Time filter

Source Type

Toronto, Canada

Kouzaki M.,Kyoto University | Masani K.,University of Toronto | Masani K.,Lyndhurst Center
Gait and Posture

To examine the age-related deterioration in postural control, we investigated the association between postural sway during quiet standing and either amplitude of physiological tremor or muscle volume of the plantar flexors in 20 young and 20 elderly adults. They maintained a quiet standing position on a force platform for 60. s with their eyes open or closed. During quiet standing, physiological tremors detected using a piezoresistive accelerometer were recorded from the soleus muscle, and the center of pressure (COP) displacement and body acceleration in the antero-posterior direction were calculated using the ground reaction forces as an assessment of postural sway. Muscle volume was predicted from muscle thickness by an ultrasonographic image. The physiological tremor of the soleus muscle during quiet standing was significantly greater in elderly than in young adults, and a positive association between physiological tremor and the amplitude of postural sway was found for young and elderly adults combined. Furthermore, physiological tremor was positively correlated with the high-frequency component of COP sway during quiet standing. A significantly negative relation between the muscle volume of the plantar flexors and postural sway was found in both age groups. These results suggest that physiological tremor reflects high-frequency fluctuations in postural sway during quiet standing in young and elderly adults, and age-related increases in the postural sway amplitude in the antero-posterior direction may be related to a decrease in muscle volume of the plantar flexors for maintaining an upright posture. © 2011 Elsevier B.V. Source

Furlan J.C.,University of Toronto | Furlan J.C.,Lyndhurst Center | Fang J.,Institute for Clinical Evaluative science | Silver F.L.,University of Toronto | And 2 more authors.
Journal of the Neurological Sciences

Introduction Thrombocytopenia may be associated with a greater risk of cerebral hemorrhage and thrombocytosis may be associated with a greater risk of cerebral thrombosis. There is a paucity of studies focused on the potential association between blood platelet count (BPC) and outcomes after acute ischemic stroke (AIS). We hypothesized that abnormal BPC is associated with poorer outcomes after AIS. Methods This study included data from the Ontario Stroke Registry on consecutive patients with AIS admitted between July 2003 and March 2008. Patients were divided into groups as follows: low BPC (< 150,000/mm3), normal BPC (150,000 to 450,000/mm3) and high BPC (> 450,000/mm3). Primary outcome measures were the frequency of moderate/severe strokes on admission (Canadian Neurologic Scale: < 8), greater degree of disability at discharge (modified Rankin score: 3-6), and 30-day and 90-day mortality. Results We included 9230 patients. Both low and high BPC were associated with higher 30-day mortality (p ≤ 0.0335) and 90-day mortality (p ≤ 0.048) following AIS. The Kaplan-Meier curves indicate that abnormal BPC is associated with greater mortality after AIS (p = 0.0002). Nonetheless, abnormal BPC was not associated with initial stroke severity (p ≥ 0.225), degree of disability (p ≥ 0.3761), or length of stay in the acute stroke care center (p ≥ 0.7818) after adjustment for major potential confounders. Conclusions Thrombocytopenia and thrombocytosis on the initial admission are associated with higher mortality after AIS. Abnormal BPC does not adversely affect the degree of initial impairment, disability at discharge, or length of stay in the acute care hospital after AIS. © 2016 Elsevier B.V. All rights reserved. Source

Vette A.H.,University of Toronto | Vette A.H.,Lyndhurst Center | Masani K.,University of Toronto | Masani K.,Lyndhurst Center | And 3 more authors.
IEEE Transactions on Neural Systems and Rehabilitation Engineering

We have recently demonstrated in simulations and experiments that a proportional and derivative (PD) feedback controller can regulate the active ankle torque during quiet stance and stabilize the body despite a long sensory-motor time delay. The purpose of the present study was to: 1) model the active and passive ankle torque mechanisms and identify their contributions to the total ankle torque during standing and 2) investigate whether a neural-mechanical control scheme that implements the PD controller as the neural controller can successfully generate the total ankle torque as observed in healthy individuals during quiet stance. Fourteen young subjects were asked to stand still on a force platform to acquire data for model optimization and validation. During two trials of 30 s each, the fluctuation of the body angle, the electromyogram of the right soleus muscle, and the ankle torque were recorded. Using these data, the parameters of: 1) the active and passive torque mechanisms (Model I) and 2) the PD controller within the neural-mechanical control scheme (Model II) were optimized to achieve potential matching between the measured and predicted ankle torque. The performance of the two models was finally validated with a new set of data. Our results indicate that not only the passive, but also the active ankle torque mechanism contributes significantly to the total ankle torque and, hence, to body stabilization during quiet stance. In addition, we conclude that the proposed neural-mechanical control scheme successfully mimics the physiological control strategy during quiet stance and that a PD controller is a legitimate model for the strategy that the central nervous system applies to regulate the active ankle torque in spite of a long sensory-motor time delay. © 2006 IEEE. Source

Furlan J.C.,Western Research Institute | Furlan J.C.,University of Western Ontario | Furlan J.C.,Lyndhurst Center | Furlan J.C.,University of Toronto | And 11 more authors.

Neoplastic metastatic epidural spinal cord compression is a common complication of cancer that causes pain and progressive neurologic impairment. The previous standard treatment for this condition involved corticosteroids and radiotherapy (RT). Direct decompressive surgery with postoperative radiotherapy (S+RT) is now increasingly being chosen by clinicians to significantly improve patients' ability to walk and reduce their need for opioid analgesics and corticosteroids. A cost-utility analysis was conducted to compare S+RT with RT alone based on the landmark randomized clinical trial by Patchell et al. (2005). It was performed from the perspective of the Ontario Ministry of Health and Long-Term Care. Ontario-based costs were adjusted to 2010 US dollars. S+RT is more costly but also more effective than corticosteroids and RT alone, with an incremental cost-effectiveness ratio of US$250 307 per quality-adjusted life year (QALY) gained. First order probabilistic sensitivity analysis revealed that the probability of S RT being cost-effective is 18.11. The cost-effectiveness acceptability curve showed that there is a 91.11 probability of S RT being cost-effective over RT alone at a willingness-to-pay of US$1 683 000 per QALY. In practice, the results of our study indicate that, by adopting the S RT strategy, there would still be a chance of 18.11 of not paying extra at a willingness-to-pay of US$50 000 per QALY. Those results are sensitive to the costs of hospice palliative care. Our results suggest that adopting a standard S RT approach for patients with MSCC is likely to increase health care costs but would result in improved outcomes. © 2012 The Author(s). Source

Discover hidden collaborations