Screening for balance disorders in mildly affected multiple sclerosis patients

Multiple sclerosis (MS) patients often complain about balance problems when Romberg's test and tandem gait are normal. The aim of the study was to determine if measures of trunk sway taken during a battery of stance and gait tasks could be used to detect subclinical balance disorders. We recorded trunk angular sway in the pitch and roll directions from 20 MS patients (EDSS 1.4 ± 0.5) and 20 age- and gender-matched healthy controls (HCs), during 12 stance and gait tasks. We filmed 22 subjects simultaneously. Two neurologists assessed the videos, deciding whether task performance was pathological. Sway measures were significantly different between patients and HCs in eight out of 12 balance tasks. The most significant differences between MS patients and HCs were pitch angle range standing on one leg with eyes open on a firm surface (mean 3.13° vs. 2.09°, p = 0.005), and on a foam support surface (mean 6.24° vs. 2.96°, p = 0.006), pitch velocity range walking 8 m with eyes closed (mean 75.5 vs. 50.2°/s, p < 0.001) and pitch velocity range walking 3 m on heels (mean 85.37 vs. 60.9°/s, p = 0.002). Multivariate analysis revealed a model with three tasks which detected balance disorders in 84% of the MS patients and 90% of the HCs correctly. The neurologists achieved accuracies of 30% for the MS patients and 82% for the HCs. Using trunk sway measures during stance and gait tasks is a sensitive screening method for balance problems in MS patients, and is more accurate than assessment by trained neurologists.     

Proprioceptive control of posture: a review of new concepts

The assumption that proprioceptive inputs from the lower legs are used to trigger balance and gait movements is questioned in this review (an outgrowth of discussions initiated during the Neural Control of Movement Satellite meeting held in Cozumel, Mexico, April 1997). Recent findings presented here suggest that trunk or hip inputs may be more important in triggering human balance corrections and that proprioceptive input from the lower legs mainly helps with the final shaping and intermuscular coordination of postural and gait movements. Three major questions were considered. First, what role, if any, do lower-leg proprioceptive inputs play in the triggering of normal balance corrections? If this role is negligible, which alternative proprioceptive inputs then trigger balance corrections? Second, what is the effect of proprioceptive loss on the triggering of postural and gait movements? Third, how does proprioceptive loss affect the output of central pattern generators in providing the final shaping of postural movements? The authors conclude that postural and gait movements are centrally organized at two levels. The first level involves the generation of the basic directional-specific response pattern based primarily on hip or trunk proprioceptive input secondarily on vestibular inputs. This pattern specifies the spatial characteristics of muscle activation, that is which muscles are primarily activated, as well as intermuscular timing, that is, the sequence in which muscles are activated. The second level is involved in the shaping of centrally set activation patterns on the basis of multisensorial afferent input (including proprioceptive input from all body segments and vestibular sensors) in order that movements can adapt to different task conditions. Copyright 1998 Elsevier Science B.V.     

苦楝化学成份的研究

从苦楝(Melia azedarach L.)果中分得苦楝新醇(Ⅰ),苦楝醇(Ⅱ)、苦楝酮(Ⅲ)、苦楝二醇(Ⅳ)、香草醛(Ⅴ)和香草酸(Ⅵ)。根据波谱(IR,MS,~1HNMR,~(13)CNMR)分析和理化常数测定,确定了它们的结构。其中苦楝新醇(Ⅰ)为新化合物,对菜青小虫有一定的拒食活性。     

Computer graphics for digitally formatted images

The increasing use of digitally formatted imaging systems requires high-quality interactive gray-scale computer raster graphics systems for the management, display, and analog film recording of digital image and alphanumeric information. These systems are a combination of computer hardware and software and implement a set of graphics protocols. This paper describes a set of interactive graphics protocols that has been developed for clinical use.     

Whiplash evokes descending muscle recruitment and sympathetic responses characteristic of startle

Whiplash injuries are the most common injuries following rear-end collisions. During a rear-end collision, the human muscle response consists of both a postural and a startle response that may exacerbate injury. However, most previous studies only assessed the presence of startle using data collected from the neck muscles and head/neck kinematics. The startle response also evokes a descending pattern of muscle recruitment and changes in autonomic activity. Here we examined the recruitment of axial and appendicular muscles along with autonomic responses to confirm whether these other features of a startle response were present during the first exposure to a whiplash perturbation. Ten subjects experienced a single whiplash perturbation while recording electromyography, electrocardiogram, and electrodermal responses. All subjects exhibited a descending pattern of muscle recruitment, and increasing heart rate and electrodermal responses following the collision. Our results provide further support that the startle response is a component of the response to whiplash collisions.     

The interdental gingiva,a visible guide for placement of mini‐implants

Authors – Chun YS, Lee SK, Wikesjö UME, Lim WH Objectives – To determine whether the tip of the interdental gingiva can serve as a visible guide for placement of mini‐implants. Setting and Sample population – Computer tomography (CT) images from 15 males and 15 females (mean age 27 years, range: 23–35 years) were used to evaluate the distance from the tip of the interdental gingiva to the alveolar crest from the central incisor to the 1st molar. The distance from a reference point to the tip of interdental gingiva was recorded from study models using a caliper. The distance between the reference point and the alveolar crest was recorded using CT and added to the model recordings thus providing the distance from the tip of interdental gingiva to the alveolar crest for the various interdental sites. Two‐way anova and Student–Newman–Keuls test for multiple comparisons were used for the statistical analysis. Results – There was no significant difference in the distance from the tip of interdental gingiva to the alveolar crest between maxilla and mandible. The distance between the tip of interdental gingiva and the alveolar crest at the central/lateral incisors was the shortest compared with that of other sites. There was also a statistically significant difference between the male and female groups except for the maxillary 2nd premolar/1st molar interradicular site. Conclusion – The tip of interdental gingiva appears a reasonable visual guide for the placement of mini‐implants for orthodontic anchorage.     

The impact of loads on standard diameter, small diameter and mini implants: a comparative laboratory study

Objectives: While caution in the use of small‐diameter (≤3.5 mm) implants has been advocated in view of an increased risk of fatigue fracture under clinical loading conditions, a variety of implant designs with diameters <3 mm are currently offered in the market for reconstructions including fixed restorations. There is an absence of reported laboratory studies and randomized‐controlled clinical trials to demonstrate clinical efficacy for implant designs with small diameters. This laboratory study aimed to provide comparative data on the mechanical performance of a number of narrow commercially marketed implants. Materials and methods: Implants of varying designs were investigated under a standardized test set‐up similar to that recommended for standardized ISO laboratory testing. Implant assemblies were mounted in acrylic blocks supporting laboratory cast crowns and subjected to 30° off‐axis loading on an LRX Tensometer. Continuous output data were collected using Nexygen software. Results: Load/displacement curves demonstrated good grouping of samples for each design with elastic deformation up to a point of failure approximating the maximum load value for each sample. The maximum loads for Straumann (control) implants were 989 N (±107 N) for the 4.1 mm RN design, and 619 N (±50 N) for the 3.3 mm RN implant (an implant known to have a risk of fracture in clinical use). Values for mini implants were recorded as 261 N (±31 N) for the HiTec 2.4 mm implant, 237 N (±37 N) for the Osteocare 2.8 mm mini and 147 N (±25 N) for the Osteocare mini design. Other implant designs were also tested. Conclusions: The diameters of the commercially available implants tested demonstrated a major impact on their ability to withstand load, with those below 3 mm diameter yielding results significantly below a value representing a risk of fracture in clinical practice. The results therefore advocate caution when considering the applicability of implants ≤3 mm diameter. Standardized fatigue testing is recommended for all commercially available implants.