Bidirectional Changes in Anisotropy Are Associated with Outcomes in Mild Traumatic Brain Injury.

BACKGROUND AND PURPOSE: Mild traumatic brain injury results in a heterogeneous constellation of deficits and symptoms that persist in a subset of patients. This prospective longitudinal study identifies early diffusion tensor imaging biomarkers of mild traumatic brain injury that significantly relate to outcomes at 1 year following injury. MATERIALS AND METHODS: DTI was performed on 39 subjects with mild traumatic brain injury within 16 days of injury and 40 controls; 26 subjects with mild traumatic brain injury returned for follow-up at 1 year. We identified subject-specific regions of abnormally high and low fractional anisotropy and calculated mean fractional anisotropy, axial diffusivity, radial diffusivity, and mean diffusivity across all white matter voxels brain-wide and each of several white matter regions. Assessment of cognitive performance and symptom burden was performed at 1 year. RESULTS: Significant associations of brain-wide DTI measures and outcomes included the following: mean radial diffusivity and mean diffusivity with memory; and mean fractional anisotropy, radial diffusivity, and mean diffusivity with health-related quality of life. Significant differences in outcomes were found between subjects with and without abnormally high fractional anisotropy for the following white matter regions and outcome measures: left frontal lobe and left temporal lobe with attention at 1 year, left and right cerebelli with somatic postconcussion symptoms at 1 year, and right thalamus with emotional postconcussion symptoms at 1 year. CONCLUSIONS: Individualized assessment of DTI abnormalities significantly relates to long-term outcomes in mild traumatic brain injury. Abnormally high fractional anisotropy is significantly associated with better outcomes and might represent an imaging correlate of postinjury compensatory processes.

A decade of DTI in traumatic brain injury: 10 years and 100 articles later.

SUMMARY: The past decade has seen an increase in the number of articles reporting the use of DTI to detect brain abnormalities in patients with traumatic brain injury. DTI is well-suited to the interrogation of white matter microstructure, the most important location of pathology in TBI. Additionally, studies in animal models have demonstrated the correlation of DTI findings and TBI pathology. One hundred articles met the inclusion criteria for this quantitative literature review. Despite significant variability in sample characteristics, technical aspects of imaging, and analysis approaches, the consensus is that DTI effectively differentiates patients with TBI and controls, regardless of the severity and timeframe following injury. Furthermore, many have established a relationship between DTI measures and TBI outcomes. However, the heterogeneity of specific outcome measures used limits interpretation of the literature. Similarly, few longitudinal studies have been performed, limiting inferences regarding the long-term predictive utility of DTI. Larger longitudinal studies, using standardized imaging, analysis approaches, and outcome measures will help realize the promise of DTI as a prognostic tool in the care of patients with TBI.

Laboratory measurements of the viscous anisotropy of olivine aggregates.

A marked anisotropy in viscosity develops in Earth's mantle as deformation strongly aligns the crystallographic axes of the individual grains that comprise the rocks. On the basis of geodynamic simulations, processes significantly affected by viscous anisotropy include post-glacial rebound, foundering of lithosphere and melt production above subduction zones. However, an estimate of the magnitude of viscous anisotropy based on the results of deformation experiments on single crystals differs by three orders of magnitude from that obtained by grain-scale numerical models of deforming aggregates with strong crystallographic alignment. Complicating matters, recent experiments indicate that deformation of the uppermost mantle is dominated by dislocation-accommodated grain-boundary sliding, a mechanism not activated in experiments on single crystals and not included in numerical models. Here, using direct measurements of the viscous anisotropy of highly deformed polycrystalline olivine, we demonstrate a significant directional dependence of viscosity. Specifically, shear viscosities measured in high-strain torsion experiments are 15 times smaller than normal viscosities measured in subsequent tension tests performed parallel to the torsion axis. This anisotropy is approximately an order of magnitude larger than that predicted by grain-scale simulations. These results indicate that dislocation-accommodated grain-boundary sliding produces an appreciable anisotropy in rock viscosity. We propose that crystallographic alignment imparts viscous anisotropy because the rate of deformation is limited by the movement of dislocations through the interiors of the crystallographically aligned grains. The maximum degree of anisotropy is reached at geologically low shear strain (of about ten) such that deforming regions of the upper mantle will exhibit significant viscous anisotropy.

Hippocampal correlates of pain in healthy elderly adults: a pilot study.

BACKGROUND: Few neuroimaging investigations of pain in elderly adults have focused on the hippocampus, a brain structure involved in nociceptive processing that is also subject to involution associated with dementing disorders. The goal of this pilot study was to examine MRI- and magnetic resonance spectroscopy (MRS)-derived hippocampal correlates of pain in older adults. METHODS: A subset of 20 nondemented older adults was drawn from the Einstein Aging Study, a community-based sample from the Bronx, NY. Pain was measured on 3 time scales: 1) acute pain right now (pain severity); 2) pain over the past 4 weeks (Short Form-36 Bodily Pain); 3) chronic pain over the past 3 months (Total Pain Index). Hippocampal data included volume data normalized to midsagittal area and N-acetylaspartate to creatine ratios (NAA/Cr). RESULTS: Smaller hippocampal volume was associated with higher ratings on the Short Form-36 Bodily Pain (r(s) = 0.52, p = 0.02) and a nonsignificant trend was noted for higher ratings of acute pain severity (r(s) = -0.44, p = 0.06). Lower levels of hippocampal NAA/Cr were associated with higher acute pain severity (r(s) = -0.45, p = 0.05). Individuals with chronic pain had a nonsignificant trend for smaller hippocampal volumes (t = 2.00, p = 0.06) and lower levels of hippocampal NAA/Cr (t = 1.71, p = 0.10). CONCLUSIONS: Older adults who report more severe acute or chronic pain have smaller hippocampal volumes and lower levels of hippocampal N-acetylaspartate/creatine, a marker of neuronal integrity. Future studies should consider the role of the hippocampus and other brain structures in the development and experience of pain in healthy elderly and individuals with Alzheimer disease.

Hippocampal neurochemistry, neuromorphometry, and verbal memory in nondemented older adults.

BACKGROUND: Characterization of the behavioral correlates of neuromorphometry and neurochemistry in older adults has important implications for an improved understanding of the aging process. The objective of this study was to test the hypothesis that a measure of hippocampal neuronal metabolism was associated with verbal memory in nondemented older adults after controlling for hippocampal volume. METHODS: 4-T MRI, proton magnetic resonance spectroscopy ((1)H MRS), and neuropsychological assessment were conducted in 48 older adults (23 women; mean age 81 years). Average hippocampal N-acetyl aspartate/creatine ratios (NAA/Cr) and hippocampal volumes were obtained. Neuropsychological evaluation included tests of verbal memory (Buschke and Grober Free and Cued Selective Reminding Test-Immediate Recall [FCSRT-IR], Wechsler Memory Scale-Revised Logical Memory subtest) and attention and executive function (Trail Making Test Parts A and B). RESULTS: Linear regression analysis indicated that after adjusting for age, hippocampal NAA/Cr was a significant predictor of FCSRT-IR performance (beta = 0.38, p = 0.01, R (2) = 0.21). Hippocampal volume was also a significant predictor of FCSRT-IR performance after adjusting for age and midsagittal area (beta = 0.47, p = 0.01, R (2) = 0.24). In a combined model, hippocampal NAA/Cr (beta = 0.33, p = 0.03) and volume (beta = 0.35, p = 0.03) were independent predictors of FCSRT-IR performance, accounting for 30% of the variance in memory. CONCLUSIONS: These findings indicate that nondemented older adults with smaller hippocampal volumes and lower levels of hippocampal N-acetyl aspartate/creatine ratio metabolites perform more poorly on a test of verbal memory. The integrity of both the structure and metabolism of the hippocampus may underlie verbal memory function in nondemented elderly.

Melt segregation and strain partitioning: implications for seismic anisotropy and mantle flow.

One of the principal means of understanding upper mantle dynamics involves inferring mantle flow directions from seismic anisotropy under the assumption that the seismic fast direction (olivine a axis) parallels the regional flow direction. We demonstrate that (i) the presence of melt weakens the alignment of a axes and (ii) when melt segregates and forms networks of weak shear zones, strain partitions between weak and strong zones, resulting in an alignment of a axes 90 degrees from the shear direction in three-dimensional deformation. This orientation of a axes provides a new means of interpreting mantle flow from seismic anisotropy in partially molten deforming regions of Earth.

Use of antibiotic resistance analysis to identify nonpoint sources of fecal pollution.

A study was conducted to determine the reliability and repeatability of antibiotic resistance analysis as a method of identifying the sources of fecal pollution in surface water and groundwater. Four large sets of isolates of fecal streptococci (from 2,635 to 5,990 isolates per set) were obtained from 236 samples of human sewage and septage, cattle and poultry feces, and pristine waters. The patterns of resistance of the isolates to each of four concentrations of up to nine antibiotics were analyzed by discriminant analysis. When isolates were classified individually, the average rate of correct classification (ARCC) into four possible types (human, cattle, poultry, and wild) ranged from 64 to 78%. When the resistance patterns of all isolates from each sample were averaged and the resulting sample-level resistance patterns were classified, the ARCCs were much higher (96 to 100%). These data confirm that there are measurable and consistent differences in the antibiotic resistance patterns of fecal streptococci isolated from various sources of fecal pollution and that antibiotic resistance analysis can be used to classify and identify these sources.

MRI analysis of the cerebellum in bipolar disorder: a pilot study.

Since qualitative CT studies have suggested decreased cerebellar size in patients with bipolar disorder, we performed a quantitative analysis of the cerebellum in patients with bipolar disorder to determine whether high-resolution, thin slice magnetic resonance imaging (MRI) morphometry would reveal similar results. Bipolar patients hospitalized for a first manic episode (n = 16), bipolar patients with prior manic episodes hospitalized for a manic episode (n = 14), and normal volunteers (n = 15) matched for age, sex, race, and education were recruited and anatomic brain scans were acquired using a Picker 1.5 Tesla MRI scanner. Right and left cerebellar hemisphere volumes and vermal areas V1 (lobules I-V), V2 (lobules VI-VII), and V3 (lobules VIII-X) were measured. ANCOVA comparing each ROI, adjusting for race, sex, age, total cerebral volume, and substance abuse duration, revealed a significant group effect for vermal V3 area. Specifically, V3 area was significantly smaller in multiple-episode patients than in first-episode patients or healthy volunteers. Number of previous episodes of depression may contribute to this finding. These results suggest that cerebellar vermal atrophy may be a later neurodegenerative event in patients with bipolar disorder who have had multiple affective episodes. The confounding effects of medications are considered.

Brain magnetic resonance imaging of structural abnormalities in bipolar disorder.

BACKGROUND: The neuropathogenesis of bipolar disorder remains poorly described. Previous work suggests that patients with bipolar disorder may have abnormalities in neural pathways that are hypothesized to modulate human mood states. We examined differences in brain structural volumes associated with these pathways between patients with bipolar disorder hospitalized with mania and healthy community volunteers. METHODS: Twenty-four patients with bipolar disorder and mania were recruited from hospital admission records. Twenty-two healthy volunteers were recruited from the community who were similar to the patients in age, sex, race, height, handedness, and education. All subjects were scanned using a 3-dimensional radio-frequency-spoiled Fourier acquired steady state acquisition sequence on a 1.5-T magnetic resonance imaging scanner. Scans were analyzed using commercial software. Prefrontal, thalamic, hippocampal, amygdala, pallidal, and striatal volumetric measurements were compared between the 2 groups. RESULTS: Patients with bipolar disorder demonstrated a significant (A = 0.64; F6,37 = 3.4; P = .009) overall difference in structural volumes in these regions compared with controls. In particular, the amygdala was enlarged in the patients. Brain structural volumes were not significantly associated with duration of illness, prior medication exposure, number of previous hospital admissions, or duration of substance abuse. Separating patients into first-episode (n = 12) and multiple-episode (n = 12) subgroups revealed no significant differences in any structure (P>.10). CONCLUSION: Patients with bipolar disorder exhibit structural abnormalities in neural pathways thought to modulate human mood.

Frontosubcortical neuroanatomy and the continuous performance test in mania.

OBJECTIVE: The authors examined whether Continuous Performance Test scores correlate with frontosubcortical volumes in bipolar disorder. METHOD: The subjects were 17 patients hospitalized for an acute manic episode and 12 group-matched comparison subjects. They underwent magnetic resonance imaging and completed the Continuous Performance Test. RESULTS: The patients performed worse on the Continuous Performance Test and had smaller prefrontal cortical volumes than the comparison subjects. Within the patient group, Continuous Performance Test performance significantly correlated with prefrontal and hippocampal volumes. CONCLUSIONS: These results suggest that certain neuroanatomic structures may be associated with attentional dysfunction in mania.

Traumatic brain injury in individuals convicted of sexual offenses with and without bipolar disorder.

The authors examined the occurrence of traumatic brain injury (TBI) in individuals convicted of sexual offenses with and without bipolar disorder and a comparison group of patients with bipolar disorder without a history of sexual offending behaviors. Individuals convicted of sexual offenses and diagnosed with bipolar disorder had greater rates of brain injury resulting from head trauma than individuals convicted of sexual offenses without bipolar disorder and comparison patients with bipolar disorder. TBI predated the first sexual offense and/or the onset of bipolar disorder in most subjects.

Alterations in body composition after gastroplasty for morbid obesity.

Body compositional changes during rapid weight loss and after weight stabilization were prospectively studied in morbidly obese patients undergoing gastroplasty operations. Body composition was studied preoperatively and 6 and 24 months postoperatively in 23 patients by use of a total body counter (40K) and an isotope dilution technique. The mean fat mass, cell mass, and intracellular water (ICW) decreased during the first 6 months (p less than 0.001) and remained unchanged at the 24-month test. However, the mean liters of extracellular water (ECW) did not change. Consequently, the ECW/ICW ratio, high in states of malnutrition, rose above postoperative levels. A strong correlation was found between decreases in cell mass and increases in the ECW/ICW ratio.

Herpes simplex virus resistant to acyclovir. A study in a tertiary care center.

STUDY OBJECTIVE: To determine the sensitivity of herpes simplex virus isolates to acyclovir and the importance of resistant isolates in hospitalized patients. DESIGN: Retrospective incidence cohort study. SETTING: All herpes simplex virus isolates cultured over 1 year from patients followed at a tertiary care center. PATIENTS: Consecutive herpes simplex virus isolates were collected from 207 patients, including immunocompetent patients, patients with malignancy, neonates, bone marrow and organ transplant recipients, and patients seropositive for human immunodeficiency virus. MEASUREMENTS AND MAIN RESULTS: A rapid nucleic acid hybridization method was used to assess susceptibility to acyclovir. Acyclovir-resistant herpes simplex viruses were recovered from 7 of 148 immunocompromised patients (4.7%) but from none of 59 immunocompetent hosts. Clinical disease was found in all 7 patients with resistant herpes simplex virus and was more severe in pediatric patients. All resistant isolates were from acyclovir-treated patients and had absent or altered thymidine kinase activity by plaque autoradiography. CONCLUSION: Herpes simplex virus resistant to acyclovir arises relatively frequently in immunocompromised patients and may cause serious disease. Rapid detection of resistance permits antiviral therapy to be individualized. Antiviral susceptibility testing to monitor viral resistance should be encouraged, especially in tertiary care settings.

Leasing equipment minimizes capital investment.

As consumers continue to demand the most advanced technology at the lowest cost, healthcare organizations are turning to leasing as a way of acquiring equipment with a minimum amount of capital investment. Institutions considering leasing should determine their balance sheet constraints, compare the relative costs of debt financing and leasing, and assess the residual value of the equipment at the end of its use. Comparing potential lessors requires careful analysis of rate structures and the capability of the companies to commit to a contract promptly.

Environmental and typewriter control systems for high-level quadriplegic patients: evaluation and prescription.

A formal 44-month clinical evaluation was conducted to determine the suitability of selected electronic equipment for use in high-level quadriplegia. A total of 52 traumatic high-level quadriplegic patients (C-2 to C-5,6) participated in the testing of 13 commercial electronic assistive devices including 8 environmental control units, 1 self-contained telephone, and 4 typewriter systems. Most devices were pneumatically ("breath") controlled. Devices were tested in an occupational therapy laboratory, bedside, and homes. Testing yielded data on device reliability, suitability, and acceptance by patients.