Human lumbar facet joint capsule strains: I. During physiological motions.

BACKGROUND CONTEXT: The lumbar facet joint capsule is innervated with nociceptors and mechanoreceptors, and is thought to play a role in low back pain as well as to function proprioceptively. PURPOSE: In order to examine the facet capsule's potential proprioceptive role, relationships between intracapsular strain and relative spine position were examined. STUDY DESIGN/SETTING: Lumbar facet joint capsule strains were measured in human cadaveric specimens during displacement-controlled motions. METHODS: Ligamentous lumbar spine specimens (n=7) were potted and actuated without inducing a moment at the point of application. Spines were tested during physiological motions of extension, flexion, left and right lateral bending. Intervertebral angulations (IVA) were measured using biaxial inclinometers mounted on adjacent vertebrae. Joint moments were determined from the applied load at T12 and the respective moment arms. Capsule plane strains were measured by optically tracking the displacements of infrared reflective markers glued to capsule surfaces. Statistical differences (p<.05) in moment, IVA and strain were assessed across facet joint levels using analysis of variance and comparison of linear regressions. RESULTS: The developed moments and IVAs increased monotonically with increasing displacements; the relationships were highly correlated for all four motion types. Although highly variable among specimens, principal strains also increased monotonically in magnitude with increasing displacements during extension and flexion, but were more complex during lateral bending. At a given joint level, the absolute magnitudes of principal strains and IVA were largest during the same motion type. CONCLUSIONS: Distinct patterns in principal strains and IVA were identified during physiological motions, lending biomechanical support to the theory that lumbar facet joint capsules could function proprioceptively.     

Dynamic responsiveness of lumbar paraspinal muscle spindles during vertebral movement in the cat

Muscle spindles provide essential information for appropriate motor control. In appendicular muscles, much is known about their position and movement sensitivities, but little is known about the axial muscles of the low back. We investigated the dynamic responsiveness of lumbar paraspinal muscle spindle afferents from L₆ dorsal root filaments during constant velocity movement of the L₆ vertebra (the feline has seven lumbar vertebrae) in Nembutal-anesthetized cats. Actuations of 1 mm applied at the L₆ spinous process were delivered at 0.5, 1.0 and 2.0 mm/s. The slow velocity component was measured as the slope of the relationship between displacement during the constant velocity ramp and instantaneous discharge frequency. The quick velocity component was the slope’s intercept at zero displacement. The peak component was determined as the highest discharge rates occurring near the end of the ramp compared with control. The slow velocity component over the three increasing velocities was 23.9 (9.9), 21.6 (9.6) and 20.5 (9.5) imp/(s mm) [mean (SD)], respectively. The quick velocity component was 28.4 (8.6), 31.4 (9.8) and 35.8 (10.6) imp/s, respectively. These measures of dynamic responsiveness were at least 5–10 times higher compared with values reported for appendicular muscle spindles. The peak component’s velocity sensitivity was 2.9 (imp/s)/(mm/s) [0.2, 5.5, lower, upper 95% confidence interval] similar to that for cervical paraspinal muscles as well as appendicular muscles. Increased dynamic responsiveness of lumbar paraspinal muscle spindles may insure central driving to insure control of intervertebral motion during changes in spinal orientation. It may also contribute to large, rapid and potentially injurious increases in paraspinal muscle activity during sudden and unexpected muscle stretch.     

Morbidity in 303 first‐episode bipolar I disorder patients

Baldessarini RJ, Salvatore P, Khalsa H‐MK, Gebre‐Medhin P, Imaz H, González‐Pinto A, Perez J, Cruz N, Maggini C, Tohen M. Morbidity in 303 first‐episode bipolar I disorder patients.
Bipolar Disord 2010: 12: 264–270. © 2010 The Authors.
Journal compilation © 2010 John Wiley & Sons A/S. Objectives: To test the hypotheses that: (i) depressive‐dysthymic‐dysphoric (D‐type) morbidity is more prevalent than manic‐hypomanic‐psychotic (M‐type) morbidity even from first episodes of bipolar I disorder (BPD‐I) and despite treatment; (ii) initial presentations predict later morbidity; (iii) morbidity varies internationally; and (iv) early and later morbidity are similar. Methods: We followed SCID‐based, DSM‐IV BPD‐I patients (n = 303) systematically and prospectively for two years to estimate the percent of weeks in specific morbid states from first lifetime major episodes. Results: Total morbidity accounted for 44% of the first two years, and D‐type exceeded M‐type illnesses by 2.1‐fold (30%/14%) among morbidities ranking: mixed states (major + minor) ≥ dysthymia ≥ mania ≥ major depression > hypomania > psychosis. In 164 cases, morbidities at 0.5–2.5 and 2.5–4.5 years were very similar. Depressive or mixed initial episodes predicted a 3.6‐fold excess of D‐type morbidity, and initial M‐type episodes predicted a 7.1‐fold excess of M‐type morbidity over two years. Morbidity in European (EU) sites was nearly half that in the U.S., and 22% greater overall among men than women. In five comparable studies, illness accounted for 54% of follow‐up time, and the ratio of D/M morbidity averaged 3.0. Conclusions: In accord with four midcourse studies, morbidity from BPD‐I onset, despite treatment by community standards, averaged 44%, was 68% D‐type morbidity, and was strongly predicted by first‐episode polarity. Lower morbidity in EU than U.S. sites may reflect differences in healthcare or social systems.     

Cardiorespiratory noise correction improves the ASL signal

Cardiorespiratory fluctuations such as changes in heart rate or respiration volume influence the temporal dynamics of cerebral blood flow (CBF) measurements during arterial spin labeling (ASL) fMRI. This “physiological noise” can confound estimates of resting state network activity, and it may lower the signal‐to‐noise ratio of ASL during task‐related experiments. In this study we examined several methods for minimizing the contributions of both synchronized and non‐synchronized physiological noise in ASL measures of CBF, by combining the RETROICOR approach with different linear deconvolution models. We evaluated the amount of variance in CBF that could be explained by each method during physiological rest, in both resting state and task performance conditions. To further demonstrate the feasibility of this approach, we induced low‐frequency cardiorespiratory deviations via peripheral adrenergic stimulation with isoproterenol, and determined how these fluctuations influenced CBF, before and after applying noise correction. By suppressing physiological noise, we observed substantial improvements in the signal‐to‐noise ratio at the individual and group activation levels. Our results suggest that variations in cardiac and respiratory parameters can account for a large proportion of the variance in resting and task‐based CBF, and indicate that regressing out these non‐neuronal signal variations improves the intrinsically low signal‐to‐noise ratio of ASL. This approach may help to better identify and control physiologically driven activations in ASL resting state and task‐based analyses.     

A workshop on ethnic and cultural awareness for second-year students

In 1984, 50 percent of the first-year students at the University of Southern California School of Medicine felt unprepared to handle the cultural barriers between themselves and their patients during their clinical rotations. Therefore, in 1985 a group of students developed a four-hour workshop designed to teach fellow students about ethnic and cultural issues in patient care. Since then the workshop, which uses videotaped vignettes, discussions, and role-playing exercises, has become a required part of the Introduction to Clinical Medicine course for all second-year students. Evaluation of the program in 1985 compared pretest and posttest questionnaires. The participants showed improvement in understanding several specific issues discussed during the workshop, but overall no significant differences were found. In 1986 and 1987, evaluations were based upon the students' attitudes about content, format effectiveness, and subject matter. They consistently responded favorably in all these areas.