Natural history and growth rate of intracranial aneurysms in Loeys-Dietz syndrome: implications for treatment

OBJECTIVE

Loeys-Dietz syndrome (LDS) is a heritable aortopathy associated with craniofacial abnormalities and dilatation and dissection of the aorta and its branches, as well as increased risk for intracranial aneurysms (ICAs). Given the rarity of the disease, the authors aimed to better define the natural history and role for the treatment for ICAs in these patients.

METHODS

The medical records of 83 patients with LDS were retrospectively reviewed to obtain clinical and genetic history and vascular imaging of the aorta, aortic branches, and intracranial vessels. Serial radiology reports and cervical and intracranial vascular images were reviewed to determine presence, location, and size of ICAs.

RESULTS

In total, 55 patients (66.3%) had at least two screening intracranial vascular examinations, and 19 (22.9%) had at least 1 ICA detected. Aneurysms were typically small (mean ± SD 3.2 ± 1.8 mm). ICAs were most often located in the cavernous carotid, followed by the ophthalmic and anterior cerebral artery vessels. The rate of ICA growth was 0.43 ± 0.53 mm/year, similar to that of the general population. Three patients underwent intervention for an ICA, with 1 procedure complicated by stroke and resulting in transient hemiparesis. Several illustrative cases detail the authors' experience with ICA growth, de novo aneurysm formation, and ICA intervention in this rare patient population.

CONCLUSIONS

ICAs in patients with LDS are common, are frequently small, and have a growth rate similar to that of unruptured ICAs in the general population. More aggressive or earlier intervention for asymptomatic ICAs identified in LDS patients compared with the general population is likely unwarranted based on the authors' experience at their institution.

Non-invasive Auricular Vagus nerve stimulation for Subarachnoid Hemorrhage (NAVSaH): Protocol for a prospective, triple-blinded, randomized controlled trial

Background

Inflammation has been implicated in driving the morbidity associated with subarachnoid hemorrhage (SAH). Despite understanding the important role of inflammation in morbidity following SAH, there is no current effective way to modulate this deleterious response. There is a critical need for a novel approach to immunomodulation that can be safely, rapidly, and effectively deployed in SAH patients. Vagus nerve stimulation (VNS) provides a non-pharmacologic approach to immunomodulation, with prior studies demonstrating VNS can reduce systemic inflammatory markers, and VNS has had early success treating inflammatory conditions such as arthritis, sepsis, and inflammatory bowel diseases. The aim of the Non-invasive Auricular Vagus nerve stimulation for Subarachnoid Hemorrhage (NAVSaH) trial is to translate the use of non-invasive transcutaneous auricular VNS (taVNS) to spontaneous SAH, with our central hypothesis being that implementing taVNS in the acute period following spontaneous SAH attenuates the expected inflammatory response to hemorrhage and curtails morbidity associated with inflammatory-mediated clinical endpoints.

Materials and methods

The overall objectives for the NAHSaH trial are to 1) Define the impact that taVNS has on SAH-induced inflammatory markers in the plasma and cerebrospinal fluid (CSF), 2) Determine whether taVNS following SAH reduces radiographic vasospasm, and 3) Determine whether taVNS following SAH reduces chronic hydrocephalus. Following presentation to a single enrollment site, enrolled SAH patients are randomly assigned twice daily treatment with either taVNS or sham stimulation for the duration of their intensive care unit stay. Blood and CSF are drawn before initiation of treatment sessions, and then every three days during a patient's hospital stay. Primary endpoints include change in the inflammatory cytokine TNF-α in plasma and cerebrospinal fluid between day 1 and day 13, rate of radiographic vasospasm, and rate of requirement for long-term CSF diversion via a ventricular shunt. Secondary outcomes include exploratory analyses of a panel of additional cytokines, number and type of hospitalized acquired infections, duration of external ventricular drain in days, interventions required for vasospasm, continuous physiology data before, during, and after treatment sessions, hospital length of stay, intensive care unit length of stay, and modified Rankin Scale score (mRS) at admission, discharge, and each at follow-up appointment for up to two years following SAH.

Discussion

Inflammation plays a central role in morbidity following SAH. This NAVSaH trial is innovative because it diverges from the pharmacologic status quo by harnessing a novel non-invasive neuromodulatory approach and its known anti-inflammatory effects to alter the pathophysiology of SAH. The investigation of a new, effective, and rapidly deployable intervention in SAH offers a new route to improve outcomes following SAH.

Trial registration

Clinical Trials Registered, NCT04557618. Registered on September 21, 2020, and the first patient was enrolled on January 4, 2021.

Medical student specialty decision-making and perceptions of neurosurgery. Part 1: Role of gender

OBJECTIVE

Although women account for 50% of medical school graduates, less than 30% of neurosurgery residency applicants and less than 10% of neurosurgeons are female. In order to diversify the field of neurosurgery and recruit more women, it is necessary to understand why there is a disproportionately low entry rate into neurosurgery by female medical students. Factors contributing to specialty decision-making and perceptions of neurosurgery among medical students and residents, specifically differences by gender, have not been studied. The authors aimed to investigate these differences using quantitative and qualitative methods.

METHODS

A Qualtrics survey was administered at the authors' institution to all medical students and resident physicians to assess factors influencing medical specialty decision-making and perceptions of neurosurgery. Likert scale responses converted to numerical values on a 5-point scale were analyzed with the Mann-Whitney U-test. The chi-square test was performed on binary responses. Semistructured interviews were conducted in a subset of survey respondents and were analyzed by using the grounded theory method.

RESULTS

Of the 272 survey respondents, 48.2% were medical students and 61.0% were female. When making specialty decisions, female medical students considered maternity/paternity leave more (p = 0.028) than their male counterparts. Female medical students were more hesitant toward neurosurgery due to maternity/paternity needs (p = 0.031) and the technical skill required (p = 0.020) than male medical students. Across both genders, the majority of medical students were hesitant toward neurosurgery due to opportunities for work/life integration (93%), length of training (88%), malignancy of the field (76%), and perceived happiness of the people in the field (76%). Female residents indicated they were more likely than male residents to consider the perceived happiness of the people in the field (p = 0.003), shadowing experiences (p = 0.019), and elective rotations (p = 0.004) when making specialty decisions. Two major themes emerged from the semistructured interviews: 1) maternity needs were more of a concern for women and 2) length of training was a concern for many individuals.

CONCLUSIONS

Compared with their male counterparts, female students and residents consider different factors and experiences when choosing a medical specialty and have different perceptions of neurosurgery. Exposure to and education within neurosurgery, specifically maternity needs, may help address hesitancy in pursuing a neurosurgical career among female medical students. However, cultural and structural factors may need to be addressed within neurosurgery in order to ultimately increase representation of women.

Medical student specialty decision-making and perceptions of neurosurgery. Part 2: Role of race/ethnicity

OBJECTIVE

Although individuals underrepresented in medicine (URM) make up 33% of the United States population, only 12.6% of medical school graduates identify as URM; the same percentage of URM students comprises neurosurgery residency applicants. More information is needed to understand how URM students are making specialty decisions and their perceptions of neurosurgery. The authors aimed to evaluate the differences between URM and non-URM medical students and residents in terms of the factors that contribute to specialty decision-making and perceptions of neurosurgery.

METHODS

A survey was administered to all medical students and resident physicians at a single Midwestern institution to assess factors influencing medical student specialty decision-making and perceptions of neurosurgery. Likert scale responses converted to numerical values on a 5-point scale (strongly agree was the high score of 5) were analyzed with the Mann-Whitney U-test. The chi-square test was performed on the binary responses to examine associations between categorical variables. Semistructured interviews were conducted and analyzed using the grounded theory method.

RESULTS

Of 272 respondents, 49.2% were medical students, 51.8% were residents, and 11.0% identified as URM. URM medical students considered research opportunities more than non-URM medical students in specialty decision-making (p = 0.023). When specialty decision-making factors were assessed, URM residents less strongly considered the technical skill required (p = 0.023), their perceived fit in the field (p < 0.001), and seeing people like them in the field (p = 0.010) than their non-URM counterparts when making specialty decisions. Within both medical student and resident respondent cohorts, the authors found no significant differences between URM and non-URM respondents in terms of their specialty decision-making being affected by medical school experiences such as shadowing, elective rotations, family exposure, or having a mentor in the field. URM residents were more concerned about the opportunity to work on health equity issues in neurosurgery than non-URM residents (p = 0.005). The predominant theme that emerged from interviews was the need for more intentional efforts to recruit and retain URM individuals in medicine and specifically neurosurgery.

CONCLUSIONS

URM students may make specialty decisions differently than non-URM students. URM students were more hesitant toward neurosurgery due to their perceived lack of opportunity for health equity work in neurosurgery. These findings further inform optimization of both new and existing initiatives to improve URM student recruitment and retention in neurosurgery.

Deep Learning Segmentation of the Nucleus Basalis of Meynert on 3T MRI

BACKGROUND AND PURPOSE

The nucleus basalis of Meynert is a key subcortical structure that is important in arousal and cognition and has been explored as a deep brain stimulation target but is difficult to study due to its small size, variability among patients, and lack of contrast on 3T MR imaging. Thus, our goal was to establish and evaluate a deep learning network for automatic, accurate, and patient-specific segmentations with 3T MR imaging.

MATERIALS AND METHODS

Patient-specific segmentations can be produced manually; however, the nucleus basalis of Meynert is difficult to accurately segment on 3T MR imaging, with 7T being preferred. Thus, paired 3T and 7T MR imaging data sets of 21 healthy subjects were obtained. A test data set of 6 subjects was completely withheld. The nucleus was expertly segmented on 7T, providing accurate labels for the paired 3T MR imaging. An external data set of 14 patients with temporal lobe epilepsy was used to test the model on brains with neurologic disorders. A 3D-Unet convolutional neural network was constructed, and a 5-fold cross-validation was performed.

RESULTS

The novel segmentation model demonstrated significantly improved Dice coefficients over the standard probabilistic atlas for both healthy subjects (mean, 0.68 [SD, 0.10] versus 0.45 [SD, 0.11], P = .002, t test) and patients (0.64 [SD, 0.10] versus 0.37 [SD, 0.22], P < .001). Additionally, the model demonstrated significantly decreased centroid distance in patients (1.18 [SD, 0.43] mm, 3.09 [SD, 2.56] mm, P = .007).

CONCLUSIONS

We developed the first model, to our knowledge, for automatic and accurate patient-specific segmentation of the nucleus basalis of Meynert. This model may enable further study into the nucleus, impacting new treatments such as deep brain stimulation.

Toward rational use of repeat imaging in children with mild traumatic brain injuries and intracranial injuries

OBJECTIVE

Limited evidence exists on the utility of repeat neuroimaging in children with mild traumatic brain injuries (mTBIs) and intracranial injuries (ICIs). Here, the authors identified factors associated with repeat neuroimaging and predictors of hemorrhage progression and/or neurosurgical intervention.

METHODS

The authors performed a multicenter, retrospective cohort study of children at four centers of the Pediatric TBI Research Consortium. All patients were ≤ 18 years and presented within 24 hours of injury with a Glasgow Coma Scale score of 13-15 and evidence of ICI on neuroimaging. The outcomes of interest were 1) whether patients underwent repeat neuroimaging during index admission, and 2) a composite outcome of progression of previously identified hemorrhage ≥ 25% and/or repeat imaging as an indication for subsequent neurosurgical intervention. The authors performed multivariable logistic regression and report odds ratios and 95% confidence intervals.

RESULTS

A total of 1324 patients met inclusion criteria; 41.3% of patients underwent repeat imaging. Repeat imaging was associated with clinical change in 4.8% of patients; the remainder of the imaging tests were for routine surveillance (90.9%) or of unclear prompting (4.4%). In 2.6% of patients, repeat imaging findings were reported as an indication for neurosurgical intervention. While many factors were associated with repeat neuroimaging, only epidural hematoma (OR 3.99, 95% CI 2.22-7.15), posttraumatic seizures (OR 2.95, 95% CI 1.22-7.41), and age ≥ 2 years (OR 2.25, 95% CI 1.16-4.36) were significant predictors of hemorrhage progression and/or neurosurgery. Of patients without any of these risk factors, none underwent neurosurgical intervention.

CONCLUSIONS

Repeat neuroimaging was commonly used but uncommonly associated with clinical deterioration. Although several factors were associated with repeat neuroimaging, only posttraumatic seizures, age ≥ 2 years, and epidural hematoma were significant predictors of hemorrhage progression and/or neurosurgery. These results provide the foundation for evidence-based repeat neuroimaging practices in children with mTBI and ICI.

Co-occurrence of subcutaneous myxopapillary ependymoma, dermal sinus tract, and filum terminale lipoma: a review of the pathobiology of caudal spinal cord development and spinal cord tethering. Illustrative case

BACKGROUND

Myxopapillary ependymoma (MPE) is typically benign and found in the conus medullaris and/or filum terminale, although rare cases of subcutaneous and extra-axial MPE have been reported. The co-occurrence of MPE, tethered cord syndrome (TCS) with lipoma of the filum terminale, and a dermal sinus tract is extremely rare, with only 6 reported cases in the literature. Here, the authors present the first case, to their knowledge, of an extra-axial, subcutaneous MPE co-presenting with TCS, lipoma of the filum terminale, and a dermal sinus tract and discuss the underlying pathobiology.

OBSERVATIONS

A 14-month-old male who presented for evaluation of a dermal sinus tract underwent magnetic resonance imaging, which revealed a tethered cord with associated lipoma. At 14 months, the patient underwent spinal cord detethering with resection of his sacral dimple and sinus tract. Histopathological evaluation revealed an incidentally found MPE within the dermal sinus tract.

LESSONS

The authors review the underlying biology of MPEs, tethered cord syndrome, and dermal sinus tracts, and explore possible points of convergence within the developmental pathways that may result in this unique concomitant presentation. Additionally, they suggest that extra-axial MPE may be underappreciated and underdiagnosed; this case suggests that extra-axial MPE may be only effectively diagnosed with histological studies.

Cystic dissemination of choroid plexus papilloma: illustrative cases

BACKGROUND

Choroid plexus papillomas are benign tumors of the choroid plexus. Although typically focal, they can metastasize. Rarely, patients may present with numerous cystic lesions throughout the craniospinal axis.

OBSERVATIONS

The authors present three cases of pathologically confirmed fourth ventricular World Health Organization (WHO) grade 1 choroid plexus papillomas presenting with numerous cystic lesions throughout the craniospinal axis. Two cases were treated with only resection of the fourth ventricular mass; one was treated with a partial cyst fenestration. During follow-up, there was only mild interval growth of the cystic lesions over time, and all patients remained asymptomatic from their cystic lesions. The authors summarize five additional cases of cystic dissemination in the published literature and discuss hypotheses for the pathophysiology of this rare presentation.

LESSONS

Choroid plexus papillomas may present with numerous, widely disseminated cystic lesions within the craniospinal axis. Thus, the authors recommend preoperative and routine imaging of the entire neuroaxis in patients with choroid plexus tumors, regardless of WHO grade. Although the role of adjuvant therapy and cyst fenestration in the treatment of these lesions remains unclear, watchful waiting may be indicated, especially in asymptomatic patients, because the lesions often demonstrate slow, if any, growth over time.

Relationship between phenotypic features in Loeys-Dietz syndrome and the presence of intracranial aneurysms

OBJECTIVE

Loeys-Dietz syndrome (LDS) is a rare autosomal dominant condition characterized by aneurysms of the aorta, aortic branches, and intracranial arteries; skeletal and cutaneous abnormalities; and craniofacial malformations. Previous authors have reported that higher craniofacial severity index (CFI) scores, which indicate more severe craniofacial abnormalities, correlate with the severity of aortic aneurysm pathology. However, the association between syndromic features and the formation of intracranial aneurysms in LDS patients has yet to be determined. In this study, the authors evaluate the incidence of phenotypic abnormalities, craniofacial features, and Chiari malformation type I (CM-I) in a large LDS cohort and explore possible risk factors for the development of intracranial aneurysms.

METHODS

This was a retrospective cohort study of all patients with LDS who had been seen at the Marfan Syndrome and Aortopathy Center at Washington University School of Medicine in St. Louis in 2010–2022. Medical records were reviewed to obtain demographic, clinical, and radiographic data. The prevalence of craniofacial, skeletal, and cutaneous pathologies was determined. Bivariate logistic regression was performed to identify possible risk factors for the formation of an intracranial aneurysm.

RESULTS

Eighty-one patients with complete medical records and intracranial vascular imaging were included in the analysis, and 18 patients (22.2%) had at least 1 intracranial aneurysm. Patients frequently demonstrated the thin or translucent skin, doughy skin texture, hypertelorism, uvular abnormalities, and joint hypermobility typical of LDS. CM-I was common, occurring in 7.4% of the patients. Importantly, the patients with intracranial aneurysms were more likely to have CM-I (22.2%) than those without intracranial aneurysms (3.2%). The mean CFI score in the cohort with available data was 1.81, with higher means in the patients with the TGFBR1 or TGFBR2 disease-causing variants (2.05 and 3.30, respectively) and lower in the patients with the SMAD3, TGFB2, or TGFB3 pathogenic variants (CFI < 1). No significant CFI difference was observed in patients with or without intracranial aneurysms (2.06 vs 1.74, p = 0.61).

CONCLUSIONS

CM-I, and not the CFI, is significantly associated with the presence of intracranial aneurysms in patients with LDS. Surveillance for intracranial aneurysms is essential in all patients with LDS and should not be limited to those with severe phenotypes. Long-term monitoring studies will be necessary to determine whether a correlation between craniofacial abnormalities and adverse outcomes from intracranial aneurysms (growth, intervention, or rupture) exists.

Measures of Intracranial Injury Size Do Not Improve Clinical Decision Making for Children With Mild Traumatic Brain Injuries and Intracranial Injuries

BACKGROUND

When evaluating children with mild traumatic brain injuries (mTBIs) and intracranial injuries (ICIs), neurosurgeons intuitively consider injury size. However, the extent to which such measures (eg, hematoma size) improve risk prediction compared with the kids intracranial injury decision support tool for traumatic brain injury (KIIDS-TBI) model, which only includes the presence/absence of imaging findings, remains unknown.

OBJECTIVE

To determine the extent to which measures of injury size improve risk prediction for children with mild traumatic brain injuries and ICIs.

METHODS

We included children ≤18 years who presented to 1 of the 5 centers within 24 hours of TBI, had Glasgow Coma Scale scores of 13 to 15, and had ICI on neuroimaging. The data set was split into training (n = 1126) and testing (n = 374) cohorts. We used generalized linear modeling (GLM) and recursive partitioning (RP) to predict the composite of neurosurgery, intubation >24 hours, or death because of TBI. Each model's sensitivity/specificity was compared with the validated KIIDS-TBI model across 3 decision-making risk cutoffs (<1%, <3%, and <5% predicted risk).

RESULTS

The GLM and RP models included similar imaging variables (eg, epidural hematoma size) while the GLM model incorporated additional clinical predictors (eg, Glasgow Coma Scale score). The GLM (76%-90%) and RP (79%-87%) models showed similar specificity across all risk cutoffs, but the GLM model had higher sensitivity (89%-96% for GLM; 89% for RP). By comparison, the KIIDS-TBI model had slightly higher sensitivity (93%-100%) but lower specificity (27%-82%).

CONCLUSION

Although measures of ICI size have clear intuitive value, the tradeoff between higher specificity and lower sensitivity does not support the addition of such information to the KIIDS-TBI model.

Laser Interstitial Thermal Therapy in Grade 2/3 IDH1/2 Mutant Gliomas: A Preliminary Report and Literature Review

Laser interstitial thermal therapy (LITT) has become an increasingly utilized alternative to surgical resection for the treatment of glioma in patients. However, treatment outcomes in isocitrate dehydrogenase 1 and 2 (IDH1/2) mutant glioma, specifically, have not been reported. The objective of this study was to characterize a single institution’s cohort of IDH1/2 mutant grade 2/3 glioma patients treated with LITT. We collected data on patient presentation, radiographic features, tumor molecular profile, complications, and outcomes. We calculated progression-free survival (PFS) and tested factors for significant association with longer PFS. Overall, 22.7% of our cohort experienced progression at a median follow up of 1.8 years. The three- and five-year estimates of PFS were 72.5% and 54.4%, respectively. This is the first study to characterize outcomes in patients with IDH1/2 mutant glioma after LITT. Our results suggest that LITT is an effective treatment option for IDH1/2 mutant glioma.

Representation of female neurosurgeons as abstract authors at neurological surgery conferences

OBJECTIVE

Female neurosurgeon representation has increased, but women still represent only 8.4% of neurosurgeons in the US. Women are significantly underrepresented as authors in neurosurgical and spine journals, a key indicator of professional success in academic medicine. In this study, the authors aimed to assess the gender diversity of first and last authors of accepted abstracts at neurosurgical conferences in 2015 and 2019.

METHODS

Annual meeting abstracts for 2015 and 2019 of the American Association of Neurological Surgeons (AANS), Congress of Neurological Surgeons (CNS), and pediatrics, spine, stereotactic and functional surgery, and cerebrovascular AANS/CNS subspecialty sections were obtained and analyzed for gender. Partial data were obtained for tumor and pain sections. Composite gender data were obtained from the societies. Percentage differences were calculated using comparison of proportions testing.

RESULTS

Overall, female neurosurgeons accounted for only 8.3% of first and 5.8% of last authors, and 7.2% of authors overall. The pediatrics section had the highest proportion of female neurosurgeons as first (13.7%) and last (12.4%) abstract authors, while the spine section had the lowest proportions of female neurosurgeon first (4.6%) and last (2.0%) authors. Qualitatively, a higher proportion of women were first authors, while a higher proportion of men were last authors. Overall, there was no significant change in female neurosurgeon authorship between 2015 and 2019. With regard to society demographics, female neurosurgeons accounted for only 6.3% of AANS membership. The pediatrics section had the highest proportion of female neurosurgeons at 18.1% and the stereotactic and functional surgery section had the lowest of the subspecialty sections (7.6%). While female neurosurgeons represented 12.6% of spine section membership, they represented only 4.7% of first authors (-7.9% difference; p < 0.0001) and 2.4% of last authors (-10.2% difference; p < 0.0001). For the 2019 cerebrovascular section, female neurosurgeons were underrepresented as presenting authors (5.8%) compared with their membership representation (14.8%, -9.0% difference; p = 0.0018).

CONCLUSIONS

Despite an increase in the number of female neurosurgeons, there has not been a corresponding increase in the proportion of female neurosurgeons as abstract authors at annual neurosurgery conferences, and female neurosurgeons remain underrepresented as authors compared with their male colleagues.

Occipital-Cervical Fusion and Ventral Decompression in the Surgical Management of Chiari-1 Malformation and Syringomyelia: Analysis of Data From the Park-Reeves Syringomyelia Research Consortium

BACKGROUND

Occipital-cervical fusion (OCF) and ventral decompression (VD) may be used in the treatment of pediatric Chiari-1 malformation (CM-1) with syringomyelia (SM) as adjuncts to posterior fossa decompression (PFD) for complex craniovertebral junction pathology.

OBJECTIVE

To examine factors influencing the use of OCF and OCF/VD in a multicenter cohort of pediatric CM-1 and SM subjects treated with PFD.

METHODS

The Park-Reeves Syringomyelia Research Consortium registry was used to examine 637 subjects with cerebellar tonsillar ectopia ≥ 5 mm, syrinx diameter ≥ 3 mm, and at least 1 yr of follow-up after their index PFD. Comparisons were made between subjects who received PFD alone and those with PFD + OCF or PFD + OCF/VD.

RESULTS

All 637 patients underwent PFD, 505 (79.2%) with and 132 (20.8%) without duraplasty. A total of 12 subjects went on to have OCF at some point in their management (PFD + OCF), whereas 4 had OCF and VD (PFD + OCF/VD). Of those with complete data, a history of platybasia (3/10, P = .011), Klippel-Feil (2/10, P = .015), and basilar invagination (3/12, P < .001) were increased within the OCF group, whereas only basilar invagination (1/4, P < .001) was increased in the OCF/VD group. Clivo-axial angle (CXA) was significantly lower for both OCF (128.8 ± 15.3°, P = .008) and OCF/VD (115.0 ± 11.6°, P = .025) groups when compared to PFD-only group (145.3 ± 12.7°). pB-C2 did not differ among groups.

CONCLUSION

Although PFD alone is adequate for treating the vast majority of CM-1/SM patients, OCF or OCF/VD may be occasionally utilized. Cranial base and spine pathologies and CXA may provide insight into the need for OCF and/or OCF/VD.

Effect of dose rate on residual γ-H2AX levels and frequency of micronuclei in X-irradiated mouse lymphocytes

The biological risks associated with low-dose-rate (LDR) radiation exposures are not yet well defined. To assess the risk related to DNA damage, we compared the yields of two established biodosimetry end points, γ-H2AX and micronuclei (MNi), in peripheral mouse blood lymphocytes after prolonged in vivo exposure to LDR X rays (0.31 cGy/min) vs. acute high-dose-rate (HDR) exposure (1.03 Gy/min). C57BL/6 mice were total-body irradiated with 320 kVP X rays with doses of 0, 1.1, 2.2 and 4.45 Gy. Residual levels of total γ-H2AX fluorescence in lymphocytes isolated 24 h after the start of irradiation were assessed using indirect immunofluorescence methods. The terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay was used to determine apoptotic cell frequency in lymphocytes sampled at 24 h. Curve fitting analysis suggested that the dose response for γ-H2AX yields after acute exposures could be described by a linear dependence. In contrast, a linear-quadratic dose-response shape was more appropriate for LDR exposure (perhaps reflecting differences in repair time after different LDR doses). Dose-rate sparing effects (P < 0.05) were observed at doses ≤2.2 Gy, such that the acute dose γ-H2AX and TUNEL-positive cell yields were significantly larger than the equivalent LDR yields. At the 4.45 Gy dose there was no difference in γ-H2AX expression between the two dose rates, whereas there was a two- to threefold increase in apoptosis in the LDR samples compared to the equivalent 4.45 Gy acute dose. Micronuclei yields were measured at 24 h and 7 days using the in vitro cytokinesis-blocked micronucleus (CBMN) assay. The results showed that MNi yields increased up to 2.2 Gy with no further increase at 4.45 Gy and with no detectable dose-rate effect across the dose range 24 h or 7 days post exposure. In conclusion, the γ-H2AX biomarker showed higher sensitivity to measure dose-rate effects after low-dose LDR X rays compared to MNi formation; however, confounding factors such as variable repair times post exposure, increased cell killing and cell cycle block likely contributed to the yields of MNi with accumulating doses of ionizing radiation.

Ion, X-ray, UV and Neutron Microbeam Systems for Cell Irradiation

The array of microbeam cell-irradiation systems, available to users at the Radiological Research Accelerator Facility (RARAF), Center for Radiological Research, Columbia University, is expanding. The HVE 5MV Singletron particle accelerator at the facility provides particles to two focused ion microbeam lines: the sub-micron microbeam II and the permanent magnetic microbeam (PMM). Both the electrostatic quadrupole lenses on the microbeam II system and the magnetic quadrupole lenses on the PMM system are arranged as compound lenses consisting of two quadrupole triplets with "Russian" symmetry. Also, the RARAF accelerator is a source for a proton-induced x-ray microbeam (undergoing testing) and is projected to supply protons to a neutron microbeam based on the (7)Li(p, n)(7)Be nuclear reaction (under development). Leveraging from the multiphoton microscope technology integrated within the microbeam II endstation, a UV microspot irradiator - based on multiphoton excitation - is available for facility users. Highlights from radiation-biology demonstrations on single living mammalian cells are included in this review of microbeam systems for cell irradiation at RARAF.

Risk management in international manned space program operations

New, innovative joint safety policies and requirements were developed in support of the Shuttle/Mir program, which is the first phase of the International Space Station program. This work has resulted in a joint multinational analysis culminating in joint certification for mission readiness. For these planning and development efforts, each nation's risk programs and individual safety practices had to be integrated into a comprehensive and compatible system that reflects the joint nature of the endeavor. This paper highlights the major incremental steps involved in planning and program integration during development of the Shuttle/Mir program. It traces the transition from early development to operational status and highlights the valuable lessons learned that apply to the International Space Station program (Phase 2). Also examined are external and extraneous factors that affected mission operations and the corresponding solutions to ensure safe and effective Shuttle/Mir missions.

A microdosimetry chamber for low-energy X rays

A wall-less proportional counter designed to measure single event spectra produced by low energy X rays is described. The sensitive volume of the counter and the housing are made entirely of non-metallic materials to minimise distortions in the secondary electron spectrum.

Evaluation of the immunomodulatory effects of the disinfection by-product, sodium chlorite, in female B6C3F1 mice: a drinking water study

Sodium chlorite is an inorganic by-product of chlorine dioxide formed during the chlorination of drinking water. Relatively little is known about the adverse health effects of exposure to sodium chlorite in drinking water. In this study, we evaluated sodium chlorite's immunomodulatory properties using female B6C3F1 mice and a panel of immune assays that were designed to evaluate potential changes in innate and acquired cellular and humoral immune responses. Female B6C3F1 mice were exposed to sodium chlorite in their drinking water (0, 0.1, 1, 5, 15, and 30 mg/L) for 28 days, and then evaluated for immunomodulation. Overall, minimal toxicological and immunological changes were observed after exposure to sodium chlorite. Increases in the percentages of blood reticulocytes, and the relative spleen weights were both observed at different sodium chlorite treatment levels; however, these increases were not dose-dependent. An increasing trend in the number of spleen antibody-forming cells was observed over the range of sodium chlorite concentrations. This increase was not, however, significant at any individual treatment level, and was not reflected by changes in serum IgM levels. A significant increase (26%) in the total number of splenic CD8+ cells was observed in mice treated with 30 mg/L of sodium chlorite, but not at the other concentrations. Splenic mixed leukocyte response and peritoneal macrophage activity were unaffected by sodium chlorite. Lastly, exposure to sodium chlorite did not affect natural killer cell activity, although a decrease in augmented natural killer cell activity (42%) was observed at the lowest sodium chlorite treatment level. These results suggest that sodium chlorite, within the range 0.1-30 mg/L, produces minimal immunotoxicity in mice.

Methylene group modifications of the N-(Isothiazol-5-yl)phenylacetamides. Synthesis and insecticidal activity

It has been shown that oxidation at the alpha-carbon of N-(4-chloro-3-methyl-5-isothiazolyl)-2-[p-[(alpha,alpha, alpha-trifluoro-p-tolyl)oxy]phenyl]acetamide (1) is conveniently brought about using dimethylformamide dimethylacetal to give N-(4-chloro-3-methyl-5-isothiazolyl)-beta-(dimethylamino)-p-[(alpha, alpha,alpha-trifluoro-p-tolyl)oxy]atropamide (2), which has served as a common starting point for a variety of functional group transformations. These transformations were found to proceed in moderate to good yields to give derivatives of 1 that retained much of the efficacy associated with the parent amide and have allowed for an expansion of the SAR to be developed. Examples of enamines, enols, enol (thio)ethers, oximes, and hydrazones were prepared. In particular, the enamines derived from low molecular weight amines and amino acids were most active as broad-spectrum insecticides and were found to be even more active than 1 on root-knot nematode.

Intermittent pneumatic compression of legs increases microcirculation in distant skeletal muscle

Intermittent pneumatic compression has been established as a method of clinically preventing deep vein thrombosis, but the mechanism has not been documented. This study observed the effects of intermittent pneumatic compression of legs on the microcirculation of distant skeletal muscle. The cremaster muscles of 80 male rats were exposed, a specially designed intermittent pneumatic-compression device was applied to both legs for 60 minutes, and the microcirculation of the muscles was assessed by measurement of the vessel diameter in three categories (10-20, 21-40, and 41-70 microm) for 120 minutes. The results showed significant vasodilation in arterial and venous vessels during the application of intermittent pneumatic compression, which disappeared after termination of the compression. The vasodilation reached a maximum 30 minutes after initiation of the compression and could be completely blocked by an inhibitor of nitric oxide synthase, NG-monomethyl-L-arginine (10 micromol/min). A 120-minute infusion of NG-monomethyl-L-arginine, beginning coincident with 60 minutes of intermittent pneumatic compression, resulted in a significant decrease in arterial diameter that remained at almost the same level after termination of the compression. The magnitude of the decrease in diameter in the group treated with intermittent pneumatic compression and NG-monomethyl-L-arginine was comparable with that in the group treated with NG-monomethyl-L-arginine alone. The results imply that the production of nitric oxide is involved in the positive influence of intermittent pneumatic compression on circulation. It is postulated that the rapid increase in venous velocity induced by intermittent pneumatic compression produces strong shear stress on the vascular endothelium, which stimulates an increased release of nitric oxide and thereby causes systemic vasodilation.

Nitrous oxide inhalation as an adjunct to intravenous induction of general anaesthesia with propofol for day surgery

Fifty patients were randomly allocated to receive either a preinduction inhalation with nitrous oxide (50%) in oxygen or fentanyl with preoxygenation, before induction of anaesthesia with propofol. Both groups of patients showed a significant rise in arterial oxygen saturation prior to propofol induction which established similar depths of anaesthesia, determined by the acceptability of the laryngeal mask placement. In the fentanyl group there was a significant period of apnoea after induction, with 40% of the patients being apnoeic for 120s or more and requiring assisted ventilation. Reduction in arterial blood pressure was also more rapid in the fentanyl group compared with the nitrous oxide group. Preinduction inhalation of nitrous oxide (50%) in oxygen appears to be an effective and acceptable method of preoxygenating the patient and augmenting the propofol induction of anaesthesia.

Quantitative comparisons of continuous and pulsed low dose rate regimens in a model late-effect system

PURPOSE

There is increasing interest and usage of pulsed low dose rate (PDR) brachytherapy, in which a single source is shuttled through the catheters of an implant, typically for about 10 min each hour. This study was designed to compare the late effects produced in various PDR regimens with those from the corresponding continuous low dose rate (CLDR) regimens.

METHODS AND MATERIALS

A model late-responding system was used, namely, cataract induction in the rat lens. This system has the advantage of being highly quantifiable. The rats eyes were exposed to a total dose of 15 Gy either continuously over 24 h, or with three different PDR regimens, all with the same total dose and overall time. We addressed three questions: (a) are late effects increased when a CLDR regimen is replaced with 10-min pulses repeated every hour? (b) Are late effects increased if hourly 10-min pulses are replaced with 10-min pulses repeated every 4 h? (c) Are late effects increased if 10-min pulses are replaced with 100-s pulses?

RESULTS

We found that the four regimens under test, continuous, 10-min pulses each hour, 10-min pulses every 4 h, and 100-s pulses every hour, showed no significant differences in cataractogenic potential, as estimated with the Wilcoxon-Gehan test. Power tests indicated that the experimental design was adequate to detect relatively small differences in cataractogenicity between regimens.

CONCLUSIONS

The equality of late effects from CLDR and PDR in these experiments must imply that sublethal damage repair is quite slow in this model late-responding system, in agreement with trends observed in the clinic for sublethal damage repair of late sequelae. Such trends would suggest that PDR is unlikely to produce significantly worse late effects than the corresponding CLDR regimen, which is in agreement with early clinical data using PDR. Caution, however, is strongly recommended.

The endoscopic breast augmentation: the transumbilical insertion of saline-filled breast implants

Initial aesthetic breast augmentation with inflatable saline implants has always had the distinct advantage of insertion through a small breast or axillary skin incision. Adapting established techniques utilized in suction-assisted lipectomy, operative endoscopy, and tissue expansion with inflatable saline implants, breast augmentation is possible through an umbilical incision. Under general anesthesia, an incision is made in the umbilicus; a new tubular instrument with an obturator [designated an endotube (Johnson) or mammascope (Christ)] is inserted into the umbilical incision like a suction cannula; it is pushed over the abdominal fascia across the costal margin until it literally pops under the breast fascia; through this tunnel is then inserted an implant coiled like a tobacco leaf; the implant is then inflated to 50 percent more than the final volume and manipulated to help expand the pocket; finally, the excess volume is removed, methyl-prednisolone acetate is placed in the final volume, and the fill tube is removed. The endoscope (laparoscope) is utilized to visualize positioning and to document the absence of bleeding. The umbilical incision is closed after insertion of both implants through the same incision. A series of 91 young women have undergone this procedure with 188 breast implantations without significant bleeding. Implants appear to ride high initially, but they settle into place by 6 weeks. Patients have reported less chest discomfort and some visible temporary upper abdominal swelling. The long-term follow-up is currently being monitored.

Radio-frequency ablation: effect of voltage and pulse duration on canine myocardium

The purpose of this investigation was to examine in vivo the relationship of radio-frequency (RF) pulse voltage and duration on the volume of tissue injury. RF 500-kHz pulses of 20-, 40-, and 60-V amplitude (RMS) were applied to the epicardium of 18 dogs for pulsing periods of 5-20 s. Systematic and quantitative tissue analysis was then performed after 30 days. No chronic lesions were evident on microscopic examination for 20-V RF pulse applications up to 15 s. Application of 20-V pulses for 20 s produced small lesions having a volume of 2.4 +/- 0.7 mm3. At 40 V, the volume of tissue injury ranged from 39.1 +/- 10.3 mm3 for 5 s of pulse application to 128.8 +/- 24.8 mm3 for 20 s of pulse application. Over the first 15 s of 40-V pulse application, the volume of tissue injury increased as pulse application time increased. There was no further increase in tissue injury for 40-V pulsing durations greater than 15 s. At 60 V, volumes of tissue injury ranged from 122.7 +/- 33.5 mm3 at 5 s to 313.6 +/- 73.7 mm3 at 20 s. Lesion size increased significantly for pulse durations of up to 10 s. Thereafter, 60-V pulses yielded little increase in tissue injury. In addition, persistent 60-V pulsing for periods greater than 9 s duration resulted in arcing and tissue vaporization in 28% of the applications. Thus RF energy is limited in its ability to create safe and effective tissue injury.(ABSTRACT TRUNCATED AT 250 WORDS)

A bridge to the community for extended-care state hospital patients

In early 1988 a discharge assessment team surveyed the records of 421 extended-care patients at Washington's Western State Hospital to facilitate planning for patients who were able to move out of the hospital. The group as a whole manifested serious problem behaviors, both current and past. Less than 40 percent of the patients needed continued state hospital care, but most who could be discharged to the community would require intensive residential supervision and support. The authors review linkages between two kinds of residential treatment programming that exists for this population, a network of community residential treatment facilities operated by private providers and community mental health centers and a hospital-based transitional program called the Program for Adaptive Living Skills. Linkages between these programs have proved useful in the residential placement of extended-care patients.

Axillobrachial artery bypass grafting with in situ cephalic vein for axillary artery occlusion: a case report

The cephalic vein has been reported to be a suitable vascular conduit for arterial reconstructive surgery, but its use remains controversial. When used for lower extremity revascularization, its use has been complicated by elongation and dilation. Its use for upper extremity revascularization has only been rarely reported. This article represents the first published use of the cephalic vein with the in situ technique for upper extremity occlusive disease. This technique may avoid some of the complications noted when used in the reverse fashion.

Effect of voltage and charge of electrical ablation pulses on canine myocardium

Multiple paired lesions produced by a train of high-voltage low-charge rectangular pulses (20 A, 30 microsecond) and a train of low-voltage high-charge rectangular pulses (2 A, 300 microsecond) were made to the left ventricular epicardium of 23 dogs to determine the relative influence of voltage and charge delivery on injury of canine myocardium. Both pulsing methods contained equal amounts of energy (15 J) delivered over equal periods of time (100 ms), and both pulsing methods were nonarcing and therefore nonbarotraumatic. The volume of cardiac tissue injury resulting from both types of pulses was then evaluated from planimetered serial histological sections after 1, 10, and 30 days. Over the 30-day period, lesion size progressively decreased to 56% of its original value for the high-voltage low-charge pulse. In contrast, lesion size from the low-voltage high-charge pulse remained relatively constant, decreasing only 12% of its original value. These results indicate that when energy delivery is held constant, voltage, not charge, is the dominant mediator of cell injury. Also, cells subjected to high voltages appear to recover partially over time with significantly less constancy of tissue injury than that seen with low-voltage high-charge pulses.

The prevention of plasticizer migration into nutritional emulsion mixtures by use of a novel container

The presence of di-(2-ethylhexyl)phthalate in poly (vinyl chloride) has led to concern regarding the potential for plasticizer migration from this widely used material into fluids for infusion, particularly nutritional admixtures containing lipid. A novel container is reported which combines the advantages and versatility of poly(vinyl chloride) without the disadvantage of plasticizer migration into the infused fluid.

Selective, stability-indicating assay of the major ipecacuanha alkaloids, emetine and cephaeline, in pharmaceutical preparations by high-performance liquid chromatography using spectrofluorimetric detection

A selective high-performance liquid chromatographic procedure has been developed for the determination of the major Ipecacuanha alkaloids, emetine and cephaeline, in a number of linctus and pastille preparations. The reversed-phase chromatographic procedure uses an octadecyl-bonded column with a mobile phase of aqueous methanol containing an ion-pairing reagent. A spectrofluorimetric detector is used for increased sensitivity and selectivity. Sample preparation is simple, involving either straight dilution for linctus formulations or simple dissolutions for pastilles. The procedure has been shown to be stability-indicating. Validation studies, to show that the method is precise, accurate and rectilinear, have been carried out on four linctus formulations and two pastille formulations. The method has been used to determine both emetine and cephaeline at levels as low as 5 micrograms/g in formulations.

Fat embolism after liposuction

We present a case of adult respiratory distress syndrome (ARDS) after extensive liposuction. On the basis of fever, tachypnea, hypoxia, and ARDS occurring within 48 hours after surgery without evidence of cardiogenic pulmonary edema or sepsis, the etiology is believed to be fat embolism. Although liposuction is generally an effective and safe procedure, awareness of this life-threatening complication is important in order to institute prompt and appropriate treatment. Fat embolism must be differentiated from thromboembolism, as the treatment is different, and heparin is not indicated. It is recommended that training standards and guidelines be devised in order to reduce morbidity and mortality associated with this procedure.

Post-heparin triacylglycerol lipases in ovine plasma

Lipoprotein lipase and hepatic lipase have been shown to be present in the post-heparin plasma of sheep. Intravenous injection of heparin into sheep produced a rapid increase in the free fatty acid concentration and lipolytic enzyme activity of the plasma, both peaking within 5-15 min and then falling to pre-heparin levels within 30-60 min. Lipolytic activity was not detected in plasma before heparin treatment. Two distinct lipolytic activities were separated from the plasma by chromatography on heparin-Sepharose 6B. Lipoprotein lipase was identified on the basis that the lipolytic activity was dependent upon the addition of plasma, inhibited by 1M NaCl, and inhibited by a specific antiserum against lipoprotein lipase. The second lipolytic activity of plasma was identified as hepatic lipase, as it was not dependent upon plasma for activity, nor was it inhibited by 1M NaCl or antiserum against lipoprotein lipase. Its properties were identical to the lipase extracted from the liver of sheep. Lipoprotein-lipase activity, but not hepatic-lipase activity, was dependent upon the nutritional state of the sheep at the time of heparin injection. However, hepatic lipase comprised a significant proportion of the total lipolytic activity.

cDNA cloning and chromosomal localization (4q11-13) of a gene for statherin, a regulator of calcium in saliva

On the basis of the known amino acid sequence of statherin, a human salivary protein, mixed synthetic oligonucleotides were synthesized and used to screen a cDNA library constructed from human parotid-gland mRNA. A cDNA clone coding for statherin was isolated from this library and has been completely sequenced. The cDNA represents a full-length (or nearly full-length) copy of an approximately 640-bp statherin mRNA. Statherin appears to be coded by a single-copy gene that maps to chromosome 4q11-4q13 when somatic-cell hybrids are used.

The value of prophylactic antibiotics during the insertion of long-term indwelling silastic right atrial catheters in cancer patients

Over a 3.5 year period from August 1982 to December 1985, 200 Hickman catheters (Evermed, Medina, WA) were inserted into patients at the King Faisal Specialist Hospital and Research Centre (KFSHRC), Riyadh, Saudi Arabia. One hundred sixty catheters were placed in patients with malignant disease, many of whom were immunosuppressed at the time of catheter insertion. Seventy of 160 (44%) patients received prophylactic antibiotics and 90 (56%) did not. The mean age of each group was 23 years (range, 2 to 70 years), and the patients in each group were statistically similar in sex, underlying disease, and routine preoperative hematologic and biochemical evaluation. Exit-site wound infections occurred in 50 of 90 (55.5%) patients who did not receive prophylaxis and in 12 of 70 (17%) patients who received prophylaxis (P less than 0.0001). There was no statistically significant difference in the incidence of tunnel and incision site infections. The mean duration of antibiotic prophylaxis was 2.9 days (SD, 1.2 days). Organisms cultured from catheter associated infections, included Staphylococcus epidermidis 36, S. aureus 30, Klebsiella pneumoniae 1, Pseudomonas aeruginosa 3, Escherichia coli 1, and diphtheroids non-CDC-JK 3. Vancomycin was used as antibiotic prophylaxis in 64 patients, Kefzol (Eli Lilly, Indianapolis, IN) in one, oxacillin in three, nafcillin in one, and Septra (Burroughs Wellcome, Research Triangle Park, NC) in one. The data indicate that the use of intravenous antibiotic prophylaxis significantly reduces exit site infection and may reduce both tunnel and incision site infection. Prophylactic antibiotic coverage should be provided to patients during insertion of long-term indwelling right atrial catheters.

Homodyne interferometer for basilar membrane vibration measurements. II. Hardware and techniques

Selected mechanical features of the design of the homodyne interferometer are described. This interferometer was utilized for basilar membrane vibration measurements. The massive construction necessary to minimize mechanical vibration and noise is described. In order to measure basilar membrane vibrations, it was necessary to increase its reflectivity. Gold crystals were utilized as microscopic mirrors. The technique for fabrication of gold crystals is described. These crystals are small and fragile and required special handling. The method of picking up the crystals and placing them on a preselected location is described. In order to minimize the effect of the involuntary animal movements a reference mirror system is cemented to the skull. The design of the reference mirror system and the method of cementing it to the skull are described.

Central core reduction mammoplasties and Marlex suspension of breast tissue

The author describes a technique for central core reduction mammoplasty with the same technique being utilized for a mastopexy. By transposition of the nipple areolar complex, the nerve supply as well as the vascular supply is maintained on an inferiorly based dermal pedicle. This technique does not require the recall of a multitude of points or locations or other maneuvers necessary to do the markings to obtain a symmetric, aesthetically pleasing reduction. The author has also developed a technique for the use of Marlex Mesh to support the remaining breast tissue and, by attaching the mesh to the area of the second rib, the support of the breast tissue is converted from cutaneous origin to skeletal origin, giving an internal support of breast tissue and preventing subsequent early ptosis and loss in fullness of the upper portion of the breast. The mesh has been used in 43 patients over the past two years with no serious complications.

Biliary excretion and enterohepatic recirculation of practolol in man

The elimination of practolol in bile was studied in six patients who received a single oral dose of 400 mg within six days of undergoing biliary surgery. Bile collections were made from a T-tube drain left in the common bile duct after removal of multiple biliary calculi. There was wide variation in the concentration of practolol in bile and in the total amount of practolol excreted in bile during the 48 hour period after dosage. Two patients excreted 23 per cent and 41 per cent of the 400 mg dose in bile, whereas the excretion in the other four patients was only one per cent to four per cent of the oral dose. The mean urinary excretion of practolol in 48 hours was 74.2±S.E. 8.4 per cent of the ingested dose, and the total elimination (biliary plus urinary) was 86.5±S.E. 7.6 per cent. The total elimination ranged from 92 per cent to 105 per cent in four of the patients. The mean elimination half-life of practolol in blood was 6.4±S.E. 0.5 hours. This was significantly less than the half-life in normal subjects receiving the same practolol dose. Since complete or near-complete urinary excretion of practolol is found in normal subjects, the presence of large amounts of drug in the bile suggests that enterohepatic recirculation of the drug occurred in some of the patients at least. This is a possible explanation of the shortened half-life in these patients in whom drug was being removed with bile. The four patients with low excretion of practolol in bile were receiving other drugs at the time of the study. These included nitrazepam, diazepam and tetracycline which are known to have substantial biliary elimination either in animals or man. It is suggested that competition for biliary excretion may have occurred and this may represent a drug interaction of possible clinical significance.