Axial Magnetic Resonance Angiography in Evaluating Revascularization after Indirect Bypass Surgery for Moyamoya Axial Magnetic Resonance Angiography after Indirect Bypass.

INTRODUCTION: At our institution, revascularization after indirect moyamoya surgery is routinely evaluated using magnetic resonance angiography (MRA) rather than catheter angiography. In this paper, we review how revascularization can be visualized on axial MRA and compare its visualization on MRA to that on catheter angiography. We also compare clinical outcomes of patients followed with routine postoperative MRA with outcomes of patients followed with routine catheter angiography. METHODS: We retrospectively reviewed the records of all patients treated at our institution who underwent unilateral encephaloduroarteriosynangiosis (EDAS) and/or pial synangiosis between the ages of 1 and 21 years and between December 31, 2003, and May 1, 2021. We included patients who underwent EDAS/pial synangiosis at other hospitals as long as they met all inclusion criteria. Inclusion criteria included having a preoperative MRA within 18 months of surgery and a postoperative MRA 3-30 months after surgery. Clinical outcomes included development of postoperative stroke and transient ischemic attacks (TIAs) and changes in symptoms (improved, unchanged, or worsened), including seizures, balance issues, and headaches. Clinical outcomes were compared between patients who had routine postoperative MRA only versus those who had routine postoperative angiograms, with or without routine MRA. For each surgery, we determined the ratios of the diameters and areas of the donor vessel and the contralateral corresponding vessel, as well as the relative signal intensities of these two vessels, on preoperative and 3- to 30-month postoperative MRA. We did the same for the middle meningeal artery (MMA) ipsilateral to the donor artery and the contralateral MMA. We assessed changes from pre- to post-operation in diameter ratios, area ratios, relative signal intensity, ivy sign, and in brain perfusion on arterial spin labeled (ASL) imaging. MRI and MRA measures of revascularization and flow were compared to Matsushima grades in patients who had postoperative catheter angiograms. RESULTS: Fifty-one operations for 42 unique patients were included. There were no significant differences in the rates of postoperative strokes, postoperative TIAs, changes in symptoms, or new symptoms after surgeries evaluated by routine postoperative MRA versus catheter angiogram (p = 0.282, 1, 0.664, and 0.727, respectively). There were significant associations between greater collateralization on postoperative MRA and greater median increases in preoperative-to-postoperative ratios of donor-vessel-over-contralateral-vessel diameter (p = 0.0461), ipsilateral-MMA-over-contralateral-MMA diameter (p = 0.0135), and the summed donor and ipsilateral MMA diameters over the summed contralateral vessel diameters (p < 0.001). The median increase in the ratio of the donor vessel and contralateral corresponding vessel diameters was significantly higher for Matsushima grade A versus B (p = 0.036). The median increase in the ratio of the sum of donor and ipsilateral MMA diameters over the sum of the contralateral vessel diameters was significantly higher for improved-versus-unchanged perfusion on ASL imaging (p = 0.0074). There was a nonsignificant association between greater postoperative collateralization on MRA and Matsushima grade (p = 0.1160). CONCLUSION: Cerebral revascularization after EDAS and pial synangiosis can be evaluated on axial MRA by comparing the diameter and/or signal intensity of the donor vessel and corresponding contralateral vessel, as well as the ipsilateral and contralateral MMA, on postoperative-versus-preoperative MRA. The use of routine postoperative MRA rather than catheter angiography does not appear to negatively affect outcomes.

Dots and spots: A retrospective review of T2-hyperintense white matter lesions in pediatric patients with and without headache.

OBJECTIVE: We aimed to determine if T2-weighted hyperintense white matter lesions (WMLs) on brain magnetic resonance imaging (MRI) occur more frequently in pediatric patients with migraine and other primary headache disorders compared to the general pediatric population. BACKGROUND: Small foci of T2 hyperintensity in the white matter are frequently identified on brain MRI during the workup of pediatric headache. Such lesions have been reported to be more common among adults with migraine versus adults without migraine; however, this association has not been well established in the pediatric population. METHODS: We performed a retrospective cross-sectional single-center study of electronic medical records and radiologic studies, examining pediatric patients from 3 to 18 years old who underwent brain MRI between 2016 and 2021. Patients with existing intracranial disease or abnormalities were excluded. Patients with reports of headache were categorized. Imaging was reviewed to determine the number and location of WMLs. Headache-associated disability scores (Pediatric Migraine Disability Assessment) were noted, when available. RESULTS: Brain MRI of 248 patients with a diagnosis of headache (144 with migraine, 42 with non-migraine primary headache, and 62 with headache that could not be further classified) and 490 controls were reviewed. WMLs were encountered commonly among all study participants, with a prevalence of 40.5% (17/42) to 54.1% (265/490). There was no statistically significant difference comparing the number of lesions between each of the headache groups and the control group: migraine group versus control group median [interquartile range (IQR)], 0 [0-3] versus 1 [0-4], incidence rate ratio [95% confidence interval (CI)], 0.99 [0.69-1.44], p = 0.989, non-migraine headache group versus control group median [IQR], 0 [0-3] versus 1 [0-4], 0.71 [0.46-1.31], p = 0.156, headache not otherwise specified group versus control group median [IQR], 0 [0-4] versus 1 [0-4], 0.77 [0.45-1.31], p = 0.291. There was no significant correlation between headache-associated disability and the number of WMLs (0.07 [-0.30 to 0.17], rho [95% CI]). CONCLUSION: T2 hyperintense WMLs are common within the pediatric population and are not encountered more frequently in pediatric patients with migraine or other primary headache disorders. Thus, such lesions are presumably incidental and unlikely related to headache history.

Radiation dose reduction using spectral shaping in pediatric non-contrast sinus CT.

BACKGROUND: CT is the standard imaging technique to evaluate pediatric sinuses. Given the potential risks of radiation exposure in children, it is important to reduce pediatric CT dose and maintain image quality. OBJECTIVE: To study the utility of spectral shaping with tin filtration to improve dose efficiency for pediatric sinus CT exams. MATERIALS AND METHODS: A head phantom was scanned on a commercial dual-source CT using a conventional protocol (120 kV) and a proposed 100 kV with a 0.4-mm tin filter (Sn100 kV) protocol for comparison. Entrance point dose (EPD) of eye and parotid gland region was measured by an ion chamber. Sixty pediatric sinus CT exams (33 acquired with 120 kV, 27 acquired with Sn100 kV) were retrospectively collected. All patient images were objectively measured for image quality and blindly reviewed by 4 pediatric neuroradiologists for overall noise, overall diagnostic quality, and delineation of 4 critical paranasal sinus structures, using a 5-point Likert scale. RESULTS: Phantom CTDIvol from Sn100 kV is 4.35 mGy, compared to CTDIvol of 5.73 mGy from 120 kV at an identical noise level. EPD of sensitive organs decreases in Sn100 kV (e.g., right eye EPD 3.83±0.42 mGy), compared to 120 kV (5.26±0.24 mGy). Patients in the 2 protocol groups were age and weight (unpaired T test P>0.05) matched. The patient CTDIvol of Sn100 kV (4.45±0.47 mGy) is significantly lower than 120 kV (5.56±0.48 mGy, unpaired T test P<0.001). No statistically significant difference for any subjective readers' score (Wilcoxon test P>0.05) was found between the two groups, indicating proposed spectral shaping provides equivalent diagnostic image quality. CONCLUSION: Phantom and patient results demonstrate that spectral shaping can significantly reduce radiation dose for non-contrast pediatric sinus CT without compromising diagnostic quality.

Prevalence of cerebral sinovenous thrombosis in abusive head trauma.

BACKGROUND: Cerebral sinovenous thrombosis (CSVT) has been proposed in legal settings to be an atraumatic mimic of abusive head trauma (AHT). OBJECTIVE: The objective of this study was to determine the prevalence of CSVT and subdural hemorrhage (SDH) in a large AHT population. MATERIALS AND METHODS: This retrospective cohort study measured the prevalence of CSVT and SDH on magnetic resonance venograms in 243 patients diagnosed with AHT at a single center. We also reported additional intra- and extracranial injuries, head injury severity and length of hospital stay. RESULTS: Among 243 patients diagnosed with AHT, 7% (16/243) had CSVT. SDH was present in 94% (15/16) of the CSVT cases. Cytotoxic edema and subarachnoid hemorrhage were in 88% (14/16) and 69% (11/16) of the CSVT cases, respectively. Extracranial signs of abuse were also in 100% (16/16) of the patients with CSVT. Critical to maximal head injury severity (abbreviated injury scale >=5) was in 75% (12/16) of the CSVT population vs. 33% (82/243) in the total AHT population. Length of hospital and pediatric intensive care unit stay was greater in those with CSVT (10 vs. 21.9 and 3.5 vs. 7.3 days). CONCLUSION: These findings suggest that CSVT is uncommon in AHT and is associated with additional traumatic injuries and greater injury severity.

Use of the Posterior Auricular Artery for Indirect Bypass in Moyamoya: A Pediatric Case Series.

INTRODUCTION: Encephaloduroarteriosynangiosis (EDAS) for moyamoya is predominantly performed using a branch of the superficial temporal artery (STA) as the donor artery. At times, other branches of the external carotid artery are better suited for EDAS than is the STA. There is little information in the literature concerning using the posterior auricular artery (PAA) for EDAS in the pediatric age-group. In this case series, we review our experience using the PAA for EDAS in children and adolescents. CASE PRESENTATIONS: We describe the presentations, imaging, and outcomes of 3 patients in whom the PAA was used for EDAS, as well our surgical technique. There were no complications. All 3 patients were confirmed to have radiologic revascularization from their surgeries. All patients also had improvement of their preoperative symptoms, and no patient has had a stroke postoperatively. CONCLUSION: The PAA is a viable option for use as a donor artery in EDAS for the treatment of moyamoya in children and adolescents.

Age-related changes in the completeness of the circle of Willis in children.

PURPOSE: The circle of Willis is a circulatory anastomosis that supplies blood to the brain. If any of the bridging segments are hypoplastic or absent, the capacity for collateral flow in the setting of large vessel occlusion may be decreased. Outside of the neonatal period, the prevalence of a complete circle of Willis (CoW) in the pediatric population has not been well described. Our objectives include determining the prevalence of a complete CoW in children and identifying if there is an age-related "loss" of arterial segments. METHODS: Following IRB approval, angiograms of the CoW performed on a 3-T MR platform from 2016 to 2020 on patients 21 years or younger were retrospectively reviewed. Any patient with underlying arterial pathology that may affect the CoW was excluded. Patient age and gender at the time of imaging were obtained. RESULTS: In total, 592 pediatric CoW were assessed. Frequencies of completeness were calculated in two different fashions: scenario 1 where a CoW was characterized as complete even if it contained hypoplastic vessels (88.8%), and scenario 2 where it was characterized as complete after excluding hypoplastic vessels (44.0%). In both scenarios, our data showed that older age was more associated with an incomplete CoW (p < 0.0001). In addition, we found a higher percentage of males with an incomplete CoW compared with females (p < 0.0001). CONCLUSIONS: The presence of a complete CoW is greater in our pediatric population than what has been reported in adults. The prevalence of an incomplete circle of Willis also increases significantly with age.

"Growing cerebellum" requiring operative decompression following perinatal ventriculoperitoneal shunting.

INTRODUCTION: While cases of acquired Chiari I malformation following ventriculoperitoneal shunting for posthemorrhagic hydrocephalus have been reported, true disproportionate cerebellar growth is rare, with no previous cases requiring posterior fossa decompression reported. CLINICAL PRESENTATION: We present a premature neonate who underwent ventriculoperitoneal shunt placement for suspected posthemorrhagic hydrocephalus. He subsequently developed a symptomatic Chiari I malformation with volumetric measurements demonstrating disproportionate growth of the cerebellum. He did not demonstrate thickening of the supratentorial or posterior fossa cranium. The patient underwent an extradural posterior fossa decompression, with resolution of symptoms. OUTCOME AND CONCLUSIONS: We review the extant literature regarding the development of Chiari malformation type I as a manifestation of craniocerebral disproportion (CCD) following shunt placement for posthemorrhagic hydrocephalus of prematurity. Most previous reports reflect a mechanism that includes underdevelopment of the intracranial posterior fossa (or supratentorial) volume. The case presented in this report, as well as one additional case, indicates that there may exist a variant mechanism, characterized by rapid growth of the cerebellum itself, in the absence of one of the rare syndromes associated with primary macrocerebellum. While this case was effectively managed with extradural posterior fossa decompression, previous reports indicate that supratentorial cranial expansion procedures are preferable in some cases. As such, pediatric neurosurgeons should be able to distinguish the patterns of craniocerebral disproportion when considering treatment options for these patients. Further investigation regarding these uncommon patients may better describe the underlying mechanisms.

Dynamic chemical expansion of thin-film non-stoichiometric oxides at extreme temperatures.

Actuator operation in increasingly extreme and remote conditions requires materials that reliably sense and actuate at elevated temperatures, and over a range of gas environments. Design of such materials will rely on high-temperature, high-resolution approaches for characterizing material actuation in situ. Here, we demonstrate a novel type of high-temperature, low-voltage electromechanical oxide actuator based on the model material PrxCe1-xO2-δ (PCO). Chemical strain and interfacial stress resulted from electrochemically pumping oxygen into or out of PCO films, leading to measurable film volume changes due to chemical expansion. At 650 °C, nanometre-scale displacement and strain of >0.1% were achieved with electrical bias values <0.1 V, low compared to piezoelectrically driven actuators, with strain amplified fivefold by stress-induced structural deflection. This operando measurement of films 'breathing' at second-scale temporal resolution also enabled detailed identification of the controlling kinetics of this response, and can be extended to other electrochemomechanically coupled oxide films at extreme temperatures.

Temporal Variation in Single-Cell Power-Law Rheology Spans the Ensemble Variation of Cell Population.

Changes in the cytoskeletal organization within cells can be characterized by large spatial and temporal variations in rheological properties of the cell (e.g., the complex shear modulus G∗). Although the ensemble variation in G∗ of single cells has been elucidated, the detailed temporal variation of G∗ remains unknown. In this study, we investigated how the rheological properties of individual fibroblast cells change under a spatially confined environment in which the cell translational motion is highly restricted and the whole cell shape remains unchanged. The temporal evolution of single-cell rheology was probed at the same measurement location within the cell, using atomic force microscopy-based oscillatory deformation. The measurements reveal that the temporal variation in the power-law rheology of cells is quantitatively consistent with the ensemble variation, indicating that the cell system satisfies an ergodic hypothesis in which the temporal statistics are identical to the ensemble statistics. The autocorrelation of G∗ implies that the cell mechanical state evolves in the ensemble of possible states with a characteristic timescale.

Pediatric Brain: Repeated Exposure to Linear Gadolinium-based Contrast Material Is Associated with Increased Signal Intensity at Unenhanced T1-weighted MR Imaging.

Purpose To determine whether repeated exposure of the pediatric brain to a linear gadolinium-based contrast agent (GBCA) is associated with an increase in signal intensity (SI) relative to that in GBCA-naive control subjects at unenhanced T1-weighted magnetic resonance (MR) imaging. Materials and Methods This single-center, retrospective study was approved by the institutional review board and compliant with HIPAA. The authors evaluated 46 pediatric patients who had undergone at least three GBCA-enhanced MR examinations (30 patients for two-group analysis and 16 for pre- and post-GBCA exposure comparisons) and 57 age-matched GBCA-naive control subjects. The SI in the globus pallidus, thalamus, dentate nucleus, and pons was measured at unenhanced T1-weighted MR imaging. Globus pallidus-thalamus and dentate nucleus-pons SI ratios were calculated and compared between groups and relative to total cumulative gadolinium dose, age, sex, and number of and mean time between GBCA-enhanced examinations. Analysis included the Wilcoxon signed rank test, Wilcoxon rank sum test, and Spearman correlation coefficient. Results Patients who underwent multiple GBCA-enhanced examinations had increased SI ratios within the dentate nucleus (mean SI ratio ± standard error of the mean for two-group comparison: 1.007 ± 0.0058 for GBCA-naive group and 1.046 ± 0.0060 for GBCA-exposed group [P < .001]; mean SI ratio for pre- and post-GBCA comparison: 0.995 ± 0.0062 for pre-GBCA group and 1.035 ± 0.0063 for post-GBCA group [P < .001]) but not the globus pallidus (mean SI ratio for two-group comparison: 1.131 ± 0.0070 for GBCA-naive group and 1.014 ± 0.0091 for GBCA-exposed group [P = .21]; mean SI ratio for pre- and post-GBCA comparison: 1.068 ± 0.0094 for pre-GBCA group and 1.093 ± 0.0134 for post-GBCA group [P = .12]). There was a significant correlation between dentate nucleus SI and total cumulative gadolinium dose (r = 0.4; 95% confidence interval [CI]: 0.03, 0.67; P = .03), but not between dentate nucleus SI and patient age (r = 0.23; 95% CI: -0.15, 0.56; P = .22), sex (mean SI ratio: 1.046 ± 0.0072 for boys and 1.045 ± 0.0110 for girls; P = .88), number of contrast-enhanced examinations (r = 0.13; 95% CI: -0.25, 0.48; P = .49), or time between contrast-enhanced examinations (r = -0.06; 95% CI: -0.42, 0.32; P = .75). Conclusion SI in the pediatric brain increases on unenhanced T1-weighted MR images with repeated exposure to a linear GBCA. © RSNA, 2016.

A cluster of acute flaccid paralysis and cranial nerve dysfunction temporally associated with an outbreak of enterovirus D68 in children in Colorado, USA.

BACKGROUND: Clusters of acute flaccid paralysis or cranial nerve dysfunction in children are uncommon. We aimed to assess a cluster of children with acute flaccid paralysis and cranial nerve dysfunction geographically and temporally associated with an outbreak of enterovirus-D68 respiratory disease. METHODS: We defined a case of neurological disease as any child admitted to Children's Hospital Colorado (Aurora, CO, USA) with acute flaccid paralysis with spinal-cord lesions involving mainly grey matter on imaging, or acute cranial nerve dysfunction with brainstem lesions on imaging, who had onset of neurological symptoms between Aug 1, 2014, and Oct 31, 2014. We used Poisson regression to assess whether the numbers of cases during the outbreak period were significantly greater than baseline case numbers from a historical control period (July 31, 2010, to July 31, 2014). FINDINGS: 12 children met the case definition (median age 11·5 years [IQR 6·75-15]). All had a prodromal febrile illness preceding neurological symptoms by a median of 7 days (IQR 5·75-8). Neurological deficits included flaccid limb weakness (n=10; asymmetric n=7), bulbar weakness (n=6), and cranial nerve VI (n=3) and VII (n=2) dysfunction. Ten (83%) children had confluent, longitudinally extensive spinal-cord lesions of the central grey matter, with predominant anterior horn-cell involvement, and nine (75%) children had brainstem lesions. Ten (91%) of 11 children had cerebrospinal fluid pleocytosis. Nasopharyngeal specimens from eight (73%) of 11 children were positive for rhinovirus or enterovirus. Viruses from five (45%) of 11 children were typed as enterovirus D68. Enterovirus PCR of cerebrospinal fluid, blood, and rectal swabs, and tests for other causes, were negative. Improvement of cranial nerve dysfunction has been noted in three (30%) of ten children. All ten children with limb weakness have residual deficits. INTERPRETATION: We report the first geographically and temporally defined cluster of acute flaccid paralysis and cranial nerve dysfunction in children associated with an outbreak of enterovirus-D68 respiratory illness. Our findings suggest the possibility of an association between enterovirus D68 and neurological disease in children. If enterovirus-D68 infections continue to happen in an endemic or epidemic pattern, development of effective antiviral or immunomodulatory therapies and vaccines should become scientific priorities. FUNDING: National Center for Advancing Translational Sciences, National Institutes of Health.

Insights from two industrial hygiene pilot e-cigarette passive vaping studies.

While several reports have been published using research methods of estimating exposure risk to e-cigarette vapors in nonusers, only two have directly measured indoor air concentrations from vaping using validated industrial hygiene sampling methodology. Our first study was designed to measure indoor air concentrations of nicotine, menthol, propylene glycol, glycerol, and total particulates during the use of multiple e-cigarettes in a well-characterized room over a period of time. Our second study was a repeat of the first study, and it also evaluated levels of formaldehyde. Measurements were collected using active sampling, near real-time and direct measurement techniques. Air sampling incorporated industrial hygiene sampling methodology using analytical methods established by the National Institute of Occupational Safety and Health and the Occupational Safety and Health Administration. Active samples were collected over a 12-hr period, for 4 days. Background measurements were taken in the same room the day before and the day after vaping. Panelists (n = 185 Study 1; n = 145 Study 2) used menthol and non-menthol MarkTen prototype e-cigarettes. Vaping sessions (six, 1-hr) included 3 prototypes, with total number of puffs ranging from 36-216 per session. Results of the active samples were below the limit of quantitation of the analytical methods. Near real-time data were below the lowest concentration on the established calibration curves. Data from this study indicate that the majority of chemical constituents sampled were below quantifiable levels. Formaldehyde was detected at consistent levels during all sampling periods. These two studies found that indoor vaping of MarkTen prototype e-cigarette does not produce chemical constituents at quantifiable levels or background levels using standard industrial hygiene collection techniques and analytical methods.

Acute neurologic illness of unknown etiology in children - Colorado, August-September 2014.

On September 12, 2014, CDC was notified by the Colorado Department of Public Health and Environment of a cluster of nine children evaluated at Children's Hospital Colorado with acute neurologic illness characterized by extremity weakness, cranial nerve dysfunction (e.g., diplopia, facial droop, dysphagia, or dysarthria), or both. Neurologic illness onsets occurred during August 8-September 15, 2014. The median age of the children was 8 years (range = 1-18 years). Other than neck, back, or extremity pain in some patients, all had normal sensation. All had a preceding febrile illness, most with upper respiratory symptoms, occurring 3-16 days (median = 7 days) before onset of neurologic illness. Seven of eight patients with magnetic resonance imaging of the spinal cord had nonenhancing lesions of the gray matter of the spinal cord spanning multiple levels, and seven of nine with magnetic resonance imaging of the brain had nonenhancing brainstem lesions (most commonly the dorsal pons). Two of five with magnetic resonance imaging of the lumbosacral region had gadolinium enhancement of the ventral nerve roots of the cauda equina. Eight children were up to date on polio vaccination. Eight have not yet fully recovered neurologically.

Chemoenvironmental modulators of fluidity in the suspended biological cell.

Biological cells can be characterized as "soft matter" with mechanical characteristics potentially modulated by external cues such as pharmaceutical dosage or fever temperature. Further, quantifying the effects of chemical and physical stimuli on a cell's mechanical response informs models of living cells as complex materials. Here, we investigate the mechanical behavior of single biological cells in terms of fluidity, or mechanical hysteresivity normalized to the extremes of an elastic solid or a viscous liquid. This parameter, which complements stiffness when describing whole-cell viscoelastic response, can be determined for a suspended cell within subsecond times. Questions remain, however, about the origin of fluidity as a conserved parameter across timescales, the physical interpretation of its magnitude, and its potential use for high-throughput sorting and separation of interesting cells by mechanical means. Therefore, we exposed suspended CH27 lymphoma cells to various chemoenvironmental conditions--temperature, pharmacological agents, pH, and osmolarity--and measured cell fluidity with a non-contact technique to extend familiarity with suspended-cell mechanics in the context of both soft-matter physics and mechanical flow cytometry development. The actin-cytoskeleton-disassembling drug latrunculin exacted a large effect on mechanical behavior, amenable to dose-dependence analysis of coupled changes in fluidity and stiffness. Fluidity was minimally affected by pH changes from 6.5 to 8.5, but strongly modulated by osmotic challenge to the cell, where the range spanned halfway from solid to liquid behavior. Together, these results support the interpretation of fluidity as a reciprocal friction within the actin cytoskeleton, with implications both for cytoskeletal models and for expectations when separating interesting cell subpopulations by mechanical means in the suspended state.

Mechanical fluidity of fully suspended biological cells.

Mechanical characteristics of single biological cells are used to identify and possibly leverage interesting differences among cells or cell populations. Fluidity-hysteresivity normalized to the extremes of an elastic solid or a viscous liquid-can be extracted from, and compared among, multiple rheological measurements of cells: creep compliance versus time, complex modulus versus frequency, and phase lag versus frequency. With multiple strategies available for acquisition of this nondimensional property, fluidity may serve as a useful and robust parameter for distinguishing cell populations, and for understanding the physical origins of deformability in soft matter. Here, for three disparate eukaryotic cell types deformed in the suspended state via optical stretching, we examine the dependence of fluidity on chemical and environmental influences at a timescale of ∼1 s. We find that fluidity estimates are consistent in the time and frequency domains under a structural damping (power-law or fractional-derivative) model, but not under an equivalent-complexity, lumped-component (spring-dashpot) model; the latter predicts spurious time constants. Although fluidity is suppressed by chemical cross-linking, we find that ATP depletion in the cell does not measurably alter the parameter, and we thus conclude that active ATP-driven events are not a crucial enabler of fluidity during linear viscoelastic deformation of a suspended cell. Finally, by using the capacity of optical stretching to produce near-instantaneous increases in cell temperature, we establish that fluidity increases with temperature-now measured in a fully suspended, sortable cell without the complicating factor of cell-substratum adhesion.

Quantifying cell-to-cell variation in power-law rheology.

Among individual cells of the same source and type, the complex shear modulus G(∗) exhibits a large log-normal distribution that is the result of spatial, temporal, and intrinsic variations. Such large distributions complicate the statistical evaluation of pharmacological treatments and the comparison of different cell states. However, little is known about the characteristic features of cell-to-cell variation. In this study, we investigated how this variation depends on the spatial location within the cell and on the actin filament cytoskeleton, the organization of which strongly influences cell mechanics. By mechanically probing fibroblasts arranged on a microarray, via atomic force microscopy, we observed that the standard deviation σ of G(∗) was significantly reduced among cells in which actin filaments were depolymerized. The parameter σ also exhibited a subcellular spatial dependence. Based on our findings regarding the frequency dependence of σ of the storage modulus G('), we proposed two types of cell-to-cell variation in G(') that arise from the purely elastic and the frequency-dependent components in terms of the soft glassy rheology model of cell deformability. We concluded that the latter inherent cell-to-cell variation can be reduced greatly by disrupting actin networks, by probing at locations within the cell nucleus boundaries distant from the cell center, and by measuring at high loading frequencies.

Ophthalmic manifestations of ruptured arachnoid cysts in children.

BACKGROUND: Intracranial arachnoid cysts are relatively common in the pediatric population. Rarely, they rupture, leading to acute subdural fluid collections, which can cause a sudden increase in intracranial pressure. The purpose of this study was to characterize ophthalmic sequelae in a large cohort of these patients. METHODS: The medical records of all children treated for ruptured arachnoid cysts who presented at a single tertiary pediatric hospital for initial assessment between 2009 and 2021 were reviewed retrospectively. RESULTS: Of 35 children treated for ruptured arachnoid cysts during the study period, 30 received ophthalmological examination. Papilledema was found in 57% of these children, abducens palsy in 20%, and retinal hemorrhages in 10%. Of the 30 children, 22 were seen in outpatient follow-up, of whom 5 had a best-corrected visual acuity of 20/40 or worse in one or both eyes at most recent follow-up. Cranial nerve palsies resolved in all cases without strabismus surgery. CONCLUSIONS: Given high rates of papilledema, cranial nerve palsies, and vision loss, all children with ruptured arachnoid cysts should be evaluated by pediatric ophthalmologists.

Imaging of Congenital Spine Malformations.

Congenital malformations of the spine and spinal cord are a large and diverse group of diagnoses, which are often broadly referred to as spinal dysraphisms (SDs). Derived from the Greek words dys (bad) and raphe (suture), the term dysraphism describes missteps in the process of forming a midline seam during the zipper-like fusion of the neural folds in primary neurulation. As such, the term "spinal dysraphism" is a designation that should technically be reserved for malformations resulting from aberrations in primary neurulation. In medical practice, however, it is a catch-all designation regularly used to describe any of the numerous abnormalities demonstrating incomplete midline closure of mesenchymal, osseous, and nervous tissue, occurring at any point during embryologic development. For the sake of clarity and completeness, this article will also include that breadth in the discussion of congenital abnormalities of the spine.

A 14-year-old Girl with Right-Sided Weakness and Speech Difficulty.

We herein report a case of Childhood Primary Central Nervous System (CNS) Angiitis. This case consisted of a 14-year-old girl who presented with right-sided weakness, aphasia, and a fever. A Magnetic Resonance Imaging of the brain showed multifocal areas of ischemia. Magnetic Resonance Angiography of the head and neck showed narrowing and irregularities of the left middle cerebral artery and right posterior cerebral artery. Cerebrospinal Fluid studies showed a lymphocytic pleocytosis and brain biopsy revealed leptomeningeal and perivascular inflammation. The epidemiology, presenting symptoms, work-up, pathophysiology, diagnostic criteria, and treatment of Childhood Primary CNS angiitis are discussed. This case serves as a reminder that when pediatric patients present with stroke-like symptoms inflammatory etiologies including Primary CNS Angiitis must be considered and treated appropriately in a time sensitive manner.

Fetal MRI Neuroradiology: Indications.

Fetal MRI is a safe, noninvasive examination of the fetus and placenta, a complement to ultrasonography. MRI provides detailed CNS evaluation, including depicting parenchymal architecture and posterior fossa morphology, and is key in prenatal assessment of spinal dysraphism, neck masses, and ventriculomegaly. Fetal MRI is typically performed after 22 weeks gestation, and ultrafast T1 and T2-weighted MRI sequences are the core of the exam, with advanced sequences such as diffusion weighted imaging used for specific questions. The fetal brain grows and develops rapidly, and familiarity with gestational age specific norms is essential to MRI interpretation.