent that the complex changes initiated by traumatic brain injury are ‘processes’ rather than ‘events’ it may become possible for components of injury to be halted or reversed. Pharmacological therapy given early after injury may be able to reduce the harmful events initiated by the injury. Head injury management is multidisciplinary. Improvements in head injury outcome have come about through better organisation of services — efficient retrieval, early investigation and removal of clots, and management in experienced intensive care units. Australian neurosurgeons have played a leading role in defining standards of care, in organizing services and in raising public health issues related to head injury. With the increasing and necessary involvement of other specialists and the greater dependence on technically demanding intensive monitoring and medical management, it is important that neurosurgeons remain at the forefront of the care of patients with head injury and not simply be reduced to managing the surgical complications on request.86

Axonal injury (AI), one of the principal determinants of clinical outcome after head injury, may evolve over several hours after injury, raising the future possibility of therapeutic intervention during this period. A new head impact model of AI in sheep was developed to examine pathological and physiological changes in the brain resulting from a graded traumatic insult. In this preliminary study 10 anesthetized and ventilated Merino ewes were used. Head injury was produced by impact from a humane stunner to the temporal region of an unrestrained head. Eight sheep were studied for 1, 2, 4, or 6 h after impact. Two sham animals (no impact, 6 h survival) were also examined. Arterial blood pressure, intracranial pressure, and cerebral blood flow were monitored continuously. A physiological index of injury severity was calculated by weighting the percentage shift from preinjury values for each monitored parameter over the first hour after injury. Immunostaining with amyloid precursor protein (APP) was used as a marker of axonal damage and the distribution of APP positive axons was recorded according to a sector scoring method (APPS). Widespread AI was identified in 7 of the 8 impacted animals, around cerebral contusions and in hemispheric white matter, central gray matter, brain stem, and cerebellum, and was detected as early as 1 h after injury. The degree of axonal injury (APPS) correlated well with an index of physiological response to injury (r = 0.83, p = 0.005).

The Kittlitz’s Murrelet (Brachyramphus brevirostris) is a broadly distributed but uncommon seabird species endemic to coastal Alaska and eastern Russia. Although northern Alaska constitutes a large portion of this species’ range, little is known about Kittlitz’s Murrelets in this vast region. We studied nesting activity of Kittlitz’s Murrelets in the Kakagrak Hills, Cape Krusenstern National Monument, in northern Alaska during summer 2014. Between 15 and 26 June, we located two active Kittlitz’s Murrelet nests by walking line transects in 28 sampling blocks (250 × 250 m) that were stratified by two habitat types (Alpine Alkaline Barrens and Alpine Dryas Dwarf Shrub) and selected randomly. We found one additional active nest opportunistically while walking between blocks. All three nests were located in Alpine Alkaline Barrens habitat, and all failed during the egg stage. Causes of failure were nest abandonment (n = 1), depredation (n = 1), and unknown (n = 1). Overall mean nest density was 0.80 nests/km2 (SE = 0.52). Although our sample of nests was small, our results demonstrate that Kittlitz’s Murrelets nest regularly in northern Alaska. However, the apparently low productivity raises questions about the reproductive value of this region to this cryptic and secretive species.

A prospective observational study was performed to assess the reliability of fibreoptic oximetric catheters and to identify the incidence and causes of jugular bulb oxygen desaturation in patients with acute closed head injury. There were twenty- five patients (30± 16 years) with GCS ≤8 in this study. Jugular bulb oximetry, mean arterial pressure, intracranial pressure, end-tidal CO2 and pulse oximetry were monitored continuously. Catheter calibration against a laboratory oximeter was performed post insertion and thereafter eight-hourly. Cerebral venous desaturation was defined as a jugular bulb oxygen saturation 10 minutes duration. There was a poor correlation for the first in vivo calibration (r2 = 0.602, P2 = 0.868, P Validation with a laboratory oximeter is essential prior to continuous jugular bulb oximetry. Sustained episodes of cerebral venous desaturation are frequent within the first 48 hours following acute head injury. Factors such as hypocapnia and cerebral hypoperfusion that primarily reduce cerebral blood flow are predominant.

Background Gangliogliomas are rare low grade, typically well-differentiated, tumors that are composed of mature ganglion cells and neoplastic glial cells. These tumors can appear at virtually any location along the neuroaxis but classically occur in the temporal lobe of young patients. In a small number of cases, gangliogliomas have presented as masses in the brainstem or involving cranial nerves. With the exception of vestibular schwannomas, bilateral tumors in the region of the internal auditory canal (IAC) or cerebellopontine angle (CPA) are exceedingly rare. Case description We report a case of a 58-year-old male who presented with hearing loss, tinnitus, and vertigo. Initial magnetic resonance imaging revealed bilateral nonenhancing IAC/CPA tumors. Based on this finding, a presumptive diagnosis of neurofibromatosis Type II was made, which was initially managed conservatively with close observation. He returned for follow-up with worsening vertigo and tinnitus, thus prompting the decision to proceed with surgical resection of the symptomatic mass. Intriguingly, pathological study demonstrated a WHO Grade I ganglioglioma. Description We report a case of a 58-year-old male who presented with hearing loss, tinnitus, and vertigo. Initial magnetic resonance imaging revealed bilateral nonenhancing IAC/CPA tumors. Based on this finding, a presumptive diagnosis of neurofibromatosis Type II was made, which was initially managed conservatively with close observation. He returned for follow-up with worsening vertigo and tinnitus, thus prompting the decision to proceed with surgical resection of the symptomatic mass. Intriguingly, pathological study demonstrated a WHO Grade I ganglioglioma. Conclusion This is the first reported case of bilateral IAC/CPA gangliogliomas. When evaluating bilateral IAC/CPA lesions with unusual imaging characteristics, ganglioglioma should be included in the differential diagnosis.